1. Linac Coherent Light Source (LCLS) Low Level RF Status

2. Safety First and Second and Third…..to Infinity
Hazards in the LLRF system
RF 1kW at 120Hz at 5uS = 0.6 Watts average,
2 Watt average amps at 2856MHz,
60W average amps at 476MHz
Hazards – RF Burns / Cataracts
Mitigation – Avoid contact with center conductor of energized connectors. All employees working with LLRF systems are required to have the proper training.
110VAC Connector
Hazards - Shock
Mitigation - Don’t touch conductors when plugging into outlet.
All chassis are inspected by UL trained inspector.

3. Status of Hardware for Injector Turn-on
Linac Sector 0 RF Upgrade
All 3 RF Chassis completed and Installed (Master Oscillator, Master Amp, PEP phase Shifter
Control Module ready for test – higher phase noise levels if not installed
Sector 20 RF distribution system
Phase and Amplitude Controllers (PAC) – 5 units
Phase and Amplitude Detectors (PAD) – 2 units
Phased Locked Oscillator – Use SPPS unit for Turn On
LO Generator – Complete - 75% tested – looks good so far
Multiplier – 476MHz to 2856MHz – Complete
4 distribution chassis – Complete 102MHz, 2056MHz, MHz
Laser Phase Lock – Needs testing – Only high risk item
Distribution Amplifiers – 10W, 2850MHz due Oct 25, 102MHz Amp being built
LLRF Control and Monitor System
1 kW Solid State S-Band Amplifiers – 5 units – Design Complete, In Fab
PAD – 12 units – 6 required for turn on
PAC – 6 units
Bunch Length Monitor Interface – Will use PAD to collect data
Beam Phase Cavity
Will use 2 channels of PAD Chassis
Pill box cavity with 2 probes and 4 tuners – 2805MHz 3 units Complete

4. Status of Software for Injector Turn-on
PAD Software
Operational
PAC Software
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.
RF Gun Temperature Feedback
In Design
Calibration and Test
High Level Applications
In progress (This means we are working on specifications.)
Storing of boot params, serial numbers, etc in flash or on the board for PAD and PAC

5. Status of Documentation + Reviews
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
The goals of the review were:
Injector 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

6. LCLS Layout
P. Emma

7. LCLS RF Jitter Tolerance Budget
Lowest Noise Floor Requirement
0.5deg X-Band = 125fS
Structure Fill time = 100nS
Noise floor = 11GHz 10MHz BW
476MHz
X-band X-
0.50
RMS tolerance budget for <12% rms peak-current jitter or <0.1% rms final e− energy jitter. All tolerances are rms levels and the voltage and phase tolerances per klystron for L2 and L3 are Nk larger, assuming uncorrelated errors, where Nk is the number of klystrons per linac.
P. Emma

8. Slow Drift Tolerance Limits
(Top 4 rows for De/e < 5%, bottom 4 limited by feedback dynamic range)
Gun-Laser Timing
2.4*
deg-S
Bunch Charge
3.2 %
Gun RF Phase
2.3
Gun Relative Voltage
0.6
L0,1,X,2,3 RF Phase (approx.) 5
L0,1,X,2,3 RF Voltage (approx.)
(Tolerances are peak values, not rms)
P. Emma, J, Wu
* for synchronization, this tolerance might be set to 1 ps (without arrival-time measurement)

9. Linac Sector 0 RF Upgrade
LCLS must be compatible with the existing linac operation including PEP timing shifts
Master Oscillator is located 1.3 miles from LCLS Injector
1.3 Miles to LCLS Injector
Measurements on January 20, 2006
at Sector 21
show 30fS rms jitter in a bandwidth from 10Hz to 10MHz
PEP PHASE SHIFT ON MAIN DRIVE LINE
MDL RF with TIMING Pulse – Sync to DR

10. RF Distribution Lab vs. MDL Measurements
Existing Linac MDL Sector 0
126fS rms Jitter 10Hz to 10MHz
LCLS Reference System Lab Measurements
20fS rms Jitter 10Hz to 10MHz
If PEP IQPAU Chassis is not commissioned we may not meet LCLS specifications
John Byrd LBNL

11. Sector 20 RF Distribution
MDL from Sector 0
LO and 102MHz resync by adjusting 2856MHz PAC while monitoring S MHz
Laser resync with laser PAC while monitoring difference in 119MHz laser and FIDO out

12. Lab Test Setup Reference, 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.
There is only one Dayle, spare is not in the budget.

