Ultra-cryogenics for advanced resonant detectors (C2) G.Frossati Kamerlingh Onnes Laboratory Leiden, The Netherlands Second ILIAS-GW Meeting October Palma de Mallorca

Sensitivity Minimum detectable energy T eff =T/  Q +2T N Need  ~0.05; Q~2x10 6 : T~30 mK

SQUID noise decreases with T 0.38  0

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.

MiniGRAIL Cryogenics

Next: 33 ton sphere ? Project together with the Roma group to be submitted to INFN h QL ≈4x /√Hz h QL ≈4x /√Hz

Cooling from 300K Fill liquid helium

Forced flow MiniGRAIL ton N L 800 L He

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 250K PT400 60W at 60K and 1W at 4.2k Heat to remove ~70J/gm ~2.8x10 9 J Cool-down time ~2 weeks to 4k SFERA ton N L He !

Dilution Refrigeration; Schematic view CIRCULATION SYSTEM  STILL  HEAT EXCHANGER  M IXING CHAMBER  HEAT ABSORPTION REGION 1k POT HEAT FLOW T MC

Pulsed tube dilution refrigerator 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

Strain sensitivity 2m CuAl6% sphere  f=1000 Hz  f=100 Hz  f=10 Hz MiniGRAIL