1. Calva update Nicolas Leroy for the CALVA group (LAL, ESPCI, LAPP, LMA) Main Laser Cavity 1Cavity 2 Aux. Laser L1 L2 M1M2M3

2. Infrastructure/Mechanics Both clean rooms built All vacuum system installed and tested 3 vacuum tanks and 50m+5m long tubes Residual pressure : ~ 6 10 -7 mbar

3. Optics Mephisto lasers (1064 and 1319 nm) installed in final position All 3 mirrors are installed in the vacuum tanks Coated by LMA 1 long 50m cavity, finesse 620 1 long 5m recycling cavity, finesse 15 Local controls installed on the long cavity Last mirror will be very soon equipped Beam size matching for the cavities have been retuned

4. Software and electronics Electronic: Digital : used Annecy's system (tolm, ADCs,...) Analogic : home made (coil drivers, DAC,...) Software: Used Virgo software Only some adds to take into account different optical scheme and specific parts

5. First tests We have start we the high finesse cavity in 5m Tests electronics, software and controls Mirrors free then under local controls Reflection Transmission

6. First locks First lock on 1319 nm (DC transmission signal) δL ~ 3nm Reflection Transmission

7. First locks Then move to 1064 nm – δL ~ 100 pm Not lot of force needed for the transition Reflection Transmission

8. Present status Since we move to the 50m cavity Problem with lock acquisition  We are able to lock on 1319 nm  No more lock on 1064 nm Simulation studies show that the frequency noise of the 1064 nm is at the limit  Usual noise ie 10 4 /f Hz/sqrt(Hz)  Only changing the frequency noise shape between 10/20 Hz and 100 Hz will be enough  Using Laurent Derome measurments (PhD thesis) and Romain Gouaty tests (logbook entry 28709), the Virgo OMC could be enough to act as reference  Edwige kindly give us one of the spare to perform some tests – currently under installation

9. CALVA Simulation and Lock Acquisition Simulation of a double cavity in Siesta A new Siesta module have been developed to simulate the CALVA layout Field propagation in two cavities "a la OPcavity" Quasi-static and full dynamic methods have been implemented 2 lasers (or more) can be propagated simultaneously Lock Acquisition procedure We started to study different locking scenarios which are to be tested on the CALVA platform For example: 1/ lock the long cavity with a tilted recycling mirror 1319nm2/ tilt back the recycling mirror 3/ lock the recycling cavity 4/ move the locking point to catch the main resonance Transmitted power 1064nm s 1319nm 5/ lock the long cavity 1064nm6/ move the locking point to lock the recycling cavity 7/ lock the recycling cavity

10. Calva and Advanced Virgo Fabien made some simulations to study the lock acquisition of the 3-km cavities with a finesse of 450 (VIR-0656A-10) Conditions: Same algorithm for locking than for Virgo Limitation on actuation current Let the cavity free (10s) before locking Tests: Seismic noise – speed from 1.5um/s to 6 um/s Delays in control loops Force limitation

11. Calva and Advanced Virgo Ground motion: Only very large motions make problem Delay : no problem observed up to 1ms Force limitation : 5mN/A is still acceptable

12. Conclusions Calva is ready to achieve its first goal : study a new lock acquisition method on a Virgo-like setup Still some technical problems, soon behind us CALVA is not required with the current foreseen finesse for arm locking However it could still be interesting when we will have signal recycling Start to think on new physics subject : Laguerre-Gauss beams, deformable mirrors,...