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