Virgo Upgrades Toward Virgo+

Virgo UpgradesToward Virgo+

Michele PunturoVirgo Collaboration

INFN Perugia

ILIAS-GW 4th general meeting 2

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


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


Plan Construction

06/09

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GO

VS

R1

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 preparethe future upgrades

05/08

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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


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 IMCThermal effects


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


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


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)


Status TCS• Preliminary Design presented at the June

detector meeting• Updated design: next detector meeting

(12/9)• Final design: 16/10 at the Virgo+ 2nd

review meeting• Installation: Jan 2008


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 (103 instead 104)

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)


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 N

d-Y

VO

4 m

odule

s

"Passive" cooling (H20)

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 TEM00Seed = 10W, amplifier output =50W, 93% in TEM00Seed = 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 activitiesBlack: already needed in Virgo


Virgo+ amplifier related activity:new mirrors

• In the 80-200Hz 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

1 10 100 1000 1000010-23

10-22

10-21

10-20

10-19

10-18

(f)

(a) Virgo Nominal sensitivity (b) Seismic noise (c) Pendulum thermal noise (d) Mirror thermal noise (e) Shot Noise nominal Virgo (f) Shot noise 50/2W

h(f) [1/

sqrt(H

z)]

Frequency [Hz]

(a)

(b)

(c)

(d)

(e)


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.

1 10 100 1000 1000010-23

10-22

10-21

10-20

10-19

10-18

h(f) [1

/sqrt(H

z)]

Frequency [Hz]

50W/2 + new losses + F=150 50W/2 + new losses model 50W/2 + current mirrors Nominal Virgo

• 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)


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 laserand higher finesse

Reduction of the mirror thermal noise

Newmirrors

Right magnetorientation in the

input mirrors.Etalon effects

Newpayloads

Eddy currentsThermal noise

solution

Newreference masses


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


Virgo+ upgrade: monolithic suspensions

• Decisional flux diagram

Design andEngineeringdevelopment

Design of a (dielectric) RM compatible both with the monolithic and the

traditional suspension (last detector meeting)

Full monolithicpackage passes the review filter?

no

Install aTraditionalsuspension

with a new RM

Continue thedesign andengineeringdevelopmentin a Virgo++ or advVirgo framework

yes

Install afull monolithicsuspension

Restart the design andengineering development

in an advVirgo framework

06/07

10/07

05/08

06/08

Not only readiness, but also “scientific contribution”


Sensitivity with Monolithic suspensions• Thermal noise reduction due

the monolithic FS suspension

1 10 100 1000 1000010-23

10-22

10-21

10-20

10-19

10-18

h(f) [1

/sqrt(H

z)]

Frequency [Hz]

50W/2 + new losses model 50W/2 + new losses model + F=150 50W/2 + current mirrors Nominal Virgo 50W/2 + new losses mod+FS suspensions+F=150

• 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


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) MpcBHBH: 626 (250)MPc

10 100 1000 1000010-23

10-22

10-21

10-20

10-19

h(f) [1

/sqrt(H

z)]

Frequency [Hz]

50W/2 + new losses model 50W/2 + new losses model + F=150 50W/2 + current mirrors Nominal Virgo 50W/2 + new losses mod+FS suspensions+F=150 as above and Newtonian Noise as above and DAC limit

NN

DAC


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 2008.

– ADC: ADC selection done (AD7674 18bit @ 800kHz); 16 differentials channels with analog anti-alias filter at 400KHz. Digital anti-alias filters in embedded DSPs( 4 channels per DSP ADPS-21262 @150MHz ) Several production steps foreseen, but final production expected to end in March-April 2008.

– 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


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?

– t0 is depending by the end of the S5-VSR1 run• Just concluded

– t0 is depending by the content of the post-VSR1 commissioning• Now defined

– t0 is depending by the outcomes of the 2nd review meeting• 16-17 October 2007

Documents

Virgo Upgrades Toward Virgo+