RFCC Module and RF Cavity Construction

RFCC Module and RF Cavity RFCC Module and RF Cavity Construction Construction

Derun LiDerun LiA. DeMello, M. Green, S. Virostek, M. ZismanA. DeMello, M. Green, S. Virostek, M. Zisman

Lawrence Berkeley National LaboratoryLawrence Berkeley National Laboratory

MICE Collaboration Meeting 22 October 20, 2008

RFCC Module and RF Cavity Construction

Page 2Derun Li - LBNL - October 20, 2008, CM22 at RAL, UK

Progress SummaryProgress Summary• RFCC module engineering design near completionRFCC module engineering design near completion

– The coupling coil design and fabrication at ICST of HIT (Wang’s The coupling coil design and fabrication at ICST of HIT (Wang’s talk)talk)

– The MICE cavity design is heavily based on the successful MuCool The MICE cavity design is heavily based on the successful MuCool 201-MHz prototype RF cavity and lessons learned 201-MHz prototype RF cavity and lessons learned

• Fabrication and post processing Fabrication and post processing • Cavity conditioning and operationCavity conditioning and operation

– Engineering design of the cavity is completeEngineering design of the cavity is complete • CAD model of the cavity, tuners, support and vacuum system CAD model of the cavity, tuners, support and vacuum system • Fabrication schemesFabrication schemes

• Vendor qualification: visited potential vendors recentlyVendor qualification: visited potential vendors recently• RF cavity final design review at CM-22 (tomorrow)RF cavity final design review at CM-22 (tomorrow)• Possible operation at LN temperature?Possible operation at LN temperature?

– Design accommodates LN operation, but is very challenging Design accommodates LN operation, but is very challenging



RF Cavity Summary• MICE RF cavity design is based on the successful MICE RF cavity design is based on the successful

prototype cavity for the US MuCool program prototype cavity for the US MuCool program Fabrication of the prototype cavity was successfulFabrication of the prototype cavity was successful A slight reduction in cavity diameter to raise the A slight reduction in cavity diameter to raise the

frequency has been specified and analyzedfrequency has been specified and analyzed The fabrication techniques used to produce the The fabrication techniques used to produce the

prototype will be used to fabricate the MICE RF cavitiesprototype will be used to fabricate the MICE RF cavities• The cavity design was reviewed at CM21 at DLThe cavity design was reviewed at CM21 at DL• Copper sheets have been ordered and expected to Copper sheets have been ordered and expected to

arrive mid-December 2008arrive mid-December 2008• A detailed WBS schedule for the design and A detailed WBS schedule for the design and

fabrication of the MICE RF cavities has been fabrication of the MICE RF cavities has been developeddeveloped



2 RFCC Modules, 8 Cavities2 RFCC Modules, 8 CavitiesSC coupling Coil

Cavity Couplers

Vacuum Pump201-MHz cavity201-MHz cavity

Curved Be window



MICE RF Cavity DesignMICE RF Cavity Design– 3-D Microwave Studio RF parameterized 3-D Microwave Studio RF parameterized

model including ports and curved Be model including ports and curved Be windows to simulate frequency, Ewindows to simulate frequency, Epeakpeak, , etc.etc.

– Hard to reach the design frequency by Hard to reach the design frequency by spinning techniquespinning technique

– Frequencies between cavities should be Frequencies between cavities should be able to achieve within able to achieve within 100 kHz 100 kHz

– ApproachesApproaches• Modification the prototype spinning Modification the prototype spinning

form form • Targeting for higher frequencyTargeting for higher frequency• Fixed tuner to tune cavity close to Fixed tuner to tune cavity close to

design frequency (deformation of design frequency (deformation of cavity body)cavity body)

• Tuners are in push-in mode Tuners are in push-in mode lower lower frequencyfrequency



Cavity Design ParametersCavity Design Parameters• Cavity design parameters:Cavity design parameters:

– Frequency: 201.25 MHzFrequency: 201.25 MHz– ββ = 0.87 = 0.87– Shunt impedance (VTShunt impedance (VT22/P): ~ 22 MΩ/m/P): ~ 22 MΩ/m– Quality factor (QQuality factor (Q00): ~ 53,500): ~ 53,500– Be window diameter and thickness: 42-cm and 0.38-mmBe window diameter and thickness: 42-cm and 0.38-mm

• Nominal parameters for Nominal parameters for MICEMICE and cooling channels and cooling channels in a neutrino factory:in a neutrino factory: – 8 MV/m8 MV/m (~16 MV/m)(~16 MV/m) peak accelerating fieldpeak accelerating field– Peak input RF power:Peak input RF power: 1 MW1 MW (~4.6 MW)(~4.6 MW) per cavity per cavity – Average power dissipation per cavity:Average power dissipation per cavity: 1 kW1 kW (~8.4 kW)(~8.4 kW)– Average power dissipation per Be window:Average power dissipation per Be window: 12 watts12 watts (~100 (~100

watts)watts)



RF Cavity AssemblyRF Cavity Assembly



RF Cavity Fabrication RF Cavity Fabrication OverviewOverview

• Cavity half-shells to be formed by metal spinning

• Precision milling of large parts (1.2 m diameter)

• Precision turning of mid-sized parts (0.6 m dia.)

