1 FEBRUARY 2, 2001

UUPP SSeerriieess Nd:YAG Laser Ablation

Systems

Operator’s Manual (UP – 266, UP – 266 IV, UP – 213, UP – 213 IV)

New Wave Research Inc.

47613 Warm Springs Blvd.

Fremont, CA 94539

Tel: (800) 566-1743 or (510) 249-1550

Fax: (510) 249-1551

Email: lasers@new-wave.com

Website: http://www.new-wave.com

Website: http://www.merchantek.com

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Copyright 2001 by New Wave Research, Inc. All rights reserved. Printed in the U.S.A. Reproduction or translation of any part of this publication, except as permitted by the 1976 United States Copyright Act, without prior written permission of New Wave Research, Inc. is unlawful

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SAFETY 3 SAFETY SUMMARY 3

Optical Safety 3 Laser Safety 5 Electrical Safety 6 Safety Features 6

Laser Covers 6 Interlocks 6 Laser Light Emissions 6

Government Regulations 7 Laser Classification 7 Location of Safety Labels 7

HARDWARE SETUP PROCEDURES 13 SYSTEM OVERVIEW 13

Laser Module 13 Base Module 14 Laser Power Supply 14 Preparation 15

Space Requirements 15 Electrical Requirements 15

Laser Safety Requirements 16 SYSTEM INSTALLATION 17

Unpacking the UP266X 17 Base Module Installation 17 Laser Module Installation 18 Video Train Installation 19

Connecting the Laser Module to the Base Module 20 Laser Power Supply Installation 22 Cooling System 23

External Connections 24 AC Power Connections 24 Computer & System Connections 24 Mass Spectrometer Connections 25

Turning off the system 26 Starting the Software 26 Establishing Coolant Flow 27 Testing the Light Sources 28 Testing the X-Y Stages 28 Testing the Z Axis 28 Testing the Video System 28 Testing the Laser System 28

SIGNAL SPECIFICATIONS 30 Trigger In to the LAS 30 Trigger Out from the LAS 30 Circuit Diagrams 30 Trigger Out Operation 30

Disabled 32

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Laser Mode 32 Pattern Mode 32 Experiment Mode 33

Trigger In Operation 33 Pattern Mode 33 Experiment Mode 33

INTRODUCTION TO LASERS 36 THE GENERAL LASER PRINCIPLE 36 ND:YAG LASER 39

General Introduction 39 Q-switching 39

POLARIS / TEMPEST LASER 41 Optical Attenuator 41 Harmonic Generation 42

UP SERIES – SYSTEM DESCRIPTION 46 GENERAL OVERVIEW 46 LASER FORMATION 47 CRATER SIZE SELECTION 49 VIEWING THE SAMPLE 49 SAMPLE CHANGEOVER 50

SOFTWARE STEP-BY-STEP GUIDE 54 I. GETTING STARTED 54

STEP 1: Load the software 54 STEP 2: Load NIST612 glass standard 55 STEP 3: Purge the gas lines 56 STEP 4: Select online mode 58 STEP 5: Calibrate the XYZ stage 59 STEP 6: Select the light source 60 STEP 7: Select the lowest magnification 61 STEP 8: Focus on the sample surface via Z-stage 61 STEP 9: Adjust laser energy to full output 62 STEP 10: Adjust repetition rate to 20Hz 62 STEP 11: Select largest crater diameter 63 STEP 12: Selecting Continuous Ablation mode 65 STEP 13: Click on FIRE 66

II. TUNING THE ICP-MS 68 STEP 1: Select sample area 68 STEP 2: Select line pattern 68 STEP 3: Draw line on the sample 68 STEP 4:Choose line properties 69 STEP 5: Monitor masses 70 STEP 6: Run a short term stability test 70

III. SCREEN PROPERTIES AND CALIBRATION ROUTINE 71 STEP 1: Adjust Video properties 71 STEP 2: Adjust Display properties 72 STEP 3: Calibrate Screen 72

IV. LASER ABLATION PARAMETERS AND PATTERN SELECTION 75 Influence of laser parameters 75

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Preablation 75 Internal standards 75 Real Time analyses 76 Laser Pattern 76

V. RUNNING AN EXPERIMENT 80 File Options 81

VI. VIDEO OVERLAY FUNCTION 82 STEP 1: Create the sample map area 82 STEP 2: Make the sample map 83

MAINTENANCE & TROUBLE-SHOOTING 88 MAINTENANCE 88

Safety System Inspection 88 Cooling System Maintenance 88 Light Source Maintenance 89 Laser/Video Alignment 89

TROUBLESHOOTING 90 Interface Problems 90 Safety Interlock Problems 90

Laser Power Supply Interlock Failure 90 Door, Rear Cover Interlock Failure 90 Trinocular Viewer Interlock Failure 90

Laser Problems 90 Laser to Video Misaligned (the spot is not at the center of the crosshairs) 90 Laser Low Energy 90 Laser Doesn’t Fire 91

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Chapter 1

Safety

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Safety

Safety Summary

Review the following safety precautions to avoid injury and prevent damage to the Laser Ablation System or any products connected to it. To avoid potential hazards, use the system only as specified.

WARNING: The UP Series Laser Ablation System contains subsystems that present dangerous voltage, current and radiation hazards. Only qualified personnel should perform service procedures.

Optical Safety

The Standard UP Series is designed to meet Class I laser safety requirements and as such does not require special precautions under normal operation. However, configurations of the UP Series are available for some applications designated as a Class 4 laser product and the system is based on a Nd:YAG laser that generates high-energy radiation that can pose serious risks to eye safety. Infrared and ultraviolet radiation are invisible to the eye so the hazard is not immediately obvious, but the radiation can be focussed onto the retina, corona or lens. For this reason it is very important that, when performing any normal operation of Class 4, and/or maintenance or service which might expose the service personnel to internal laser radiation, service personnel wear safety glasses suitable for protection of high energy ultraviolet radiation and be aware of any possible reflections. Avoid any exposure of skin to the high energy UV radiation since it may cause cancer.

This Nd:YAG laser ablation system meets the requirements for Class I laser product when all panels are closed. The interlocks must never be defeated other than for manufacturer’s service. With any enclosure removed, or sample chamber removed or disassembled, the UP series emits Class 4 laser radiation.

The only maintenance required by the customer that will open a safety interlock is during flash lamp replacement. During flashlamp replacement the user will disconnect the AC power, remove the infrared cavity cover to access the flash lamp. The flash lamp replacement is performed without ever turning the laser on.

In addition, the tygon tubing that transports the aerosol generated during ablation from the sample chamber to the mass spectrometer is replaced periodically. This involves removing two hex head screws from the rear access cover of the Class 1 enclosure. This procedure requires tools and should be performed without firing the laser.

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Cleaning of the sample chamber window will be required periodically. This procedure requires tools and must be performed without firing the laser. Interlocks will ensure the laser does not fire during this procedure.

Access to radiation from this product is necessary only under some service conditions when interlocked panels are opened and the interlocks defeated, unless purchased as a Class 4 product. These procedures are undertaken only by staff who have been suitably trained, and approved by the manufacturer.

Laser radiation is emitted as a narrow beam of almost parallel rays, the intensity of which will remain high even at some distance from the laser. Although the radiation is non-ionizing, exposure can cause damage to living tissue as a result of heat produced during radiation absorption. The radiation of an Nd:YAG laser lies outside the visible range.

In general, the maximum permissible radiation exposure for the skin is several times greater than for eye. Safety measures with regard to radiation hazard are therefore mainly based on dangers for the eye.

WARNING: The Nd:YAG laser in the UP series laser ablation system is a Class IV high power laser whose beam is, by definition, a safety and fire hazard. Take all necessary precautions to prevent accidental exposure to both direct and reflected beams. DIFFUSE, AS WELL AS SPECULAR BEAM REFLECTIONS, CAN CAUSE SEVERE EYE AND SKIN DAMAGE.

WARNING: BECAUSE THE RADIATION OF AN Nd:YAG LASER IS INVISIBLE, THEY ARE EXTREMELY DANGEROUS. Possible wavelengths are high intensity ultraviolet, visible, and infrared radiation of 213, 266, 355, 532, and 1064 nm. Radiation passes easily through the cornea and focuses on the retina of the eye where it can cause instantaneous permanent damage including blindness. AVOID EYE AND SKIN EXPOSURE TO DIRECT OR SCATTERED RADIATION.

CAUTION: USE OF CONTROLS, ADJUSTMENTS OR PERFORMANCE OF PROCEDURES OTHER THAN THOSE SPECIFIED HEREIN MAY RESULT IN HAZARDOUS RADIATION EXPOSURE.

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Follow the instructions contained in this manual for proper and safe operation and servicing of your laser. Wear protective eyewear; selection depends on the energy and wavelength of the laser beam as well as operating conditions. Consult ANSI, ACGIH or OSHA standards for guidance. At all times during operation, and maintenance, or service of your laser, avoid exposure to the laser or collateral radiation exceeding the accessible emission limits listed in “Performance Standards for Laser Products,” 21 CFR 1040 10 (d).

(Laser Institute of America, 12424 Research Parkway, Suite 125, Orlando, FL 32826 ((407) 380-1553)

Laser Safety

WARNING: Do not power-up the Laser Ablation System before reading and understanding the operating and safety procedures. Use of controls, adjustments, or performing procedures other than those specified may result in hazardous laser radiation exposure and personal injury, laser system damage, and void the warranty.

