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Transcript
A POSSIBLE CERN CONTRIBUTION TO THE MICE RADIO FREQUENCY M. Vretenar, AB/RF – April 21st, 2004 1 1. Starting assumptions: CERN RF/Linac team is involved in the LHC (Linac2 and Ions for LHC), and next priority is the SPL little or no resources are left for other projects. However, there is still a certain inventory of RF equipment recuperated from our old linacs, which can be useful for MICE, but need a thorough reconstruction and modernization. This reconstruction can be done outside CERN, but it would be more efficient and probably less expensive to do it at CERN, where some expertise is available. In consequence, here we elaborate a scenario (to be approved by CERN management) where an old Linac RF amplifier is reconstructed and modified at CERN, to possibly achieve 4 MW. The RF tests are however left for the MICE RF team (no manpower and no test stand available at CERN). In addition to this reconstructed amplifier, CERN can contribute with a certain number of 400 kW amplifiers to be used as drivers. 2 2. The CERN Linac Amplifiers (old type) Developed in the 50’s (photo of 1959) for the old Linac1. Equipped with the TH170R triode, can deliver a maximum of 2.5 MW with an anode voltage of 40 kV. The tube is water cooled, and can operate at a maximum of 0.3% duty cycle. About 3.6 m high, 1m x 1m base. From the very beginning, these amplifiers experienced problems in reaching the peak power (2.5 MW): breakdowns in the power extraction system (presently a single loop, used up to 2 MW) and in the anode resonator. The Linac2 amplifiers are an improved version of the Linac1, with more clearance in the resonator and an improved output loop. They can (sometimes…) reach the 2.5 MW. 3 3. The last Linac1 Amplifier All the Linac1 amplifiers have been reused since Linac1 decommissioning in 1992, except one: It was a spare unit, “cannibalised” of many components and stored in a hall for more than 20 years, now in quite a bad status. However most of the mechanical parts are there, and for the missing parts some drawings probably exist to remake them. 4 4. How can we possibly reach 4 MW with this unit? We propose 3 improvements: 1. Use the TH116 triode: the socket is the same as for the TH170R, gain is higher and in the data sheet this tube is rated for 5 MW. However, at 200 MHz the size of the tube (≈/4) limits the anode current and thus the power to about 4 MW. 2. Redesign the anode resonator, using a kapton capacitor as anode blocker (presently the anode is sitting on 3 teflon insulators) and possibly taking a larger diameter external tube. 3. Use 2 output loops, to reduce to 2 MW the power per output. The outputs can then either be recombined, or feed separately 2 cavities. A kapton capacitor, built in 1995 for a 100 MHz amplifier On top of that, we have to: 5 1. apply a “standard” modernization kit for Linac1 amplifiers: improved contacts and socket design. 2. Use a cathode switch circuit, if the anode voltage is not pulsed and/or introduce HOM suppressors (not foreseen in the original design). Example: The 100 MHz amplifier for the LIS RFQ (kapton capacitor + improved socket, 100 MHz, 1 MW power). 6 5. Work organisation Principle: the reconstruction is done at CERN, and then the amplifier is transferred at another laboratory for the RF tests. At CERN: 1. Collect drawings, design modifications. 2. Machine missing and new components. 3. Dismount, clean, reconstruct amplifier. 4. Assemble ventilation circuitry. 5. Assemble filament circuit and filament regulation (PLC based, CERN standard). 6. Test filament and ventilation. For these activities, we need the maximum of external support (people or money) for: draftsman/designer, mechanic, wireman. At MICE laboratory: 1. Install cathode switch and/or HOM suppressors. 2. Connect HV and RF loads. 3. Test with RF power. Success is not guaranteed, and to reach 4 MW is a difficult task that has to be taken over by the MICE RF team. This team must be involved already in the design stage. A TH116 tube from CERN can be used for the tests at CERN, but can not be sent to RAL or elsewhere, due to the recent difficulties in TH116 production. The existing kapton capacitor developed for 100 MHz could be probably used at least for a first test (available end 2004). 7 6. Estimation of cost for CERN in this scenario: Work unit definition for the CERN part (time in Man Week = MWK): 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Collect existing drawings, documentation and parts Design 200 MHz kapton capacitor Supervision of design and construction Prepare drawings of missing/modified parts Prepare general drawing Dismount and clean amplifier parts Repair damaged parts Machine missing parts Machine capacitor parts Prepare installation for rolling capacitor Roll and assemble kapton capacitor Assemble amplifer Order components for filament regulation Cabling and mounting filament regulation Cabling and mounting cavity base Test filament and cooling TOTALS Equivalent in kCHF for B,C,E Total (kCHF) for material and temporary labour A RF engineer B Mechanical designer MWK MWK 1 1 1 3 C Mechanic MWK D Electronics Technician E Wireman FSU Material cost MWK MWK kCHF 2 4 3 1 4 2 4 2 5 15 10 2 5 1 4 0.5 1 5 12 19 25 45 10 0.5 1 10 1 1 1 3 2 55 5 50 130 Conclusion: 2 man.month of CERN staff + 8 m.m of support labor + 50 kCHF or 2 man.month of CERN staff + 130 kCHF 8