Summary of RF Sessions Derun Li Center for Beam Physics Lawrence Berkeley National Laboratory

D. Li – RF Session Summary at CM17, CERN, Switzerland (25 February 2007)D. Li – RF Session Summary at CM17, CERN, Switzerland (25 February 2007) 1

Summary of RF SessionsSummary of RF Sessions

Derun LiDerun Li

Center for Beam PhysicsCenter for Beam Physics

Lawrence Berkeley National LaboratoryLawrence Berkeley National Laboratory

MICE Collaboration Meeting at CERN, SwitzerlandMICE Collaboration Meeting at CERN, Switzerland

25 February 200725 February 2007


AgendaAgenda

9:00 AM ~ 12:30 PM, Friday, 23 February 2007 (31-3-004)9:00 AM ~ 12:30 PM, Friday, 23 February 2007 (31-3-004)

• 201 MHz RF system for MICE201 MHz RF system for MICE– by Peter CORLETT and Joe ORRETT (Daresbury Laboratory)by Peter CORLETT and Joe ORRETT (Daresbury Laboratory)

• Design of the MICE RF Cavity ModuleDesign of the MICE RF Cavity Module– by S. VIROSTEK (LBNL)by S. VIROSTEK (LBNL)

• MTA RF programs and progressMTA RF programs and progress– by Alan BROSS (FNAL)by Alan BROSS (FNAL)

Coffee breakCoffee break

• Refurbishment of CERN RF equipmentRefurbishment of CERN RF equipment– by Maurizio VRETENAR (CERN AB/RF)by Maurizio VRETENAR (CERN AB/RF)

• Multifactoring Study ProgressMultifactoring Study Progress– by Rebecca SEVIOUR (Cockroft Institute)by Rebecca SEVIOUR (Cockroft Institute)

• Progress at RALProgress at RAL– by Chris NELSON (RAL)by Chris NELSON (RAL)

• DiscussionsDiscussions


201 MHz RF system for MICE201 MHz RF system for MICEWhat needs to be done?• Build up and demonstrate operation of the amplifiers needed to power

the MICE RF cavities

• 201 MHz at ~ 2.5MW

• Two amplifier stages

• Equipment loaned to MICE from LBNL (in various states of disrepair)

Summary by P. Corlett• Most equipment for the Burle 4616 is in place

– One old tube and two new ones

• We are on track to test the 4616 system in June 2007

• Work on the TH116 systems will begin immediately after 4616 tests– This is where the hard work starts!– Major mechanical effort (4~6 months!)

• Aim to test a complete amplifier chain late 2007


MICE RF SystemMICE RF System

Ready for tests!Ready for tests!


Hardware photosHardware photosof 4616 circuitsof 4616 circuits

• Solid state amplifierSolid state amplifier• Power supplyPower supply• Rack is in placeRack is in place• Water circuits have Water circuits have

been connected & been connected & testedtested

• Old 4616 tube has Old 4616 tube has been installed.been installed.

• Two new tubes on Two new tubes on sitesite


LLRF for MICE LLRF for MICE

Functions:Functions:• RF DriveRF Drive• Amplitude Set/ControlAmplitude Set/Control• Phase Set/ControlPhase Set/Control• Pulse ControlPulse Control• SynchronisationSynchronisation

OptionsOptions• Rossendorf analogue systemRossendorf analogue system• AD9910 (new, not available yet)AD9910 (new, not available yet)

Conclusions by J. OrrettConclusions by J. Orrett• The Rossendorf analogue LLRF system provides The Rossendorf analogue LLRF system provides

a proven RF control system. However it lacks the a proven RF control system. However it lacks the flexibility and potential for upgrading the AD9910 flexibility and potential for upgrading the AD9910 has. A sensible approach is to have the has. A sensible approach is to have the Rossendorf LLRF as a proven “fallback position” Rossendorf LLRF as a proven “fallback position” whilst evaluating the AD9910. The AD9910 is not whilst evaluating the AD9910. The AD9910 is not yet commercially available but DL should be able yet commercially available but DL should be able to purchase evaluation boards in the near futureto purchase evaluation boards in the near future

SuggestionsSuggestionsPossibility for using the same LLRF as CERNPossibility for using the same LLRF as CERNSNS LLRF (LBNL FPGA based system)SNS LLRF (LBNL FPGA based system)


Design of the MICE RF Cavity Module Design of the MICE RF Cavity Module by S. Virostekby S. Virostek

• RFCC module design statusRFCC module design status• Integration of MICE Cooling channelIntegration of MICE Cooling channel

– Options for vacuum sealOptions for vacuum seal– Options for module jointsOptions for module joints


RFCC Module Design StatusRFCC Module Design Status• Prototype 201 MHz cavity is at FermiLab awaiting high power RF testing Prototype 201 MHz cavity is at FermiLab awaiting high power RF testing

with applied magnetic field.with applied magnetic field.