Laser light poses safety hazards that are not associated with conventional light sources. Special precautions must be observed when maintaining or servicing the UP series laser ablation system. The safe use of lasers requires that all personnel working in the lasers area are aware of the dangers involved.

Laser beams are intense enough to burn skin, clothing or paint. They can ignite volatile substances such as alcohol or other solvents. The beam may also cause damage if reflected from some other surface. For this reason, it is important to observe the following precautions whenever the Class I protective safety enclosure is removed and/or the safety interlocks defeated.

• Avoid eye contact with the output beam; even diffuse reflections are particularly hazardous when the protective cover is removed.

• Treat back reflections from any optic surface as you would the main laser beam. Even though the energy of such reflections is only a fraction of that contained in the main beam, it is sufficient to cause serious bodily harm, especially to the eye.

• Use protective eyewear at all times when protective housings are removed, or operation of a Class 4 designated system. Selection depends on the wavelength and the intensity of the radiation, conditions of use and visual function required.

• Operate the laser at the lowest possible beam intensity. • Avoid blocking the output beam or its reflection with any part of the body. • Establish a controlled access area during maintenance and service. Limit access to those

trained in the principles of laser safety. • Maintain a high ambient light level in the laser operation area to constrict the pupil of the eye,

reducing the possibility of injury. • Post warning signs prominently near the laser operation area. • Provide enclosures or barriers for beam paths whenever possible.

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• To prevent unnecessary reflections and scattering, set up energy absorbing targets to capture the laser beam. If laser service is required, contact New Wave Research / Merchantek Products at Tel 510 249 1550 or Fax 510 249 1551, E-mail: lasers@new-wave.com

Electrical Safety

The UP Series meets CE safety and emission standards.

WARNING: The laser head and power supply contain electrical circuits operating at lethal voltage and current levels.

Certain procedures, such as changing the water filter or cleaning optical components require removal of the protective systems. It is important that all personnel using the laser observe all safety precautions outlined in this manual. The most important rule when working with the laser is to switch it off completely.

There are no user serviceable parts on the electrical side of the Laser Power Supply. New Wave Research must carry out Service procedures on power supply electronics.

Safety Features

The following features are built into the UP series and conform to government regulations to provide safe laser operation.

Laser Covers

The Nd:YAG laser beam is enclosed in a protective housing, which prevents access to radiation in excess of Class I limits, unless purchased as a Class 4 designated product. The cover also protects against stray radiation. Do not remove the cover, except to perform maintenance procedures by trained personnel.

Interlocks

The Nd:YAG laser ablation system has a series of interlocks to prevent accidental exposure to dangerous levels of electricity or radiation. In addition, there are interlocks designed to interrupt laser operation if the laser is damaged. The interlocks are:

• Remote interlock interrupted (if utilized). • Sample cell open or removed. (if purchased). • Transluc ent Class One Enclosure Removed. • System Cover Removed. • Trinocular head (if purchased).

Laser Light Emissions

For Class 1 systems, when the laser unit is assembled and bolted to the base unit, the Nd:YAG laser beam exits into the light-tight sample chamber and is fully contained except when the safety enclosures are removed and/or the interlocks defeated. For class 4 systems, the laser beam exits the focusing objective for ablation in any customer supplied sample chamber.

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Government Regulations

New Wave Research suggests that laser users purchase a copy of the ‘American National Standard for the Safe Use of Lasers’ (ANSI Z136.1-1993). This publication provides recommendations for the safe use of lasers and laser systems that operating at wavelengths between 180 nm and 10 um. The publication is available from:

Laser Institute of America

12424 Research Parkway, Suite 125

Orlando, FL 32826

(407) 380-1553

Laser Classification

The governmental standards and regulations specify the laser must be classified according to the output power or energy, and laser wavelength. The UP series can be supplied as either a Class I or class IV laser system. In either case, when the protective enclosure is removed and/or safety interlocks defeated, the laser is classified as Class IV based on 21 CFR, subchapter J, part II, section 1040-10(d) and Class IV based on EN 60825-1, clause 9 of the European Community Standards.

Location of Safety Labels

The UP series consists of two subassemblies, the base unit and the laser unit. When assembled, the UP series is a either a Class I or Class IV system with identification labels on the back of both units. The laser danger label located on both sides of the top unit will designate the class of laser system being operated.

Class I labels are located on the laser unit as shown in Figure 2 and Figure 4. Class I protective housing interlock labels are located on the sides of the base unit and the laser unit as shown in Figure 2 and Figure 4. For Class IV systems, the labels shown in Figure 2 and Figure 4 will be replaced by class IV labels.

Class IV precautions apply when the system is not fully assembled, or when any of the Class I safety enclosures or panels are removed, and/or when the safety interlocks are defeated. The Class IV labels are for safety and identification, and can only be viewed with the Class I enclosure cover(s) removed.

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The following images, Figure 1, Figure 2, Figure 3, and Figure 4, show the location of the labels.

Figure 1

Figure 2

Figure 3

Figure 4

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The following images show the safety labels used on the UP Series Ablation Systems.

Figure 5 Interlocked housing label (Quantity 4)

Figure 6 Class 1 laser label (Quantity 2)

Figure 6A Class IV lable (Quantity 2)

Figure 7 Laser Warning Label (3)

Details referring to CDRH-IR Radiation Control Drawing (RCD) Nd:YAG, UP - 213, UP - 266

OR

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Chapter 2

Hardware Setup

Procedures

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Hardware Setup Procedures

System Overview

The UP SERIES Laser Ablation System is a compact, solid-state laser system providing a versatile method of sampling and analysis of solids for trace and ultra trace elemental composition.

The UP SERIES is a complete, integrated system providing all aspects of laser control, beam delivery, sample observation and sample manipulation under full computer control.

Laser Module

The UP SERIES incorporates a specially designed Nd:YAG laser, frequency quadrupled or quintupler to generate an ultraviolet wavelength and flat beam profile. The laser and beam delivery system provide flat beam focusing that allows sampling to a uniform depth rather than a crater, which is deep in the center and shallow at the edges. The Laser Module also contains the video system, including a high-resolution CCD camera, computer-controlled zoom, high magnification objective, light sources for sample illumination, and specified options.

Figure 8 UP Model Ablation Systems

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Base Module

The Base Module contains the system power supply, the X-Y stepper motor controller, power supply and XY stages, Z axis controller, Z axis stage, the valves for controlling the gas flow, transmitted light source with polarizer, ring and reflected lighting sample chamber, and specified options.

Laser Power Supply

The Laser Power Supply contains the high voltage power required by the laser head, laser control electronics, a closed-loop water-to-air cooling system for removing heat from the laser head.

Figure 9 Laser Power Supply

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Start Up

Preparation

The UP SERIES installation procedure is relatively simple, but does require some preparation. Prior to unpacking the system and installation, evaluate the physical arrangement of the laboratory to choose a suitable location. The following sections discuss space, electrical and laser safety requirements. Proceed with the installation once a suitable location has been selected and prepared.

Space Requirements

The Laser Ablation Base Module and Laser Module require 20” Wide x 26” Deep x 34” High (50 x 66 x 86 centimeters) of countertop space. The system weighs approximately 120lbs. In addition, space must be made for the computer monitor and keyboard if the system is not integrated with the mass spectrometer. The Laser Power Supply usually sits on the floor and occupies a 9” Wide x 15” Deep x 19” High (22 x 38 x 48 centimeters) footprint. For most applications, the sample flow path should be short. Therefore, the Laser Ablation System needs to be placed close to the mass spectrometer.

Electrical Requirements

The Laser Power Supply is shipped configured as either a 110 VAC, 10 A, 50/60 Hz or a 220 VAC, 5A, 50/60 HZ system. The Laser Ablation System is shipped configured as either a 110 VAC, 5 A, 50/60 Hz or a 220 VAC, 3A, 50/60 HZ system.. In either case, the system should be located within 6 feet (2 meters) of four power outlets for the: Base Module, Laser Power Supply, Computer, and Computer Monitor.

DANGER – HIGH VOLTAGE: Both the Laser Module and the Laser Power Supply contain electrical circuits operating at lethal voltage and current levels. Always disconnect and wait at least one minute to allow capacitors to bleed down before servicing any part of the laser system.

WARNING: Do not power-up the Laser Ablation System before reading and understanding the operating and safety procedures. Use of controls, adjustments, or performing procedures other than those specified may result in hazardous laser radiation exposure and personal injury, laser system damage, and void the warranty.

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A power cord set that meets the requirements of the country in which the system was purchased is provided with every system. If the system is used in another country, a power cord set that meets the requirements of that country must be used. User replacement fuses provide electrical overload protection.

WARNING: This system is designed for connection to a grounded outlet. The grounded type plug is an important part of the safety design. To avoid the risk of electrical shock or damage to the system, do not disable or remove this feature.

Laser Safety Requirements

The standard UP Series ablation system is a Class I laser product that does not emit hazardous laser radiation during normal operation and therefore, may be installed and operated in any typical laboratory. However, any Class IV UP Series system, and the Nd:YAG laser used in the UP SERIES is a Class IV device and exposure to the laser may be necessary during system service. To protect personnel under these conditions the following guidelines are recommended:

Establish a controlled access area for laser operation where entry is controlled and limited to individuals trained in laser safety practices.

The area should be well lighted, and enclosed by solid walls (no windows) and ceilings.

“Danger – Laser in Operation” warning signs should be prominently posted at all approaches outside of the laser operation area.

Use ANSI/OSHA approved UV laser protective eyewear at all times.