• Precision manufacture of smaller parts• CMM measurements throughout the process• To limit any annealing and maintain cavity

strength, e-beam welding will be used for all cavity welding• cavity equator, stiffener rings, nose

rings, port annealing and port flanges• Cavity inside surfaces are finished by

electro-polishing

Engineering CAD

Model of the RF Cavity

Prototype RF Cavity

The same fabrication techniques used to make the prototype cavity will be used for the MICE RF cavities



Recent ProgressRecent Progress• RFCC engineering CAD model refinedRFCC engineering CAD model refined• RF and engineering design of 201-MHz RF cavity RF and engineering design of 201-MHz RF cavity

completecomplete• Integration and interface issues addressedIntegration and interface issues addressed• Vendor identification and qualification near completeVendor identification and qualification near complete



Recent Progress (procurement Recent Progress (procurement && fab) fab)

•The large copper sheets used in the fabrication of the cavity shells have been ordered and will arrive at LBNL in mid-December

•A series of vendor qualification visits has been conducted•Applied Fusion - San Leandro, CA (e-beam welding, machining)•Meyer Tool & Mfg., Inc. - Chicago, IL (machining)•Sciaky, Inc. - Chicago, IL (e-beam welding)•Roark Welding & Engineering - Indianapolis, IN (e-beam welding,

machining)•ACME Metal Spinning – Minneapolis, MN (cavity shell spinning)

•Other vendors have been identified•Midwest Metal Spinning, Inc. –Bedford, IN (cavity shell spinning)



Cavity Fabrication SummaryCavity Fabrication Summary•The twenty Ø1524 mm copper sheets used in the The twenty Ø1524 mm copper sheets used in the

fabrication of the cavity shells have been purchased and fabrication of the cavity shells have been purchased and will arrive at LBNL the second or third week of will arrive at LBNL the second or third week of DecemberDecember

•Quotes from two metal spinning vendors (one local to Quotes from two metal spinning vendors (one local to San Francisco Bay area and the other ACME in San Francisco Bay area and the other ACME in Minnesota) have been received Minnesota) have been received

•A third spinning vendor possibility in Bedford, Indiana A third spinning vendor possibility in Bedford, Indiana has been identified has been identified

• If necessary a process of pre-polishing the copper sheet If necessary a process of pre-polishing the copper sheet before spinning will be used to help eliminate scratches before spinning will be used to help eliminate scratches on the inside of the spun cavity shellon the inside of the spun cavity shell

•The two spare half shells from the prototype program The two spare half shells from the prototype program will be re-spun to the new profile, polished and used for will be re-spun to the new profile, polished and used for e-beam parameter testinge-beam parameter testing



Cavity Fabrication Summary Cavity Fabrication Summary (cont’d)(cont’d)

• Detail drawings of parts needed to fabricate the cavities Detail drawings of parts needed to fabricate the cavities are nearly completeare nearly complete• Three possible e-beam welding vendors have been Three possible e-beam welding vendors have been

identified (one local to San Francisco Bay area and the identified (one local to San Francisco Bay area and the other two in Illinois and Indiana) other two in Illinois and Indiana) • Request for quote documents will be sent to fabrication Request for quote documents will be sent to fabrication

and welding shops before the end of 2008and welding shops before the end of 2008• LBNL has the machining equipment necessary to fabricate LBNL has the machining equipment necessary to fabricate

the complete RF cavity (minus e-beam welding and the complete RF cavity (minus e-beam welding and spinning) and will be considered depending on cost and spinning) and will be considered depending on cost and schedule prioritiesschedule priorities



Other Module ComponentsOther Module Components

Beryllium Window

Dynamic Tuners

Cavity Suspension

Vacuum System

RF Coupler



Other Module Components (cont’d)• Beryllium window design is complete; windows are

in the process of being ordered (8 per module needed)

• Design and analysis of the cavity frequency tuners is complete, drawings to be done soon

• A hexapod cavity suspension system has been incorporated in the design

• The RF coupler will be based on the SNS design using the off the shelf Toshiba RF window

• The vacuum system includes an annular feature coupling the inside and the outside of the cavity (further analysis of vacuum rupture scenarios TBD)



• Each cavity has two Be windowsEach cavity has two Be windows– 42-cm diameter and 0.38-mm thick 42-cm diameter and 0.38-mm thick – Window is formed at high temperature and later brazed to copper Window is formed at high temperature and later brazed to copper

frames frames – Thin TiN coatings on both sides of the windowThin TiN coatings on both sides of the window

