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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,

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Thomas Jefferson National Accelerator Facility

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Charles E. Reece Charles E. Reece Charles E. Reece Charles E. Reece

SRF Workshop, July 11, 2005 SRF Workshop, July 11, 2005

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

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Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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Thomas Jefferson National Accelerator Facility

6 GeV CEBAF 11

CHL CHL-

  • 2

2

12

Upgrade magnets Upgrade magnets and power and power supplies supplies

Two 0.6 GV linacs 1.1

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Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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Thomas Jefferson National Accelerator Facility

Cryomodule Requirements for 12 GeV CEBAF Cryomodule Requirements for 12 GeV CEBAF

  • Voltage:

≥ 109 MV CW, 1497 MHz

  • Heat budget:

— 2.07 K ≤ 300 W — 50 K ≤ 300 W

  • Tuner resolution: ≤ 2 Hz
  • FPC:

7.5/13 kW

  • HOM damping:

Z < 6 x 108 Ω, dipoles, to avoid BBU

  • Length

~8.5 m between beamline flanges

Ten new CW cryomodules are required

(26 W static, 241 dynamic, 33 W contingency) (29 W/cavity + 9 W input couplers)

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Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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Thomas Jefferson National Accelerator Facility

Evolution of CEBAF CW Cryomodule Evolution of CEBAF CW Cryomodule Design Parameters Design Parameters

  • 1st Prototype – (SL21) installed in

CEBAF South Linac — CEBAF Cavity Shape with 2 HOM couplers — Al-Mg Seals on beamline — 8 kW Waveguide — New Tuner Design with coarse and fine tuning capability — Implemented space frame concept — Re-used end can design (200 W rating)

  • 2nd Prototype – (FEL03) installed in

FEL — Improved piping design — Added He-II heat station to FPC waveguides

  • 3rd Prototype – (Renascence) built and

ready for testing — Implemented High-Gradient and Low-Loss cavity shapes with 4 HOM couplers — Improved HOM feedthroughs — Cold Tuner (coarse/fine) — 13 kW Waveguide — Revised Helium Vessel Design — Low-profile Radial-Wedge flange

  • n beamline

— Improved Thermal Shield Design — Incremental improvements to vacuum vessel for fiducialization — End cans useable up to 350 W (verified by testing) — Serpentine-shaped Al-Mg gasket

  • n FPC rectangular waveguide

— All Al-Mg Seals (no indium)

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Thomas Jefferson National Accelerator Facility

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)
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Thomas Jefferson National Accelerator Facility

Renascence-style Cold Mass Renascence-style Cold Mass

Helium circuit and cavity beamline

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Thomas Jefferson National Accelerator Facility

Flange sealing improvements Flange sealing improvements

  • Radial wedge clamp

—Low profile for beamline flanges

US Pat. # 6,499,774

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Thomas Jefferson National Accelerator Facility

LHe LHe Header Piping eader Piping

Ti / SST Transition, 3.5” IPS ~ 5” OD Bellows, between each cavity Return Header, 5” OD SST Tube x 0.063” Wall Supply Line, 1.5” OD SST Tube x 0.063” Wall ~ 1.5” ID Bellows, between each cavity Liquid Level Standpipe

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Thomas Jefferson National Accelerator Facility

Comparison : Original & Upgrade Helium Vessels Comparison : Original & Upgrade Helium Vessels

  • Two cavities per helium vessel
  • Five cells per cavity
  • Indium vacuum seals
  • Beamline components
  • Beamline-to-helium
  • Beamline-to-insulating vacuum
  • Bellows between cavity pairs
  • Tuner mechanism immersed in

liquid helium

  • One cavity per helium vessel
  • Seven cells per cavity
  • Hard metal vacuum seals
  • Beamline components
  • Beamline-to-insulating vacuum
  • Beamline-to-air (FPC)
  • No bellows between cavities
  • Tuner mechanism in insulating

vacuum space CEBAF Helium Vessel Assembly Upgrade Helium Vessel Assembly

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Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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Thomas Jefferson National Accelerator Facility

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

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Thomas Jefferson National Accelerator Facility

LL Cavity System

Warm ceramic RF window Cu-plated waveguide between RT and 2 K l/4 waveguide RF input coupler Piezo element (2) Stepper motor tuner drive Titanium helium vessel RF reference probe HOM coupler (4)

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Thomas Jefferson National Accelerator Facility

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 1000/16/40 VS25) Dicronite-coated Beryllium Copper Drive Screw, M12 x 1.5

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Thomas Jefferson National Accelerator Facility

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 103 (2x/day, 365 day/yr, 40 yrs) Piezo Actuator 7.0 x 106 (20x/hr,24 hr/day, 365 d/yr, 40 yrs) Radiation Limit (rads) > 106 > 108 Tuning Method Tension

  • Load at full stroke (kN)

14.0 ~ 22.2 Travel (mm) 2 3.3

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Thomas Jefferson National Accelerator Facility

