LLRF Tests in the FEL and CEBAF with the Cornell Digital LLRF System - - PowerPoint PPT Presentation

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LLRF Tests in the FEL and CEBAF with the Cornell Digital LLRF System - - PowerPoint PPT Presentation

Dec 03, 2022 246 likes •543 views

LLRF Tests in the FEL and CEBAF with the Cornell Digital LLRF System JLAB: C. Grenoble, K. Davis, A. Hofler C. Hovater, T. Plawski, E. Pozdeyev, and T. Powers Cornell: Sergey Belomestnykh, Roger Kaplan, and Matthias Liepe JLAB-Cornell

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SLIDE 1

LLRF Tests in the FEL and CEBAF with the Cornell Digital LLRF System

JLAB: C. Grenoble, K. Davis, A. Hofler

  • C. Hovater, T. Plawski, E. Pozdeyev, and T. Powers

Cornell: Sergey Belomestnykh, Roger Kaplan, and Matthias Liepe

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SLIDE 2

JLAB-Cornell Collaboration Background

  • 2001-2003: Cornell, DESY and JLAB hold semi-regular

VC’s to discuss LLRF Issues.

  • 2003: Cornell develops LLRF system for CESR-C and as

a prototype for the their ERL proposal.

  • June 2004: Charlie Sinclair suggests that it would be

beneficial for the two Labs to collaborate on LLRF testing using the JLAB FEL.

  • We bite ……. Send a delegation (Rimmer, Areti,

Pozdeyev, and Hovater) to Cornell in July.

  • This is where the story begins …………….
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SLIDE 3

JLAB Energy Upgrade Task Description 2

  • 2. Use FEL-3 as a test bed to benchmark high gradient cavity

performance and RF control systems: FY04 ($75K) and FY05($50K) The second “First Generation Upgrade CM” (known as FEL-3) will be used as a test bed to benchmark the lessons learned from SL-21. These changes include: 1) doubling of the cavity cooling, and 2) doubling of the waveguide

  • cooling. Prototype components for RF control of high gradient cavities

will also be tested. Risk Reduction: Reduction in technical risk through validation of design features the high-performance cryomodules need for system cost minimization; cost and schedule risk are also reduced. Deliverable: Benchmark of 12 GeV specifications for RF and cryogenic performance, and component testing of RF control system prototypes. Completion date: 28-Feb-05

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SLIDE 4

JLAB Specific Goals for the Collaboration

As they support the12 GeV Upgrade

  • Operate a High Q SRF cavity, beam loaded with a

digital LLRF controller

  • Demonstrate acceptable phase and amplitude control
  • Demonstrate cavity recovery under strong Lorentz

detuning

  • Demonstrate cavity recovery from Cryogenic crash
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SLIDE 5

Cornell Project Goals

  • Operate LLRF system in an ERL using a

cavity with high QL

  • Benchmark system performance
  • Improve system phase noise
  • Algorithm development
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SLIDE 6

Simple RF System

Power Amplifier (klystron, tetrode etc.) Reflected Power Forward Power Superconducting Cavity Waveguide Coupler RF Controls

Master Reference Control System Interface

Field Probe Signal

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SLIDE 7

Cornell RF System

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SLIDE 8

Cornell Digital Card Cornell ADC Receiver Card

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SLIDE 9

Cornell LLRF System

LLRF System in VME Crate System Clock Quadrature Modulator

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SLIDE 10

CESR-C Cryomodule Prototype Single Cell Copper Cavity ~ 499 MHz

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SLIDE 11

The Original Plan !

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SLIDE 12

Project Facts

  • Project used existing JLAB RF control module

for source RF, HPA control and cavity interlocks.

  • FEL03-3 was chosen (high gradient) and a stub

tuner installed.

  • Cornell LLRF was stand alone, so no interface to

EPICS was needed (beyond what the JLAB LLRF system provided).

  • JLAB would provide all of the hardware

adaptations to make the Cornell LLRF compatible with our HPA-cavity system.

