B. Vullierme

Measurement of the Thermo-Hydraulic Behaviour of LHC Dipole Prototypes after Quench

The superconducting dipole magnets under design for the Large Hadron Collider (LHC) at CERN operate in pressurized static baths of superfluid helium at a pressure of 1 bar and at a temperature of 1.9 K1. Several prototype magnets have been tested. We have measured for different quench conditions the development of pressure, temperature and helium content of the cryostat after a quench. Temperature data of the collar, yoke and the helium, both inside the cryostat and after discharge from the cryostat, were taken. Pressures were measured in the cryostat end-volumes and at three locations along the beam pipe. We present the results obtained as a function of the relevant quench parameters like energy released to the cryostat and discharge valve opening time.

Automatic Management Systems for the Operation of the Cryogenic Test Facilities for LHC Series Superconducting Magnets

Prior to their final preparation before installation in the tunnel, the ∼1800 series superconducting magnets of the LHC machine shall be entirely tested at reception on modular test facilities. The operation 24 hours per day of the cryogenic test facilities is conducted in turn by 3‐operator teams, assisted in real time by the use of the Test Bench Priorities Handling System, a process control application enforcing the optimum use of cryogenic utilities and of the “Tasks Tracking System”, a web‐based e‐traveller application handling 12 parallel 38‐task test sequences. This paper describes how such computer‐based management systems can be used to optimize operation of concurrent test benches within technical boundary conditions given by the cryogenic capacity, and how they can be used to study the efficiency of the automatic steering of all individual cryogenic sub‐systems. Finally, this paper presents the overall performance of the cryomagnet test station for the first complete year of operation at high p...

First assessment of reliability data for the LHC accelerator and detector cryogenic system components

The Large Hadron Collider (LHC) cryogenic system comprises eight independent refrigeration and distribution systems that supply the eight 3.3 km long accelerator sectors with cryogenic refrigeration power as well as four refrigeration systems for the needs of the detectors ATLAS and CMS. In order to ensure the highest possible reliability of the installations, it is important to apply a reliability centred approach for the maintenance. Even though large scale cryogenic refrigeration exists since the mid 20th century, very little third party reliability data is available today. CERN has started to collect data with its computer aided maintenance management system (CAMMS) in 2009, when the accelerator has gone into normal operation. This paper presents the reliability observations from the operation and the maintenance side, as well as statistical data collected by the means of the CAMMS system.

Commissioning and First Operation of the Cryogenics for the CERN Axion Solar Telescope (CAST)

A new experiment, the CERN Axion Solar Telescope (CAST) was installed and commissioned in 2002. Its aim is to experimentally prove the existence of an as yet hypothetical particle predicted by theory as a solution of the strong CP problem and possible candidate for galactic dark matter. The heart of the detector consists of a decommissioned 10‐m long LHC superconducting dipole prototype magnet, providing a magnetic field of up to 9.5 T. The whole telescope assembly is aligned with high precision to the core of the sun. If they exist, axions could be copiously produced in the core of the sun and converted into photons within the transverse magnetic field of the telescope. The converted low‐energy solar axion spectrum, peaked around a mean energy of 4.4 keV, can then be focused by a special x‐ray mirror system and detected by low‐background photon detectors, installed on each end of the telescopes twin beam pipes. This paper describes the external and proximity cryogenic system and magnet commissioning as w...

Thermal behaviour and cryogenic performance of the first CERN/INFN prototype dipole cryomagnet for the CERN LHC project

Abstract The first 14 m long LHC prototype dipole magnet produced in industry has been mounted on the measurement test bench and operated at 1.8 K in a static bath of pressurized helium II. During tests its thermo-mechanical and cryogenic behaviour has been measured. The cooldown under different conditions, the resulting temperature gradients and the thermo-hydraulic consequences of resistive transitions have been investigated.