DANGER – INVISIBLE LASER RADIATION: The UP SERIES uses a Class IV Nd:YAG Laser. The output beam is, by definition, a safety and fire hazard. Precautions must be taken during the use and maintenance to prevent accidental exposure to direct or reflected radiation from the laser beam.

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System Installation

Unpacking the UP266X

The UP SERIES Laser Ablation System has been carefully inspected and packaged for shipment. Inspect the external packaging immediately upon receipt for shipment damage. If damage is evident, immediately file a claim against the carrier and notify New Wave Research / Merchantek Products. Inspect all items during unpacking with a factory-authorized representative, and notify the carrier immediately of any concealed damage. Be sure to save all packing materials in case a future shipment is needed.

The UP SERIES laser ablation system will arrive in two (3) crates. One crate will include the top half of the system with attached laser umbilical. The second crate will include the base system platform, with the third crate containing the laser power supply, and accessory box. If a computer was ordered with the system there will be two (2) additional boxes which contain the computer monitor and computer with pre-installed video card and software.

If the UP SERIES is shipped or removed from storage during cold weather, allow the system 4 to 8 hours to attain room temperature before opening and exposing to warm, humid air.

WARNING: If condensation forms on or inside the UP PLATFORM, allow it to dry thoroughly before connecting to the AC power source and operating. Failure to do so may cause injury or equipment damage.

Base Module Installation

Remove the Base Module from the shipping container and place on a clean, flat surface, located near the mass spectrometer. The top surface of the base unit should be clear of any debris. Remove any tape or packing material that may have been deposited during shipping. Figure 10 shows the UP Base Module ready for installation of the Laser Module. The coax lighting fiber is coiled up in the base unit. Open the light source access door and uncoil the fiber.

Figure 10

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Laser Module Installation

Remove the top Laser Module from the shipping container and place on a clean, flat surface. Remove any tape and wrapping materials used during shipping. Remove both the front bezel and main cover from the Laser Module by removing the (10) 6-32 screws located around the bottom edge and the (4) 6-32 screws connecting the front bezel to the main cover. The front bezel will slide forward for removal, while the main cover must be removed by lifting from the back edges.

Remove the Protective sheet metal housing by loosening the 5 captive straight slot screws. Figure 11 shows the top Laser Module with the protective cover installed.

Figure 11

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Figure 12 shows the top Laser Module with the covers removed and ready for installation onto the Base Module.

Figure 12

Two people are necessary to place the top Laser Module onto the Base Module. With one person on each end of the Laser Module, carefully lower the Laser Module onto the Base Module. The cabling connected to the z-axis on the Base Module must be guided through the rectangular cutout on the Laser Module. The Base Module has two ¼” locating pins used to properly locate the Laser Module onto Base Module. Use the (11) 10-32 x 5/8” screws, supplied in the accessory box, to secure to Laser Module onto the Base Module.

Video Train Installation

The video train for the system is removed for shipping. The video train may or may not contain a trinocular head, depending on if this feature was ordered.

Place the dovetail located at the base of the video train into the circular cutout on the video tower at the front portion of the Laser Module. Do not release the video train at this point, for it will fall and damage the system. Rotate the video assembly so that the small knurled knob on the front side of the video adapter is facing forward to the system. Align the video train facing squarely to the front of the system. Securely tighten the three # 8 set screws with the supplied 5/64” hex driver.

Connect the video harness located in the Laser Module to the camera. Insure that the BNC connector is connected to the mating connector labelled “VIDEO”.

Aligning the video train may be necessary. Detailed instructions for this procedure are listed below.

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Connecting the Laser Module to the Base Module

The following electrical connections are required to connect the Laser Module to the Base Module.

• Connect and secure the 25-pin D-sub connector located in the back right corner of the Laser Module shown in Figure 13.

• Connect the two small black connectors shown in Figure 14. One of smaller of the two connectors is connected to the left side of the video tower, to the Z-axis limit board. The larger of the two connectors is connected to the circuit board located on the left side of the Laser Module.

• • Connect the Coax Fiber to the Coax Lens Assembly located on the left side of the video tower frame.

The Fiber must be inserted through the 5/16” hole in the optical base plate over the top of the light source. Run the fiber around the left side of the laser head. Cable tie the fiber on top of the cable bundles located over the top of the circuit boards.

Figure 13

Figure 14

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Replace the protective sheet metal housing (if included) onto the Laser Optical Deck. Be careful not to bump the optical mounts. Secure this cover in place with the 5 captive straight slot screws.

Place the Main Cover onto the Laser Module. To install this cover, place the back end of the cover over the back bulkhead panel. As the front end of the cover is lowered into place, spread the two lower front corners over the base optical plate. As the cover is placed over the optical plate, slide the cover forward until flush with the back panel. Secure into place with the (6) 6-32 screws that were earlier removed. Place the Front Bezel onto the Laser Module. Secure into place with the (2) 6-32 around the front of the base, and the (4) screws on the Video Tower.

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Laser Power Supply Installation Remove the Laser Power Supply from the shipping container and place on the floor near the Laser Ablation System. Connect the following:

• Laser Power Supply to the corrugated umbilical cable connected to the Laser Module and tighten the knurled collar to secure the connector.

WARNING: Secure all connectors. Operating the Laser Ablation System with cables loose or disconnected may cause equipment damage.

• Install the 9-pin to 15-pin power supply interface cable from the Laser Module to the Laser Power

Supply. Connect the 15-pin end of the cable to the 15-pin connector labeled Remote on the rear panel of the Laser Power Supply. Connect the two BNCs to the Fire Lamp and Fire Qsw connectors on the rear panel of the Laser Power Supply. Connect the 9-pin end of the cable to the 9-pin connector on the Laser Module labeled Power Supply Interface.

Figure 15 (Back View of Laser Power Supply) shows the cable interconnects to the Laser Power Supply.

Figure 15 (Back View of Laser Power Supply)

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Cooling System

The UP SERIES system includes an integrated liquid to air heat exchanger that removes heat from the laser. A squeeze bottle and distilled water are supplied to aid in filling the system. Removing the Laser Power Supply cover is not necessary to add coolant to the system. To fill the system:

• Remove the fill plug located on the front of the Laser Power Supply. • Remove the jumper tube located on the rear of the Laser Power Supply. This connects the water in and

water out ports. • Use the squeeze bottle to force water into the water return connector on the rear of the Laser Power

Supply until the reservoir is half full. The level of the reservoir is viewed through the slot on the front of the Laser Power Supply.

• Again using the squeeze bottle, force water into the water out connector on the rear of the laser Power Supply until the reservoir is ½” from the top of the slot.

• Again using the squeeze bottle, force water into the tubes coming from the Laser Module until water is forced out the second tube and all air is removed from the laser.

• Quickly plug both tubes from the Laser Module into the rear of the Laser Power Supply. • If the water reservoir is not filled ½” from the top, squeeze water into the front fill plug until the proper

level is achieved.

Figure 16 Adding coolant the Laser Power Supply

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WARNING: To avoid laser head damage, use only fresh distilled water to fill the cooling system.

External Connections

AC Power Connections

Verify that the available power is the correct voltage and install the power cords for the Laser Power Supply and Base Unit. The Laser Power Supply and UP Ablation System will be configured for 110VAC or 220VAC operation. Be careful not to connect the wrong voltages to the Laser Power Supply. At this time, connect both units to AC source.

WARNING: To avoid the risk of electrical shock or damage to the Laser Ablation System, verify that the correct voltage is provided.

Computer & System Connections

Setup the computer per the instructions provided. Refer to the Coreco Bandit manual for installation of the video board. Install the RS-232 9-pin serial cable from a COM port to the connector labelled RS-232 on the Base Module. Install the S-Video cable from the video board on the computer to the connector labelled S-Video on the Laser Module.

Figure 17

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Mass Spectrometer Connections

Plastic Swag type fittings are provided for connecting the carrier gas to the mass spectrometer tubing. Connect the three fitting to the Gas Inlet, Gas Outlet to the Mass Spectrometer, and purge to a waste location. The Gas Flow Control module can be removed for ease of access. To remove the Gas Flow Control module, loosen the two retaining screws along the front edge of the module. The gas lines must be disconnected from the sample chamber, and slid out of the retaining slots. If lines are connected to the inlet, outlet, and purge on the back panel, these lines must also be disconnected.

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Turning on the system

To operate the system, turn on the power to the computer and monitor, and then turn on the power to the Base Module (switch located on the back), Laser Power Supply (key switch located in front, and switch located on the back), before starting the UP SERIES software.

Note: To insure stabile output energy, the system should be allowed to warm-up for a minimum of 20 minutes with the power switch on the back of the power supply turned on. It is recommended that this switch be left on at all times, even when the system is not being used for extended periods. The Laser Power Supply key switch should be turned on only during the period when the system is being used.

Turning off the system

To shut down the system, close the UP SERIES software then turn off the power on the Base Module (switch located on the back) and the Laser Power Supply (key switch located in front).

Starting the Software

Use the Start button on the Windows Task Bar to locate the New Wave Research / Merchantek Products folder. Choose the MEO Laser Ablation icon to run the software.

As the software loads, a system self-test and subsystem resource verification will be performed. The results of the subsystem resource verification are reported in the Start-up screen (see Software Chapter 5). Any errors detected during the self-tests will be reported in special message windows.

The Start-up screen provides the following status information concerning the results of the resource verification.