13. 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

14. RF Cable Routing
All cables are routed from devices in temperature stabilized area to the centrally located, temperature stabilized, RF Hut in the linac gallery.
RFHUT
Cables run down through penetration which is enclosed by the RF Hut
Picture taken from Carl Rago’s Talk

15. RF System Cables / Specifications
LCLS Specifications:
Laser, RF Gun – 2.3pS
L0A, L0B, L1S, L1X, L2, L3 – 5pS

16. 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

17. Linac Station 21-1 Tests

18. 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.

19. 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.

20. LLRF Commissioning – no high power RF, no beam
Low Level Lab Tests and Calibration PACs and PADs
Set at Operational Temperature
PAC Tests and Calibration – SSB Modulator : Set offsets and gain
PAD Tests
ADC Board – SNR Cross Talk – Sine Wave histogram
Chassis – Two Tone or Single Tone - SNR, Noise Floor, IP3
Installation of PACs and PADs – Other systems required to be complete
LLRF Racks - installed
Water System
Trigger system
AC Rack power
Test RF Cables - Measure Attenuation and Phase Stability
Installation of Solid State Sub-Boosters (SSSB)
Installation of RF VME Crate
Installation of network switches
Get devices booting from afsnfs2
Test VME connectivity to PAD by sending I and Q avgs.
Connection of PADs, PACs, and VME IOCs to network
Initial Set-up of PAC triggers
Align 119MHz trig to 102MHZ clocks for PACs and PADs
PAD Calibrations
Enter channel calibration factors (APCs, Power Scale Factors – coupler ratios…)
PAC Calibration
Calibration with spectrum analyzer
Calibration with PAD channel
Phase Noise Measurements
102MHz Clock : MHz LO : 2856MHz RF : Laser Lock to RF

21. LLRF Commissioning - high power RF, no beam
Timing System setup
Line up PAC and PAD triggers to existing modulator triggers
Adjust PAC waveforms for 6 Klystron stations
Adjust PAD window length and offset to fit waveform
Commission local Feedback loops
Gun Tune
Gun Phase
Gun Amplitude
L0A Phase
L0A Amplitude
L0B Phase
L0B Amplitude
Tcav Phase
Tcav Amplitude
L1S Phase
L1S Amplitude
L1X Phase
L1X Amplitude
Test Standby Timing and BCS functions

22. LLRF Commissioning - high power RF, with beam
Timing System setup
Adjust PAC and PAD triggers to align waveforms to beam time
119MHz PAD/PAC triggers must move in increments of 14 ticks to keep all phases aligned (~117.6nS).
PAD window must move in increments of four 102MHz cycles to keep phase reading the same. (~39.2nS). Increments of 9.8nS will cause 90 degree phase shifts in readings.
Commission local Feedback loops
Gun Phase - Phase to beam (Rotate phase to get max beam energy)
Gun Amplitude - Check Cal (RF power to maximum energy gain)
L0A Phase - Phase to beam
L0A Amplitude - Check Cal
L0B Phase - Phase to beam
L0B Amplitude - Check Cal
Tcav Phase - Phase to Beam
Tcav Amplitude - Check Cal
L1S Phase - Phase to Beam
L1S Amplitude - Check Cal
L1X Phase - Phase to Beam
L1X Amplitude - Check Cal

23. High Level 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

24. END of TALK