mice rf system - status

MICE RF System - Status

Alan BrossFermilab

RF Cavities for MICE I

Eight 201-MHz cavities in the MICE cooling channel

• First five cavities arrived at LBNL last year and have been measured

• Second batch of five cavities will be complete by Oct. 2010 MICE Project Board September 23, 2010 Alan

Bross

RF Cavity Design Parameters• The cavity design parameters

– Frequency: 201.25 MHz– β = 0.87– Shunt impedance (VT2/P): ~ 22 MΩ/m– Quality factor (Q0): ~ 53,500– Be window diameter and thickness: 42-cm and 0.38-mm

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

MICE Project Board September 23, 2010 Alan Bross

• Cavity has been tested successfully without magnetic fields• Be windows can withstand high RF power in strong magnetic

field without damage

NCRF Cavity for Muons


RF cavities for MICE III

•

• Production of the second batch of five MICE cavities going well at Applied Fusion Company in California

Nose ringsPort extruding and flangesBrazing water cooling tubes Modified extruding techniqueExperimented using the test cavityNeed argon gas purge to prevent oxidation of cavity surfaceMeasure oxidation layer thickness


The RF Cavity at LBNL

MICE Project Board September 23, 2010Alan Bross

CMM Scans of MICE Cavity• Special probe to measure the

inside profile of the cavity• Cavity interior profile being

measured with special probe ( 1,800 points per scan)• The profile will be used to verify

cavity RF models

-650 -600 -550 -500 -450 -400 -350 -300 -250 -200 -150

-50

0

50

100

150

200

250


RF Measurements, Results

S11 measurements

S21 measurements


Measurement Results• Two cavities have been measured in different

window configurations using Be windows #1 and #2• MICE cavity #1: S21 measurements (2 probes) with all

ports shorted: Q 44,000 – 44, 600 (over 80% of the design Q)

• MICE cavity #4: S21 measurements (2 probes) with all ports shorted: Q 43,600 – 44, 000 (over 80% of the design Q)

Window 1) 2) 1) (2 (1 (2 (2 (1Frequency 200.990

MHz199.786

MHz201.179

MHz201.179

MHz

Window 1) 2) 1) (2 (1 (2Frequency 200.642

MHz199.454 MHz

200.839 MHz


RF Cavity Electro-polishingNext Crucial Step


•The inside surface of each RF cavity will be electropolished

•Discussions under way with local company

Electro-polish tank dimensions: 12' Long x 5' Wide x 6' Deep

Large SS piping weldment at AET

RF Cavity Frequency Tuners


• 24 Dynamic Cavity Frequency Tuners per Module• Tuner Actuator

•Tuners operate in a bi-directional “push - pull” mode (±2mm)•Tuning automatically achieved through a frequency feedback loop

Cavity Frequency Tuner Components

• Dual – action actuator

• Flexure tuner arm

• Actuator is

screwed intothe

tuner arm• Fixed

connection

• Forces are transmitted to the stiffener ring by means of “push-pull” loads applied to the tuner lever arms by the dual action actuator assembly

•Tuner/actuators are thermally independent of the vacuum vessel

12MICE Project Board September 23, 2010

Alan Bross

RF Cavity Frequency Tuner Progress Summary

• Tuner design is complete• ¼ scale model has been fabricated to test flexure

concept• One full size tuner arm (for testing the system) has

been fabricated• Aluminum test cylinder (1/6 of cavity) has been

fabricated• Actuator mechanical components have been

fabricated• Actuator bellows have been delivered to LBNL• Assembly of an actuator has begun at LBNL• Control system components have been delivered to

LBNL 13MICE Project Board September 23, 2010

Alan Bross

Cavity RF Coupler

Section view of cavity RF coupler

•Based on successful SNS design with a Toshiba window•Detailed fabrication drawings of the major components are

complete


Alan Bross

Cavity RF Coupler Design Summary

• Detail drawings of major components are complete

• Sources for fabrication materials (e.g. 4” outer coax tube) have been identified

• Assembly method has been determined


Alan Bross

Schedule Summary


Alan Bross

RF Power Systems


Alan Bross

RF system components

Andrew Moss

2 MW Amplifier

2 MW Amplifier

Master OscillatorControls etc

201 MHz Cavity Module

2 MW Amplifier

2 MW Amplifier

201 MHz Cavity Module

LBNL CERN

300 kW Amplifier

300 kW Amplifier

300 kW Amplifier

300 kW Amplifier

HT Supplies

HT Supplies

Daresbury

DL Test SystemAt present

Auxiliary Systems

Auxiliary Systems

Not found

Test system at Daresbury

Andrew Moss

Amplifier status

Andrew Moss

• First medium power (300kW) amplifier and power supply system tested 2008

• Refurbishment and rebuild of first high power (2MW) amplifier complete October 2009

• Power supplies for first 2MW amp 95% complete• Two further 300kW amplifiers awaiting repair• Two refurbished 2MW CERN amplifiers partly

tested, awaiting assembly and high power test• Still need to build 3 more sets of power supplies• One more 300kW amplifier to buy/acquire