Input RF Waveguide Input RF Waveguide

Renascence Waveguide

Bellows Bellows 50K Heat St 50K Heat Station ation Stiffeners Stiffeners Warm Warm Window Window O-ring O-ring Groove Groove Protective Protective Cover Cover

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Thomas Jefferson National Accelerator Facility

Thermal Analysis of Input RF Waveguide Thermal Analysis of Input RF Waveguide

Nominal Conditions (12GeV) Worst- Case Conditions (12GeV) (Designed for 13kW)

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Thomas Jefferson National Accelerator Facility

HOM coupler probe/feedthrough HOM coupler probe/feedthrough

  • DESY-style HOM coupler depends on

resonant rejection of the fundamental. — Qe-fundamental > 3×1011 — Typical Qe-fundamental > 1 ×1012

  • Operation of the SNS cavities with CW RF

had serious heating problems with the HOM 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.

  • The pickup probe is exposed to significant

fundamental fields (10% of Hmax), so must be superconducting and thermally stabilized.

T= 2.01 K 1.E+09 1.E+10 1.E+11 5 10 15 20 25 Eacc [MV/m] Qo Without Cu outputs in HOMs Heating of Cu HOM outputs+ bad feedthroughs

Field emissio n

  • Initial testing of Renascence prototypes

with Cu HOM coupler probes showed serious Q degradation and long thermal time constants.

drawin g

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Thomas Jefferson National Accelerator Facility

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:

Confidently better, and available < 6.9 K < 5 K JLab sapphire- dielectric design Acceptable and demonstrated < 9.2 K 5.5 K JLab/CeramTech design Not viable ! 16 K > 13 K Kyocera design used

  • n TTF and SNS

(pulsed RF)

Ttip @ 20 mW Ttip @ 10 mW

RF Feedthrough Design

Used on Renascence

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Thomas Jefferson National Accelerator Facility

HOM coupler probe/feedthrough HOM coupler probe/feedthrough

  • JLab single-crystal-sapphire dielectric HOM probe feedthroughs

JLab licensed the technology to Accel Instruments, GMBH, for commercial exploitation/application

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Thomas Jefferson National Accelerator Facility

Renascence Cavity Fabrication Renascence Cavity Fabrication

  • Production set

—5 HG and 4 LL 7-cell cavities —RRR 347 Nb —Nb55Ti flanges and helium vessel transition plate —Endgroups on HG and LL are identical —Developed standard production drawings and procedures —Refined assembly sequence details for efficiency and QA —Mix of internal/external shop machining —All in-house chemistry and EBW

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Thomas Jefferson National Accelerator Facility

Cavity Testing - Cavity Testing - HG

  • Planned 12 GeV

cavity temp: 2.07 K

  • Allocated

dynamic heat budget: 29 W HG design

  • No MP

encountered

  • Only HG004 was

FE-limited

  • Q-drop 18-20

MV/m observed without radiation 7-cell HG Cavities - VTA Performance

1.0E+09 1.0E+10 1.0E+11 5 10 15 20 25

Gradient (MV/m) Q0

12 GeV Project Spec HG 29 Watts HG002 HG003 HG004 HG005 HG006 HG001 HG007 T= 2 K

HG 29 W

7/6/05 cer

CEBAF spec

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Thomas Jefferson National Accelerator Facility

Cavity Testing - Cavity Testing - LL

LL design

  • No MP

encountered

  • No FE-limited

cavities

  • Q-drop 17-21 MV/m
  • bserved without

radiation

  • 120 C bake

improved Q0 < 15 MV/m only (Input coupler heating suspected)

LL Cavities for Renascence - VTA Performance

1.0E+09 1.0E+10 1.0E+11 5 10 15 20 25

Gradient (MV/m) Q0

12 GeV Project Spec LL 29 Watts LL001 LL002 LL003 LL004 T= 2.07

LL 29 W

3/28/05 cer

CEBAF spec

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Thomas Jefferson National Accelerator Facility

Microphonics Microphonics

For lightly beamloaded CW accelerator applications the expense of RF regulation is very significantly influenced by microphonics. One would like to approach simply matching RF power to the beam with little overhead. Understanding and controlling microphonics is an important part of system design.

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Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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Thomas Jefferson National Accelerator Facility

Microphonics Microphonics

Reduced microphonics

— Elimination of inter- cavity bellows — Addition of cavity stiffening rings — Elimination of HOM waveguide elbows — Suspension from space frame rather than vacuum tank Microphonic detuning measured to be factor of 3 less in upgrade design CM

SL21, Cav 1, Background Microphonics Histogram (CEBAF Tunnel)

0.00E+00 5.00E-03 1.00E-02 1.50E-02 2.00E-02 2.50E-02 3.00E-02 3.50E-02

  • 6
  • 4
  • 2

2 4 6 Cavity Detuning (Hz) Probability Std Dev = 1.261588 Hz

Microphonic Microphonic detuning histogram detuning histogram Upgrade cryomodule SL21 in CEBAF Upgrade cryomodule SL21 in CEBAF Cavity detuning (Hz) Cavity detuning (Hz)

σ = 1.26 Hz 1.26 Hz

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Thomas Jefferson National Accelerator Facility

Optimum Matching with Microphonics Optimum Matching with Microphonics

Design optimization

— Design choice for input coupling strength (Ql) depends strongly on microphonics < 15 Hz detuning is credible for the upgrade CM design. With Ql of 3.4*107 ±1.5 dB, operation to 25 MV/m CW will be possible with 13 kW klystrons.

