Superfluid Helium cooling and compact Heat Exchanger for HL-LHC D2 Recombination Dipoles

B Rousset,A Perin,R Van Weelderen,F Millet,S Claudet,P Nivelon,F Bancel

doi:10.1088/1757-899x/502/1/012114

Abstract

New D2 recombination dipoles with a larger aperture than in the LHC dipoles are required for the future High Luminosity LHC at CERN. These 13.5 m-long D2 magnets are proposed to be conduction cooled in a static bath of pressurized He II. Their cooling is provided via pressurized He II channels located in the D2 iron yoke and thermally connected to a saturated bath installed at one end of each D2 dipole. The heat transfer between the pressurized He II static bath and the bath pumped down to 16.4 mbar (1.8 K) is performed in a heat exchanger under study at CEA. Various design solutions were studied and evaluated to define the more suitable solution fulfilling on the one hand D2 cooling requirements (up to 70 W) and on the other hand D2 cryostat integration constraints. The paper will report on the D2 cooling needs and constraints, present the studied options and detail the main design features of the selected solution for a compact heat exchanger for D2 dipoles.

Highlights

The High Luminosity Upgrade of the LHC (HL-LHC) at CERN will provide instantaneous luminosities up to five times larger than the LHC nominal value
New D2 recombination dipoles with a larger aperture than in the LHC dipoles are required for the future High Luminosity LHC at CERN
Their cooling is provided via pressurized He II channels located in the D2 iron yoke and thermally connected to a saturated bath installed at one end of each D2 dipole

Summary

Introduction

The High Luminosity Upgrade of the LHC (HL-LHC) at CERN will provide instantaneous luminosities up to five times larger than the LHC nominal value. O The He II thermal conductivity function (TCF) is assumed to be constant in the pressurized and saturated baths (i.e. independent of the temperature for small temperature differences (~0.02 K)). That imposes that the pressurized He II sector (from the magnet towards the cold source) gradually releases the heat flux to the saturated He II sector To fulfill this criterion, we apply the “classical” He II heat transport equation in a 1D-pipe of length. The longitudinal temperature difference ∆Tlong along one of the HX-D2 sectors can be calculated once the cooling power to be extracted, the cross sections and the length of the sectors are defined. If ∆Ttotal is higher than ∆Tmax, some of the geometrical parameters (length, maximum cross section or pipe diameter) are adjusted and iterative calculations are performed to define the optimum parameters

HX-D2 selected design

Conclusions and perspectives