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ET- WP2 , Thermal noise issuesFulvio Ricci
Assergi (L’Aquila)
Laboratori Nazionali del Gran Sasso, February, 9th 2008
WP2 - Mission Pave the road to get the sensitivity of a GW detector as near as possible to 1 Hz, by seismic and thermal noise
Passive and active seismic attenuation
Low dissipation materials for mirror suspensions
Cryogenics: safety and noise compatibility in the underground environment
Next ET- WP2 workshop26-27 February 2009
@Sapienza - University of Romehttp://agenda.infn.it/conferenceDisplay.py?confId=1047
• The workshop will be devoted to the thermal noise issues in GW future detectors. We will review the thermal noise models for advanced detectors and thermal noise issues for ET.
• A large part of the meeting will be devoted also to the upper suspension configuration.
Tasks and involved Groups
Definition of substrates and coating properties at low temperature: Groups: LMA, Glasgow, INFN- Firenze/Urbino, INFN-Genova, INFN-
Perugia, INFN-Padova/Trento………Science team: Jena, Trieste(Cantatore)………
Design of Upper Suspensions: Groups: INFN-Pisa, EGO………
Design of Lower Suspension Mechanics:Groups: INFN- Roma1,INFN-Firenze, INFN-Perugia, INFN-Pisa,
Glasgow…….
Design of Cooling System:Groups: INFN- Roma1, INFN-Roma2……..
Design of Lower Suspension Sensing and Actuation:Groups: INFN-Roma2, INFN-Napoli, INFN-Padova/Trento, INFN-
Roma1…… Science Team: Genova (Vaccarone)……..
Design of Lower Suspension Fibers:Groups: Glasgow, INFN-Firenze/Urbino, INFN-Perugia, INFN-
Pisa………
Major impact on
ET Infrastruc
tures
Major impact on
ET Infrastruc
tures
10-19
10-20
10-21
10-22
10-23
10-24
10-25
Credit: M.Punturo
LIGO
Advanced LIGO/Virgo (2014)
Virgo
GEO-HF2011
Einstein Telescope
1 10 102 103 104
Frequency (Hz)
Ad LIGO/Virgo NB
[Hz -1/2 ]
Frequency [Hz]
Assuming a Sensitivity Target for ET
LIGOVIRGO
66
Design of the cooling systemDesign of the cooling system
•The upper part is thermally insulated by thermal screens
•The upper part is thermally insulated by thermal screens
Cryo-Compatible Cryo-Compatible Superattenuator Superattenuator designdesign
Cryo-Compatible Cryo-Compatible Superattenuator Superattenuator designdesign
Tanks to R. Passaquieti
The Pulse Tube Cryogenerator
Second stage
First stage
Compressor
High pressure linesLenght up to 20 m
Typical Performance of a double stage PT cryogenerator (PT 405)
The Prototype The Prototype of Cryogenic Payload installed at the EGO West hall @1.5 kmof Cryogenic Payload installed at the EGO West hall @1.5 km
Payload detailss
Marionette Reaction Mas100 kg Aluminums
Marionette100 kg s. steel and tungsten
Mirror Reaction Mass~20 kg aluminum
Mirror (silicon (20 kg)
Frame~40 kg saluminum
Cinese hatTitanium Ti6Al 4V
Cooling is started
Preliminary Displacement Spectra
Room Temperature: Pulse Tubes OFF Mirror Temperature 126 K: Pulse Tubes ON
How to overcame the problem.on the way- Active damping of the harmonic excitations
How to overcame the problem.on the way- Active damping of the harmonic excitations
1414
The Free Vibration Cryostat and its control chainThe Free Vibration Cryostat and its control chain
Slide 0Slide 0
S. Caparrelli, et al. Rev. of Sci. Inst. 77, 095102 (2006).
T. Tomaru et al. Cryogenics, 44 (2004). ( Passive vibration insulation system for the cryocooler) i
S. Caparrelli, et al. Rev. of Sci. Inst. 77, 095102 (2006).
T. Tomaru et al. Cryogenics, 44 (2004). ( Passive vibration insulation system for the cryocooler) i
1515
Vibration of the cold head reduced (@T=4K)Vibration of the cold head reduced (@T=4K)
The vibration reduction scheme works, but we need to improve it.The sensing will be modify to reduce the noise floor at closed loop.
displacement noisedensity
€
ΔxOL
ΔxCL
=117 @ 1Hz
€
Δx = 29 μm / Hz[ ] @1 Hz
The alternative scheme based on the production of Supefluid HeliumThe alternative scheme based on the production of Supefluid Helium
Cryostat design based on the so-called Claudet bath principleCryostat design based on the so-called Claudet bath principle
Cryogenic Infracture RequirementsThe PT solution
Cryogenic Infracture RequirementsThe superfluid Helium solution
Further studies are needed• PT solution
– Increase the active damping efficiency– Increase the length of the high pressure lines– Increase the refrigeration power
• Superfluid helium solution- evaluation of the noise impact of the cryogenic facility - thermo acoustic insulation of the long transfer lines
Upper part suspension
• …..see the presentation of Adalberto Giazotto