• Two 42 cm Two 42 cm curved Be windows have been fabricated by Brush curved Be windows have been fabricated by Brush

Wellman. 3rd window is under way.Wellman. 3rd window is under way.

• Coupling coil design is under way at ICST in Harbin. Details of Coupling coil design is under way at ICST in Harbin. Details of

ICST/LBNL collaboration are being worked out.ICST/LBNL collaboration are being worked out.

• Base mounting scheme for RFCC and other MICE modules has been Base mounting scheme for RFCC and other MICE modules has been

established by RAL.established by RAL.


Joint Seal OptionsJoint Seal Options

RF ModuleAFC Module

Weld

~36 Bolts

Metal Wire Seal or O-ring

Commercial Bellows

Weld Lip

Long discussions:Long discussions:• O-rings vs metal sealsO-rings vs metal seals• Summary on Pros and Cons (see S. Virostek’s talk)Summary on Pros and Cons (see S. Virostek’s talk)

R&D program for seals?R&D program for seals?


MTA RF Progress by A. BrossMTA RF Progress by A. Bross


MTA Hall InstrumentationMTA Hall Instrumentation

805

201

CsI

Plastic Scintillator

Magnet

Chipmunk


Focus of the RF R&DFocus of the RF R&D

• Study the limits on Accelerating Gradient in NCRF Study the limits on Accelerating Gradient in NCRF cavities in magnetic fieldcavities in magnetic field

• HoweverHowever– We believe that the behavior of RF systems in general can be We believe that the behavior of RF systems in general can be

accurately described (predicted) byaccurately described (predicted) by• Tensile strength of the material(s) used in the cavity fabrication (T)Tensile strength of the material(s) used in the cavity fabrication (T)

• Local surface field enhancements (Local surface field enhancements (eqeq))

EEsurfsurf = = 2T/2T///eqeq

– This applies to all accelerating structuresThis applies to all accelerating structures• In SC structures local heating becomes problem firstIn SC structures local heating becomes problem first

– Follows universal curve Follows universal curve


Status and PlansStatus and Plans• 805 MHz pillbox cavity test magnetic fields805 MHz pillbox cavity test magnetic fields

– Confirmed previous experimental resultsConfirmed previous experimental results– Switch to button tests in a few weeksSwitch to button tests in a few weeks

• 201 MHz cavity had run well before without magnetic field, but 201 MHz cavity had run well before without magnetic field, but – Full RF power reflection, appears to be shorted Full RF power reflection, appears to be shorted – Low power measurement found no problemLow power measurement found no problem– The problem seemed to stem from the fact that parts from multiple The problem seemed to stem from the fact that parts from multiple

vendors where used in the 4” coax runvendors where used in the 4” coax run• Power couplerPower coupler• Straight sectionsStraight sections• ElbowsElbows

– At the interfaces between parts from different vendors, the fit-up was At the interfaces between parts from different vendors, the fit-up was not idealnot ideal

• Inner conductor specifications seemed to varyInner conductor specifications seemed to vary• This has now been fixedThis has now been fixed• In addition we will be using pressurized (12 pisg) SF6 in the 4” In addition we will be using pressurized (12 pisg) SF6 in the 4”

coax run as the insulating gas instead of aircoax run as the insulating gas instead of air


Rad Mon #1 vs Grad with 2.5 justa-positioned with no Field

0

200

400

600

800

1000

1200

0 5 10 15 20 25 30 35

Grad mV/m

Ra

dia

tio

n m

Re

m/h

r

2.5 T Line

Lines Without Magnetic Field


Latest Electric field limit Data at 2.5-T and Latest Electric field limit Data at 2.5-T and 1.25-T in the LBNL Single Cell Cavity with 1.25-T in the LBNL Single Cell Cavity with

Curve Be Windows coated with TiNCurve Be Windows coated with TiN

The Asymptotic limit line shown indicates the continuous Gradient sparking limit. In all the cases studied including Lab G this line as predicted the Gradient Limit for the cases under Study.

For the 1.25 T case the Save operating limit has been shown to be

20 MV/m 0

10

20

30

40

50

60

70

80

90

13 15 17 19 21 23 25 27

Gradient MV/m

Rad

iatio

n m

R/H

r

2.5 T Data

1.25 T Data

RF Conditioning without Magnetic Field

Asymptotic Gradient limit line at 1.25 T


High Pressure HHigh Pressure H22 Filled Cavity Work Filled Cavity Work

Muons Inc.Muons Inc.• High Pressure Test CellHigh Pressure Test Cell

• Study breakdown properties of materials in HStudy breakdown properties of materials in H22

• Run in B fieldRun in B field

– No degradation in M.S.G. up to No degradation in M.S.G. up to 3.5T 3.5T

Gas filled CavityGas filled Cavity


Refurbishment of CERN RF equipment Refurbishment of CERN RF equipment for MICEfor MICE

M. VretenarM. Vretenar

CERN AB/RFCERN AB/RF


CERN Linac1 amplifiersCERN Linac1 amplifiers

Developed in 1956-59.Developed in 1956-59.

