SPARC review committee ENEA Frascati 16112005 RF low

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

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 - ● 13 devices to be controlled - ● waveform and phase monitor systems ready to use 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 stability specifications • 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) • Seeding@SPARC and/or next-generation experiments: ± 0. 1° control of the bunch longitudinal position

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

Synchronization system Oscillator characterization Rhode&Schwarz SMT: Measured RMS Phase Noise @2. 5 GHz: - 130 fs (PLL BW=5 k. Hz) - 65 fs (PLL BW=75 k. Hz) @2. 856 GHz: - 183 fs (PLL BW=5 k. Hz) - 92 fs (PLL BW=75 k. Hz) HP 8663 A: @2. 5 GHz: - 85 fs (PLL BW=5 k. Hz) - 72 fs (PLLBW=75 k. Hz)

Synchronization system Laser time jitter measurements

Synchronization system Laser time jitter measurements Laser oscillator phase noise IR pulses, 79. 33 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 SPARC hall • Main oscillator (2856 MHz) • RF amplifier • Splitter • Demodulation board 1 • Demodulation board 2 • Distribution board • Fast interlock board • Industrial PC • DC voltage power supply

Installation Modulator hall • 2 Milmega klystron drivers Cable installation • 13 FSJ 4 -50 B (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 FSJ 4 cables

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

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 - 1 d. B compression point • cables - attenuation - time delay •

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

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