--The magnet system for ihc ATLAS delcctor at CERN cnnsists of a Barrel Toroid (RT), two End-Cap Toroids (ECT) and a Ccntral Solenoid (CS). The overall dimensions of the system are 20 m in diameter by 26 m in length. B c h c underground installation all coils will be tested on surfacc fn a magnet test facility which Is under construction. Moreover two model coils are testcd as well ns siibsystemu. hi this paper the design and construction of the test facility Is presented, I. INTItOUUCTIONThe ATLAS Magnet System [ 1,2] comprises the superconducting magnets, the power supply system, the cryogenics system, thc vacuum system and thc control and sakety sysicm. The magtat system hm overall dimension of 26 meters in length and 20 meters in diameter (see Fig. 1 In order to verify the constniction concepts on BO and themafter the correct operation of thc othcr coils, the tests must represent the mal configuration. The iirfrastnicturc requircd to pcrform thc tcsts compriscs: a rather complex cryogenic plant with a He refrigerator, a pre-cooling unit, a cryostat with intcgratcd i m " e d centriflugal pumps for liquid He flows above 80 g/s to cool the magnct cold masses and a distribution system: the vacuum system with a pumping system sblc to provide 10" mbar; the electrical system fur coil cnergizing with R 6VIUkA power supply; appropriate qucnch protcction units as well as systems for control and diagnostics. Prcliminary test of the BO coil wirh a magnetic mirror to simulate thc clcclcomagiictic load and the full set of instrumcntation is planned by s u m " 2000. Duo to the exceptional size of the B'C system, each coil will be individually tested on the ground at nominal current with the magnetic mirror so as to reproduce the actual load, before lowering them down in the cavern. gach of the two ECT magnets and thc CS magnet will bc Cully asscmbled and testcd on the surface, before the installation as complete systems in the cavern. 11, THE BOO AN13 BO MODEL COnSThe first coil Single pancake winding made with CS conductor.
A method of producing a polarised positron beam from e + e -pair production in a target by circularly polarised γ-radiation is being investigated. Polarised photons are to be generated by the passage of a high energy electron beam (250 GeV as anticipated in the International Linear Collider -ILC) through a helical undulator. For production of 20 MeV photons, an undulator with a period of 14 mm, a bore of approximately 4 mm and magnetic field on axis of 0.8 T is required. First prototypes have been constructed using both superconducting and permanent magnet technologies which are capable of producing the necessary magnetic field configuration in the undulator. This paper details the design, construction techniques and field measurement results of the first superconducting prototype and compares the results with simulation.
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.
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