1 Phase Camera CRE S. Bigotta, L. Bonelli, A. Di Lieto, A. Toncelli, M.Tonelli INFN – Pisa University P. La Penna EGO

Motivation Thermal lensing effects are posing serious limitations to the correct operation of Virgo interferometer, limitations that demand a prompt solution. The study of the RF sidebands could give a better understanding of the problem, solving thermal lensing issues and eventually optimizing the sensitivity of the VIRGO detector  a spectrum analyzer (SFP) for the Virgo beam have already been set up  phasecamera is natural evolution and enhancement of the SFP (improved frequency resolution, spatial info about amplitude and phase of each sideband)

to keep the scheduling time as short as possible, the proposed phasecamera will be an adaptation of the LIGO project to the VIRGO needs a great amount of information is readily available, and, more important, we don’t have to start from scratch in the realization of this device Technical description The test field is superposed on a reference field Two galvanometers move the beams over the surface of a photodetector A demodulator gives the spatial amplitude and phase of any frequency component of a laser field

4 Task 1: phase locking This task includes the study of the control electronics. The possible choices for the control loop include homemade controller (low cost but need some time and manpower)homemade controller (low cost but need some time and manpower) modification of commercially available controllers such as, for instance, those sold by Toptica ( ) (higher cost (~8000 €), but should be less consuming in terms of time and manpower).modification of commercially available controllers such as, for instance, those sold by Toptica ( ) (higher cost (~8000 €), but should be less consuming in terms of time and manpower).

5 Task 2: Realization of the detector 6.26MHz 10MHz 6.26MHz 10MHz 6.26MHz 10MHz The use of the programmable frequency synthesizer will allow to keep the reference laser to always locked to the carrier of the test laser ref laser test laser PLL programmable synthesizer IF amp PD2 PM /2 PD1 pinhole band pass filter LO (90 o ) RF (0 o ) I Q

6 Task 2bis: Implementation of the galvanometers In this task we should implement the galvanometer system being developed by the INFN group of Napoli. The exact nature of this task haven’t yet been investigated. The delay introduced by this task in the implementation plan must be investigated.

7 Task 3: Realization of the test beam generator Frequency stabilization ~100 kHz Difficult to adapt to simulate VIRGO parameters Time & money consuming

8 Task 3: Realization of the test beam generator Scenario a: test beam without the MC cavity In this scenario the test beam generator is realized, but in a different way with respect to the work done by Goda et al. The technical specifications of the Mephisto laser from InnoLight state that the frequency drift of this device is less than 1 MHz/min. Since the phasecamera is expected to perform a single acquisition in less than 200 ms, this means a maximum drift of few kHz during the scan. It would be easier, faster and more affordable to test the phasecamera without cleaning the test beam. A simple phase modulation of the test beam by means of an electro-optical modulator should be enough for our purposes. Scenario b: no test beam is used, test of the detector on site In this scenario the test beam generator is not realized and the phasecamera is tested directly on the detection bench. Obviously there’s nothing to do on this task for this scenario.

9 Task 4: Testing & tuning of the phasecamera Both the scenarios In this task the testing and the tuning of the phasecamera will be performed. The device will be checked to be compliant to the VIRGO requirements. The phasecamera is not expected to influence the other devices on the detection bench (it requires, however, a new optical layout of the detection bench in order to free some space on it). Scenario b Contrary to scenarios a, this scenario will involve a massive use of shifts on the detection bench to tune the device and will interfere with VIRGO normal commissioning. This fact is a serious drawback of this scenario and should be taken into account.

10 People M. TonelliINFN, Pisa UniversityAssociate professor S. BigottaINFN, Pisa Universitypostdoc L. BonelliINFN, Pisa UniversityPhD student A. Di LietoINFN, Pisa UniversityAssociate professor A. ToncelliINFN, Pisa Universityresearcher P. La PennaEGO

11 Planning [1] [1] This task may delay the implementation plan Implementation Plan Tasks and DeliverablesJulAugSepOctNovDecGenFeb Tasks Lasers and phase-locking electronics set-up Realization of the detector itself Implementation of the galvanometers [1] [1] Realization of the test beam generator(scenario a) Testing & tuning of the phasecamera(scenario a) Realization of the test beam generator(scenario b) Testing & tuning of the phasecamera(scenario b) Deliverables Phasecamera(scenario a) Phasecamera(scenario b)

12 Involved Virgo sub-systems and EGO infrastructure # InfrastructureDescription of the involvement OpticsLaboratory, equipment, participation to test and installation Mechanical workshopHelp with mechanical part and assemblies ElectronicsHelp with the control electronics #Subsystem NameDescription of the involvement 1Detectionnew optical layout 2Electronics and Software 3Data acquisition

13 Budget #ItemContractor / supplier Cost (€)Charged to (EGO/Virgo) 2Mephisto laser 200 mWInnoLight45,00020,000 2Galvanometers6,000 Mirrors, mirror mounts and breadboard 4,000 EO modulator5,000 Electronics and detectors13,000 2Beam expanderLinos2,000 Optics4,000 Total cost (€): 79,000 Request to EGO (€) 54,000