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Photoinjector for the ILC test facility at Fermilab

Photoinjector for the ILC test facility at Fermilab. Sergei Nagaitsev Fermilab May 24, 2007. Fermilab NML plans. Fermilab is constructing the NML facility at the existing building (called New Muon Lab) for the ILC tests and generic accelerator research

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Photoinjector for the ILC test facility at Fermilab

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  1. Photoinjector for the ILC test facility at Fermilab Sergei Nagaitsev Fermilab May 24, 2007

  2. Fermilab NML plans • Fermilab is constructing the NML facility at the existing building (called New Muon Lab) for the ILC tests and generic accelerator research • The NML is being constructed to address primarily the ILC S2 R&D list • However, our plans go beyond S2. We would like to include elements of S4 R&D tasks (crab-cavities), diagnostics development, personnel training, and accelerator R&D. • The NML facility is staged (1 CM, 2 CMs etc); when complete, it would include 1 (or 2) rf units running ILC-like beam at 5 Hz. • 1 rf unit with beam requires building an extension tunnel and a new cryo-plant • The progress is resource limited S. Nagaitsev

  3. NML inside (now) S. Nagaitsev

  4. Outline of our plans • Cryomodule delivery • 1st (Type 3+) cryomodule is planned to be delivered in fall, 2007 • 2nd (Type 3+) CM – summer 2008 • 3rd (ILC Type 4) CM – Mid FY09 • Replace all three CMs with ILC Type 4+ in FY2010 • The NML facility will start as a Cryomodule Test Stand in FY07-08 • FY08: add beam; start civil construction of the building extension • Convert to an ILC RF Unit beam test facility in FY11 S. Nagaitsev

  5. NML Schedule (Phase-1) • Phase - 1 (FY07 thru early FY08) • Prepare Facility for Testing of Capture Cavity II (CCII) and 1st Cryomodule (CM1) without Beam • Building Infrastructure (AC Power, Water, Air, Mechanical) • Electrical Infrastructure (Racks, Trays, Cables) • Build Cave to Test these Devices (~ 3/4 of Full Cave) • RF Systems (3MW for CM and 300kW for CCII) • Cryogenic System (1st Refrigerator, Feed Can, Feed Cap, End Cap, Distribution) • Control Room • LLRF, Controls, Safety Systems, Instrumentation (non-beam) • Move CCII from Meson Detector Building (MDB) to NML • Cool-down and Power Testing S. Nagaitsev

  6. Phase 1: 1st CM (end of CY07) A used 3-MW Klystron, 10-MW, 1.5-ms modulator CC2 RF system Capture cavity 2 in its final location for the injector Type 3+ cryomodule S. Nagaitsev

  7. NML Schedule (Phase-2 & 3) • Phase - 2 (FY08) • Testing of 1st and 2nd Cryomodule without Beam, Prepare Facility for Beam • Receive, Install, Power, Cool-down 1st Cryomodule • Install New Gun and Relocate Injector to NML • Extend Cave • Install Beam Lines and Dumps • Install Additional RF Systems needed for CCI and Gun • Receive, Install, Power, Cool-down 2nd Cryomodule • Begin Building Extension needed for Phase-3 • Phase - 3 (FY09) • Testing of Full RF Unit with Beam • Complete Building Extension • Begin Testing with Beam • Install 3rd Cryomodule • Upgrade Cryomodule RF system to 10 MW S. Nagaitsev

  8. Two CMs with beam The existing building is perfect for testing two cryomodules with ILC-like beam. The building can be extended to fit 3 cryomodules. S. Nagaitsev

  9. ILC-like beam? • 3.2 nC/bunch @3 MHz, up to 3000 bunches @ 5Hz • Bunch length: 300-μm rms • Transverse emittance: not important (~5 μm) • Energy: 30-40 MeV (to avoid overfocusing in the CM operating at 31 MV/m) • Need “known and frozen” beam parameters at the cryomodule entrance S. Nagaitsev

  10. Existing Fermilab Photoinjector The existing photoinjector and the laser will be moved to NML in 2008. 13m (CC-1) S. Nagaitsev

  11. Fermilab Photo Injector • The PhotoInjector has been in operation since late 90’s and has been a training ground for SCRF technology • Provides 17MeV bunches (up to few hundred) at 1 MHz rate at 1 pulse/sec • Two 1.3-GHz klystron-based RF systems power the RF Gun and Capture Cavity • RF systems will be moved to NML in 2008 Capture Cavity and beamline S. Nagaitsev

