Thermal Analysis of the ALICE Detector for the LHC

In the same fashion as for the other LHC detectors, ALICE requires stringent conditions of temperature stability in time and space and adequate absolute values, which vary for each sub-detector. For the design of the cooling and ventilation systems inside the detector, three different studies have been undertaken. The first investigates the temperature distribution and hot spots in the volume enclosed by the L3 magnet for different ventilation configurations. The second study deals with the cooling of the muon chambers inside the dipole magnet and, in particular, analyses the possibility of air-cooling pairs of muon chambers to remove the residual heat flux by forced convection. The third study examines the contribution of the surroundings to the temperature gradients in the drift gas (Ne/CO2) of the TPC sub-detector. The different computational results will be shown and some design proposals presented

Thermal Behaviour of the Preshower Galvanic Feedthrough

The active components of the read-out planes in the CMS Preshower work at a temperature of about -10oC. An assembled Preshower detector appears as a closed vessel. Electrical services have to cross this container in a gas-tight manner, and they have to be disconnectable from both Preshower outside and inside. To this end, special gas-tight feedthroughs have been designed. As they are located on the cold/warm barrier, their heat inleak can be a potential source of problems. Condensation on the outside surface shall be avoided. This paper presents the behaviour of two different configurations is presented and resulting temperature values at the external surface are compared to the guaranteed maximum dew point temperature

Argon spill in the hall of the ATLAS experiment

A hazard analysis is in progress to determine the operation mode of the ventilation system in the ATLAS hall in case of an Argon spill. Two risk scenarios have been investigated so far. In the first, the behaviour of an Argon gas pool is calculated for different ventilation strategies. In the second, the behaviour of Argon gas leaking from the bottom part of the detector is studied for different flows. The description of the study, results and conclusions are presented

Upgrading of the Air-conditioning of the Computer Room in the Computer Centre for the LHC era

Built in the beginning of 1970's, the Computer Centre air-conditioning and cooling systems were designed to be modular and easily adaptable to the unpredictable future needs of computing. The infrastructure of LHC-computing that will be housed in the existing Computer Room with its five Computing farms and over 11000 PC's increases the requirements of cooling and air-conditioning power to a new level. The nominal thermal loads from the equipment rise from the current design maximum of 1MW to estimated maximum of 2MW in the future. This paper presents calculations and proposes solutions to meet the new nominal requirements. The air-conditioning system must also be able to cope with a situation of power cut in the main supply. A calculation of the temperature evolution during the power cut and a justified operation strategy for this scenario is also presented

Strategy for the Operation of Cooling Towers with variable Speed Fans

Within the SPS Cooling Water Project at CERN aimed at the reduction of water consumption, this primary open cooling loop will be closed and all the primary cooling circuit components will be upgraded to the new required duty and brought to the necessary safety and operability standards. In particular the tower fans will be fitted with variable frequency drives to replace the existing two speed motors. This paper presents a study to optimize the operation of SPS cooling towers taking into account outdoor conditions (wet and dry bulb temperatures) and the entirety of the primary circuit in which they will operate

Design of the second series 15 m LHC prototype dipole magnet cryostats

A first series of six LHC 10 m long prototype dipole magnets and cryostats have been manufactured in European Industry and the assembled cryo-magnets tested singly and connected in series in a test string at CERN between March 1994 and December 1996. During the same period, an evolution in the requirements for LHC cryogenics distribution has lead the project management to adopt a separate cryo-distribution line running parallel to the LHC machine1. The former standard LHC half-cell, made up of a short straight section unit and four 10 m dipoles, has been discarded and replaced with one composed of a short straight section unit and three 15 m dipoles. The new 15 m LHC dipole magnet cryostats are described. These units house the dipole magnet cold mass standing on three low heat in-leak support columns, and enclosed within an actively cooled radiation screen operating at 4.5-20 K and an actively cooled thermal shield operating at 50-75 K

Characterisation of net type thermal insulators at 1.8 K low boundary temperature

The Large Hadron Collider's superconducting magnets are cooled by superfluid helium at 1.8 K and housed in cryostats that minimise the heat inleak to this temperature level by extracting heat at 70 and 5 K. In the first generation of prototype cryostats, the radiative heat to the 1.8 K temperature level accounted for 70 % of the total heat inleak. An alternative to enhance the cryostat thermal performance incorporates a thermalised radiation screen at 5 K. In order to avoid contact between the 5 K radiation screen and the cold mass, insulators are placed between both surfaces. Sets of commercial fibre glass nets are insulator candidates to minimise the heat inleak caused by a accidental contact between the two temperature levels. A model to estimate their performance is presented. A set-up to thermally characterise them has been designed and is also described in the paper. Finally, results as a function of the number of the spacer nets, the boundary temperatures and the compressive force in the spacer are presented

Cooling process of the LHC energy extraction resistors

The energy stored in all the LHC dipoles, about 11 GJ, can potentially cause severe damage to the magnets, bus bars and current leads. In order to protect the superconducting elements after a resistive transition, the energy is dissipated into dump resistors switched in series with the magnet chains. This paper describes the cooling process of the resistors and explains the choice process for the main components of the cooling equipment

Comparison of floating and thermalized multilayer insulation systems at low boundary temperature

The Large Hadron Collider (LHC) is 26.7 km circumference particle collider using high-field superconducting magnets operating in superfluid helium. An efficient and robust thermal insulation system is therefore required to minimize the residual heat in leak to the large surface area at 1.9 K constituted by the stainless steel wall of the helium enclosure. The baseline solution uses "floating" multilayer reflective insulation. Moreover, an alternative consists of a combination of multilayer reflective films and a soft screen, partially thermalized to the 5 K level and supported away from the cold wall by net-type insulating spacers. This chapter establishes the improvement potential of the alternative over the baseline solution, and compares their insulation performance on the basis of measured characteristics of thermal contacts and spacers