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LCLS Machine Stability Tolerance Budget

Linac Coherent Light Source (LCLS) LLRF Preliminary Design Review Overview and Controls Interface and Timing (Linac Sector 0 Modifications) September 26, 2005 Ron Akre. X -. X-band. LCLS Machine Stability Tolerance Budget. Lowest Noise Floor Requirement 0.5deg X-Band = 125fS

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LCLS Machine Stability Tolerance Budget

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  1. Linac Coherent Light Source (LCLS) LLRF Preliminary Design ReviewOverview andControls Interface and Timing(Linac Sector 0 Modifications)September 26, 2005Ron Akre

  2. X- X-band LCLS Machine Stability Tolerance Budget Lowest Noise Floor Requirement 0.5deg X-Band = 125fS Structure Fill time = 100nS Noise floor = -108dBc/Hz @ 11GHz 5MHz BW -134dBc/Hz @ 476MHz 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

  3. LINAC RF and Timing System 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 PEP PHASE SHIFT ON MAIN DRIVE LINE MDL RF with TIMING Pulse – Sync to DR

  4. Linac Phase Reference System • Main Drive Line - 3 1/8 Rigid Coax Anchored to Concrete Floor Every Sector • Phase Reference Line - Each Sector Independent 1/2 “ Heliax • Must not introduce noise over 2 miles

  5. Linac Phase Reference System • Phase Reference Line • ½ inch Heliax Cable with 1.2 Watts • Phase Reference for 8 PADs (Klystrons) in the sector • Length = 1 Sector, 0.5 furlongs, 332ft, 400kS in ½” Heliax • Temperature Coefficient 4ppm/C • Waveguide Water T = 0.1C rms • 85% of the cable is regulated to 0.1C rms • 15% may see variations of 2C rms • Average Temperature Variation = 0.4C rms •  = 0.64S rms • Main Drive Line • 3 1/8 inch Rigid Coax with 30watts input power 30mW out • Length = 31 Sectors, 15.5 furlongs 2miles, 3km, 1e7 S: Velocity = 0.98c • Anchored at each sector next to coupler and expansion joint • Purged with dry nitrogen • Phase Length Range 100S/Year • Phase Length Range 40S/Day • Accuracy Based on SLC Fudge Factor • 0.5S/Sector Total Variation • 0.2S rms / Sector

  6. Phase Noise of SLAC Main Drive Line Old Oscillator New Oscillator Noise Floor -120dBc/38Hz = -136dBc/Hz = 120fS rms Jitter in 5MHz BW Noise Floor -143dBc/38Hz = -158dBc/Hz < 16fS rms Jitter in 10MHz BW New Oscillators Have a noise floor of -157dBc/Hz @ 476MHz

  7. Phase Noise of SLAC Main Drive Line Old Oscillator New Oscillator Integrated noise levels from 5MHz down to Start point New Oscillator integrated jitter is <12fS from 38Hz to 5MHz

  8. SLAC Linac RF The PAD measures phase noise between the reference RF and the high power system. The beam sees 3.5uS of RF from SLED cavity which the klystron fills and is then dumped into the accelerator structure.

  9. LINAC RF MEETS ALL LCLS SPECIFICATIONS for 2 Seconds when running well Amplitude fast time plots show pulse to pulse variation at 30Hz. Standard deviation in percent of average amplitude over 2 seconds are 0.026% for 22-6 and 0.036% for 22-7. Phase fast time plots show pulse to pulse variation at 30Hz. Standard deviation in degrees of 2856MHz over 2 seconds for the three stations are 0.037 for 22-6 and 0.057 for 22-7.

  10. LINAC RF is Out of LCLS Specs in 1 Minute Phase 22-6 1.2 Deg pp Amplitude 22-6 0.20%pp Amplitude 22-7 0.43%pp Phase 22-7 1.2 Deg pp 14 minutes data taken using the SCP correlation plot Note that 22-6 and 22-7 are correlated in phase and amplitude They also track the temperature of the water system

  11. Phase as Seen by Electron is Difficult to Measure • Accelerator Water Temperature Effects on the Phase Through the Accelerator-8.6 S / F • SLAC Linac Accelerator Water TemperaturesT< .08Frms • Phase Variations Input to Output of Accelerator > 0.5ºS-Band rms • Single Measurement Can’t Determine the Phase the Beam Sees Passing Through the Structure to LCLS Specifications • Feedback on Input Phase, Output Phase, Temperature, Beam Based Parameters (Energy and Bunch Length) is Required to Meet LCLS Specifications

  12. SLAC Linac 1 GeV 30 GeV e- Energy (MeV) Linac Phase Stability Estimate Based on Energy Jitter in the Chicane BPM 9 GeV sE/E0 0.06% Df 21/2< 0.1 deg (100 fs) P. Emma

  13. Electro-Optical Sampling Timing Jitter (20 Shots) 200 mm thick ZnTe crystal Single-Shot e- <300 fs Ti:Sapphire laser e- temporal information is encoded on transverse profile of laser beam 170 fs rms Adrian Cavalieri et al., U. Mich.

  14. LCLS Phase Noise Associated Time Referenced to Beam Time • LCLS Laser ~200uS Off Scale Below • LCLS Gun 1.1uS • SLED / Accelerator 3.5uS • Phase Detector (Existing) 30nS • Distribution System 200nS • 1km @ c-97%c=100nS • Far Hall Trigger 2uS • 3km @ c-80%c=2uS Except for the LASER common mode noise levels below ~100kHz would not cause instabilities – the entire system would track the deviations -3.5us SLED Starts to Fill -2uS Far Hall Trig RF Starts Trip -1.1uS Gun Starts to Fill Beam Time 0 Reference TIME

  15. Controls Interface and Timing Replace PEP Phase Shifters and Master Amplifiers

  16. Controls Interface and Timing Linac Phase Noise Measurements August 17, 2004 R. Akre, K. Schaffold Integrated Noise - Timing Jitter fs rms Integral end 5MHz 10kHz Integral start 1M 100k 10k 1k 100 10 Master Osc. 9 10 10 10 5 8 PEP Phase 11 13 17 18 60 60 Master Amp 24 27 31 37 68 72 MDL 24 28 31 37 72 76 Sector 30 27 30 33 38 75 82

  17. Controls Interface and Timing (Status) • Master Amplifier (Bo Hong) • Prototype Complete - Needs testing • PEP Master Phase Shifter • RF Chassis (R.Akre) • Complete – Needs testing and Calibration • Camac Module (J. Dusatko) • Board out for Fab • Install during October 2005 Down Time • Phase Measurements to Follow

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