• Laser Controller Present. • X-axis Stage Controller Present. • Y-axis Stage Controller Present. • Z-axis Stage Controller Present. • Coax Light Source Present. • Ring Light Source Present. • Transmitted Light Source Present. • Gas Valve Controller Present.

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Figure 2-9: Software Opening Screen

If any of these controllers are not located, contact a New Wave Research / Merchantek Products representative as the system may require maintenance.

Once the self-tests are complete, the Start-up screen disappears and main program window appears.

Establishing Coolant Flow

The Laser Power Supply is interlocked to shut down the laser due to inadequate coolant flow. Upon start-up, air bubbles in the line may cause the Laser Power Supply to shutdown. To establish coolant flow, right click the mouse over the Laser button. Toggle the Laser Power Supply using the Enable Laser Power Supply menu item to start the Laser Power Supply pump. If air remains in the lines, the Power Supply will again shut down. Continue cycling the enable command until the pump runs without shutting down. After coolant flow is established, check the coolant level and add additional distilled water if necessary using the front fill port.

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Testing the Light Sources

Install a thin film section or thin sheet of paper into the sample chamber. Select the transmitted light source using the button located on the top left of the screen. Move the slider right to verify the light source properly illuminates the object. Move the slider back to the left to turn off the transmitted light source. Note that you can have the transmitted light source on in combination with the ring or coax source. Change to the ring or coax light repeat these steps for both ring and coax light sources. Coax and ring lighting do not have a slider bar. You must hold down the light or dark control button to adjust the intensity.

Testing the X-Y Stages

Press the right mouse button over the Position button and select Home Stages to verify the stages properly home. Move the stages back to the center position to verify the jog and step buttons are working properly.

Testing the Z Axis

Deactivate the autofocus if installed. Using the focus toolbar, move the Z-axis up and down until the object is in focus to verify smooth operation of the Z-axis. If auto focus is installed, defocus the object and activate autofocus to verify the system finds focus.

Testing the Video System

Focus the system and deactivate the autofocus. Zoom out and locate any feature in the center of the screen - zoom in, focus and center the feature. Zoom out and verify the feature stays focused and centered on the screen.

Testing the Laser System

Set the laser to Continuous mode, 50-micron spot size, 4 Hz, and 75% energy level. Fire the laser and observe the crater that should be well formed and centered on the crosshair.

The surface of the sample should be approximately the same height as the surface of the cell insert that surrounds it

Only fire the laser when the sample is in focus

NOTE: A solid blue screen indicates that the video card is not receiving a camera signal. If this occurs, verify the Base Unit power is on, the 25-pin cable is connected between the Base Module and Laser Module, and the S-video cable is connected between the Laser Module and the computer.

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If the auto-focus option is being used, only fire the laser when the auto-focus has locked on to the sample and is not moving. Always flow gas through the sample chamber when firing the laser.

If the above precautions are not followed it may result in damage to the

laser objective lens and / or the sample cell.

Connection diagram

The following diagram shows the various cable connections for a typical -UP system.

This document describes the proposed specifications for the synchronization and trigger signals interface between a mass spec (MS) system and the New Wave Research / Merchantek Products UP Laser Ablation System (LAS).

Figure 18 System Interconnect

Change this figure

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Signal Specifications

Trigger In to the LAS

An input to the LAS is provided on the LAS back panel. See Figure 18 System Interconnect. This input can be configured via a jumper to accept either a TTL-level trigger signal, or a contact closure. The input is optically isolated from the rest of the LAS by an opto-isolator.

Trigger Out from the LAS

An output from the LAS to the MS is provided on the LAS back panel. See Figure 18 System Interconnect. This output can be configured via a jumper setting to be either a TTL-level output (max of 25mA drive), or a contact closure.

Circuit Diagrams

The diagrams below show the electrical details for the interface signals when configured for either switch closure or TTL interface.

Figure 19 System configured for switch closures

Figure 20 System configured for TTL Signals

Trigger Out Operation

The Trigger Out signal is controlled by the LAS, and can be set via the LAS software to one of three states: Disabled, Laser Mode, Pattern Mode, or Experiment Mode.

Note: A pattern is a specific type of scan (raster, spot, grid etc.) at a particular location; an experiment is a set of one or more patterns.

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Figure 21 Trigger Commands

Figure 22 Trigger Signal Properties

Disabled

No trigger signal is generated.

Laser Mode

The trigger out signal is active while the laser is firing during a scan. The signal goes active when the laser first starts firing during a scan, remains active while the laser continues to fire, and goes inactive once the laser stops firing.

The signal is not active during a pre-ablation pass, even when the laser is firing.

If a raster grid or line grid scan pattern is defined, the signal will be inactive during the pause between sites on the grid.

Pattern Mode

The trigger out signal goes active N1 msecs after the scan of an each pattern is initiated, remains active while the scan is being performed, and goes inactive N2 msecs after the scan of each pattern is complete. The values for N1 and N2 are user-selectable, between 0 and 9999 msecs.

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The signal is not active during a pre-ablation pass.

If a raster grid or line grid scan pattern is defined, the signal will be active during the pause and movement between sites on the grid.

Experiment Mode

The trigger out signal goes active N1 msecs after an experiment run is started, stays active during the rest of the run, and goes inactive N2 msecs after the last scan pattern in the experiment is complete. The values for N1 and N2 are user-selectable, between 0 and 9999 msecs.

The signal remains active during the pause and movements between scan pattern locations, and remains active during the pre-ablation pass.

Trigger In Operation

The MS generates the trigger in signal to trigger the LAS to start a scan. The LAS software defines two modes of operation for the trigger in signal: Pattern Mode, and Experiment Mode.

Pattern Mode

After the user presses the Run Experiment button, the LAS waits for the trigger in signal to go active before performing the scan of the first pattern. The LAS will perform the scan, and then check the trigger in signal again – it won’t proceed with the next pattern until/unless the trigger signal is active. Thus, the LAS checks the state of the trigger in signal at the start of each pattern scan, and only proceeds with the scan if the signal is active.

Experiment Mode

After the user presses the Run Experiment button, the LAS waits for the trigger in signal to go active before starting the experiment run. The LAS checks the state of the trigger in signal only at the start of the experiment run.

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Chapter 3

Fundamentals

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Introduction to Lasers

The General Laser Principle

The principle of lasers, the Light Amplification by Stimulated Emission of Radiation is best explained when looking at the process of photon emission. This process, from an excited state takes place statically and is described as spontaneous emission. The opposite process, the process of absorption, occurs when light hits an atom – a photon can be absorbed if the energy corresponds to the excitation energy of the atom.

E2-E1 + h * v12

After absorption, the atom is in excite state 2, so apart from being excited by electrons, atoms can also be excited by photons. However, in distinction to electron excitation, the photon energy of the absorbed radiation has to correspond to the transition energy. The third interaction process is a process that is essential for the generation of laser light, the stimulated emission. It can occur when photons with energy h v12 collide with an atom in state 2 and the decay energy corresponds to the incident photon energy

h v12 + (E2-E1) = 2 h v12

The incident photon thus stimulates a radiation process. When the emitted photon has the same direction as the incident photon, the phases of the two emitted wares are also the same. Stimulated emission allows the construction of a light amplifier in the optical region of the spectrum.

The following three illustrations demonstrate the formation of this laser.

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Figure 23 First stage of laser formation

Figure 24 Second stage of laser formation

Figure 25 Final stage of laser formation

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First a laser medium must be created which is suitable as an optical amplifier. For this, N2 > N1 is the sole condition, which is necessary in a two-level system. This is indicated by a pump arrow and is independent of its realisation in individual cases. In order to prevent the spontaneous emission from destroying the inversion, these losses have to be compensated for by pumping. On two sides of the laser medium, mirrors are placed to form a resonator. One mirror is partially reflecting. As spontaneous emission always generates photons, a photon field will be created along the resonator as a result of the amplification in the laser medium and the feedback by the resonator. This photon field is emitted through the partially reflecting mirror as laser emission. The laser emission shows a high degree of directionality and can therefore achieve a high energy density.

There are many different classification of the various lasers, i.e. solid state lasers such as Nd:YAG lasers, gas lasers such as He-Ne or Excimer lasers as well as liquid lasers and semiconductor lasers.

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Nd:YAG Laser

General Introduction

The Nd:YAG laser uses traditional flash lamp pumping. Distilled water cools the lamp and gain medium, reducing thermal lensing. When electrically pulsed, the lamp emits light that excites the laser gain medium, an Nd:YAG rod. The laser crystal is an yttrium aluminium garnet single crystal, doped with neodymium ions (hence the term Nd:YAG).

Similar to a capacitor storing electrical energy, the Nd:YAG rod absorbs the flash lamp’s optical energy. Neodymium atoms that have been excited to a higher electronic state (the lasing level) store this energy. These atoms remain excited for a fraction of a millisecond before spontaneous emission starts.

In the absence of Q-switching, spontaneous emission (lasing, or light amplification through stimulated emission) begins as soon as the cavity gain overcomes its losses. The duration of this spontaneous laser pulse is almost as long as the driving lamp pulse. This non Q-switched pulse has high energy, but its peak power is low, because of its relatively long width. The Q0switch improves performance by both increasing the amount of energy stored in the rod and by preventing or delaying spontaneous emission.

Whilst closed, a Q-switch in the laser cavity introduces an additional loss and blocks spontaneous emission, allowing the number of excited atoms in the rod to build further. When instantaneously opened, it releases the cavity’s stored energy in a shorter pulse with both higher average and peak power.

