Transcript Virgo Upgrades - ego

Virgo Upgrades
Toward Virgo+
Michele Punturo
Virgo Collaboration
INFN Perugia
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
• To reduce these
noise sources we
need:
– Commissioning
– Upgrades
Un-modeled
Shot noise
dominated
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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
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~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
10/07
05/08
~1 year of
Commissioning after the last
“major” upgrade
07/08
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06/09
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Science mode in parallel with eLIGO
Major upgrades time window
VSR1
Plan Construction
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
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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
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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
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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
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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)
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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
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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 l/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)
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Virgo+ upgrade: Laser Amplifier
4 Nd-YVO4 modules
• 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
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
• Already available and under
test in the Nice labs
20W seed
– Installation in May-June
08
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"Passive" cooling (H20)
50W out
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Cascade effect on the ITF
• Obviously the laser power increase will affects all the ITF
Red: new activities
Black: already needed in Virgo
Reshuffling of the LB: Pre-MC,
new FIs, remote tuning of the
injected power
Heavier mirror
and payload,
better quality
mirror
Reshuffling of
the EIB
Remote
tuning of the
FI, Thermal
lensing
issues,
dihedron
modification?
Cleaner mirror &
thermal
compensation,
New mirrors
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Virgo+ amplifier related activity:
new mirrors
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(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
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h(f) [1/sqrt(Hz)]
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(b)
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(d)
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(a)
(e)
(f)
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1
10
(c)
100
1000
10000
Frequency [Hz]
• 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
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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
10
current 50.
50W/2 + new losses + F=150
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h(f) [1/sqrt(Hz)]
• New coatings alchemy (lower
mechanical dissipation)
• New cleanliness procedures
50W/2 + new losses model
50W/2 + current mirrors
Nominal Virgo
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10
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– Special protecting film provided by
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the coaters (Lyon)
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NSNS: 69.8 (27.9)
BHBH: 355 (142)
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100
Frequency [Hz]
1000
10000
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New payloads
Reduction of the
shot noise
High power laser
and higher finesse
New
mirrors
Reduction of the
mirror thermal noise
New
payloads
Right magnet
orientation in the
input mirrors.
Etalon effects
Eddy currents
Thermal noise
solution
New
reference masses
• 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?
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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
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Virgo+ upgrade: monolithic suspensions
• Decisional flux diagram
06/07
10/07
Design of a (dielectric) RM compatible
Design and
both with the monolithic and the
Engineering
traditional suspension (last detector meeting)
development
no
Full monolithic
package passes
the review filter?
yes
05/08 Continue the
design and
Install a
Traditional
06/08 engineering
development suspension
Install a
with
a
new
RM
in a Virgo++
full monolithic
suspension
or advVirgo
Not only readiness,
framework
but also “scientific
Restart the design and
contribution”
engineering development
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in an advVirgo 18
framework
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
•
•
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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
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h(f) [1/sqrt(Hz)]
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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:
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1
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100
1000
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Frequency [Hz]
– Insertion of a resistor in series
to the coil
– Introduction of an emphasis
filter
•
These patches are converging
to the production of a new ILIAS-GW 4th general meeting
model of coil drivers
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Contribution to the sensitivity
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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)
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DAC
h(f) [1/sqrt(Hz)]
•
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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
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NN
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100
1000
Frequency [Hz]
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NSNS: 122 (49) Mpc
BHBH: 626 (250)MPc
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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
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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
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