10 kW linear RF Power for 460 uA of beam and LL 7-cell

0 Hz 50 Hz 1 10 100

Loaded Q (10^6) Allowed detuning

21.2 MV/m 25 MV/m 15 Hz 19.25 MV/m 27 MV/m 25 Hz 23.5 MV/m

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Thomas Jefferson National Accelerator Facility

String Assembly String Assembly

  • Waveguide/window units preassembled and leak checked
  • String assembled - one cavity per day
  • No issues during assembly
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Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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Thomas Jefferson National Accelerator Facility

Transfer of cavity string Transfer of cavity string

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Thomas Jefferson National Accelerator Facility

Cryomodule Assembly Cryomodule Assembly

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Thomas Jefferson National Accelerator Facility

Cryomodule Assembly

Beamline mid-point Interface between cavities

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Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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Thomas Jefferson National Accelerator Facility

Cryomodule Assembly Cryomodule Assembly

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Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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Thomas Jefferson National Accelerator Facility

Cryomodule Assembly Cryomodule Assembly

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Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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Thomas Jefferson National Accelerator Facility

Cryomodule Assembly Cryomodule Assembly

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Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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Thomas Jefferson National Accelerator Facility

Cryomodule Assembly Cryomodule Assembly

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Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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Thomas Jefferson National Accelerator Facility

Cryomodule Assembly Cryomodule Assembly

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Thomas Jefferson National Accelerator Facility

Cryomodule Assembly Cryomodule Assembly

Sealing up vacuum tank July 7, 2005 Sealing up vacuum tank July 7, 2005

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Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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Thomas Jefferson National Accelerator Facility

Plans Plans

  • Renascence assembly complete this week
  • Testing in JLab CMTF (17 kW CW rf available) – 6 week

program begins next week

  • Static heat loads – primary and shield
  • Qe FPC
  • Tuner function – mechanical and piezo
  • Cavity performance – Q0 vs. Eacc
  • Dynamic cryogenic loads – including capacity challenge
  • HOM Qext each port - polarization analysis, potential

count reduction

  • Magnetic shielding effectiveness
  • Microphonic analysis (accelerometers on one cavity)
  • Microphonic compensation test with piezo & prototype

LLRF

  • Installation and commissioning in September
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Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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Thomas Jefferson National Accelerator Facility

Summary Summary

  • Renascence, the final prototype cryomodule for the

12 GeV Upgrade, has built on experience with “SL21”, “FEL03”, and the SNS production run.

  • This latest version includes several design

improvements

  • Cavity performance spec was met in VTA tests
  • Assembly is complete
  • Documentation is in good order
  • Testing and commissioning now begins
  • We anticipate a better-than-100 MV CW cryomodule

25 MV/m x 0.7 m x 8 cavities = 140 MV, with 275 W @ 2 K A credible goal !

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Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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Thomas Jefferson National Accelerator Facility

Acknowledgements Acknowledgements

  • Cryomodule design

— Al Guerra — Joe Preble — Ed Daly — Jean Delayen — Robbie Hicks — Danny Machie — Jim Henry — Jim Takas — Tim Rothgeb

  • Cavity design

— Jacek Sekutowicz — Peter Kneisel — Gigi Ciovati

  • Cavity fabrication

— Bob Manus — Steve Manning — Rich Bundy — Sam Morgan — Larry Turlington — Gary Slack

  • HOM feedthroughs

— Genfa Wu — Larry Phillips — Tom Elliott

  • Cavity processing and testing

— John Mammosser — Danny Forehand — Byron Golden — Cliff Burden — Ralph Afanador — Isiah Daniels — Chris Graves — Pam Morrison — Joe Ozelis — Pete Kushnick

  • HOM analysis

— Haipeng Wang

  • Microphonic analysis

— Kirk Davis

  • Cryomodule testing

— Mike Drury — Tom Powers — Christiana Grenoble

  • QA and Data Management

— Brian Carpenter — Bonnie Madre — Valerie Bookwalter

  • Cryomodule assembly

— Kurt Macha — Jeff Saunders — John Hogan — John Fischer — Ken Worland — Jody Brock — Jim Gordon — Debbie Hedrick — Frank Humphrey — Henry Whitehead — Dave Bigelow — Leonard Page — Henry Whitehead — Mike McCrea — Charles Lassiter — Steve Dutton — Jeff Campbell

  • Management support

— Warren Funk

Funded under Contract

  • No. DE-AC05-84ER-40150