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A 100 MV Cryomodule For CW Operation A 100 MV Cryomodule For CW Operation A 100 MV Cryomodule For CW Operation A 100 MV Cryomodule For CW Operation Charles E. Reece Charles E. Reece Charles E. Reece Charles E. Reece SRF Workshop, July 11, 2005 SRF Workshop, July 11, 2005 Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

12 11 6 GeV CEBAF Upgrade magnets Upgrade magnets and power and power supplies supplies CHL- -2 2 CHL 1.1 Two 0.6 GV linacs Thomas Jefferson National Accelerator Facility Page 2 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Cryomodule Requirements for 12 GeV CEBAF Cryomodule Requirements for 12 GeV CEBAF Ten new CW cryomodules are required ≥ 109 MV CW, 1497 MHz • Voltage: • Heat budget: (26 W static, 241 dynamic, 33 W contingency) — 2.07 K ≤ 300 W (29 W/cavity + 9 W input couplers) ≤ 300 W — 50 K • Tuner resolution: ≤ 2 Hz • FPC: 7.5/13 kW Z < 6 x 10 8 Ω , dipoles, to avoid BBU • HOM damping: • Length ~8.5 m between beamline flanges Thomas Jefferson National Accelerator Facility Page 3 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Evolution of CEBAF CW Cryomodule Evolution of CEBAF CW Cryomodule Design Parameters Design Parameters 1st Prototype – (SL21) installed in 3rd Prototype – (Renascence) built and • • CEBAF South Linac ready for testing — CEBAF Cavity Shape with 2 HOM — Implemented High-Gradient and couplers Low-Loss cavity shapes with 4 HOM couplers — Al-Mg Seals on beamline — Improved HOM feedthroughs — 8 kW Waveguide — Cold Tuner (coarse/fine) — New Tuner Design with coarse and fine tuning capability — 13 kW Waveguide — Implemented space frame concept — Revised Helium Vessel Design — Re-used end can design (200 W — Low-profile Radial-Wedge flange rating) on beamline 2nd Prototype – (FEL03) installed in — Improved Thermal Shield Design • FEL — Incremental improvements to — Improved piping design vacuum vessel for fiducialization — Added He-II heat station to FPC — End cans useable up to 350 W waveguides (verified by testing) — Serpentine-shaped Al-Mg gasket on FPC rectangular waveguide — All Al-Mg Seals (no indium) Thomas Jefferson National Accelerator Facility Page 4 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Cryomodule Design Overview Cryomodule Design Overview Cavity String • • Compact beamline design enables 5.6 m active cavity length between beamline flanges 8.5 m apart • 8 cavities with hermetic sealing valves on end of string • No inter-cavity bellows • New beamline flange design (radial wedge clamp) Thomas Jefferson National Accelerator Facility Page 5 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Renascence-style Cold Mass Renascence-style Cold Mass Helium circuit and cavity beamline Thomas Jefferson National Accelerator Facility Page 6 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Flange sealing improvements Flange sealing improvements Radial wedge clamp • — Low profile for beamline flanges US Pat. # 6,499,774 Thomas Jefferson National Accelerator Facility Page 7 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

LHe LHe Header Piping eader Piping Return Header, ~ 5” OD Bellows, Ti / SST 5” OD SST Tube x between each Transition, 3.5” 0.063” Wall cavity IPS Supply Line, ~ 1.5” ID Bellows, Liquid Level 1.5” OD SST Tube between each Standpipe x 0.063” Wall cavity Thomas Jefferson National Accelerator Facility Page 8 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Comparison : Original & Upgrade Helium Vessels Comparison : Original & Upgrade Helium Vessels CEBAF Helium Vessel Assembly Upgrade Helium Vessel Assembly • Two cavities per helium vessel • One cavity per helium vessel • Five cells per cavity • Seven cells per cavity • Indium vacuum seals • Hard metal vacuum seals • Beamline components • Beamline components • Beamline-to-helium • Beamline-to-insulating vacuum • Beamline-to-air (FPC) • Beamline-to-insulating vacuum • No bellows between cavities • Bellows between cavity pairs • Tuner mechanism in insulating • Tuner mechanism immersed in vacuum space liquid helium Thomas Jefferson National Accelerator Facility Page 10 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Cryomodule Design Overview Cryomodule Design Overview Internal support structure - Space Frame • — Cold Mass Support (cavities, helium distribution, shields, …) — Cavity Alignment relative to fiducials — Roll in and out of vacuum vessel Thomas Jefferson National Accelerator Facility Page 11 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