Q-switching

The Q-switch consists of a crystal, quarter wave plate and a vertical polarizer, placed in the laser cavity between its end mirrors. The lamp pumps the gain medium while the Q-switch is closed (there is no voltage applied to its crystal, and the crystal does not rotate light). While closed, light exiting the rod cannot return to stimulate spontaneous emission, and the rod’s energy storage capacity increases. Horizontally polarized light exiting the gain medium never returns; it is always blocked by the vertical polarizer. When the Q-switch is closed, it also blocks vertically polarized light: this light passes unchanged through the vertical polarizer and the crystal, then rotates 450 transiting the quarter wave plate. On its return path, it rotates another 450. Now horizontally polarized, the vertical polarizer prevents it from re-entering the rod.

After maximum storage occurs (about 100 microseconds after the lamp begins pumping), the Q-switch opens: a Marx bank suddenly applies a high voltage to the crystal. When so energized, the crystal now rotates the light another 900 (450 in each direction through the Q-switch). Vertically polarized light now rotates a total of 1800, so it retains its polarization travelling through the Q-switch, and can re-enter the laser rod. This light is now free to oscillate between the cavity end mirrors. During these oscillations, the light increases in energy by extracting the energy stored in the gain medium. The resultant laser pulse is 3-5 nanoseconds long, with high peak and total power.

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Theory of Harmonic Generation

The laser can produce laser light at other frequencies besides the natural, or fundamental frequency of its Nd:YAG gain medium. In some crystals, a non-linear process known as harmonic generation produces additional frequencies that are multiples (double, triple, quadruple etc) of the fundamental.

For a crystal to be suitable for harmonic generation, it must transmit both the fundamental and the harmonic it produces, withstand high peak intensity laser beams without damage, and convert the fundamental to the harmonic efficiently. Non-linear materials transmit light at differing speed, depending on the light’s angle to the crystal’s non-linear axis and on the light’s polarization relative to that axis. This second property is called birefringenence.

During doubling, two 1064nm photons enter the crystal collinear and with the same (circular) polarization. This would allow the two photons to combine into a single photon, provided that the resulting photon conserves both energy and momentum. A combined (doubled) photon with a doubled frequency satisfies energy conservation. Angular momentum conservation gives the output photon a different (horizontal) polarization. Momentum conservation requires the combined photon to have the same velocity as the incoming photon pair. In the non-linear crystal, there is a particular angle (the phase matched angle); at which the crystal’s birefringence equalizes the velocities of the input photons and the differently polarized combined photon. Satisfying these three conservation conditions permits doubling, provided that the two input photons enter the crystal close together. The high peak power of the laser generates a sufficiently large photon density inside the crystal for efficient doubling to occur.

Quadrupling is simply a two-stage doubling process: the 532nm output of the doubling crystal is stripped of the fundamental, and this beam enters a second doubling crystal, where it doubles again.

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Polaris / Tempest Laser

This chapter provides an introduction to the New Wave Research Polaris Nd:YAG laser used in the UP - 266 laser ablation system. The optical layout of the head is explained in the following section, including the different Polaris head configurations. This section also includes the location of harmonic generators. This section gives an introduction to the optical layout in the Polaris Nd: YAG laser. The standard Polaris configuration is a wide body, with room for installing the optional attenuator and harmonics. The Polaris is shown with optional items in Figure 26 Layout of the POLARIS Laser Head with Options.

Figure 26 Layout of the POLARIS Laser Head with Options

The POLARIS employs a flash lamp-pumped Nd: YAG rod in a thermally compensated resonator to generate radiation at 1064 nm. The resonator is very compact, mechanically isolated from the laser housing, which makes the system relatively insensitive to vibrations and temperature change. The IR head is housed in a separate sealed area that requires no adjustments in normal operation. The only time the IR head needs to be opened is on the rare occasion that the flash lamp needs to be changed during a maintenance procedure.

Optical Attenuator

The optional optical attenuator serves to control the laser energy without affecting the beam quality. The optical attenuator is designed to work on the 1064 nm beam, so it is placed directly after the IR head, before any harmonic generation crystals.

Polaris Laser

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The optical attenuator consists of a half wave plate, followed by a polarizer. The half wave plate is secured to a motorized rotating mount. The servo motor controlled angle is set by input from the control panel. The polarizer is permanently aligned to transmit vertically polarized light. This maintains the polarization of the IR light as emitted from the IR head in the standard configuration.

Harmonic Generation

The 1064 nm laser pulse exits the IR head and then different harmonic wavelengths may be generated if these options have been installed. The second harmonic at 532 nm is generated by passing the IR beam through an angle tuned KTP crystal. The Polaris uses Type II phase matching in KTP to generate the second harmonic, so the polarization of the IR beam must be adjusted to maximize SHG intensity. Dichroic mirrors separate the second harmonic from the fundamental light and direct the beam to the output port. The second harmonic light is vertically polarized.

The third harmonic at 355 nm may be generated in the Polaris if the option has been purchased and installed. The third harmonic at 355 nm is generated by combining one photon at 532 nm with one photon at 1064 nm. Third harmonic generation is accomplished by Type I phase matching in BBO. The second harmonic must be detuned slightly to achieve the maximum third harmonic conversion efficiency. The third harmonic light is separated from the fundamental and second harmonic using a pair of dichroic mirrors. The third harmonic light is vertically polarized.

The fourth harmonic of Nd: YAG at 266 nm can be generated by doubling the 532 nm second harmonic light. This is done by placing the correct BBO crystal in the optical path and combining two photons at 532 nm to give one photon at 266 nm. The light at 266 nm is separated using a pair of dichroic mirrors to select only the fourth harmonic light. The fourth harmonic light is vertically polarized.

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Chapter 4

Laser Description

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UP series – System Description

General Overview

In laser ablation ICP-MS, a laser is focused through an optical beam path on to a sample. The sample is situated in an ablation cell, when the laser starts ablating the sample; the particles of the sample are swept in a carrier gas towards the plasma of the ICP-MS system. The ionization takes place in the plasma, and the running conditions of the mass spectrometer are similar to other dry plasma techniques. Viewing optics are provided through a binocular and a video camera, coupled to a monitor to ensure the visual focus of the sample, the identification of the areas to be analysed and the observation of the laser ablation process.

Almost all different kinds of samples can be analysed directly, with minimal sample preparation. Samples only have to be cut to size in order to fit into the sample cell and powders should be pressed into pellets. A wide variety of samples can be analysed, from geological samples including fluid inclusion analyses and thin section, as well as dating samples to archaeological, forensic, material characterization, life science etc. The advantage of laser ablation is the ability to perform feature, bulk and depth profile analyses.

The UP series is specifically designed to be couple to ICP-MS and ICP-OES systems. The Nd:YAG laser is operated in the UV region at either 266nm (UP - 266) or 213nm (UP - 213).

Figure 27 UP System with covers removed shows the UP series with the covers removed to view the integral parts of the system which will be described in more detail.

Figure 27 UP System with covers removed

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The following figure shows a detailed schematic of the UP system:

Figure 28 Schematic of UP Opto-Mechanical System

Laser Formation

The following figure shows the doubling crystals to quadruple the fundamental wavelength of 1064nm to 266nm. For further details of the laser fundamentals and the generation of harmonic wavelength, please refer to chapter 2, Fundamentals.

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Figure 29 Laser quadrupling area

The laser fires with a fixed pulse energy, optimising its efficiency and stability. The energy of the beam is focused onto the sample, then attenuated, in accordance with the energy appropriate to the crater size required and the matrix at the target site. The energy attenuator enables the continuous adjustment of the laser energy without changing the voltage of the flash lamp.

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Crater Size Selection

The laser then passes through a beam expander and an aperture wheel. A combination between them determines the resulting crater size on the sample. They are under full software control and their function is described in chapter 5, Software.

Figure 30 Beam Expander and Aperture Wheel

Viewing the Sample

The ablation target can be viewed in-situ through a color CCD camera, and through a binocular (optional) for precise location of the analysis site.

Figure 31 Viewing the Sample

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Samples can either be viewed through transmitted light, reflective light or coaxial light. The type of light source and the brightness is under computer control.

Samples are mounted in a cell on a high precision XY stage. The stage is fully under software control. Automatic operation permits the storage of sampling patterns and coordinates for automated, unattended analysis. The laser cell is flushed with argon and/or helium gas, carrying the ablated material to the plasma for ionization and subsequent analysis in the mass spectrometer.

Sample Changeover

The gas bypasses the cell when loading or unloading samples, then the cell is purged of air before the gas is routed back to the torch. The operation of the different gas lines is under software control. For easy sample changeover, the whole sample cassette can be removed as shown in the following sequence.

Figure 32: Sample changeover – step 1: Lift the two cam levers after selecting BYPASS on the main screen.

Sample Chamber Cam Levers

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Figure 33: Sample changeover – step 2: Pull the sample cassette out

Figure 34: Sample cell with NIST glass sample loaded

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Chapter 5

Software Step-by-Step

Guide

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Software Step-by-Step Guide

This software step-by-step guide is intended to enable a fast familiarisation with the software. It will explain the most important software functions, but it will not cover every detail – please refer to the Software Manual for a detailed description of each function.

The software will control all of the laser functions as well as all of the laser patterns.

The step-by-step guide will cover the following areas:

I. Getting Started

II. Tuning the ICP-MS

III. Screen Calibration routine

IV. Running an experiment

V. Ablation pattern

VI. Video overlay function

I. Getting Started

STEP 1: Load the software

To install the software insert the floppy disk, the software package is self-extracting and will guide the user through the installation. Once installed, the software is started by clicking on the icon or via PROGRAMS in the Start menu.

