1. Linac Coherent Light Source (LCLS) LLRF Preliminary Design Review LLRF Monitor and Control System September 26, Ron Akre

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
Mitigation – Avoid contact with center conductor of energized connectors
Training, do not disconnect cables and stick them in your eye. This is true even if they don’t have RF on them.
Do not use your tongue to test for RF
110VAC Connector
Hazards - Shock
Mitigation - Don’t touch conductors when plugging into outlet.

3. LCLS Layout
P. Emma

4. LLRF Control system spans Sector 20 off axis injector to beyond Sector 30

5. LCLS Machine Stability Tolerance Budget
Lowest Noise Floor Requirement
0.5deg X-Band = 125fS
Structure Fill time = 100nS
Noise floor = 11GHz 5MHz BW
476MHz
X-band X-
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

6. Bandwidth of S-Band System
Upper Frequency Limit – 10MHz
Beam seen due to structure fill time ~ 1.2MHz
Structure RF Bandwidth ~ 16MHz
5045 Klystron ~ 10MHz
Lower Frequency Limit – 100kHz
Fill time of SLED Cavity = 3.5uS about 100kHz
Laser – Needs to be measured ~ 100kHz

7. Noise Levels RF Reference Noise Floor Integrated Noise
Oscillator -148dBc/Hz SSB at 2856MHz
RF -138dBc/Hz SSB at 2856MHz
Integrated Noise
-138dBc/Hz at 10MHz = -65dBc = 32fS rms
SNR = 65dB for phase noise
Added noise from MIXER (LO noise same as RF)
SNR of 62dB
ADC noise levels
SNR of 70dB – 14bit ADS5500 at 119MSPS 8.5MHz

8. RF Control and Monitor Points Summary
RF Gun 1 Klystron 3 RF monitors
Beam Phase Cavity 1 IQ modulator 1 RF monitor
L0-A Accelerator 1 Klystron 2 RF monitors
L0-B Accelerator 1 Klystron 2 RF monitors
L0-T Transverse Accelerator 1 Klystron 2 RF monitors
L1-S Station 21-1 B, C, and D accelerators
1 Klystron 4 RF monitors
L1-X X-Band accelerator X-Band
S25-Tcav 1 Klystron 2 RF monitors
S24-1, 2, & 3 Feedback 3 Klystrons
S29 and S30 Feedback 2 IQ modulators 476MHz
Totals 2856MHz 10 modulators 16 monitors

9. RF Monitor LO 2830.5MHz : RF 2856MHz
IF 25.5MHz (8.5MHz x 3 in sync with timing fiducial)
Double-Balanced Mixer
Mixer IF to Low Pass Filter and Amp
Amp output to ADC (119MSPS or 102MSPS)?

10. SLAC Linac RF – New Control
The new control system will tie in to the IPA Chassis with 1kW of drive power available. Reference will be from the existing phase reference line or the injector new RF reference
I and Q will be controlled with a 16bit DAC running at 119MHz. Waveforms to the DAC will be set in an FPGA through a microcontroller running EPICS on RTEMS.
Existing System

11. Status Monitor Controller Board (J. Gold)
Single channel ADS5500 tested to specifications
Four channel ADS5500 board in layout
RF Monitor Board in preliminary design (H. Schwarz, B.Hong)
Control Boards (J. Olsen)
Fast Control Board in design
Slow control board not started
RF Control Board in preliminary design (H. Schwarz, B. Hong)
Software (D. Kotturi)
EPICS on RTEMS done
Drivers
Algorithms
Initial Testing – May 2005
System Completion - December 2005

12. MPS – PPS Issues Addressed by Controls Group Not Reviewed Here
Vacuum
New vacuum system summary to be fed to each klystron existing MKSU.
PPS System
Injector modulators will be interlocked by Injector PPS system.
PPS requirements for radiation from the injector transverse accelerator needs to be determined. Radiation levels will be measured during testing in the Klystron Test Lab.