  12. Existing rf gun • Very high dark current • rf break down for pulses longer than 300us • We will not use this gun cavity at NML RF Gun prior to solenoid installation S. Nagaitsev

  13. Proposed NML Injector Layout 22m (CC-1, CC-2) (intended initially for ILC crab cavity tests) P. Piot S. Nagaitsev

  14. NML injector layout 1 – Gun cavity, 2 – Coaxial rf coupler, 3 – dark current kicker, 4 – laser mirror cross, 5 – current monitor & BPM, 6 - collimator, 7 – Tesla cavity (CC1), 8 – Tesla cavity (CC2) 6 4 8 1 2 5 3 7 S. Nagaitsev

  15. NML cathode system Gun Transfer Transport System GUN S. Nagaitsev

  16. Fermilab plans for the rf gun • We are planning to copy (and improve) a DEZY-PITZ gun • RF gun sub-systems needed at NML: • Cathode system -- need new, will be supplied by INFN Milano • UV laser system -- exists, needs upgrades • Gun cavity – need new, will be supplied by DESY • Focusing solenoids – need new • Coaxial coupler – need new • Dark current kicker – need new • Laser mirror cross – need new • RF system (5-MW or more, 1.5-ms modulator) – exists (needs updrades) • Water, temperature control system -- exists S. Nagaitsev

  17. Cathode system • The cathode system is being provided to us by INFN-Milano. • Two sub-systems: • A stand-alone vacuum chamber for cathode preparation with Cs and Te sources • A cathode loading chamber connected to the gun cavity. • Discussions underway on how to redesign the cathode socket (and spring) in the gun cavity. Goal: reduce the dark current • Would like to “hide” the rf contact spring • See next slides S. Nagaitsev

  18. RF spring contact (from D. Sertore, INFN) • Two different spring types have been used, in the same insert! • The insert was designed for a WELDED Watch-band type spring. • Cantend coil spring • CuBe uncoated. • Available coated with Ag, Au etc… • Welded by the manufacturer • Watch-band type • CuBe hard, silver coated spring • Difficult to weld (becomes hard) • Critical number of convolutions S. Nagaitsev

  19. Our latest proposal to INFN and DESY Two springs – one for centering and one locking S. Nagaitsev

  20. UV laser system • Already have at photoinjector • Needs some upgrading • Will be moved to NML in Jan 2008 • Can run a single gaussian pulse or stacked (4) pulses at 3MHz S. Nagaitsev

  21. Gun cavity • Have all DESY drawings at Fermilab. Do not yet have a complete set of procedures (brazing, tuning etc) • Would like to make some modifications to design: cathode socket, rf probe, reduce max. fields • Will take time to develop expertise. • DESY has agreed to make a gun cavity for us at DESY. • Currently negotiating small changes to their design (cathode) • We will start making our own gun cavity and the coupler shortly after DESY will start the manufacturing. • KEK STF has asked us to supply a gun cavity for them. No official agreement yet. S. Nagaitsev

  22. RF probe - possible location S. Nagaitsev

  23. Focusing solenoids • Will make two identical solenoids (like main solenoid above) instead of two different ones • Present bucking coil design interferes with a possible rf probe installation at the gun cavity cathode wall. • Solenoids can be ordered from Danfysik (they have drawings, fixtures) $30k each • PS needed: 500A, 50V, 10 ppm 27k Eur S. Nagaitsev

  24. Laser mirror • Have drawings from DESY • Laser mirror alignment will be difficult because coaxial coupler inner diameter is small S. Nagaitsev

  25. RF system • Already have a 5MW Klystron at the photoinjector • TH 2104C • Need a new 1.5-ms modulator and a pulse transformer • Planning to build at Fermilab • Plan to run the gun at 40 MV/m at the cathode • From DESY simulations: gradient ≈ 23 MV/m·(P[MW])1/2 • For 40 MV/m need about 3 MW. For conditioning need more power. S. Nagaitsev

  26. Water system • Temperature stability is crucial: • Average power at 1ms flattop, 5 Hz: 15 kW • Simulations freq. shift: -23 kHz per one-degree C • Plan temperature control to 1F (0.5 degree C) S. Nagaitsev

  27. Overall summary • Would like to have beam at NML in Apr 2008 • The rf gun will be capable of providing ILC-like beams. For 4-stacked laser pulses at 40 MV/m @ cathode • 3.2 nC per bunch • 4.2 MeV kinetic energy at gun exit • 4-μm rms norm emittance • 2.4 mm rms bunch length • 1.2% rms momentum spread S. Nagaitsev

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