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Ultra-cryogenics for advanced resonant

detectors (C2)

G.Frossati

Kamerlingh Onnes LaboratoryLeiden, The Netherlands

Second ILIAS-GW Meeting October 24-25 2005Palma de Mallorca

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Sensitivity

Minimum detectable energy

Teff=T/Q +2TN

N B NE = k T =1 h with = 3KHz

-7NT 1.5×10 K

Need~0.05; Q~2x106: T~30 mK

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SQUID noise decreases with T

0.38 0

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ROG SQUID

• Double SQUID made of a sensor d.c. SQUID, developed by the Institute of Photonic and Nanotechnologies of CNR, and a commercial Quantum Design d.c. SQUID as a preamplifier.

• Open input and in open loop configuration: 28hbar at 4.2 K and 5.5hbar at 0.9 K.

• Feedback network :37hbar in closed-loop open-input 4.2K. 

• With a high-Q resonant input load :70hbar at 2 K.

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MiniGRAILCryogenics

www.minigrail.nlNext: 33 ton sphere ?Project together with the Roma

group to be submitted to INFN

hQL ≈4x10-24/√Hz

hQL≈4x10-23/√Hz

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Cooling from 300K

Fill liquid helium

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Forced flow

MiniGRAIL 1.3 +1 tonN2 1200 L800 L He

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ROG-Leiden-Geneva project: to be submitted to INFN

Use 4 GM cryocoolers for pre-cooling from 300K to 20K

Use 4 PT410 for cooling to 4K and for the

dilution refrigerator

GM600 (Cryomech) 1200W at 250KPT400 60W at 60K and 1W at 4.2k

Heat to remove ~70J/gm ~2.8x109JCool-down time ~2 weeks to 4k

SFERA33 +7 ton20000 N2

14000 L He !

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Dilution Refrigeration; Schematic view

CIRCULATIONSYSTEM

STILL

HEAT EXCHANGER

MIXING CHAMBER

STILLQ

HEAT ABSORPTION REGION

1k POT

HEAT FLOW

MCQ

STILLQ

TMC

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Pulsed tube dilutionrefrigerator

Joule Thompson heat exchanger replaces the 1K pot: No need for Helium bath

JT Heat exchanger

PTR

Mixing Chamber

50K

4K

600 mK

60 mK

10 mK

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www.minigrail.nlStrain sensitivity

2m CuAl6% sphere

f=1000 Hz

f=100 Hz

f=10 Hz

MiniGRAIL