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SLIDE 13

JLAB Tasks for JLAB-Cornell LLRF Tests

  • Design and build receiver and transmitter

(C. Hovater, C. Cox)

  • Design and build low phase noise LO, IF

synthesizer and clock (T. Plawski )

  • Cavity characterization, microphonic and

mechanical modes (K. Davis, T. Powers)

  • PZT Driver/Amplifier (K. Davis)
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SLIDE 14 550 MHz LPF

CMK-705s DC Block ZFL-500HLN LO 1485.1 MHz 20 dBm A TTN TBD RF 1497 MHz 20 dBm Max 17 dBm

  • 5.5 dBm

15 dB A TTN

550 MHz LPF

DC Block ZFL-500HLN A TTN TBD RF 1497 MHz 20 dBm Max Forward Power

  • 5.5 dBm

15 dB A TTN

550 MHz LPF

DC Block ZFL-500HLN A TTN TBD RF 1497 MHz 20 dBm Max Reflected Power

  • 5.5 dBm

15 dB A TTN 6 dB Directional Coupler 3-W ay Divider ZFM-2000 ZFM-2000

1497 MHz BPF

DC Block ZFL-2000 A TTN TBD IF 11.9 MHz 0 dBm Max Reference 0 dBm 15 dB A TTN ZFM-2000 IF 11.9 MHz IF 11.9 MHz IF 11.9 MHz RF 1497 MHz

1497 MHz Receiver Transmitter LO, IF and Clock Synthesizer

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SLIDE 15
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SLIDE 16

The FEL Test Station & LLRF Rack

Cornell LLRF FEL Zone 03

LLRF System VME Crate Quadrature Modulator Transceiver System Clock & Synthesizer

Blue: JLAB Supplied

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SLIDE 17

1st LLRF Test in FEL w/o Beam (November)

  • Demonstrated acceptable phase and amplitude control with a digital LLRF

controller

Phase: ~ 0.02 degrees rms. (Required 0.24 degrees rms.) Amplitude: ~ 3 x 10-4 rms. (Required 4.5 x 10-4 rms.)

  • Demonstrated cavity recovery under strong Lorentz detuning (Fast turn on

algorithm)

0 to 12 MV/m in ~ 80 ms using Piezo Tuner (PZT)

  • Demonstrated cavity recovery from Cryogenic crash (Resonance hunting

algorithm)

Recovered cavity from 30 kHz away from nominal 1497 MHz

  • Operated cavity at high QL ~ 1x108

LLRF system controlled field to required stability

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SLIDE 18

Why Lorentz Compensation is Needed

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

  • 1,000
  • 800
  • 600
  • 400
  • 200

200

Detuning (Hz) E n e r g y C o n te n t ( N o r m a liz e d ) CEBAF 6 GeV CEBAF Upgrade

  • For the CEBAF Upgrade (QL = 2 x

107) if KL = 2 then the frequency deflection at 20 MV/m (the required gradient) would be 800 Hz. This is greater than 10 cavity bandwidths away from nominal 1497 MHz!

  • Considering that at one bandwidth you

need twice the power to operate, it is

  • bvious why this can be a problem,

especially for quick cavity recovery.

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SLIDE 19

Cavity Recovery with QL = 2x107

Recovery test: 0 to 12 MV/m

  • 2.0

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0

0.000 0.020 0.040 0.060 0.080 0.100 0.120 0.140 0.160

time [sec] gradient [MV/m] phase gradient Pforward

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SLIDE 20

Cavity Recovery with QL ~ 1 x 108

High Q/ Recovery test 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 0.5 1 1.5 2 2.5 3 3.5 4 4.5 time [sec] gradient [MV/m] gradient

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SLIDE 21

Gradient Stability w/o and w PZT

Note: there was no electronic feedback on and cavity QL was ~ 1x108!

Cavity Gradient PZT Turned on

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SLIDE 22

2nd Test Run FEL & CEBAF (January)

  • CEBAF Operations
  • Operated LLRF system (10 MV/m) at beam currents up to 400 uA
  • Saw no appreciable difference in field stability w/wo current

Amplitude: ~ 2x10-4 rms. Phase: < ~ 0.05 degrees rms.

  • Ran production beam to Hall B during the test
  • Cavity QL was adjusted to 4.2x107 making the system 5x more

susceptible to the background microphonics.

  • FEL Operations
  • Operated LLRF system (12.3 MV/m) at beam currents up to 5 mA

in recirculated mode.

  • Tests Included:

Operation at QL’s of 2x107 and 1.2x108 Phasing +/-40 degrees off crest

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SLIDE 23
  • M. Liepe/Cornell
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SLIDE 24
  • M. Liepe/Cornell
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SLIDE 25
  • M. Liepe/Cornell
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SLIDE 26
  • M. Liepe/Cornell
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SLIDE 27

The Team

MCC The “Big” Screen South Linac

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SLIDE 28

Summary

  • Cavity and beam testing was successful.

The digital system controlled cavity field within specification through a variety of conditions (QL, w & w/o beam etc.).

“A digital LLRF system has no problem controlling

cavity field even with the most horrendous microphonics.”

  • Both Labs benefited from the collaboration and

we are discussing future tests.

Helpful assistance from the CEBAF & FEL operations staff and beam time from Nuclear Physics made these tests possible