1. Low Level RF Status Outline Overview showing hardware instances
Refresher – status at time of last review
Progress since last review
Top level LLRF GUI
System performance and reliability
Near term (next 1-2 months) tasks
Far term (> 2 months) tasks

3. Refresher – status at time of last review
As of October 2006:
Several instances of LLRF Phase and Amplitude Detectors (PADs) and several instances of LLRF Phase and Amplitude Controllers (PACs) existed
LLRF VME crate and powerpc were in-house
Timing hardware for LLRF VME was in-house
All algorithms for the different flavors of PADs were written and one was tested in both the lab and gallery (details in Appendix)

4. Progress since last review
LLRF hardware installation complete for sectors 20 and 21
Eight feedback loops have been commissioned. Top level GUI shown on slide 5. Loops control:
phase and amplitude of S-band klystrons 20-5, 20-6, 20-7, 20-8, 21-1 and X-band klystron GUIs on slides 7-9 show 21-1 loop
laser phase. GUI shown on slide 9
gun temperature. GUI shown on slide 10
Diagnostics PAD for klystron 21-2 installed
System uses save and restore tool to recover its configuration at boot
System uses bootp to determine IOCs network parameters from host. No locally stored values.

11. Laser Stability: FB off vs on
Beam Current
Actual Laser
Phase
Feedback off
Feedback on

12. Laser Oscillator RF Phase Stability
LCLS Jitter Specification for 2 Seconds is 0.5 pS
Feedback ON 20 Second Plot shows
Phase Jitter degrees 476MHz 1.0 pS
Feedback ON 20 Second Plot shows
Phase Jitter degrees 476MHz
0.98 pS
Short Term RF Jitter Specification for Laser Oscillator are not met. Needs work. No complaints from physicists. Photodetector is possible jitter source. Phase cavity may solve this.

13. RF Gun RF Stability
LCLS Jitter Specification for 2 seconds is 0.1% amplitude and 0.1 degree Phase
Feedback OFF 20 Second Plot shows
Phase Jitter degrees
Amplitude Jitter 0.034%
Feedback ON 20 Second Plot shows
Phase Jitter degrees
Amplitude Jitter 0.04%
Short Term RF Jitter Specification for the RF Gun are met.
Need to work on reduction of flyers, adjust modulator thyratron.

14. L0A RF Stability
LCLS Jitter Specification for 2 seconds is 0.14% amplitude and 0.14 degree Phase
Feedback ON 20 Second Plot shows
Phase Jitter degrees
Amplitude Jitter 0.22%
Feedback ON 20 Second Plot shows
Phase Jitter degrees
Amplitude Jitter 0.21%
Short Term RF Jitter Specification for L0A are not met.
Need to work on reducing 2-state variations.

15. L0B RF Stability
LCLS Jitter Specification for 2 Seconds is 0.14% Amplitude and 0.14 degree Phase
Feedback ON 20 Second Plot shows
Phase Jitter degrees
Amplitude Jitter 0.022%
Feedback ON 20 Second Plot shows
Phase Jitter degrees
Amplitude Jitter 0.024%
Short Term RF Jitter Specification for L0B are well Exceeded.
This is as good as it gets – Don’t tell Physicists or they will expect it.

16. L1S RF Stability
LCLS Jitter Specification for 2 Seconds is 0.14% Amplitude and 0.14 degree Phase
Feedback ON 20 Second Plot shows
Phase Jitter degrees
Amplitude Jitter 0.042%
Feedback ON 20 Second Plot shows
Phase Jitter degrees
Amplitude Jitter 0.043%
Short Term RF Jitter Specification for L1S are met.

17. L1X RF Stability
LCLS Jitter Specification for 2 Seconds is 0.25% Amplitude and 0.5 degree Phase
Feedback ON 20 Second Plot shows
Phase Jitter 1.28 degrees
Amplitude Jitter 0.63%
Feedback ON 20 Second Plot shows
Phase Jitter 1.18 degrees
Amplitude Jitter 0.62%
Short Term RF Jitter Specification for L1X are not met.
Needs work.

18. TCav RF Stability
LCLS Jitter Specification for 2 Seconds is 1.0 degree Phase
Feedback ON 20 Second Plot shows
Phase Jitter degrees
Amplitude Jitter 0.011%
Feedback ON 20 Second Plot shows
Phase Jitter degrees
Amplitude Jitter 0.017%
Short Term RF Jitter Specification for TCav are met.
Need to work on reduction of flyers, adjust modulator thyratron.

19. Near term (in next 1-2 months) tasks
Beam synchronous data acquisition (BSA) on phase and amplitudes
SLC-aware (after BSA complete)
Access security – define and implement
Alarm handler configuration definition
Klystron diagnostic PADs (20-5, 20-6, 20-7, 20-8 and 21-1)
Software configuration adaptation to project standards (evolving) re: version control, tagging, layout, nodename hierarchy for startup files

20. Far term (> 2 months) tasks
Sector 24 PAC, TCav PADs and PAC
Sector 29 PAC
Sector 30 PAC
Switch PADs and PACs to talk to VME over private network
Switch PADs to use second ethernet port to send whole waveform (will allow phase and amplitudes for EACH point in sample)
HPRF

21. Appendix

22. PAD Software Different LLRF apps need different calculations
There are 5 different algorithms:
AVG+STD – calculate average I and Q and variance of I and Q
RF WF – calculate average I and Q
WF – calculate average of sample
RF WF2 – calculate average I and Q of two samples
IQ Cal – send 64K raw data waveform
Each channel on a PAD can run a different algorithm with its own sample size and offset
Each PAD can run in CALIBRATION or RUNNING mode, which use different algorithms

23. PAC Software
PACs can run in either CALIBRATING or RUNNING mode. A state machine keeps track.
If CALIBRATING, calibration waveforms are loaded into FPGA and I and Q gains and offsets can be adjusted.
If RUNNING, I and Q gains and offsets are fixed, operational waveforms are loaded into FPGA and I and Q adjustments can be applied at the operational frequency.

