Commissioning of the Cryogenic System for the ATLAS Superconducting Magnets

Abstract

The paper describes the test results of the helium cryoplant for the superconducting magnets of the ATLAS particle detector at CERN. It consists of two refrigerators used in common by all the magnets and of two proximity cryogenic systems (PCS) interfacing respectively the toroids and the central solenoid. Emphasis is given to the commissioning of the refrigerators: the main unit of 6 kW equivalent capacity at 4.5 K and the thermal shield refrigerator providing 20 kW between 40 K and 80 K. The first unit is used for refrigeration at 4.5 K and for the cooling of three sets of 20 kA current leads, while the second one provides, in addition to the 20 kW refrigeration of the thermal shields, 60 kW for the cool-down to 100 K of the 660 ton cold mass of the magnets. The tests, carried out with the equipment in the final underground configuration, are extended to the PCS that includes the large liquid helium centrifugal pumps (each providing 1.2 kg/s) for forced-flow cooling of the magnets and the complex distribution system needed to fulfil their different operating requirements. COMMISSIONING OF THE CRYOGENIC SYSTEM FOR THE ATLAS SUPERCONDUCTING MAGNETS ABSTRACTThe paper describes the test results of the helium cryoplant for the superconducting magnets of the ATLAS particle detector at CERN. It consists of two refrigerators used in common by all the magnets and of two proximity cryogenic systems (PCS) interfacing respectively the toroids and the central solenoid. Emphasis is given to the commissioning of the refrigerators: the main unit of 6 kW equivalent capacity at 4.5 K and the thermal shield refrigerator providing 20 kW between 40 K and 80 K. The first unit is used for refrigeration at 4.5 K and for the cooling of three sets of 20 kA current leads, while the second one provides, in addition to the 20 kW refrigeration of the thermal shields, 60 kW for the cool-down to 100 K of the 660 ton cold mass of the magnets. The tests, carried out with the equipment in the final underground configuration, are extended to the PCS that includes the large liquid helium centrifugal pumps (each providing 1.2 kg/s) for forcedflow cooling of the magnets and the complex distribution system needed to fulfill their different operating requirements.

Cryogenic Characteristics of the ATLAS Barrel Toroid Superconducting Magnet

“…A detailed description of the ATLAS magnet cryogenic system can be found in [2], and the results of the first cooldown and operation at 4.5 K is described elsewhere [3] in this proceedings collection. With reference to Fig.…”

First operational experience and performance optimization of the ATLAS magnet cryogenic system

“…ATLAS, the largest detector operated at the LHC, has a magnet system consisting of four superconducting magnets: one barrel toroid, two end-cap toroids and one central solenoid [1][2][3][4][5]. The complete cryogenic system to cool-down and maintain at 4.5 K these magnets has been based on two helium refrigerators used in common by all magnets and on two proximity cryogenic systems interfacing respectively the toroids and the central solenoid [2,3].…”

First Cool-Down and Test at 4.5 K of the ATLAS Superconducting Barrel Toroid Assembled in the LHC Experimental Cavern

“…On 31st August 2006, once we had accumulated more than 3'000 liters of liquid helium in the phase separator located at the outlet of the coils [4], [5], we could start the centrifugal pump providing a total circulation of 0.6 kg/s ( 5 L/s) of liquid helium through the 8 coils.…”

“…To cope with these cryogenic tasks, two separate helium refrigerators have been installed and commissioned in a side-cavern close to the detector [4]. The main refrigerator (MR) has an equivalent cooling power of 6 kW at 4.5 K. It is used to cool-down the magnets from 100 K to 4.5 K and then ensure their steady-state operation at 4.5 K which also includes the cooling of the current leads.…”

“…2 presents a simplified process flow diagram of the complete ATLAS magnets cryogenic system. Detailed description of these various cryogenic components can be found in [2] and [4].…”