The first opening screen when for the software looks like below:

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Figure 5-I.1. Software opening screen

When passing the mouse over each function, the description of this particular function will be displayed. The icons on the upper row of the software screen enable the functions such as the selection of the illumination source and the brightness, the zoom function of the monitor, the mode of ablation, the frequency, the crater spot size and laser on/off function.

STEP 2: Load NIST612 glass standard

Load NIST612 glass standard or another appropriate sample.

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STEP 3: Purge the gas lines

There are three gas control buttons (Online, Bypass and Purge). The system is set to ONLINE during analysis. In this position the sample cell is continuously flushed by a stream of carrier gas, which transports ablated material to the ICP-MS.

Select BYPASS for sample changeover. In this mode the gas stream bypasses the sample cell and goes directly to the ICP-MS.

Figure 5-1.2. Select Bypass

Figure 5-I.3. Bypass schematic

Purge is selected after sample changeover to flush any air out of the chamber for a fixed user defined period before automatically switching back to ONLINE. The PURGE timeout may be edited via a pull down menu, which can be opened by a right hand mouse click on any of the gas control buttons.

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Figure 5-I.4. Activate Valve

Click on SET PURGE TIMEOUT and enter the amount of time in seconds. Then click on OK. Typically a purge timeout of 30 seconds is sufficient.

Figure 5-1.5. Purge Timeout

Connect the laser to the ICP-MS and purge the gas lines for a few minutes.

Figure 5-1.6. Select purge

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Figure 5-1.7. Purge schematic

STEP 4: Select online mode

Click on online to connect the ablated material transport tube to the torch.

Put the ICP-MS into OPERATE mode.

Figure 5-I.8. Select online

Figure 5-I.9. Online schematic

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STEP 5: Calibrate the XYZ stage

When the software is first switched on, the X Y Z POSITION windows for the stage read back shows the ‘? ‘ symbols. In order to read the real X Y Z coordinates back, the stage has to be calibrated prior to running the instrument, whenever the software is switched on. The calibration will allow accurate repeatability of the spot locations.

Figure 5-I.10. Position readback

Click once on the POSITION icon on the tool bar, and confirm the calibration of the stage by clicking on YES.

Figure 5-I.11. Acknowledge system calibration

When the calibration routine has completed the stages are at their HOME positions. The stage position window opens as shown below. A previously stored stage position may be selected from a list, or the stage may be driven manually using the scroll bars or the joystick controls. If the CENTRE position has been stored previously, select it and the stage will move to the centre of the stages or any other previous stored position.

Figure 5-I.12. Stage position list

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To save a new position, drive to the new position, then click on DEFINE NEW POSITION, enter the new file name and click on SAVE.

Figure 5-I.13. Save position

In the case that the CENTRE position has not been stored previously, drive the stage manually to 25mm in X and Y direction and 0 in Z direction. It is recommended to always load your sample into the centre of the stage to enable an easy focussing in just adjusting the Z stage.

STEP 6: Select the light source

Select the light source from the pulldown menu. Select the source of the light in accordance to the sample used – e.g. for transparent samples use the transmitted light and for bulk sample the reflected light source, and adjust the brightness of the light source for the sample type used. The brightness can be adjusted using the slider bar. Turn the slider bar to the maximum.

Figure 5-I.14. Illumination options

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STEP 7: Select the lowest magnification

In order to view a new sample it is always recommended to use a low magnification, click on the downward arrow next to ZOOM and select 0% for the zoom lens or type in the value using the keyboard.

The sample is viewed on the PC monitor through a zoom lens. This lens gives a magnification range of 100x to 1000x on the monitor. The zoom lens may be set in steps of 25% via the pull down menu as shown below or by editing the zoom level from 0-100%.

Figure 5-I.15. Zoom control

Alternatively, click once the magnifying glass icon and this window will be shown to enter the magnification manually.

Figure 5-I.16. Manual zoom control

STEP 8: Focus on the sample surface via Z-stage

The Z-stage can be moved up and down via the arrows. Use the Z-stage position to bring the sample surface into focus. When the sample is placed into the centre of the stage, and the CENTRE stage position has been selected, the sample can be brought into focus by just changing the Z-axis.

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Figure 5-I.17: Focus via the Z-stage

STEP 9: Adjust laser energy to full output

Adjust the laser energy to full power output (100%) to maximise the laser crater. A large crater diameter gives more signal and is therefore recommended for the set-up and tuning process.

Figure 5-I.18: Adjust laser energy

STEP 10: Adjust repetition rate to 20Hz

The repetition rate can be varied between 1 and 20 Hz. Click on the upward or downward arrow to increase or decrease the repetition rate, 20Hz means that the laser will fire 20 times per second. A high repetition rate is recommended for the set-up and tuning process, as more material will be removed.

Figure 5-I.19. Selecting the frequency

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STEP 11: Select largest crater diameter

There are 15 pre-selected different spot sizes available. To select a spot size, click on the downward arrow next to the spot size symbol, situated next to the frequency icon and select the required spot size from the pull down menu.

Select the largest crater diameter of 400µm to remove more material for the set-up and tuning process.

Figure 5-I.20. Spot size selection

For the spot size calibration, click once with the right mouse button on the icon and the following display box will appear.

Figure 5-I.21. Manual control of the spot size

The preset Crater sizes may be changed by editing the iris and expander settings in the lookup table or by manually editing the current iris and expander settings.

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Figure 5-I.22. Beam size calibration table

Figure 5-I.23. Manual spot size control

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STEP 12: Selecting Continuous Ablation mode

There are three different Laser firing modes. Click on the downward arrow to display the following laser mode firing options: CONTINUOUS FIRING, SINGLE SHOT and BURST OF SHOTS. The icon will change accordingly.

In Continuous mode the laser will fire continuously or as long as the time specified in an ablation pattern.

Figure 5-I.24. Laser firing modes

In SINGLE SHOT mode, the laser will just fire one single shot.

Figure 5-I.25. Single shot mode

In BURST MODE, a specified number of bursts will be fired, to select the number of burst, click the burst icon once with the right mouse and the following menu will appear.

Figure 5-I.26. Shots per Bursts

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Figure 5-I.27. Entering the pulses per bursts

Enter the number of bursts for this mode.

For the Getting Started guide, select the continuous mode of ablation.

STEP 13: Click on FIRE

It is also possible to ablate a sample without the need to define a pattern on the sample surface. By clicking on the FIRE button the laser will ablate the sample at the viewing crosshair using the currently defined ablation settings. Each pattern or single spot may be highlighted and deleted by right-clicking and selecting DELETE in the pull-down menu.

Figure 5-I.28. Fire button

A large crater should now form in the sample. A signal on La139 should be obtained on the ICP-MS. This proves that the laser is functioning and that the laser ablation signal reaches the ICP-MS, the gas lines are therefore connected correctly.

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Figure 5-I.29: 400µm crater on video screen

The LA-ICP-MS is now ready to start the tuning process.

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II. Tuning the ICP-MS

STEP 1: Select sample area

Load the NIST612 glass sample and select a clean area on the sample surface over a few mm, avoiding any previous craters.

STEP 2: Select line pattern

The line pattern is the recommended ablation pattern for the tuning process. Click on TOOLS and select LINE.

Figure 5-II.1: Choosing the ablation pattern

STEP 3: Draw line on the sample

Draw the line on the sample image by clicking on the start of the ablation line in the image and drag the cursor to the end of the ablation line. It is possible to drag the cursor outside the visible image and the stage will adjust the movements automatically.

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Figure 5-II.2: Drawing the line on the sample

STEP 4:Choose line properties

Select the following line properties by right hand mouse click on the line in the selected pattern window:

Passes: 1

Scan Speed: 10µm/sec

Depth/Pass: not applicable for one pass

Energy: 100%

Rep. Rate: 20Hz

Spot Size: 400µm

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Figure 5-II.3. Line pattern properties

STEP 5: Monitor masses

Monitor masses across the whole periodic table, e.g. B9, La139 and U238 on the ICP-MS. Tune the ICP-MS:

Torch box position

Gas flows

Ion Optics

For maximum sensitivity.

STEP 6: Run a short term stability test

Run a short term stability test, e.g. 5 runs over a long laser line. Each single run should be approximately 30secs duration. Include the following elements: B, Co, Sr, La, REE, Pb, U.

The LA-ICP-MS system is now ready for analysis.

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III. Screen Properties and Calibration Routine

To adjust the video and display properties or to calibrate the screen, click once with the right mouse button anywhere on the sample screen to open up the SCREEN OPTIONS window.

Figure 5-III.1. Select video properties

STEP 1: Adjust Video properties

Select the VIDEO PROPERTIES and the following dialogue appears, adjust the HUE, SATURATION, BRIGHTNESS or CONTRAST to your requirements. The video properties window is used to adjust colour and light properties in order to achieve the best imaging of the sample.

Figure 5-III.2. Setting the video properties

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STEP 2: Adjust Display properties

The DISPLAY PROPERTIES give the following options: It allows the user to customise the colours of the video crosshairs and the colour of the ablation patterns.

Figure 5-III.3. Setting the display options

STEP 3: Calibrate Screen

Calibrate Screen enables the setting of the correct magnification. A SCREEN CALIBRATION WIZARD guides through the calibration.

The CALIBRATE SCREEN function is used to calibrate the video screen for accurate measurement of the crater diameter and distance across the sample surface. To achieve the most accurate results it is recommended to carry out the calibration at 0%, 25%, 50%, 75% and 100% zoom settings in turn.

