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MICE RF System - Status Alan Bross Fermilab
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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 Page 2 MICE Project Board September 23, 2010 Alan Bross
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RF Cavity Design Parameters The cavity design parameters –Frequency: 201.25 MHz – β = 0.87 –Shunt impedance (VT 2 /P): ~ 22 MΩ/m –Quality factor (Q 0 ): ~ 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) Page 3 MICE Project Board September 23, 2010 Alan Bross
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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 Page 4 MICE Project Board September 23, 2010 Alan Bross
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RF cavities for MICE III Production of the second batch of five MICE cavities going well at Applied Fusion Company in California Nose rings Port extruding and flanges Brazing water cooling tubes Modified extruding technique Experimented using the test cavity Need argon gas purge to prevent oxidation of cavity surface Measure oxidation layer thickness Page 5 MICE Project Board September 23, 2010 Alan Bross
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The RF Cavity at LBNL Page 6 MICE Project Board September 23, 2010 Alan Bross
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CMM Scans of MICE Cavity Special probe to measure the inside profile of the cavitySpecial probe to measure the inside profile of the cavity Cavity interior profile being measured with special probeCavity interior profile being measured with special probe ( 1,800 points per scan) ( 1,800 points per scan) The profile will be used to verify cavity RF modelsThe profile will be used to verify cavity RF models Page 7 MICE Project Board September 23, 2010 Alan Bross
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RF Measurements, Results S 11 measurements S 21 measurements Page 8 MICE Project Board September 23, 2010 Alan Bross
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Measurement Results Two cavities have been measured in different window configurations using Be windows #1 and #2 MICE cavity #1: S 21 measurements (2 probes) with all ports shorted: Q 44,000 – 44, 600 (over 80% of the design Q) MICE cavity #4: S 21 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 (1 Frequency 200.990 MHz 199.786 MHz 201.179 MHz Window 1) 2) 1) (2 (1 (2 Frequency 200.642 MHz 199.454 MHz 200.839 MHz Page 9 MICE Project Board September 23, 2010 Alan Bross
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RF Cavity Electro-polishing Next Crucial Step Page 10 MICE Project Board September 23, 2010 Alan Bross The inside surface of each RF cavity will be electropolished Discussions under way with local company Electro-polish t ank dimensions: 12' Long x 5' Wide x 6' Deep Large SS piping weldment at AET
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RF Cavity Frequency Tuners Page 11 MICE Project Board September 23, 2010 Alan Bross 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
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Cavity Frequency Tuner Components Dual – action actuator Flexure tuner arm Actuator is screwed into the 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 12 MICE Project Board September 23, 2010 Alan Bross
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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 13 MICE Project Board September 23, 2010 Alan Bross
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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 14 MICE Project Board September 23, 2010 Alan Bross
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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 15 MICE Project Board September 23, 2010 Alan Bross
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Schedule Summary 16 MICE Project Board September 23, 2010 Alan Bross
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RF Power Systems 17 MICE Project Board September 23, 2010 Alan Bross
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RF system components Andrew Moss 2 MW Amplifier Master Oscillator Controls etc 201 MHz Cavity Module 2 MW Amplifier 201 MHz Cavity Module LBNLCERN 300 kW Amplifier HT Supplies Daresbury DL Test System At present Auxiliary Systems Not found
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Test system at Daresbury Andrew Moss
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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
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Current status of components Andrew Moss
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Predicted hall layout for RF components Andrew Moss
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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
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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
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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
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What about the RF in Magnetic Field Problem?
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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 Page 27 MICE Project Board September 23, 2010 Alan Bross
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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 Page 28 MICE Project Board September 23, 2010 Alan Bross
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805 Pillbox Post-Mortem Significant damage observed –Iris –RF coupler –Button holder However –No damage to Be window Page 29 MICE Project Board September 23, 2010 Alan Bross
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201 MHz Cavity Test Treating 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! Page 30 MICE Project Board September 23, 2010 Alan Bross
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201 MHz Cavity Running Spark Data Page 31 MICE Project Board September 23, 2010 Alan Bross B=0 Running Design Gradient MICE Gradient
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201 MHz Prototype Note: Stored energy available to sparks 100J (100X that of 805) Page 32 MICE Project Board September 23, 2010 Alan Bross
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Coupler Ceramic Page 33 MICE Project Board September 23, 2010 Alan Bross TiN Coated Ceramic
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201 MHz Cavity B Field Tests Summary Sparking @ B=0 did condition the 201 cavity Sparking @ B 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 Page 34 MICE Project Board September 23, 2010 Alan Bross
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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 resolved Page 35 MICE Project Board September 23, 2010 Alan Bross
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Acknowledgements: Derun Li, Steve Virostek (Cavities) Andy Moss (RF Power) MICE Project Board September 23, 2010 Alan Bross 36
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Backup Slides MICE Project Board September 23, 2010 Alan Bross 37
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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 #12345 (spare)* Freq. (MHz)201.084200.888201.247200.740201.707 Page 38 MICE Project Board September 23, 2010 Alan Bross
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RF measurements, Team Work! Be window installation Page 39 MICE Project Board September 23, 2010 Alan Bross
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RF Cavity Tuner System Schematic 40 MICE Project Board September 23, 2010 Alan Bross
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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 41 MICE Project Board September 23, 2010 Alan Bross
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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 42 MICE Project Board September 23, 2010 Alan Bross
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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
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Coax layout for each cavity Andrew Moss
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Damage to Coupler Ceramic Window? Page 45 MICE Project Board September 23, 2010 Alan Bross
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201 MHz Cavity Running Summary I (B=0) Design Gradient Limited by RF Power Page 46 MICE Project Board September 23, 2010 Alan Bross
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