Low Level RF Status

1
Low Level RF Status

• Outline
• LLRF controls system overview
• LLRF controls software status for
• Phase and Amplitude Detector (PAD)
• VME local feedback and timing trigger source
• Phase and Amplitude Controller (PAC)
• Host applications
• LLRF controls software testing status
• LLRF documentation and review status
• See SC1/SC2 Accelerator Systems LLRF Status and
  Design presentation for safety, hardware status,
  system requirements, cable routing and
  commissioning test plan

2
(No Transcript)
3
Status of Software for Injector Turn-on

• PAD Software
• Operational
• PAC Software
• Operational
• Local Feedback (in VME)
• Data analysis shows simple feedback algorithm
  will work.
• Optimization of algorithm continues.
• Time measurement measure time needed for data
  acq, for transfer to VME, for VME processing, for
  transfer to PAC.
• Time measurement needed for multiple local
  loops. Eg. Measure scalability from 1 to N
  instances.
• This IOC needs to be SLC-aware
• This IOC uses EVR and needs to set up trigger
  delays in response to timing events
• RF Gun Temperature Feedback
• In Design
• Calibration and Test
• Operational
• Host Applications
• In process of specifying
• Storing of boot params, serial numbers, etc in
  flash or on the board for PAD and PAC

4
PAD Software

• Different LLRF apps need different calculations
• There are 5 different algorithms
• AVGSTD 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

5
PAD GUI here
6
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.

7
PAC GUI here
8
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(P0PWT0 P1PWT1 P2PWT2
  P3PWT3)/4(SPWTi)
• Aavg(A0AWT0 A1AWT1 A2AWT2
  A3AWT3)/4(SAWTi)
• Local or global feedback corrections are applied
  (0 lt A lt 1)
• Pcor A(Pdes Pact) (1-A)Pcorn-1
• Pcorn1 A(Pdes n1 Pactn1) (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

9
Local feedback
10
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

11
Beam Phase Cavity calculation of freqency and
phase from a line through 2 points
12
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

13
VME GUI here
14
Host Applications

• Generic
• 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

15
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, 2007. The
  designs of the prototype PADs and PACs have been
  built and tested. Fabrication is scheduled for
  October, 2006. 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

16
Lab Test SetupReference, PAC, PAD
The LCLS RF system duplicated in the lab and used
for testing of PADs and PACs. At least two of
each frequency generation chassis is built to
measure phase noise levels. Most components will
have development chassis which can be used as a
spare.
17
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
18
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
19
Linac Station 21-1 Tests (Aug.18, 2006)
20
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 2830.5MHz 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.
21
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 0.068
degrees.
Exponential Smoothing Yields the Following
Results. Lowest noise is with a time constant of
about 2 points.