First select the lowest ZOOM position at. 0%.

Figure 5-III.4 Screen calibration wizard

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Then use the MEASURE tool, which is the last icon in the row of tools and drag it a known distance on the video window. This may be done using the optical standard supplied by New Wave Research or simply by measuring a distance previously recorded by reading back the stage positions, e.g. use stage read-back positions to measure the distance between the two craters. The image of the optical standard at 0% zoom looks as shown in Figure 5-III.5.

Figure 5-III.5: Optical standard at 0% zoom

Figure 5-III.6. Selecting the measuring tool

Figure 5-III.7 Screen calibration wizard – step 2

Drag the measuring tool over a distance of e.g. 20mm of the optical standard. It is very important not to move the stage during this process. For best results use two points as far apart on the video image as possible as this will reduce the error in the calculations since the measurement is made over a wider distance. If you are not using the optical standard, ensure that the exact distance between the two points chosen is known accurately.

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The distance is then reported back by the software. If the distance reported is inaccurate the correct value may be entered by the user and applied.

Figure 5-III.8. Screen calibration wizard – step 3

Repeat this process for all different zoom positions e.g. 25%, 50%, 75% and 100%. It is important that the screen will be calibrated at all zoom levels.

For example, the optical standard at 100% zoom is shown in Figure 5-III.9. Now the two widest points apart stretch only over an area of 4mm. Drag over this distance with the measuring tool to calibrate the screen at highest magnification.

Figure 5-III.9: Optical standard at 100% zoom

Now the screen calibration routine is completed.

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IV. Laser Ablation Parameters and Pattern Selection

This section discusses the principles of analytical methodology, explaining the effects of the laser operating modes and patterns on sample surfaces and the general effects of varying the principal operating parameters of the laser. An understanding of the broad effects of the principal laser parameters is essential when selecting the correct conditions to suit a variety of analytical tasks.

The sensitivity in laser ablation is a function of the ablated volume, the smaller the laser craters the less material transported to the ICP-MS for subsequent analysis. The relation between the crater volume and the resulting analytical capabilities needs careful evaluation. The precision is also a function of the ablated volume, corresponding to the count rate obtainable. The larger the crater the more material is ablated, leading to improved precision and detection limits.

Influence of laser parameters

The operating parameters of the laser energy, the repetition rate and the crater size selection through Beam Expander/IRIS combination determine the rate of the ablated material. The power of the laser (energy per shot) is varied by the energy attenuator, which allows continuous adjustment of the laser energy. The rate of ablation is affected by changing the laser repetition rate through the software. The higher the repetition rate, the deeper the crater; it does not influence the crater diameter. For soft materials such as powders or polymers the typical repetition rate is less than 10Hz. Harder materials such as glasses or geological samples can be analysed with higher repetition rates, typically higher than 10Hz. However, the repetition rate should be optimised for each matrix type. The thickness of the sample can also influence the choice of the repetition rate. For petrological thin section a lower frequency is typically used to extend the analysis time.

Pre-ablation

Prior to the acquisition of data there are several advantages to be gained by adopting a period of preconditioning the sample. Using a pre-ablation time, prior to the bulk analysis can improve the stability of the density and composition of laser ablated aerosols. The direct sampling of solids may be affected by surface contamination, even when surfaces have been milled or ground prior to analysis. A period of pre-ablation before acquisition serves to clean the samples so that such contamination is reduced. Sensitivity is seldom enhanced by pre-ablation of the sample. The greatest effects are found in the reproducibility and precision of repeat analyses. The pre-ablation of sample is of use only in bulk analysis applications. The analysis of small features and surface layers does not generally permit lengthy periods of pre-ablation.

Internal standards

The use of an internal standard for quantitative and semi-quantitative analyses is highly recommended. The use of an internal standard, a minor isotope of the matrix element or a known concentration of a trace or minor element can be selected as an aid to quantitation. In cases where there is no certified element concentration available, a user value for the LA-ICP-MS can be chosen.

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Many laser sampling application areas are not well furnished with certified reference materials, and so semi-quantitative analysis routines are common. The choice of internal standard and the correct use of calibration routines then becomes a key factor in the generation of accurate data.

Real Time analyses

In REAL Time analysis mode a relationship between mass, intensity and time can be acquired. In conjunction with laser ablation sampling, the time-axis of this relationship may be used as an expression of a physical dimension across a sample if the laser is used to sample from different region of the sample during the acquisition. Alternatively if sampling continues at a fixed site, the time axis can be assumed to correspond to depth of penetration into the sample, yielding a depth-profile plot. The technique is a powerful means of acquiring a great deal of information pertaining to the homogeneity of materials, and can also be used in the examination of compound or complex solid samples, for example, for zonation studies. The graphics associated with Real time analyses facilitate the visual appraisal of collected data and easy identification of areas where inclusion or other anomalous features have occurred. Individual time slices or groups of time slices may be defined as discrete samples and this integrated data may be used for analyses.

Laser Pattern

There is a range of different laser patterns available to suit the application requirement.

Raster

Grid of Spots

Line

Line of Spots

Single Spot

Whilst many feature laser sampling application involve ablation from a single site, it is sometimes advantageous to acquire data from a larger areas, as for most bulk analyses applications. Some applications, such as the analysis of fluid inclusions, may require refocusing during the ablation process, particularly if the fluid inclusion is not near the sample surface. Isotope ratio calculations may also require longer than normal acquisition times. For such applications, the software is designed to give incremental control of the Z stage during the acquisition, to keep the laser in focus throughout.

The laser pattern are under software control and can describe rectangular raster and lines of shots on a sample surface, covering a much wider surface area than single spot analysis. During raster or line sample, a single acquisition that contains data representative of the entire sampled areas is taken. The sample can also be acquired in Real Time mode.

Users can define the size of a raster pattern by entering an appropriate number of points and distance between the points. The raster area can be placed at any position on the sample and therefore repeat analyses can be completed on the same area of the sample or on an entirely new area. The number of shots per raster co-ordinate can be varied, as well as the distance between the shots and the number of passes.

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To select the ablation pattern, click on the downward arrow next to the TOOL icon.

Figure 5-IV.1. Ablation Pattern

When the required pattern has been selected the ablation conditions may be viewed and edited by right hand mouse clicking in the selected pattern next to the TOOLS button.

For each pattern the spacing, the number of passes, scan speed, the Depth per Pass, the repetition Rate and Spot Size can be selected.

Raster set-up

Figure 5-IV.2. Raster set-up

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Grid set-up

For the GRID SET-UP there is an intersite pause that can be selected by the user.

Figure 5-IV.3. Grid set-up

Line of spots

Figure 5-IV.4. Line of spots set-up

Line Set-up

Figure 5-IV.5. Line setup

Single site setup

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For single spot ablation, a single click in the sample image selects the ablation site.

Figure 5-IV.6. Single spot set-up

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V. Running an Experiment

An ablation pattern can be applied to the sample by holding down the left mouse button to select the ablation start point and releasing at the required end point. The figure below shows a series of ablation patterns drawn on the sample image. As each pattern is drawn it is added to the list in the DEFINED PATTERN window on the left hand side of the screen. An individual pattern may be selected by clicking on the relevant pattern in the DEFINED PATTERNS LIST. When a pattern is selected, it changes colour from green to yellow on the screen.

To start an ablation experiment, click on the START EXPERIMENT button. An experiment window opens. The user can choose to run the whole experiment or just those individually selected pattern in this window. To start ablation, click the ENABLE LASER box and then click RUN.

Figure 5-V.1. Ablation pattern experiment

It is also possible to ablate a sample without the need to define a pattern on the sample surface. By clicking on the FIRE button the laser will ablate the sample at the viewing crosshair using the currently defined ablation settings. Each pattern or single spot may be highlighted and deleted by right-clicking and selecting DELETE in the pull-down menu.

The pattern property of each pattern can be viewed by right hand clicking on the selected pattern. All laser parameters such as the energy output; repetition rate, crater size etc. can be edited in this window.

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File Options

There are five utilities in the FILE menu. Experiment details may be saved or opened or a new experiment started. Experiment details may be printed out and the sample image on the PC screen may be saves as a Bitmap (*.bmp), Tagged Image File (*.tiff) or a True vision Targa (*.TGA).

Figure 5-V.2. File options

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VI. Video Overlay Function

A sample map is a composite image of the sample by overlaying smaller images together to produce an image of a large area of the sample. This is a most useful tool to navigate simply around the sample. It is then possible to click on the sample map and the stages will automatically move to that location. The sample map is displayed in the lower left corner of the main screen.

STEP 1: Create the sample map area

Click on the sample map icon above the map display area in the main window to display the Sample Map Management window, alternatively click on VIEW and select SAMPLE MAP from the pulldown list.

Figure 5-VI.1. Create a sample map – step 1

In this SAMPLE MAP MANAGEMENT AREA it is now possible to define the area of the sample for the map creation. It is also possible to save and recall existing maps to and from files on the computer.

• The grey area represents the total area of the range of motion on the XY stage.

• The blue box represents the current size and location of the area to be mapped. This blue box can be dragged with mouse to change the location of the sample map.

• The green box shows the current position of the stage.

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The MAP CENTER LOCATION offers three choices for the position of the map area:

• CENTER OF SAMPLE AREA: the map will be centered within the area of the total travel of the XY stages.

• CURRENT STAGE POSITION: the map will be centered at the current stage position, as long as the map is not outside the travel range of the stages.

