1 LESSONS FROM VIRGO+ May 17th 2010 E. Calloni for the Virgo collaboration

2 Difficulties and hopes Control of many degrees of freedom Aberrations Environmental noises Definitions of mid term scientific goals Stability of the mirrors Use of NDRCs for high power ITF Long work expected on environmental noises Involve theoreticians in time scheduling?

3 Some remarks on VSR2 Science Mode duty cycle > 80% Locked duty cycle > 85% Interferometer working mode particion Start July End January

4 Sensitivity and Horizon Sensitivity of Virgo+ during VSR2 (red) compared with theorical sensitivity (black) Horizon for NSNS solar masses for a typical lock

5 Sensitivity in good agreement with Noise Budget projections Recent noise budget with input power P0=17Watts. The total noise (pink curve) also includes the expected thermal (pendulum and mirror) noises

6 Difficulties of control many degrees of feeedom Alignment – the present control of alignment degrees of freedom is already complex and at the limit of noise reintroduction Residual (before closing the global alignement ) picth RMS about 0.8  rad Having the quiet mirrors also helps in lock acquisition (0.1  m/s) and in reducing control noises

7 Complexity of ADV detectors More degrees of freedom NDRCs lower the higher order modes thus error signal amplitudes High circulating power  radiation pressure effects Important to start with qiuet mirrors

8 Remarks on thermal noise During VSR2 the noise between Hz was in agreement with the expected Thermal noise + a small contributions of the other measured noises in the band

9 Installation monolithic suspensions Comment: the lowering of noise at low frequency appears to require long commissioning time both for control noises and environmental noises. The incoming operation of ITF with monolithic suspensions is expected to give important contribution for Adv detector Presently Virgo has two monolithic suspensions (input mirrors) installed and it is on going the installation of the other couples of monolithic suspensions (end mirrors) Nominal sensitivity of Virgo+ with monolithic suspensions (black) and VSR2 sensitivity (red). At very low frequency the nominal Virgo+MS sensitivity is comparable with Adv-Virgo

10 Aberrations From this picture it is seen how the NDRC maintain a much higher recycling of the sidebands with respect to MSRC configurations. This is also true for the carrier for high aberration

11 The sidebands in VSR2 We used about 1 of TCS per mirror to obtain the above shape of the sidebands and 15 recycling gain The amount of TCS was limited to 1 Watt due to noise reintroduction (before TCS power stabilization (early october) ) and to not available time for otpimization during the run During VSR2 with about 1 W of TCS per mirror Figure: sideband (left and right) and carrier (center) amplitudes at the output port of the ITF. As expected the carrier is highly aberrated (it is on dark fringe). The sidebands “should” be gaussian

12 Before and after installation of the two input monolithic suspensions Comparison of sidebands and carrier shapes at the output port before (upper) and after (lower) the installation of the first couple of monolithic suspensions and new input mirrors VSR2 Present Lower SB Carrier Upper SB

13 Control during VSR2 In these conditions of sidebands the control loops were not affecting the sensitivity. The projected noise with higher finesse and some tuning of loops is already compatible with Virgo+MS  Adv-Virgo The lesson from aberrations is somewhat “difficult”  the early Adv detectors will probably be injected with “low power” (around 25 Watt ) and use only power recycling. Anyway the locking of the ITF can be acquired and maintained in presence of not negligible aberrations  encouraging for the Adv

14 Environmental noise Up conversion of low frequency seismic noise Seismic and acustic noise due to Air conditioning machines, cooling fans….. Magnetic noise….. Modal analysis of NEB optical bench: (Left) measured map of bench motion with respect to ground; (Right) simulation of bench first structural mode.  stiffen the legs damp the resonances……

15 Environmental noises reduction Reduction of diffused ligth noise (bench alignments, isolation of pumps and funs), magnetic studies and reductions, dust protections TCS Power stabilization Time – frequency plot of dark fringe spectrum before and after turbo pump replacement with a smaller one Free running (blue) and controlled relative intensity noise of CO2 laser

16 Environmental and glitchness Rates of glitches for different SNR (central frequency < 150 Hz) for the whole VSR2. Each point correspond to 6 hours of data After the commissioning break of early October the high SNR glitches rate is greatly reduced, to less Hz, mediated on 6 hours of data, in normally quiet (not high microseism) conditions. Comment: the reduction of environmental noises can profit of a good collaboration between commissioners /data analysts (Data Quality) and should be encouraged in Adv detector

17 Experimentalists and theorists Horizon for NSNS solar masses for a typical lock Horizon as a function of total binary mass system for Virgo in June (blue curve) and in October (green), compared with the two Ligo detectors in the same period Comparison with Ligo detectors show that for high solar mass systems Virgo maintains a remarkable horizon, but it is very difficult to work in coincidence for high masses of the system.

18 The case of Virgo+ Monolithic suspensions Virgo+ with monolithic suspensions will leave a short life: it will be closed in July 2011 to start Adv-construction. Probably it will not have time to reach his potential sensitivity. A tight collaboration among experimentalists and theorists could define better where to strengthen the commissioning efforts. In the same way in case of Adv-Virgo a tight collaboration between theorists and experimentalists could be important in the various stages of the evolution of the sensitivity Medium term expected sensitivity for Virgo+MS Anticipating in very low frequency the sensitivity of Adv what could be searched for? Can we help in shortening the “desert crossing” of data?