Fast Wire Scanner Project

Galil Controller Assignment, Motor Driver Assignment, and Potentiometer

Assignment

Author: Benjamin (Sheng Yen) Tsai

Date: 05-04-2013

Student ID: 301121384

Adviser: Bill Rawnsley

Team: Diagnostics

Contents

Page Number

Acknowledgement ___________________________________________ 1

Abstract ___________________________________________________ 1

Company Information _______________________________________ 1-2

Job overview and assignment description ________________________ 2

How does the Fast Wire Scanner run on the electron beam line? ___ 2-3

How do we build and test fast wire scanner? ____________________ 4-5

Schematic of motor driver box _________________________________ 5-6

Schematic of wire scanner ____________________________________ 6-7

Schematic of Galil controller box _______________________________ 7-8

3D modeling of boxes _______________________________________ 8-10

Schematic of potentometer ___________________________________ 10-12

Fast wire scanner test _______________________________________ 12-13

Conclusion: What did I learn? _______________________________ 13-14

Reference _________________________________________________ 14

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Acknowledgement

Firstly, I would like to take this opportunity to thank David P Cameron, my co-worker,

Paul Dirksen, mechanical designer of Wire Scanner, and Bill Rawnsley, my supervisor,

for their constant encouragement without which this assignment would not be possible.

I would especially like to thank my mentor during this period, David Cameron, for

guiding me through the project and providing me with plenty of feedback and help when

necessary.

I also take this opportunity to express a deep sense of gratitude to Scott Kajioka and Scott

Kellogg, both Mechanical Technicians, for their cordial support and guidance, which

helped me tremendously in completing this project and learning machining skills.

Lastly, I would like to thank all my group members for making my 8 months co-op work

term a very pleasing experience.

Abstract

My 8-month co-op job assignment revolves around the fast wire scanner project.

In my first 4-month co-op, I completed building the prototype of Galil controller box. In

the second 4-month period, Solidworks software is used to design the 3D model of Galil

controller box and ANAHIEM step motor driver box, which will be installed in the new

electron beam line under ARIEL project. In addition, a new potentiometer circuit and

PCB layout is designed with Altium software, which can record the position of the can on

the fast wire scanner. This document provides general fast wire scanner information to

the detail of my circuit testing and wiring.

Company Information

As one of the world’s leading subatomic physics laboratories, TRIUMF brings

together dedicated physicists and interdisciplinary talent, sophisticated technical

resources, and commercial partners in a way that has established the laboratory as a

global model of success. TRIUMF’s research brings advances that will enhance the

health and quality of life of millions of Canadians, launch new high-tech companies,

create new high specificity drugs, help us to understand the environment, enable the

development of new materials, and spur the imaginations of our children who want to

know their place in the universe. [1]

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The Advanced Rare Isotope Laboratory (ARIEL) is TRIUMF's flagship facility

that will expand capabilities to produce and study isotopes for physics and medicine. It

demonstrates a high-power superconducting electron accelerator using state-of-the-art

technology to produce exotic isotopes for research and development. [1]

Job overview and assignment description

My job responsibility involves building the controller and motor driver box for

fast wire scanner. I built and tested the prototype controller box in first four month. In the

second term, I constructed and wired the final version of the controller box and motor

driver boxes, and I designed and tested the potentiometer circuit. I run the tests manually

using the Galil Suite software and oscilloscope. If an issue occurs, I am responsible for

collecting the data, changing schematic, and rewiring the electronics again. I also am in

charge of purchasing the all the parts I need for building electronics boxes for four fast

wire scanners. Finally, building and wiring the electronics of the boxes and testing the

circuits are also part of my duties.

How does the fast wire scanner work on the electron beam line?

Wire scanner is a diagnostic device to measure the profile of a high energy electron

beam. A beam profile resolution of 25µm is desired, along with a wire speed greater than

3m/s to prevent wire from melting caused by beam heating. A signal proportional to the

beam cross-section is recorded from a downsteam scintillator and photomultiplier. Two

perpendicular wires will move through the beam at 45 degrees to the beam line. There

exist two modes of operation. For low duty cycle beam pluses, wire motion may be

paused for each measurement. For high power beams, the wires will fly though as quickly

as possible. The wires will retract through a gap to shield them from the magnetic field of

the beam when they are in the home position. Similar to previous designs [2], a rotary

motor will turn a drum with a helical slot machined into its surface. A coil will move in

the channel and push the wire holder fork through the beam. The pitch is 144mm per

revolution in the constant speed zone. At the home position, the pitch is small so that the

motors holding torque will prevent the vacuum force from pulling the fork into the beam.

