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

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. Parameter Fast < 1s Slow > 1s 0.24 o (rms.) Phase Stability (correlated) infinite Phase Stability (uncorrelated) 0.5 o (rms.) 3.0 o 2.2 x 10 -5 Amplitude (correlated) NA Amplitude (uncorrelated) 4.5 x 10 -4 NA 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 P KLY DRIVE • T Three modules in baseline design, LLRF, Interlocks PF and PZT Amplifier. P LLRF R • 70 MHz Modules may be VME format. However, the AND primary function of the backplane is power 1427 MHz EPICS distribution and shared signal distribution. ETHERNET IOC TO LAN • IOC imbedded in LLRF module with direct Ethernet connection to operating system local area network. ETHERNET* – Working towards a NIOS core imbedded in the FPGA. – May change to imbedded processor. ARC INTERLOCKS AND IR AND • Ethernet* protocol for communication between MOTOR interlocks and LLRF. MOTOR, DRIVE LIMIT SW – Four wires standard two-way Ethernet protocol. – Two wires RF permit from interlocks. – Two wires serial DAC link for the PZT amplifier. FIBER • Fiber optic link to PZT amplifier, which is a 750 V, PZT 0.5 A output device. AMPLFIER PZT DRIVE Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

LLRF Block Diagram Mother Board AD6645 Beam Synch (LEMO) WJ HMJ5 14 bit ADC Spare VME BUS BPF Six 16 Bit REFL Power Front Panel (LEMO) DACs WJ AH2 FWD Power Transmitted Power FPGA 70 MHz Altera Stratix 499 MHz 14 bit BPF Rot Matrix DAC PID SMA 70 MHz A TTN EPICS IO 429 MHz 56 MHz 429 MHz 56 MHz Clock WJ AH2 generator SMA LO VXI Card SMA SMA 10 dBm Master Osillator Chassis (LO and Reference) LO = 429 MHz, Clock 10 MHz Cavity +20 dBm max Amplifier 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 of 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 T=N t t N(f +1) o f f f 1 =Nf o • 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. Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

Relative Magnitude of Harmonics 1.0 MAGNITUDE OF HARMONIC 0.9 0.8 0.7 fo 0.6 fs-fo 0.5 fs+fo 0.4 0.3 0.2 0.1 0.0 2 3 4 5 6 7 8 9 10 OVER SAMPLING RATIO (fs/fo) • Relative magnitude of the three harmonics out of an ADC when the sampling frequency, fs, is near the signal frequency, fo. Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Depart. Of Energy

3-X DDS T=4 t t 8 MHz Filter 5f o f f f 1 =4f = 56 MHz o 70 MHz • 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: π + ϕ π ± + ϕ = A sin 2 f B A sin 2 kf f t where k 0 , 1 , 2 ... 0 k S 0 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 10 o to 50 o C • Results – Phase: 0.13 o /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

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 VME Motherboard & 499 MHz Transceiver 2005 (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 buncher cavity CEBAF separator 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