LL Cavity System RF reference probe Stepper motor tuner drive l/4 waveguide RF HOM coupler (4) input coupler Piezo element (2) Titanium helium vessel Cu-plated waveguide between RT and Warm ceramic 2 K RF window Thomas Jefferson National Accelerator Facility Page 13 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Tuner and Helium Vessel Assy Tuner and Helium Vessel Assy Motor: Phytron VSS-52, 52 in*oz., Harmonic Drive: HDC-14-100-2ASP With 100:1 Reduction Piezo Actuator in SST Cartridge – 40mm Stack (Model # PSt Dicronite-coated 1000/16/40 VS25) Beryllium Copper Drive Screw, M12 x 1.5 Thomas Jefferson National Accelerator Facility Page 15 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Tuner Requirements Tuner Requirements Parameter Requirement Actual � Range (kHz) 400 1000 � Resolution (Hz) < 100 < 3 � Backlash (Hz) < 25 < 10 Piezo Range (Hz) 1000 1200 (est.) � Piezo Resolution (Hz) < 1 < 1 (est.) � Cyclic Life Mechanical Tuner 29 x 10 3 (2x/day, 365 day/yr, 40 yrs) 7.0 x 10 6 (20x/hr,24 hr/day, 365 d/yr, 40 yrs) Piezo Actuator � Radiation Limit (rads) > 10 6 > 10 8 � Tuning Method Tension - � Load at full stroke (kN) 14.0 ~ 22.2 � Travel (mm) 2 3.3 Thomas Jefferson National Accelerator Facility Page 16 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Input RF Waveguide Input RF Waveguide Protective Protective Cover Cover 50K Heat Station 50K Heat St ation Stiffeners Stiffeners Renascence Waveguide Warm Warm O-ring O-ring Bellows Bellows Window Window Groove Groove Thomas Jefferson National Accelerator Facility Page 17 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Thermal Analysis of Input RF Waveguide Thermal Analysis of Input RF Waveguide (Designed for 13kW) Worst- Case Conditions (12GeV) Nominal Conditions (12GeV) Thomas Jefferson National Accelerator Facility Page 18 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

HOM coupler probe/feedthrough HOM coupler probe/feedthrough DESY-style HOM coupler depends on • resonant rejection of the fundamental. — Q e-fundamental > 3 × 10 11 — Typical Q e-fundamental > 1 × 10 12 drawin Operation of the SNS cavities with CW RF • had serious heating problems with the HOM g couplers – probes were Cu, weak thermal conduction through the sealing dielectric. HOM couplers (4) were moved closer to end • cells in HG and LL for maximum damping. T= 2.01 K The pickup probe is exposed to significant 1.E+11 • fundamental fields (10% of H max ), so must Without Cu outputs in HOMs Heating of Cu HOM outputs+ bad feedthroughs be superconducting and thermally Qo stabilized. 1.E+10 Initial testing of Renascence prototypes Field • with Cu HOM coupler probes showed emissio serious Q degradation and long thermal n time constants. 1.E+09 0 5 10 15 20 25 Eacc [MV/m] Thomas Jefferson National Accelerator Facility Page 19 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

HOM coupler probe/feedthrough HOM coupler probe/feedthrough Heat load (BCS) on Nb probe in HG & LL cavity at 20 MV/m CW: • 2 - 5 mW @ 6 K — — 11- 20 mW @ 8 K Feedthrough thermal conduction is critical • Testing and FE modeling of three designs: • T tip @ T tip @ RF Feedthrough 10 mW 20 mW Design Kyocera design used on TTF and SNS > 13 K 16 K Not viable ! (pulsed RF) JLab/CeramTech Acceptable and 5.5 K < 9.2 K design demonstrated JLab sapphire- Confidently better, < 5 K < 6.9 K dielectric design and available Used on Renascence Thomas Jefferson National Accelerator Facility Page 20 Operated by the Southeastern Universities Research Association for the U.S. Department of Energy