A stepper motor will be used as they are relatively radiation-resistant. An Anaheim

Automation 34Y314D-LW8 stepper motor with 200 steps per turn will provide up to

1700 oz·in of torque. It will be powered by an Anaheim MLA10641 microstepper driver

which provides a 160VDC bus, 10A peak output current and bipolar operation. An open

loop step program will be used, since the speed of the wire scanner will be too fast for

closed loop feedback. An EPICS IOC will communicate with a ProDex VME motor

controller card (Fig. 1). An interface bus and card will transfer the signals to the motor

driver. This system is well proven at TRIUMF, but only for slow speed motors. A

radiation- resistant, wire wound linear potentiometer may be used to check that the motor

does not miss any step. The wires are carried by a machined Macor fork. They are spring-

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loaded to allow for thermal expansion and their continuity will be monitored. The wire

currents will be measured by passing them through resistors and measuring the resulting

voltage with a transient recorder. The signal may also be derived from a downstream

scintillator and photomultiplier. The two titanium wires are separated from each other.

Therefore, the scanner can carry wires of two different orientations across beam and

scans in x and y directions. At the downstream of the scanner, a photomultiplier detector

(PMT) is arranged. When the wire scanner is crossing the electron beam, the signal

produced by the interaction of beam particle and the wire will be detected by PMT. The

signal is proportional to the electron beam density. For example, the signal is stronger

when the wire is at the beam center than at the edge of beam. According to the position of

the wire and the signal variation, the electron beam density distribution can be obtained.

E-linac wire scanner measurement system includes sets of wire scanners at the exit for

accurate measurements of beam size and emittance. It can be performed with no adverse

impact on electron beam and no interruption to normal machine operation.[3] Currently,

the complete version of fast wire scanner is tested and will be installed to the E-linac

beam line, which is going to operate in May 1st.

Figure 1: A block diagram of the proposed electronics for the wire scanner.

How do we build and test fast wire scanner?

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Normally, we can test fast wire scanner by using Galil Suite software to control Galil

Controller and Anaheim step motor driver. In addition, the main part of my assignment is

to finish electrical wiring of prototype Galil controller box (Fig. 2) in the first four month.

Therefore, I had time to test the wire scanner with aluminum stand before Christmas

break. Since fast wire scanner is going to run at 3m/s, which will cause a huge vibration

of electron beam line, we need to test the stability of the aluminum stand for the wire

scanner before installing the wire scanner (Fig. 3).

Figure 2: Prototype of wire scanner Galil controller box

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Figure 3: A snapshot of wire scanner aluminum stand test.

Schematic of motor driver box

Schematic of the motor driver box (Fig. 4) contains two 10A MLA10641 motor drivers,

two cooler fan, and two solid state relays. The MLA 10641 motor driver will be used to

drive the motor on the fast wire scanner. In addition, solid state relay is controlled by

Galil controller to enable and disable the motor driver as a safety measure. The motor

driver box did not have cooler fan until I did a basic temperature test for motor driver box.

The result showed that the air temperature would be higher than 45 degree Celsius when

we enabled the motor driver for 3 minutes, and it would increase to around 55 degree

Celsius. As a result, my supervisor decided to include a cooler fan per motor driver to

keep the box close to room temperature.

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Figure 4: Schematic of motor driver box.

Schematic of wire scanner

Schematic in Fig. 5 includes the electrical wiring of wire scanner. It contains four limit

switches and one solenoid. The four limit switches include forward limit switch, reverse

limit switch, home limit switch, and safety limit switch. Forward switch is at the end

point of potentiometer to prevent potentiometer overdrive toward the beam line and let us

know the exactly position of wire scanner. Same applies to the reverse switch, which is at

the start point of potentiometer. In addition, catch safety switch is controlled by solenoid.

If enable output it means the motor is turned on. The catch safety switch is sensitive to air

flow – the catch will be released when any air enter the wire scanner. The home limit

switch is used to make sure the can of the wire scanner starts the exactly same position

after we restart the motor driver.

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Figure 5: Schematic of fast wire scanner.

Schematic of Galil controller box

The schematic of the Galil controller box (Fig. 6) is done by Altium designer software. It

includes a Galil controller, which is the main device inside the box, a pulse generator

circuit, and couple terminal blocks. Galil motion controller includes optically isolated I/O,

high-power outputs capable of driving brakes or relays, and analog inputs for interfacing

to analog sensors. The DMC-40x0 controller and drive unit accepts power from a single

20-80 VDC source. The DMC-4040 is available in one through four axis formats, and

each axis is user-configurable for stepper or servo motor operation. It means one Galil

controller can control four wire scanners. In addition, the relay module in the terminal

block is using for interlock circuit, which is controlled by the output of Galil controller.

Interlock circuit is used to help prevent a machine from harming its operator or damaging

itself by stopping the machine when tripped. Since the Galil controller has a problem in

Ethernet connection, I had to install a pulse generator circuit inside the Galil box, which

will send a pulse signal to reboot the Galil controller when Ethernet connection fails.

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Figure 6: Schematic of Galil controller box.