• One window curves into the cavity and one curves outOne window curves into the cavity and one curves out• Already tested up to 5 MW in 201-MHz cavity at MTA, FNAL Already tested up to 5 MW in 201-MHz cavity at MTA, FNAL

42-cm42-cm

201 MHz Beryllium Windows201 MHz Beryllium Windows



Cavity Tuner Design FeaturesCavity Tuner Design Features•Six tuners spaced evenly

around each cavity provide individual frequency adjustment through a feedback loop

•Layout is offset by 15º from vertical to avoid conflict with cavity ports

•Tuners touch cavity and apply loads only at the stiffener rings

•Tuners operate in “push” mode only (i.e. squeezing)



Tuner System Analysis - Deformation

• ANSYS FEA of one tuner on 1/6 cavity segment• Input pressure of 1.38 MPa (200 psi) is applied to actuator piston

•Deformation at the stiffener ring in the 2 mm range•Movement of the arm at the actuator is in the 3 mm range



Hexapod Strut ArrangementHexapod Strut Arrangement•Analysis of a hexapod strut system is complete

•Each cavity will contain a dedicated set of 6 suspension struts arranged in a hexapod type formation

•This system spreads the gravity load of the cavity across several struts

Example of a hexapod stage



ANSYS FEA Analysis - StressANSYS FEA Analysis - Stress

•Maximum stress in the strut suspended cavity, due to gravity alone, is in the 20-30 MPa (2900-4350 psi) range•Yield strength of cavity is in the 275 MPa range



Vacuum SystemVacuum System

•A NEG pump has been chosen because it will be unaffected by the large magnetic field

•A vacuum path between the inside and outside of the cavity eliminates the risk of high pressure differentials and the possible rupture of the thin beryllium window

NEG (non-evaporable getter) pump

Cross sectional view of vacuum system



Vacuum Vessel and Support Vacuum Vessel and Support SummarySummary

• Engineering 3D CAD model of the vacuum vessel mechanical design is complete

• Standard machining and manufacturing methods will be used

• A plan for attaching the coupling coil and the vacuum vessel together has been developed

• Conceptual design of the support stand is complete (analysis will need to be performed)

• A method for assembling the cavities into the vacuum vessel has been formulated

• A conceptual design of the cavity water cooling feedthrough system is finished



Vacuum Vessel FabricationVacuum Vessel Fabrication•Vacuum vessel material must be non-magnetic and strong therefore

304 stainless steel will be used throughout•The vacuum vessel will be fabricated by rolling stainless steel sheets

into cylinders•Two identical vessel halves will be fabricated with all ports and

feedthroughs Main 1400mm

rolled tube

Smaller diameter rolled

tube

Bellowsflange



Vacuum Vessel and Coupling Vacuum Vessel and Coupling CoilCoil



Vacuum Vessel/Coupling Coil Vacuum Vessel/Coupling Coil IntegrationIntegration

• LBNL will weld in gussets that fit between the coupling coil and the vacuum vessel

• Sixteen special gussets are welded between the coupling coil magnet’s cold mass support tubes and the magnet housing

• The gussets will transfer the magnetic loads between the coupling coil and the vacuum vessel



RFCC Support StandRFCC Support Stand• RFCC support stand must withstand a

longitudinal force of 50 tons transferred from the coupling coil

• Bolted gussets and cross bracing provide shear strength in the axial direction (analysis will confirm the stand design)



Liquid Nitrogen Cooling Considerations

•Suspension of cavities on struts provides low heat leak from cavity to vacuum vessel

•Beryllium window FEA thermal analysis will need to be performed with new parameters

•The cavity frequency will be shifted (approximately 600 kHz), therefore tuning system or RF power source modifications will be needed

•Insulators will need to be added to the RF couplers•Coaxial LN feedthrough tubes will be needed to insulate the connection outside of vacuum



Schedule OverviewSchedule Overview•RFCC design and fabrication project originally RFCC design and fabrication project originally expected to be a 3–year project (10/06 to 10/09)expected to be a 3–year project (10/06 to 10/09)

•Coupling coil effort began in 2006 at ICST (Harbin)Coupling coil effort began in 2006 at ICST (Harbin)•Design and fabrication of other RFCC module Design and fabrication of other RFCC module components was scheduled to begin 10/07components was scheduled to begin 10/07

•Start was delayed due to lack of availability of Start was delayed due to lack of availability of qualified manpowerqualified manpower

•Earlier this year, mechanical engineer A. DeMello Earlier this year, mechanical engineer A. DeMello joined MICE to work on RFCC module design (FTE)joined MICE to work on RFCC module design (FTE)

•Additional manpower required to make up scheduleAdditional manpower required to make up schedule



Schedule SummarySchedule Summary

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RFCC Module and RF Cavity Construction

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