Transient quasi-static thermal stresses in a bar subject to transverse 2D-Gaussian heating and to lateral cooling

Many of the CERN secondary-particle production targets are plate shaped, and intercept a centred 'slow' extracted (order of ms) primary beam, which heats the material. This heat distribution can be modelled as Gaussian profiles in both the horizontal and vertical transverse planes. Modern techniques such as finite element methods provide fast and reliable analyses of the transient thermal and mechanical response of such a 'slow' process (no dynamic effects). However, it is of interest to compare these results wih those obtained by simplified anlytical calculations which, moreover, allow an easier optimisation of the various geometrical and physical parameters

Design studies of the LHC beam dump

This paper is a compilation of the results of the recent 5 years studies of the beam dump system for the LHC proton collider at CERN, with a special emphasis on feasibility of the central absorber. Simulations of energy deposition by particle cascades, optimisation of the beam sweeping system and core layout, and thermal analysis have been completed; the structural deformation, stress and vibration analyses are well advanced, and a new concept of the shielding design has recently been approved. The material characteristics, geometry, performance parameters and safety precautions for different components of the beam dump are actually close to completion, which augurs well for the start of construction work according to schedule

Beam Dumps and Beam Stoppers for LHC and CNGS Transfer Lines

Three new beam transfer lines are presently under construction at the SPS: TI2 and TI8 which will transfer protons and ions to the LHC, and TT41 which will transfer protons to the CNGS neutrino target. Three beam dumps (TED) and two beam stoppers (TBSE) will be installed in TI2 and TI8, and one TBSE in TT41. Both types of equipment are required to intercept the 450 GeV SPS beams concentrated in very short pulses (7.8 µs-10.5 µs) at intensities up to ~ 5 10**13 protons, every 16.8 seconds for the TED and as single shot for the TBSE. The outer TED iron shielding will be identical to the existing SPS one, while dimensions and material composition of both TED and TBSE cores have been optimised to cope with the new beam conditions. The optimised TED inner core consists of a Ø80 mm graphite cylinder 2.9 m long, housed into a Ø80/160 mm aluminium blind tube 3.5 m long, itself fitted into a Ø160/310 mm copper blind tube 4.3 m long. The TBSE is made of the same graphite cylinder, housed into a Ø80/120 mm aluminium blind tube 3.5 m long, itself fitted into a Ø120/240 mm iron blind tube 4 m long. The maximum allowed beam intensity for a safe operation is given as a function of the pulse duration, including slow pulses as presently aborted on SPS dumps. The analytical methods set out in the thermo-mechanical part of this study are of general application, and may help in many other axi-symmetrical beam deposition analyses

LHC beam dump design study; 1, simulation of energy deposition by particle cascades; implications for the dump core and beam sweeping system

This first part of the LHC beam dump design study is devoted to problems requiring simulation of energy deposition by particle cascades, which determine the physical state of the dump immediately after absorption of the beam. Each of the twin LHC beam dumps should safely intercept the 540~MJ energy of a 4~mm diameter beam of 4.8$\cdot$10$^{14}$ protons at 7~TeV, in 86~$\mu$s. Calculations favour graphite as a candidate material for the upstream core of the dump, followed by 1~m Al and 2~m Fe downstream absorbers. The dumped beam must be diluted, in order to reduce maximum deposited energy density to an acceptable level. In a 70$\times$70$\times$700~cm graphite core, the optimised dilution profile reduces maximum energy density to 3.1~MJ/kg and maximum instantaneous temperature rise to a safe level of about 1800~K, at maximum beam intensity. Many of the results obtained here are related to this ultimate intensity, as they represent the most severe design constraints; complementary results related to other conditions are also mentioned. Thermal and mechanical analyses, involving dissipation of the initial energy in a longer time scale and requiring a finite element approach, will be described in subsequent parts of this study

LHC beam dump design study; part 2, thermal analysis; implications for abort repetition and cooling system

This second part of the LHC beam dump design study is devoted to transient and steady state nonlinear heat transfer analysis. Heat generation loads are imported from Part - I: simulation of energy deposition in the graphite by particle cascades induced by the LHC primary protons, and superposition of identical energy distribution from each bunch along positions defined by the beam sweep profile on the upstream face of the core. A parametric finite element model of the dump including graphite core, aluminium frame, base plate with cooling channels, and shielding blocks, is elaborated and resolved by means of the ANSYS Engineering System, providing the transient evolution of internal temperature fields. Steady state analysis is then performed, by means of numerical approximations using a limited number of ANSYS results as an interpolation -- extrapolation base. Only periodic aborts are considered. The first conclusion is that the dump requires several hours of cooling after each beam abort. Influence of natural cooling and thermal contact, and performance of a proposed water cooling system, are considered for single and repetitive beam dumping. At the ultimate intensity of 4.8 \[10^14] protons per beam, the dump assembly needs necessarily to be cooled to permit abort cycles as short as 13 h. At the nominal intensity of 3 \[10^14] protons, periodic aborts once per 5 h can be achieved without cooling. At any intensity, however, water cooling reduces the safe abort period by at least a factor 2. A third part of this study will concern mechanical analyses leading to graphite material specification

The SPS Target Station for CHORUS and NOMAD Neutrino Experiments

A new SPS target station, T9, has been constructed for the CHORUS and NOMAD neutrino experiments at CERN. The heart of the station is the target box : 11 beryllium rods are aligned in a cast aluminium box ; they are cooled by a closed circuit helium gas with adjusted flow to each rod. The box is motorised horizontally and vertically at both ends, to remotely optimise the secondary particle production by aligning the target with the incident proton beam. Radiation protection around the station is guaranteed by more than 100 tons of shielding material (iron, copper, marble). This presentation describes briefly the various components of the target station ; it emphasises particularly the thermal and mechanical calculations which define a safe maximum beam intensity on the beryllium rods. Over the first two years of successful operation, the station has received more than 21019 protons at 450 GeV/c, with intensity peaks of 2.81013 protons per machine cycle

CERN West Area neutrino facility beam line alignment

This papers describes the alignment of the West Area Neutrino Beam Line at CERN to the two neutrino experiments CHORUS and NOMAD. The T9 neutrino (n) target position and the position of the magnetic horn were optimised using the secondary muon intensity profiles from the muon pits in the shielding. In the experiments the improved geometry provides a better centred beam (< 5 cm) and a measured increase in the n flux of 8%