RF Field Control for 12 GeV Upgrade Tom Powers K. Davis, J. - - PowerPoint PPT Presentation

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

RF Field Control for 12 GeV Upgrade

Tom Powers

• K. Davis, J. Delayen, H. Dong, A, Hofler,
• C. Hovater, S. Kauffman, G. Lahti,
• J. Musson, T. Plawski,

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

12 GeV Cryomodule LLRF Requirements

Tight cavity field control is needed to meet CEBAF’s energy spread specification.

NA 4.5 x 10-4 Amplitude (uncorrelated) NA 2.2 x 10-5 Amplitude (correlated) 3.0o 0.5o (rms.) Phase Stability (uncorrelated) infinite 0.24o (rms.) Phase Stability (correlated) Slow > 1s Fast < 1s

Parameter

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

12 GeV Requirements (cont’d)

• Fault Recovery < 1 s

– Must compensate for large Lorentz detuning on cavity turn on.

• Keep down-time low

– Intelligent diagnostics that can quickly isolate problem RF-cavity systems. – Hot swap capable for all modules.

• Seamless integration with existing RF-Klystron-Cavity

systems. – LLRF system should be compatible with existing RF HPA and cavity.

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Recent LLRF Development Activities

• Cornell – JLAB Collaboration

– A very successful collaboration between the two institutions tested the Cornell LLRF system in the JLAB FEL and in CEBAF

• LLRF Requirements:

– An in-depth requirement package detailing, top level, functional and hardware requirements was completed May 30.

Many thanks to S. Simrock, B. Chase, M. Champion and R. Ursic for review!

• Subsystem Prototyping

– 1497 MHz Receiver/Transmitter prototype: Tested on cryomodule – 499 MHz LLRF System: In production. – Piezo tuner concepts: tested with Cornell LLRF system – Digital signal processing modeled and streamlined

• Model/ Algorithm Development/Firmware

– Electronic Damping Modeled: PAC 2005 (A. Hofler and J. Delayen) – Resonance Control: (Collaborating with Cornell) test in CMTF/FEL fall 2005

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Proposed System Layout

• Three modules in baseline design, LLRF, Interlocks

and PZT Amplifier.

• Modules may be VME format. However, the

primary function of the backplane is power distribution and shared signal distribution.

• IOC imbedded in LLRF module with direct Ethernet

connection to operating system local area network.

– Working towards a NIOS core imbedded in the FPGA. – May change to imbedded processor.

• Ethernet* protocol for communication between

interlocks and LLRF.

– Four wires standard two-way Ethernet protocol. – Two wires RF permit from interlocks. – Two wires serial DAC link for the PZT amplifier.

• Fiber optic link to PZT amplifier, which is a 750 V,

0.5 A output device.

KLY DRIVE ETHERNET* PZT DRIVE FIBER LIMIT SW MOTOR, AND IR ARC

AMPLFIER PZT DRIVE MOTOR AND INTERLOCKS IOC EPICS AND LLRF

R P PF TO LAN ETHERNET 1427 MHz 70 MHz T P

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

LLRF Block Diagram

Clock generator Master Osillator Chassis (LO and Reference) LO = 429 MHz, Clock 10 MHz 429 MHz 70 MHz 56 MHz 56 MHz FPGA Altera Stratix Rot Matrix PID EPICS IO 14 bit DAC 499 MHz FWD Power REFL Power VME BUS A TTN Six 16 Bit DACs Cavity Amplifier 429 MHz BPF 70 MHz Beam Synch (LEMO) WJ AH2 LO SMA SMA

SMA

+20 dBm max 10 dBm Transmitted Power

BPF

AD6645 14 bit ADC SMA

VXI Card Mother Board

WJ AH2 WJ HMJ5 Spare Front Panel (LEMO)

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

LLRF FEATURES

• Makes used of existing master oscillator distribution system at

1427 MHz, 70 MHz and 10 MHz.

• 56 MHz sample clock generated on mother board.
• Down convert to 70 MHz IF.
• ADC clock frequency is 1.25 cycles of 70 MHz, providing +I, +Q, -I,
• Q, +I, +Q . . . data stream or I and Q at 14 MHz.
• Altera Stratix FPGA for phase and amplitude control as well as

interface to control system.

• Direct digital synthesis for IF generation using the third sideband
• f the ADC output. (Larry Doolittle “Plan for 50 MHz Analog Output” Aug. 8, 2002)
• Because ADC and DAC are run with the same 56 MHz clock, slow

phase drifts, etc. of the clock are not seen on the output.

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Direct Digital IF Signal Generation

• Concept use one of the harmonics out of your ADC for your IF frequency.
• For a 10-X system two disadvantages to using second or third harmonic

frequencies are: – Small signal content. – Analog filter requirements.

f t t f f

• N(f +1)
• =Nf

1 T=N

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Relative Magnitude of Harmonics

• Relative magnitude of the three harmonics out of an

ADC when the sampling frequency, fs, is near the signal frequency, fo.

