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

2. 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

3. Present architecture

4. 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

5. Future architecture

6. 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 k€
Splitting box k€
Best EO electronics for PLL k€
Locking Electronics (motor controller) 13k€
Thermalized system enclosure k€

7. Cost estimation – Fiber links
Point-to-point distribution with a jitter <10fsRMS
2x Stabilized fiber links k€
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)

8. 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

9. 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€

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

11. 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
Performance of <50fsRMS of relative jitter
Total quotation fro MENLO systems is 360k€
We are studying alternatives to some proposed devices