LCLS RF Stability Requirements LCLS Requirements The SLAC Linac SLAC Linac Stability Data SPPS Measurements LCLS RF System

LCLS INJECTOR / LINAC P. Emma

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 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

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

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.

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.

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

Linac Phase Reference System Main Drive Line - 3 1/8 Rigid Coax Anchored to Concrete Floor Every Sector Phase Reference Line - Each Sector Independent ½ inch Heliax MDL 200fS rms / Sector PRL 640fS rms

Phase as Seen by Electron is Difficult to Measure Accelerator Water Temperature Effects on SLED Phase[1] The tuning angle of the SLED cavity goes as:  = tan -1 (2QLT), Where T = L/L = -/ QL= 17000 = 10-5 / F Thermal expansion of copper. =tan -1 (0.34T) Where T is in F. For small T, (S)= 20T(F) The relation between the tuning angle  and the measured output phase of the klystron  varies with the time after PSK with about the following relation:  /  = 0.35 just after PSK (S)= 7T(F)  /  = 0.50 800nS after PSK (S)= 10T(F)  / T~ +8.5 S / F for SLED Cavity Accelerator Water Temperature Effects on the Accelerator Phase[2] The phase change of the structure goes as follows:  =  f Where  = phase through structure  = Angular frequency f = Filling time of structure  =  f = / x f / = -L/L = -T = -10-5 T / F for copper  = -10-5 T / F22856MHz0.84S = -0.15 T rad/F = -8.6 T S / F  / T = -8.6 S / F for Accelerator Structure Water / Accelerator Temperature Variation is 0.1F rms  through structure is 0.86F rms [1] Info from D. Farkas [2] Info from P. Wilson

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

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

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 LASER to BEAM Jitter Adrian Cavalieri et al., U. Mich.

SPPS Laser Phase Jump Tracking R. Akre, A. Cavalieri

SPPS Laser Phase Jump Tracking ~ 200uS Laser Phase Error – Output Phase to Input Reference - Modulated with 1 Hz Square Wave 0.25pS pk Square Wave 2.0pS pk Square Wave

SPPS Laser Amplitude of Phase Transfer Function Phase Modulation placed on RF Reference and measured on Diode at Laser output. During the Blue part of the curve the modulation amplitude was reduced by 12dB to prevent laser from unlocking. Data taken 10/22/03

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

RF Distribution Phase Noise New Master Oscillator in Linac Front End Less than 25fS rms jitter in Bandwidth from 38Hz to 5MHz R. Akre, K. Schaffold

RF Distribution Phase Noise Integrated Noise - Timing Jitter fs rms Integral end 5MHz 10kHz Integral start 1M 100k 10k 1k 100 10 Master Osc. 18 20 20 20 10 16 PEP Phase 22 26 34 36 120 120 Master Amp 48 54 62 74 136 144 MDL 48 56 62 74 144 152 Sector 30 - 2 miles 54 60 66 76 150 164 Need to lower phase noise in PEP Phase Shifter and Master Amplifier

LINAC SECTOR 20 – LCLS INJECTOR RF Stability < 50fS rms : Timing/Trigger Stability 30pS rms Using LASER as LCLS RF OSCILLATOR is UNDER CONCIDERATION

LCLS RF System – Sector 20 Layout 100ft ½” Heliax = 0.3ºS/ºF Tunnel Temperature < 0.1deg F rms

Beam Trigger for User Facility Single Pulse with 30fS stability (1Hz to 3GHz BW) Tightest Noise Tolerance of LCLS Wide Bandwidth Low Phase Noise 30fS Stability today 10fS Stability tomorrow 1fS The Day After Currently users are expected to use local beam timing measurement, EO, to achieve this.

LCLS RF System Injector RF – FY06 X-Band RF system – FY06 Upgrade of existing system / Lower Noise Timing requirements Injector/L1 Phase Reference System Phase and Amplitude measurement system Solid State Sub-Boosters Beam Phase Monitor System X-Band RF system – FY06 Linac Phase Reference System – FY07 Linac Feedback Control – FY07 Feedback Development – FY07 Far Hall Trigger – FY08

Near Term (6 Month) Tasks Measure Phase Noise of SPPS Laser Lower phase noise in PEP phase shifter and Master Amplifiers Determine Type of RF Phase and Amplitude Measurement System

FY05/06 Tasks and Resources Ready to Ramp Up Start on X-Band system Complete SLAC Linac Front End Upgrades Complete Design of Phase Reference System Complete Design of LLRF Control System Define Beam Phase Cavity Monitor Further Studies on Linac Stability SLAC Klystron Department to Support 75% of RF manpower Manpower available from other SLAC groups (ARDA, ARDB, NLC, and Controls) and LBNL