Virgo Upgrades Toward Virgo+ Michele Punturo Virgo Collaboration INFN Perugia

ILIAS-GW 4th general meeting2 Upgrades Motivations The motivations of these upgrades (including the Virgo+ packages) are (obviously) science-driven –To understand it let start from the current sensitivity and budget noise Longitudinal and actuation control noises Shot noise dominated Un-modeled To reduce these noise sources we need: –Commissioning –Upgrades

ILIAS-GW 4th general meeting3 Overall strategy Virgo+ needs a series of preliminary upgrades interlaced with the commissioning activity –Coil drivers, thermal compensation, fast centering quadrant PHD, … The Virgo+ upgrade strategy must respect the following –Aim: To maximize the detection probability –To maximize the coincidences with eLIGO –Constrains: Need of an intense and “enough long” commissioning after VSR1 to understand the low-medium frequency noise of Virgo Have an enough long (~1 year) post-upgrade commissioning period Be back in science mode in (middle) 2009 Have a Virgo+ sensitivity comparable with eLIGO in a wide frequency range

ILIAS-GW 4th general meeting4 Plan Construction 06/09 Science mode in parallel with eLIGO VSR1 10/07 ~1 year of Commissioning after the last “major” upgrade 07/08 ~6-7 Months of commissioning and upgrading to understand our noise budget, recover as much as possible the nominal sensitivity and prepare the future upgrades 05/08 Major upgrades time window

ILIAS-GW 4th general meeting5 Post VSR1-Commissioning (2007) Aim –Understanding of the machine and reduction of the noises that could make inefficacy the foreseen Virgo+ upgrades Foreseen activities: –See Bas talk

ILIAS-GW 4th general meeting6 Virgo+ upgrades Let start again from the noise budget: Causes of the discrepancy: –Lower power recycling factor –OMC matching –Lower injected power Laser max power 21W Laser power at the LB exit: 17W Currently injected power 12.5W Power after the IMC: 8W Power loss in the IMC Thermal effects

ILIAS-GW 4th general meeting7 New IMC payload The motivations requiring the replacement of the current IMC end mirror payload are antecedent to the VIRGO+ project: –Certified bad substrate quality is the main culprit of the power loss and scattering in the ISYS The contribution of the other mirrors is unknown –The very light substrate causes many troubles (solved) in the control due to the deviation by a simple pendulum transfer function and to the spring effect of the radiation pressure New payload under construction New mirror polished The replacement of the IMC end mirror will occur in parallel to the installation of the laser amplifier

ILIAS-GW 4th general meeting8 Thermal lensing and sidebands The main limitation to the injected power increase is the thermal lensing in the input mirrors Correlation between sidebands ratio and injected power

ILIAS-GW 4th general meeting9 Thermal lensing mitigation The first action to reduce the thermal lensing is the reduction of the absorbed power: –Input mirror cleaning Under evaluation with the experts –Some technical difficulty –Temporary and uncertain solution –“Final solution”: TCS (Thermal compensation system) Solution already adopted in LIGO –Similar principle, but original implementation because of different geometry –Implementation expected in Jan2008 Error signal generation –Use a holed mirror and a couple of PHD –Implementation expected before end 2007 (Nov)

ILIAS-GW 4th general meeting10 Status TCS Preliminary Design presented at the June detector meeting Updated design: next detector meeting (12/9) Final design: 16/10 at the Virgo+ 2 nd review meeting Installation: Jan 2008

ILIAS-GW 4th general meeting11 Thermal related upgrades A set of upgrades are foreseen to mitigate the other thermal effects we are suffering in Virgo The installation of these upgrades, before the increase of the laser power, will simplify our transition to the Virgo+ design –Remote tuning of the injected laser power A remotely controlled /2 waveplate will be installed in the laser bench to adjust the injected power according to the detector needs –Remote adjustment of the suspended Faraday Isolator Optical isolation of the suspended FI is lower (10 3 instead 10 4 ) because of some thermal effect (Verdet’s constant) –A solution as been designed and it will work also in Virgo+ FI thermal lensing in Virgo+ is expect to be corrigible through the telescope adjustment (but further solution under design)

ILIAS-GW 4th general meeting12 Virgo+ upgrade: Laser Amplifier The new laser amplifier is the core upgrade that will permit the reduction of the shot noise at high frequency below the nominal sensitivity It is a “standard” device (produced by LZH/GEO and adopted also in eLIGO) 4 pump diodes fiber 4 Nd-YVO4 modules "Passive" cooling (H 2 0) 20W seed 50W out Already available and under test in the Nice labs –Installation in May-June 08 For nominal amplifier pumping Seed = 1W, amplifier output = 24W, 90 % in TEM00 Seed = 10W, amplifier output =50W, 93% in TEM00 Seed = 20W, amplifier output =65W, 94% in TEM00 Reduced amplifier pumping (72% from nominal) Seed = 20W, amplifier output = 50W, 73% in TEM00

13 Cascade effect on the ITF Obviously the laser power increase will affects all the ITF Reshuffling of the LB: Pre-MC, new FIs, remote tuning of the injected power Reshuffling of the EIB Remote tuning of the FI, Thermal lensing issues, dihedron modification? Heavier mirror and payload, better quality mirror Cleaner mirror & thermal compensation, New mirrors Red: new activities Black: already needed in Virgo

