Analysis of the 15m LHC Cryo-Dipole Radiation Screen during a Magnet Quench

The cost of extracting 1 Watt from a temperature of 1.9 K is about 8 times higher than that of extracting it from the 5 K to 20 K temperature range. In the LHC prototype half-cell cryostats,1 having only one thermalised screen at 70 K, about 70% of the heat inleak to the 1.9 K temperature level comes from radiation. To enhance the cryostat performance, the second generation of prototype cryostats incorporates a second actively cooled screen operating in the 5 K to 20 K temperature range. This screen, which is manufactured in industrially pure aluminium alloy sheets 2 mm thick, is situated very close to the dipole magnet cold mass. The rapid collapse of the dipole field during a resistive transition (quench) will induce forces and displacements. An analytical, 2 D study to estimate this effect is presented.