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 2 3 4 5 6 7 8 9 10 OVER SAMPLING RATIO (fs/fo) MAGNITUDE OF HARMONIC fo fs-fo fs+fo

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

• Ratios of f3 to f1 is 1:5.
• 70 MHz component is 14 MHz away from nearest neighbor.
• Commercial drop in 8 MHz BW filter available for $30.
• One can show that the harmonic contains the proper phase signal

and is:

3-X DDS

70 MHz 8 MHz Filter

f t t f f

• 5f
• =4f = 56 MHz

1 T=4

( ) ( ) ( )

... 2 , 1 , where 2 sin 2 sin = + ± ⇒ + k t f kf A B f A

S k

ϕ π ϕ π

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Minimizing Thermal Drifts

• Receiver designed with

“Thermopad” variable tempco attenuators in an effort to null out drifts.

• Monitored phase and

amplitude of the new LLRF system for drifts between 10o to 50o C

• Results

– Phase: 0.13o/C – Amplitude: 0.1%/C

>10x better than present CEBAF LLRF

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

VME Motherboard & 499 MHz Transceiver 2005

Current 1497 MHz Prototype System

• Prototype 1497 MHz and production

499 MHz LLRF systems designed around a “generic” processor motherboard – Extended VME motherboard uses Altera Stratix FPGA for PID and cavity resonance control. – Can support transceivers at our different cavity frequencies (499 MHz & 1497 MHz). – RF receivers, RF transmitter, ADC and DAC located on the daughter card.

• Prototype testing controlled through

EPICS

Proto - EPICS Control Screen

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Normal Conducting LLRF at 499 MHz: Status

• Prototype system has been tested on a Separator

cavity in CEBAF

• 15 Production systems are being manufactured
• Eight systems to be installed and commissioned in

January 2006

CEBAF separator cavity CEBAF buncher cavity

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

System Modeling

• Matlab/Simulink Modeling

– Simulink models are based on DESY’s Simulink Library for SRF systems (Varadanyan, Ayvazyan, & Simrock EPAC’02) – Matlab modeling scripts based on transfer function representations of systems

• Electronic Damping for 12 GeV Upgrade

Cavities

• Warm RF and SRF cavity systems

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Electronic Damping

• Electronic damping uses ponderomotive forces to intentionally

deform the cavity in a manner opposing microphonic effects.

• An analytical model for the system has been developed and verified

using numerical simulations.

• Electronic Damping can be used to damp microphonic vibrations

– In lightly beam loaded superconducting cavity applications (JLab 12 GeV Upgrade, RIA, and possibly ERLs) – Simulations indicate that one can achieve a 50% decrease in phase error accompanied by 3x10-5 increase in amplitude error

• We are currently expanding model to include effect of multiple

mechanical modes.

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Test Programs

• Proof of principal system built with Altera Stratix development kit.

March 2004

• JLAB-Cornell Digital-LLRF Collaboration Sept. 2004 through Jan.

2005.

• Environmental testing of 499 MHz system April 2005
• 499 MHz System tested with warm cavity May 2005.
• 1497 MHz System low power tests with cold CEBAF upgrade cavity
• Aug. 2005
• 1497 MHz system high power tests with cold cavity NEXT WEEK
• 1497 MHz system high power tests with resonance controls THE

WEEK AFTER NEXT.

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

CORNELL - JEFFERSON LAB COLLABRATION

• Opportunity for two labs to test and operate hardware

and firm ware algorithms on a height loaded-Q superconducting cavity.

• Cornell provided the

– Digital LLRF system – DSP/FPGA algorithms, – PZT analog drive and – Tuner motor drive.

• JLAB provided the:

– Downconverters, – up converters – reference clocks – PZT amplifer – Operating accelerators with beam.

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

JLAB-Cornell Digital-LLRF Collaboration

• Phase and amplitude control on a real cavity with beam loading

– Conditions: CW beam up to 400 uA – Result: Met specifications

• Phase stability: ~ 0.02 degrees rms.
• Amplitude stability:

~ 2 x 10-4 rms.

• Cavity recovery under strong Lorentz detuning

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

• Cavity recovery from simulated CHL crash

– Initial condition: Cavity resonance frequency 30 kHz off master

• scillator frequency

– Result: Successful hands-off recovery.

• Operated cavity at high QL ~ 1x108

– Result: Met phase and amplitude control specifications

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

2 4 6 8 10 12 14 20 40 60 80 100 120 140 160

Time (msec)

Gradient (MV/m)

0.5 1 1.5 2 2.5 3 3.5

Forward power (kW)

Gradient (MV/m) Forward Power (kW)

Cavity Recovery after Fault

FEL03-3 with QL = 2x107

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

LLRF Test with 1497 MHz SC Cavity /Renascence Cryomodule

Control Room Test cave with cryomodule “Renascence” Low RF power (1W) test result for SC cavity (Loaded-Q = 8e+6) Closed Loop yes RMS Phase Noise 0.06 deg Open Loop Gain 183 RMS Gradient Noise 0.02 % Integral Gain 4 Integral Time 840 ms

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

I/Q Space Measurements

(Low Power SRF Cavity)

System on the edge

• f stability.