ILIAS-GW 4th general meeting14 Virgo+ amplifier related activity: new mirrors In the Hz range the high power gain is completely spoiled by the thermal noise expected for the Virgo Herasil end mirrors We need to change the mirrors if we want to profit of the larger injected power, but the replacement of the mirrors is suggested also by the cited contamination issues and by some effect (etalon effect), measured during the VSR1

ILIAS-GW 4th general meeting15 New mirrors and coatings New Suprasil end and input mirrors –Under polishing at the GO Delivery expected for end 2007-beginning 2008 –According to the Penn’s noise model the loss angle expected for this material is of about 10 -9, opening a new window in the intermediate frequency regime To exploit this window an higher finesse is needed: F=150 instead of the current 50. New coatings alchemy (lower mechanical dissipation) New cleanliness procedures –Special protecting film provided by the coaters (Lyon) NSNS: 69.8 (27.9) BHBH: 355 (142)

ILIAS-GW 4th general meeting16 New payloads The need to have new payloads is driven by many motivations –Since we have to replace the payloads, could we profit to foresee the installation a new kind of suspension? Reduction of the shot noise High power laser and higher finesse Reduction of the mirror thermal noise New mirrors Right magnet orientation in the input mirrors. Etalon effects New payloads Eddy currents Thermal noise solution New reference masses

ILIAS-GW 4th general meeting17 Virgo+ upgrade: monolithic suspensions Monolithic fused silica suspension development is an heavy activity in Virgo (and in LIGO) –Joint effort of the Perugia, Roma 1, Firenze labs with the EGO and LMA support –Trial suspension almost successful, but still many delicates points: Robustness of the suspension Controllability –Angular-to-translation coupling Cleanliness Recoverability after a failure –Activity progressing thanks the full immersion of the involved groups, but there are strong indications that the needed time is incompatible with the overall Virgo+ planning

ILIAS-GW 4th general meeting18 Virgo+ upgrade: monolithic suspensions Decisional flux diagram Design and Engineering development Design of a (dielectric) RM compatible both with the monolithic and the traditional suspension (last detector meeting) Full monolithic package passes the review filter? no Install a Traditional suspension with a new RM Continue the design and engineering development in a Virgo++ or advVirgo framework yes Install a full monolithic suspension Restart the design and engineering development in an advVirgo framework 06/07 10/07 05/08 06/08 Not only readiness, but also “scientific contribution”

ILIAS-GW 4th general meeting19 Sensitivity with Monolithic suspensions Thermal noise reduction due the monolithic FS suspension We should take in account the Newtonian noise limit But, mainly, we should take in account our experience with the detector: the actuation noise In the low frequency the current sensitivity is locally limited by the actuation noise mainly because of non linear effects this is known and a progressive reduction of the actuation noise has been performed in the past through: –Insertion of a resistor in series to the coil –Introduction of an emphasis filter These patches are converging to the production of a new model of coil drivers

ILIAS-GW 4th general meeting20 Contribution to the sensitivity The role of the actuation noise is and will be important in the Virgo+ expected sensitivity Since the determination of the expected noise level of the new coil drivers is still under investigation, we report a conservative evaluation (DAC/3 instead of DAC/8) NSNS: 122 (49) Mpc BHBH: 626 (250)MPc

ILIAS-GW 4th general meeting21 Control & DAQ electronics New DSP development in Pisa (important for the low frequency part), and a series of upgrades of the DAQ electronics has been foreseen and supported by EGO Design activity progressing in Annecy: –Development of new timing system (obsolescence of the hardware) GPS receiver/signal generator (tested, patched and ready; more boxes to be purchased) TDBox (Timing distribution box): design ready for production MUX/DeMUX: router for the optical links between TOLM and ADC boards. Prototype available. Production and tests on September-October 2007 TOLM: A prototype available and used for ADC tests, TOLM /DSP interface tested. Two versions expected to be produced: PMC and PCI64 formats. Production expected for the March –ADC: ADC selection done (AD kHz); 16 differentials channels with analog anti-alias filter at 400KHz. Digital anti-alias filters in embedded DSPs( 4 channels per DSP ) Several production steps foreseen, but final production expected to end in March-April –Tests of regular PCs: These tests have shown that the main Virgo control loop (photodiode readout and global control) could run up to 40 KHz on a commercial PC running a real time version of Linux. This will provide more computing resource for various control loops (global and local). Installation: –Foreseen in May 2008

Planning

ILIAS-GW 4th general meeting23 Planning status A planning is available since many months, but is still unfrozen. Currently: –220 tasks (commissioning + Virgo+ installations) –22 macro-activities A first man power budget has been evaluated –62 physicists/engineers involved in the activities –Amount affected by the lack of response of some team A money (EGO) budget is available Why the planning is unfrozen? –t 0 is depending by the end of the S5-VSR1 run Just concluded –t 0 is depending by the content of the post-VSR1 commissioning Now defined –t 0 is depending by the outcomes of the 2nd review meeting October 2007