Status of Synchronization System M. Bellaveglia On behalf of the LNF timing, synchronization and LLRF group

Synchronization issues RF to laser pulses Example: COMB Multiple e-bunches injected in the same RF bucket Critical injection phase for RF compression Request: ΔtRMS≈100fs e-bunch to laser Example: PLASMONX SPARC and Flame beams injected together Synchronization at the level of the plasma wave period Request: ΔtRMS<30fs

Present architecture

Present architecture RF distribution through coaxial cables Feedbacks: Temperature drifts (BW<<1Hz) RF-to-laser (BW≈5kHz) (PC laser PLL problem) RF-to-RF (BW≈1MHz) System performance Detection resolution: <50fsRMS RF-to-LLRF: 40÷100 fsRMS Laser-to-LLRF: <250fsRMS (resolution problem) e-bunch-to-LLRF: <150fs (resolution limit) Enough for COMB, but not for LWPA with external injection

Future architecture

Cost estimation - OMO RMO already at LNF Low f noise depeds upon RMO (≈70fsRMS) High f phase noise <10fs OMO Femtosecond Fiber Laser 50k€ Laser amplifier 26k€ Splitting box 12k€ Best EO electronics for PLL 31k€ Locking Electronics (motor controller) 13k€ Thermalized system enclosure 15k€

Cost estimation – Fiber links Point-to-point distribution with a jitter <10fsRMS 2x Stabilized fiber links 120k€ Due to our limited client distance (50m maximum), we are planning to avoid the active links, by means of special fibers with low Thermal Coefficient of Delay (TCD)

Stabilized Fibers Figure shows measurements performed at DESY: FURUKAWA fibers 3.3fs/°K/m from specs 65k€/km LINDEN fibers 5fs/°K/m not specified price much lower FURUKAWA fibers with coating added by german company 18fs/°K/m Normal SMF 40fs/°K/m

Cost estimation - Optical phase detection Phase detection resolution in the range of attoseconds Client locks in the worst case with a jitter well below 50fsRMS Custom Cross-Correlator 1550nm x 800nm To be used in the SPARC and FLAME lasers 2x Custom OptoMech 30k€

Single pulse time arrival monitor Use of a Mach-Zender 10GHz EO modulator Already purchased (1.5k€) and benchmarked in the lab

Conclusion Present system with coaxial distribution Resolution should be upgraded for: Photocathode laser-to-RF PLL and arrival time monitor Diagnostics for bunch arrival time monitor We can achieve a performance of ≈100fsRMS of sub- systems relative jitter Future system with optical distribution It is mandatory in case of LPWA (external injection) It is already developed and installed by MENLO systems in FERMI@ELETTRA Performance of <50fsRMS of relative jitter Total quotation fro MENLO systems is 360k€ We are studying alternatives to some proposed devices