Current status of components

Andrew Moss

Predicted hall layout for RF components

Andrew Moss

Hall design in progress• Working with 3D CAD engineer to plan layout between the

amplifiers and cavities• Measurements of system dimensions at Daresbury have been

taken • First step is a simple block diagram showing all components

and how they are interconnected• Then understand how to optimise components with the layout

of the hall and the space available• Result will be a complete parts list required for each cavity

that we can go out for tender for when appropriate

Andrew Moss

Future plans for this year• Test of first large amplifier is priority - expected this month• Amplifier testing likely to take 4 – 6 weeks to optimise the

system using old tubes, then replace with new MICE tubes and repeat tests carefully

• Assembly of the first CERN amplifier, refurbished unit however many small parts, CERN have offered to send two people for a few days to aid with the assembly of the unit – we will take up this offer

• Would need to buy more coax components to test this amplifier in our system – coax bends, straights and a combiner

• Test of CERN amplifier scheduled for March 2011• First amplifier will be delivered and installed in the MICE hall

Andrew Moss

Conclusion• Complete RF amplifier system ready for test, results

expected by end September • Design of hall components between amplifiers and

cavities is in progress and will lead to a formal design of the coax system, how it will be supported and the sequence of installation

• Funding will allow building of CERN amplifier and possible refurbishment of other LBNL amplifier systems

Andrew Moss

What about the RF in Magnetic Field Problem?

RF Test Facility

• MuCool Test Area (MTA)– RF power

• 201 MHz (5MW)• 805 MHz (12 MW)

– Class 100 clean room– 4T SC solenoid

• 250W LHe cryo-plant– Instrumentation

• Ion counters, scintillation counters, optical signal, spectrophotometer

– 400 MeV p beam line


The RF Challenge

• Significant degradation in maximum stable operating gradient with applied B field

• 805 MHz RF Pillbox data– Curved Be windows– E parallel B– Electron current/arcs focused by B

• Degradation also observed with 201 MHz cavity

– Qualitatively, quite different


805 PillboxPost-Mortem

• Significant damage observed– Iris– RF coupler– Button holder

• However– No damage to

Be window


201 MHz Cavity TestTreating NCRF cavities with SCRF processes

• The 201 MHz Cavity – Achieved 21 MV/m– Design gradient – 16MV/m – At 0.75T reached 10-12 MV/m However, No observed damage!


201 MHz Cavity RunningSpark Data


0.00E+00 2.00E+06 4.00E+06 6.00E+06 8.00E+06 1.00E+07 1.20E+070

5

10

15

20

25

GradientSparksB

Number of pulses

Num

ber o

f spa

rks,

gra

dien

t MV/

m a

nd M

agne

tid fi

eld

in T

esla

x10

in T

B=0 Running

Design Gradient

MICE Gradient

201 MHz Prototype

Note: Stored energy available to sparks » 100J (100X that of 805)


Coupler Ceramic


TiN CoatedCeramic

201 MHz Cavity B Field TestsSummary

• Sparking @ B=0 did condition the 201 cavity• Sparking @ B ¹ 0 causes damage (B relatively low)• Re-conditioned @ B=0.• But upon inspection of the cavity

– No observed damage in cavity• SCRF processing techniques help

– Some “arcing” evidence on ceramic disk of coupler may be indicative and needs further study• Plan to remove and inspect towards the end of this

month


Conclusions• Work on the 201 MHz cavities is well underway

and progressing nicely• Although we have seen problems with the 201

prototype operating in B, at MICE gradient (8 MV/m) there appear to be no issues– Coupler damage needs to be investigate– Caveat: Not operated in B of MICE lattice yet!

• RF power systems component work is also progressing nicely– Some minor delays due to manpower availability, but

have been resolvedMICE Project Board September 23, 2010

Alan Bross

Acknowledgements:Derun Li, Steve Virostek (Cavities)

Andy Moss (RF Power)

MICE Project Board September 23, 2010Alan Bross 36

Backup Slides

MICE Project Board September 23, 2010Alan Bross 37

RF cavities for MICE II

•

• The first five MICE cavities have been measured in three different window configurations using Be windows #1 and #2 (reference windows)

*no water cooling tube brazed to the cavity body

Cavity # 1 2 3 4 5 (spare)*

Freq. (MHz) 201.084 200.888 201.247 200.740 201.707


RF measurements, Team Work!

Be window installation


RF Cavity Tuner System Schematic


Alan Bross

Actuator Design

•Actuator design incorporates a sealed enclosure between vacuum and air.

• Actuator is mounted to the tuner arm only

• Bellows allows angular movement for actuator

• Piston plates are joined at the perimeter

• Piston plates incorporate hard stops


Alan Bross

Cavity RF Coupler Future Work

•16 Toshiba windows (plus spares) need to be ordered soon because of long lead times

• Myat RF couplers need to be purchased• Prototype of the outer coax will be fabricated to verify assembly method

• Vendor selection process will be started


Alan Bross

2MW amplifier summery

• Final electrical checks September 2010 – crowbar/cathode modulator systems

• Amplifier connected to test load via coax

• Water system, air blowers and compressed air have all been on

• Filament test to 500A on tube• HT system /earth system

checked out and signed off• Safety paperwork needs

completing before we power system

Andrew Moss

Coax layout for each cavity

Andrew Moss

Damage to Coupler Ceramic Window?


201 MHz Cavity RunningSummary I (B=0)

Design Gradient

Limited by RFPower


mice rf system - status

Documents

mice project board

mice cavities

design q mice cavity

alan bross cavity

alan bross5the rf cavity

cavity rf modelspage

mice cooling channel

damage ncrf cavity