• USER DEFINED LOCATION: the map is centered around the user defined location, which can be either entered manually by typing in the XY values or by dragging the blue box in the map preview to the required location.

The MAP SIZE is defined by the number of images. The more images are used the larger the area covered for the sample map. It is recommended to create the sample maps with the zoom set to 0%, as the zoom setting will affect the total size of area sampled. The estimated time for creating the map is displayed in the status line the bottom of the window.

STEP 2: Make the sample map

Click on the MAKE button to start to create the sample map. The process can be viewed in-situ.

Figure 5-VI.2: Creating the sample map – step 2

The current position displayed as the green box, can be viewed throughout the complete process of creating the map. At the end of the process, all images overlaid can be viewed, as shown in Figure 5-VI.3.

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Figure 5-VI.3. Creating the sample map – step 3

Click on OK and the sample map will now be shown in the left lower corner of the main menu. It is now possible to click anywhere on the map and the stages will automatically move to that new position. The actual image of that particular location can then be viewed under high magnification.

Figure 5-VI.4. Creating the sample map – step 4

A sample map can be saved for reuse. By default, they are saved in the Maps subdirectory of the folder where the program was installed (usually C:\Program Files\Merchantek EO\Laser Ablation\Maps). A sample map is saved as a Windows bitmap file.

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Chapter 6

Maintenance & Trouble-shooting

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Maintenance & Trouble-shooting

The UP SERIES Laser Ablation System is designed to be reliable. The following service and maintenance procedures will assist help to ensure dependable performance.

Maintenance

Safety System Inspection

The Class I laser enclosure includes a number of interlocks that allow user access to areas exposed to the Class IV UV laser. The areas interlocked are the sample chamber access door, rear Base Module cover and trinocular assembly (if installed). The interlocks prevent the laser from firing whenever these areas are exposed. The trinocular assembly prevents the laser from firing whenever the trinocular is set for user viewing. To insure a safe environment, test the interlock functions once a month. Using appropriate safety eyewear, attempt to fire the laser with each of the covers open, verifying that the system does not fire the laser and the interlock warning is displayed. To test the trinocular assembly, attempt to fire the laser in the two user view modes however, do not look into the eyepieces.

For Class IV systems, the sample chamber may or may not be supplied, and therefore, an interlock for this devise may not be supplied.

Cooling System Maintenance

The Laser Power Supply contains a small water-cooling system to remove heat from the laser head. The cooling system includes a small pump, liquid-to-air heat exchanger, small reservoir, and a di-ionizing cartridge. Low or no flow, over heating or contaminated water may cause damage to the laser head. The system includes temperature and flow interlocks to prevent damage due to over heating and/or low coolant flow.

The coolant level may be observed through the slot on the front of the Laser Power Supply. Check the water level once a week. Maintain a water level between .25 - .75 inches from the top of the slot. Under normal use, coolant should not need to be added. If the coolant level continuously drops during use, contact a New Wave Research / Merchantek Products representative.

Note: To avoid the corrosive effects of stagnate water, the system should operated and the water circulated for at least 15 minutes every a week.

The coolant may become contaminated over time and should be replaced every six months.

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Light Source Maintenance

The UP SERIES contains three light sources: transmitted light in the Base Module, coaxial light, and ring light in the Laser Module. To remove light bulbs in the transmitted light source and coaxial light source, disconnect and turn counter clockwise. To remove the ring light, disconnect and lift out.

Laser/Video Alignment

The laser alignment (spot on the sample) to the video crosshairs may drift from shipping or extended use. Two small holes on the right side of the Laser Module provide access to a turning mirror used to bring the laser back into alignment. To align the laser:

• Remove the front system covering the access holes. • Place an object (coin, etc) into the sample chamber. • Set the laser for 4Hz, 35% power and a 40-micron spot.

While firing the laser, adjust the turning mirror until the laser is centered on the crosshair.

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Troubleshooting

Interface Problems

System fails to find the UP SERIES

• Check serial cable installation between the computer and Base Module. • Check the COM port selection. • Check the Base Module power.

Safety Interlock Problems

Laser Power Supply Interlock Failure • Check that the Laser Power Supply power is plugged in and enabled. • Check that the remote interlock connector on the back of the Laser Power Supply is installed. • Check that all cable connections between the Laser Power Supply and Laser Module are secure. • Check that the coolant level is within .5” of the top of the view port. • Remove the return coolant line from the laser Module on the rear of the Laser Power Supply. Enable

the Power Supply and verify water flows out from the laser.

Door, Rear Cover Interlock Failure • Check that the rear cover is secured. • Check that the sample access cover is secured. • Remove rear cover and check the interlock on the right of the unit for proper mounting and installation. • Open the sample access cover to verify the magnet is securely mounted to the cover (inside, right -hand

side), and the switch mounted inside (right side of the front panel) is properly mounted and connected.

Trinocular Viewer Interlock Failure • Check the microscope to insure it is in the 100% transmission mode

Laser Problems

Laser to Video Misaligned (the spot is not at the center of the crosshairs) • Use the turning mirror to realign the laser. See Laser/Video Alignment on preceding page.

Laser Low Energy • Check the energy setting. • Check the Iris (open).

NOTE: To verify full energy, the iris should be 100% open and the beam expander set for minimum spot size.

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• Check both BNCs are attached to the correct points on the rear of the Laser Power Supply. • Verify that the switch labeled Fire Q-SW is in the Ext position.

Laser Doesn’t Fire • Check that all interlocks are ok. • Check both BNCs are attached to the correct points (rear of the Laser Power Supply). • Check the large connector on the umbilical (rear of the Laser Power Supply). • Key switch on

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A

AC Power Connections ...................................21 American National Standard for the Safe Use of

Lasers ..........................................................6 analytical methodology ...................................71

B

Base Module Installation.................................16 Beam size calibration table ..............................60 BURST OF SHOTS........................................61 BYPASS........................................................52

C

Calibrate Screen.............................................68 CENTRE position...........................................55 Circuit Diagrams ............................................27 Class I laser......................................................2 Class IV...........................................................2 Connection diagram........................................26 Continuous Ablation mode ..............................61 Coolant Flow..................................................24 Cooling System..............................................20 Coreco Bandit ................................................21

D

DEFINE NEW POSITION..............................56 depth-profile ..................................................72 Display properties...........................................68

E

Electrical Requirements ..................................14 Electrical Safety ...............................................4 energy radiation................................................2 excitation .......................................................32 Experiment.....................................................76 External Connections ......................................21

F

fifth harmonic .................................................38 File Options ...................................................77 fill plug ..........................................................20 FIRE button ...................................................62 flash lamp ......................................................35 Focus .............................................................57 fourth harmonic ..............................................38 fundamental frequency....................................36

G

gas control .....................................................52 Getting Started ...............................................50 Government Regulations ...................................6 Grid set-up.....................................................74

H

Harmonic Generation......................................36 HOME positions .............................................55

I

installation procedure......................................14 interlocks .........................................................2 Internal standards ...........................................71 IR head..........................................................37

L

Laser Ablation Parameters...............................71 Laser Classification ..........................................6 Laser Covers....................................................4 laser energy....................................................58 laser formation ...............................................33 Laser Light Emissions .......................................5 laser medium..................................................34 Laser Module .................................................12 Laser Module Installation................................17 Laser Power Supply ........................................13 Laser Power Supply Installation ......................19 Laser Principle ...............................................32 Laser Safety .....................................................3 light source ....................................................56 Light Sources .................................................25 Line of spots ..................................................74 Line Set-up ....................................................74 Load the software...........................................50

M

magnification .................................................57 Manual spot size control .................................60 Mass Spectrometer Connections ......................22 MEASURE tool .............................................68 Polaris laser....................................................37 Monitor masses ..............................................66

N

Nd:YAG laser .......................................... 12, 35

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O

ONLINE........................................................52 Optical Attenuator ..........................................37 Optical Safety...................................................2 optical standard ..............................................69

P

Pattern Selection.............................................71 photons ..........................................................34 POSITION icon..............................................55 Power Supply Interface.................................19 Preablation.....................................................71 Purge .............................................................52

Q

Q-switch........................................................35 Quadrupling ...................................................36

R

radiation...........................................................2 Raster set-up ..................................................73 Real Time analyses.........................................72 repetition rate .................................................58 resource verification .......................................23 RS-232 ..........................................................21

S

safety hazards...................................................3 Safety Labels....................................................6 sample map....................................................78 Screen Properties...........................................67 sensitivity.......................................................71 SET PURGE ..................................................53 short term stability test....................................66 Signal Specifications.......................................27 SINGLE SHOT..............................................61 Single site setup..............................................75 Software Step-by-Step Guide ..........................50 Space Requirements........................................14

spontaneous emission................................ 32, 34 spot size calibration ........................................59 Startup screen.................................................23 stimulated emission ........................................32 S-Video cable .................................................21 switch closures ...............................................27 system calibration ...........................................55 System Connections........................................21 System Installation .........................................16 system off ......................................................23 system on.......................................................23 System Overview ...........................................12

T

TOOL icon.....................................................73 Trigger In.......................................................27 Trigger Out ....................................................27 TTL signals ....................................................27 tuning process ................................................58

U

umbilical cable ...............................................19 Unpacking......................................................16

V

Video Overlay Function..................................78 Video properties .............................................67

W

water reservoir................................................20

X

X Y Z POSITION...........................................55

Z

zonation studies..............................................72 ZOOM...........................................................57