RF low level control & synchronization A. Gallo, M. Bellaveglia, L. Cacciotti SPARC review committee – ENEA Frascati – 16/11/2005

Summary ● RF general layout and control system ● Synchronization tests and results -demodulation channel resolution -oscillator characterization -time jitter measurements of laser system ● Hardware installation in the SPARC area -RF distribution, demodulation and interlock boards -klystron driver amplifiers -cable connections -hardware calibration

RF general layout

RF control system ● 25 signal to be monitored -waveform and phase monitor systems ready to use ● 13 devices to be controlled -signal and power phase shifters -signal and power attenuators -each device is under control ● To do - we are finishing to modify the main architecture to include phase feedback and devices control

Synchronization system SPARC phase I : ± 3° between the Laser pulse and the Linac RF (RF gun mainly) SPARC phase II : ± 0.5° between the Laser pulse and the Linac RF (RF gun and RF compressor mainly) and/or next-generation experiments: ± 0.1° control of the bunch longitudinal position SPARC phase stability specifications

Synchronization system Resolution of the Phase Jitter Measurement Equipment (CW) Measured Equivalent RMS Phase Noise  20 fs

Synchronization system Oscillator characterization Rhode&Schwarz fs (PLL BW=5kHz) - 65 fs (PLL fs (PLL BW=5kHz) - 92 fs (PLL BW=75kHz) - 85 fs (PLL BW=5kHz) - 72 fs (PLLBW=75kHz) Measured RMS Phase Noise

Synchronization system Laser time jitter measurements

Synchronization system Laser time jitter measurements Laser oscillator phase noise IR pulses, MHz rep rate Measured phase noise 650 ÷ 750 fs rms Laser output phase noise UV pulses, 10 Hz rep rate Measured phase noise 630 fs ÷ 1 ps rms

Synchronization system Laser time jitter measurements ● Preliminary phase noise measurements are marginally worse than system specifications ( 500 fs ) and factory characterization of the laser oscillator ( 350 fs ); ● The measured phase noise values include contributions from the frequency down-conversion board, laser synchro-lock system and photodiodes; ● The measured rms jitter is sensitive to the laser system set up (synchro-lock parameters) and power level; ● More experimental activity is necessary to identify the major phase noise sources and try to reduce their contribution; ● The measured phase noise levels are already inside the basic specification of SPARC.

Installation Main oscillator (2856MHz) RF amplifier Splitter Demodulation board 1 Demodulation board 2 Distribution board Fast interlock board Industrial PC DC voltage power supply SPARC hall

Installation Modulator hall 2 Milmega klystron drivers Cable installation 13 FSJ4-50B (for RF distribution and signal monitoring) 2 multipolar cables for interlock signals 2 RG-223 cables for RF pulse timing signals Thanks to Alfredo Specacenere for setting up FSJ4 cables

Installation RF low-level equipment Timing & Laser RF distribution RF monitor RF timing Cabling

Installation Hardware calibration demodulator channels - amplitude and phase offset - gain diodes - gain motorized phase shifters - encoder vs. phase shift - insertion loss voltage controlled attenuators - voltage vs. attenuation - voltage vs. phase shift RF switches - 1dB compression point cables - attenuation - time delay

Installation Some typical calibration curves Voltage controlled attenuator Demodulator channel Motorized phase shifter

Conclusions ● synchronization measurements meet specification for SPARC–phase 1 ● control system is ready for first operations ● hardware installation in SPARC area is completed RF low-level system is ready to begin tests on waveguides and RF gun