50 mV/div 10 mV/div

PID Loop optimized

(D = zero gain)

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Phase noise measurement for 1497 MHz SC cavity

Fig.1 open loop- cavity microphonics cause extensive phase noise of 1.3 deg RMS Fig.2 closed loop- RMS phase noise reduced from 1.3 deg down to 0.06 deg Carrier 1.497 GHz X: Start 10 Hz Stop 100 kHz RMS Noise: 22.7076 mrad / 1.30105 deg RMS Jitter: 2.41416 psec Carrier 1.497 GHz X: Start 10 Hz Stop 100 kHz RMS Noise: 1.0532 mrad / 60.34 mdeg RMS Jitter: 111.967 fsec

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Upper part of the picture shows forward power spectrum for closed loop and

• ptimized regulation. It

reflects microphonics compensation. Lower graph shows cavity microphonics spectrum measured with PLL and dedicated instrument “Cavity Resonance Monitor” , performed for the same cavity a few days earlier.

Digital LLRF system makes microphonic measurements easier !

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

LLRF Next Steps

• 1497 MHz tests in CMTF/FEL

Fall 05

• Instalation & Comm. of NC LLRF

January ‘06

• Complete vertical slice tests with 13 kW Winter ’07

tube and high gradient cavity (>15 MV/m) LLRF on a cavity in CMTF

• 8-seat test cryomodule test of LLRF on FEL-3 fall, 07

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Summary

• We continue to have a successful collaborations with

Cornell, DESY, SNS and Berkley during the development process.

• Cornell Collaboration: Demonstrated that a Digital LLRF

system is capable of meeting the CEBAF phase & amplitude control specifications using SRF cavities.

• Successful operation of both warm and cold structures

with the JLAB prototype systems.

• High power testing of JLAB prototype system with SRF

cavities to occur in the next few weeks.

• JLAB is well on the way to developing a LLRF system for

it’s 12 GeV upgrade. However, much work remains in hardware, firmware and software optimization.

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Digital Signal Processing

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Resonance Control

(Hardware Schematic)

VXI Crate L L R F I O C PC running ActiveX EPICS-LabViews Interface National Instruments FW-7344 National Instruments MID-7604 Mechanica l Tuner Piezoelectri c Tuner High Voltage Amplifier Cavit y Channel Access I & Q

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Electronic Damping

Comparison of Phase (left) vs. Frequency (right) Feedback for a Single Mechanical Mode at 34 Hz

25 30 35 40 45 0.5 1 1.5 2 2.5 3 3.5 4 4.5 x 10

−3

3(a) δφ: Frequency and kω Response with θf = 0 Driving Frequency (Hz) δφ (radians) kω = 0 kω = 0.0001 kω = 0.0002 kω = 0.0003 kω = 0.0004 25 30 35 40 45 1 2 3 4 5 6 7 x 10

−5

3(b) δv: Frequency and kω Response with θf = 0 Driving Frequency (Hz) δv kω = 0 kω = 0.0001 kω = 0.0002 kω = 0.0003 kω = 0.0004 25 30 35 40 45 0.5 1 1.5 2 2.5 3 3.5 4 4.5 x 10

−3

2(a) δφ: Frequency and θf Response with kω = 0 Driving Frequency (Hz) δφ (radians) θf = 0 θf = −0.05 θf = −0.1 θf = −0.15 θf = −0.2 25 30 35 40 45 2 4 6 8 x 10

−4

2(b) δv: Frequency and θf Response with kω = 0 Driving Frequency (Hz) δv θf = 0 θf = −0.05 θf = −0.1 θf = −0.15 θf = −0.2

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Resonance Control

(Software Layout)

PC running ActiveX EPICS- LabViews Interface IOC running VxWorks Resonance Control Task EPICS database LLRF DAC EPICS accessible global variables Channe l Access Memory Mapped Write Access HV Amplifier National Instruments FW- 7344

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Resonance Control

• Prototype system

– Based on two systems

• Cornell’s digital LLRF system under development for

its proposed ERL and CESR-c RF systems

• Auto-track resonance tacking system used for the

CEBAF 6 GeV cavities

– vxWorks-based task

• memory mapped write access to DAC to high voltage

amplifier for piezoelectric tuner

• communicate through EPICS and ActiveX EPICS-

LabViews interface to mechanical tuner system

• Ready for testing in Cryomodule Test Facility

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Digital LLRF subsystems

LLRF

Algorithms & software Receiver/Transmitter at Proper Frequency Interlocks EPICS Interface Signal Processing EPICS software Resonance Controls