3D modeling of boxes

The two figures below (Fig. 7, 8) are the 3D drawings of the Galil controller box and the

motor driver box using Solidworks software. By drawing the 3D model of the two boxes,

I can adjust the space the wire inside the box and my co-worker Paul helps me to check

and sent the drawings to TRIUMF machine shop. The benefit of drawing the 3D model of

controller box and motor driver box is to make sure every component fit in the box and

help save time for the next person building them. The 3D schematic of Galil box can also

help me calculate the wire length from Galil controller to terminal blocks and connectors

on front panel. It saves me a lot of time when I physically built the Galil controller box.

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Figure 7: 3D schematic of Galil controller box.

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Figure 8: 3D schematic of motor driver box.

Schematic of potentiometer

Below is the schematic of potentiometer circuit (Fig. 9), which took me two weeks to

design and approved by my supervisor. The circuit was simulated using Spice program. I

purchased the components needed for circuit testing and updated schematic accordingly.

Since this potentiometer circuit needs to run at around 175kHz, I selected AD847J

opamps to build the circuit. I had a hard time testing the circuit because it is a high

frequency circuit and it has different frequency of oscillation. The circuit inlcudes a

differential amplifiler to accept two signals from the potentiometer, and then the signal is

passed to an inverting buffer per output channel. On the other hand, one of the output

channels is going to the SIS3302 struck, which has 50-ohm input impedance and a one-

pin Lemo connector that only accepts voltage between 2.5 to -2.5 volts. For driving 50-

ohm impedance and providing the voltage range of struck input, I calculated the offset

needed and then installed an offset opamp such that ouput = input*2.5 + 10 (volts). There

is a background noise in the box’s current location, so I put a voltage-contolled current

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source and a transistor buffer stage inside the current source to reduce influence of the

noise. After the schematic was aproved by my supervisor, I started drawing the PCB by

using Altium designer software (Fig. 10). During the process, I also learned more about

the differences between surface mount and dip through hole PCB layouts.

Figure 9: Schematic of the potentionmeter circuit as seen in Altium designer software.

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Figure 10: PCB board layout of the potentiometer circuit.

Fast wire scanner test

Fast wire scanner was tested by two titanium wires that are perpendicular to each other.

The photo shown in Fig. 11 was taken by Manta camera in a very short exposure time.

Since the exposure time is very short and wire scanner is running at 3.25m/s, the photo

only showed the instant movement of wires. In this test, I tried to adjust the straightness

of those two wires. The straightness of wires would affect the measurement uncertainty

of beam profile, as the two titanium wires moved 45 degrees towards the electron beam.

The newest data from the latest wire scanner test showed that the actual angle between

the two titanium wires is 89.25 degrees.

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Figure 11: Wire scanner testing at running 3.25m/s

Conclusion: What did I learn?

Wire Scanner project is my first and second co-op job assignment. A lot of things I have

learned during the co-op are hands-on and are not taught in school. I have acquired a lot

of lab equipment setup skills, and it is very interesting to learn to wire the electronics by

using the right type of wires, some of which are radiation-resistant and can survive longer

in radiation zones. When I use Spice software to simulate the potentiometer circuit, I gain

a deeper understanding of how to design a circuit and solve oscillation problems. These

skills will be very valuable when I return to school. The most important aspects I have

learned to complete this assignment are to communicate technical information

professionally and efficiently with other professional engineers, and to take initiative in

learning things about the project that I did not know before. My supervisor always

encourages me to ask more questions, and when I do, they are not only very open, but

also provide me with helpful tips from their years of experience. As well, my co-workers

are very supportive – when I ask them about the circuits, they not only answer patiently,

but also point out related information. Working at TRIUMF makes me feel like I am part

of a family. I have a exceptional work experience in the past 8 month at TRIUMF.

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The experience is very valuable and exceptional. By applying the knowledge I gained

during this co-op, I believe I can better perform my duties as an electrical engineer in the

future.

Finally, I would say working at TRIUMF is a lesson of life. Most of the things I

encounter are new and have never been taught in class. I not only learn what I should do,

but also how I should do it. Communicating with people, dealing with technical

difficulties, and learning continuously are all required for one to become a successful

engineer. These characteristics are rarely well-learned at school, and can only be

appreciated fully through a co-op opportunity like this.

REFERENCES [1] “TRIUMF website” http://www.triumf.ca/ariel

[2] U. Hahn, N.V. Bargen, P. Castro, O. Hensler, S. Karstensen,

M. Sachwitz, H. Thom, “Wire scanner system for FLASH at

DESY,” DESY, Hamburg, NIM A 592 (2008) 189-196.

[3] J.M. Abernathy, D. Karlen, M. Pfleger, P. Poffenberger, D. Storey, F. Ames, P.

Birney, D.P. Cameron, J. Van Holek, S.Y. Kajioka, S. Kellogg,M. Lenckowski, B.

Minato, W.G. Rawnsley, J.E. Richards, V.A. Verzilov, “BEAM DIAGNOSTIC

SYSTEMS FOR THE TRIUMF E-LINAC_” MOPPR003