24. VME Software Generic Feedback algorithm:
Phase and amplitude are calculated from I and Q averages from each channel of the PAD
Phases are corrected by phase offset correction
Amplitudes are corrected by amplitude power correction
Phase and amplitudes are weighted by configurable weighting factors to determine one average phase and amplitude
Pavg=(P0*PWT0 + P1*PWT1 + P2*PWT2 + P3*PWT3)/4*(ΣPWTi)
Aavg=(A0*AWT0 + A1*AWT1 + A2*AWT2 + A3*AWT3)/4*(ΣAWTi)
Local or global feedback corrections are applied (0 < A <= 1)
Pcor = A(Pdes – Pact) + (1-A)Pcorn-1
Pcorn+1 = A(Pdes n+1 – Pactn+1) + (1-A)Pcorn
For amplitude, (Pdes – Pact) is replaced by Pdes/Pact
Corrected phase and amplitude is converted to I and Q
Corrected I and Q values are sent to PAC

25. Local feedback

26. VME Software Beam Phasing Cavity algorithm (for Laser Timing):
Two sets of I and Q averages arrive (since there are two windows of interest)
Phase1 is calculated from I1 and Q1
Phase2 is calculated from I2 and Q2
Measured beam phase is the y-intercept of the equation to the line of phase as a function of FIFO position
Frequency is the slope of the line
Amplitude is calculated from I1 and Q1 (only)
Phase is corrected by phase offset correction
Amplitude is corrected by amplitude power correction
Local feedback corrections are applied
Corrected phase and amplitude is converted to I and Q
Corrected I and Q values are sent to laser PAC

27. Beam Phase Cavity: calculation of freqency and phase from a line through 2 points

28. VME Software Other calculations For RF Reference Distribution
Phase and amplitude are calculated from I and Q averages from each channel of the PAD
Phases are corrected by phase offset correction
Amplitudes are corrected by amplitude power correction
Standard deviation of I and Q is calculated from I and Q variances from each channel of the PAD

29. Host Applications Generic Distribution System PAC PAD Testing
Correlation plots
Calibration of power levels using beam energy
Distribution System
Rotate Phase 360 degrees
Monitor Phase Errors in Dividers
Correct Divider Phase Errors
PAC
Calibration Mode Operation
Generate and Load Waveforms
Panels for Phase and Amplitude Adjustment
PAD Testing
Crosstalk, SNR, Noise Floor
Sine Wave Histogram
Panels for Phase and Amplitude Monitoring
Local Feedback Control Panels

30. Status of Documentation + Reviews
All documentation and reviews are accessible from LLRFhomepage
Recent milestones:
LLRF Control Design Specification
This Engineering Specification Document was signed off by Project Office on 9/27/2006.
LLRF Final Design Review
This review was held on 9/19/2006.
The scope of the review covered:
RF Distribution Reference System for Injector Commissioning
RF System for Injector Commissioning
PAD
PAC
VME
These were the goals given to the committee last September:
Injector RF turn on is January 3, The designs of the prototype PADs and PACs have been built and tested. Fabrication is scheduled for October, Please review analysis of test data and the proposed design and comment on the proposed systems' ability to meet LCLS specifications.
Review our test plans and suggest improvements

31. LCLS New Reference System Lab Measurements
Lab Tests Show Reference System Noise Levels Meet All LCLS Requirements
2856MHz = 70fSrms
2830.5MHz = 70fSrms
25.5MHz = 2pSrms
102MHz = 2pSrms
2856MHz : 22fSrms 10Hz to 10MHz
2830.5MHz : 22fSrms 10Hz to 10MHz
John Byrd - LBNL
25.5MHz : 152fSrms 10Hz to 1MHz
102MHz : 281fSrms 10Hz to 10MHz

32. SLAC Linac RF – New Control
The new control system will tie in to the IPA Chassis with 800W of drive power available. The RF Reference will be from the new RF reference system.
Solid State Sub-Booster PAC
I and Q will be controlled by the PAC chassis, running 16bit DACs at 102MHz. Waveforms to the DACs will be set in an FPGA through a microcontroller running EPICS on RTEMS.
Existing System

33. Linac 21-1 Test Set-up
Power Coupled out from 476MHz MDL drives a 476MHz Amplifier which feeds a 6X Multiplier from 476MHz to 2856MHz.
The 2856MHz out drives both the LO generator and the PAC.
The MHz LO and 102MHz CLK Generator supplies the LO and CLK to the PAD. A CLK output of the PAD drives the PAC CLK.
The PAC output drives the SSSB.
The SSSB drives the existing IPA chassis
The klystron output coupler is used to measure phase and amplitude with the new PAD.

34. Linac 21-1 Test Results
Tests were done in the gallery with no temperature regulation on cables. Average RMS value of 2 second sliding average is degrees.
Exponential Smoothing Yields the Following Results. Lowest noise is with a time constant of about 2 points.