Photo taken in 1959 for the oldPhoto taken in 1959 for the old Linac1 amplifier Linac1 amplifier

Frequency 202.56 MHz, equipped with the TH170R Frequency 202.56 MHz, equipped with the TH170R triode, can deliver a maximum of 2.5 MW with an triode, can deliver a maximum of 2.5 MW with an anode voltage of 40 kV, but near delivered for more anode voltage of 40 kV, but near delivered for more than 1.7 MW.than 1.7 MW.

The tube is water cooled, and can operate at a The tube is water cooled, and can operate at a maximum of 0.3% duty cycle. maximum of 0.3% duty cycle.

The unit is about 3.6 m high, 1m x 1m base.The unit is about 3.6 m high, 1m x 1m base.

Only 2 units left, one was modified for 101 MHz and Only 2 units left, one was modified for 101 MHz and then 88 MHz (gradient test for bunch rotation cavities then 88 MHz (gradient test for bunch rotation cavities in NF), the other is a cannibalised spare, stored in a in NF), the other is a cannibalised spare, stored in a hall for 50 years.hall for 50 years.


CaveatsCaveats

The refurbishment of the linac amplifiers for MICE has been The refurbishment of the linac amplifiers for MICE has been authorized by the AB Department (Nov. 06), but there are still authorized by the AB Department (Nov. 06), but there are still some doubts concerning the level of UK support to CLIC…some doubts concerning the level of UK support to CLIC…

The CERN Linac RF team is heavily involved in Linac4 and The CERN Linac RF team is heavily involved in Linac4 and from next year will work 100% on this project from next year will work 100% on this project it is now or it is now or never, this year we still have a window for at least starting never, this year we still have a window for at least starting refurbishing the amplifiers, from next year it will be very difficult.refurbishing the amplifiers, from next year it will be very difficult.


Organisation of workOrganisation of workPrinciple: the reconstruction is done at CERN, up to the testing of filament. Then, Principle: the reconstruction is done at CERN, up to the testing of filament. Then,

the amplifier is transferred to RAL or Daresbury for the RF tests.the amplifier is transferred to RAL or Daresbury for the RF tests.

At CERN:At CERN:1.1. Collect drawings, and design modified parts.Collect drawings, and design modified parts.2.2. Make inventory of existing and missing parts.Make inventory of existing and missing parts.3.3. Machine mechanical parts.Machine mechanical parts.4.4. Dismount, clean, reconstruct amplifiers.Dismount, clean, reconstruct amplifiers.5.5. Assemble ventilation circuitry.Assemble ventilation circuitry.6.6. Assemble filament circuit and filament regulation (PLC based, CERN standard)Assemble filament circuit and filament regulation (PLC based, CERN standard)7.7. Test filament and ventilationTest filament and ventilation

These activities can be realized with minimum support of CERN staff if temporary These activities can be realized with minimum support of CERN staff if temporary labor is used for: draftsman/designer, mechanic, wireman.labor is used for: draftsman/designer, mechanic, wireman.

At MICE:At MICE:1.1. Install cathode switch circuit (eventually also HOM suppressors).Install cathode switch circuit (eventually also HOM suppressors).2.2. Connect HV and RF loads.Connect HV and RF loads.3.3. Test with RF power.Test with RF power.

Suggestions: involvement of MICE peopleSuggestions: involvement of MICE people


SummarySummary• 201 MHz RF system (DL and CERN)201 MHz RF system (DL and CERN)• RF R&D with magnetic fields at FNALRF R&D with magnetic fields at FNAL

– 805 MHz button tests805 MHz button tests– 201 MHz cavity conditioning 201 MHz cavity conditioning – Multipactoring studiesMultipactoring studies

• RFCC module integrationRFCC module integration • Progress at RAL Progress at RAL by Chris NELSON was not covered here, but can by Chris NELSON was not covered here, but can

be found at MICE web site soon. be found at MICE web site soon. Lots progresses inLots progresses in– Decay solenoidDecay solenoid– BeamlineBeamline– Presented with 5o+ photos Presented with 5o+ photos – ……

• No plan for MICE cavity yetNo plan for MICE cavity yet• Pending issues: cavity amplitude and phase measurement and Pending issues: cavity amplitude and phase measurement and

stabilitystability– A joint session with DAQ group futureA joint session with DAQ group future

Documents

Summary of RF Sessions Derun Li Center for Beam Physics Lawrence Berkeley National Laboratory