The CUORE Cryostat: A 1-Ton Scale Setup for Bolometric Detectors

Abstract

The cryogenic underground observatory for rare events (CUORE) is a 1-ton scale bolometric experiment whose detector consists of an array of 988 TeO 2 crystals arranged in a cylindrical compact structure of 19 towers. This will be the largest bolometric mass ever operated. The experiment will work at a temperature around or below 10 mK. CUORE cryostat consists of a cryogen-free system based on pulse tubes and a custom high power dilution refrigerator, designed to match these specifications. The cryostat has been commissioned in 2014 at the Gran Sasso National Laboratories and reached a record temperature of 6 mK on a cubic meter scale. In this paper, we present results of CUORE commissioning runs. Details on the thermal characteristics and cryogenic performances of the system will be also given.

The commissioning of the CUORE experiment: the mini-tower run

“…The CUORE detector array is hosted in a custom dilution cryostat [3] (figure 1). Its peculiarity, apart from the extraordinary size, is that it is cryogen-free: in place of the liquid Helium five Pulse Tubes (PT) are used in the first phase of the cooling down.…”

“…When the temperature of 100 K is reached, five PTs are used to bring the apparatus down to 4 K. Finally the base temperature of 10 mK is reached thanks to a customized Dilution Refrigerator (DR), produced by Leiden Cryogenics in Netherlands, with a nominal cooling power of 5 µW at 12 mK. The DR acts thanks to a mixture of 3 He/ 4 He that continuously flows through two condensing lines and reaches the mixing chamber. The condensing lines, they are two for redundancy, are termalized with two PTs in order to have the precooling, at 4 K, of the incoming mixture.…”

The CUORE and CUORE-0 experiments at LNGS

“…Its nominal cooling power is 5 µW at 12 mK (3 mW at 120 mK), and the minimum reachable temperature is around 5 mK (for more details on the CUORE cryostat see [5]). The dimensions (> 10 m 3 ), the mass (∼ 25tons) and the cooling power (3µW at 10mK) make it the today's biggest and most powerful dilution cryostat in the world.…”

The CUORE and CUORE-0 experiments at LNGS

“…The detector array is cooled down to 10 mK by a multistage cryostat unique of its kind: the first stage at ∼ 4K is obtained by means of 5 two-stage Cryomech PT415 Pulse Tubes (PTs), with nominal cooling power of 1.5 W at 4.2 K and 40 W at 45 K each.The base temperature is then provided by a DRS-CF3000 continuous-cycle 3 He/ 4 He Dilution Refrigerator (DR), customized by Leiden Cryogenics for CUORE purpouses. Its nominal cooling power is 5 µW at 12 mK (3 mW at 120 mK), and the minimum reachable temperature is around 5 mK (for more details on the CUORE cryostat see [5]). The dimensions (> 10 m 3 ), the mass (∼ 25tons) and the cooling power (3µW at 10mK) make it the today's biggest and most powerful dilution cryostat in the world.…”