Accelerator Report: A quench of an LHC interior triplet magnet causes a small leak with main penalties
At 1.00 a.m. + 17 seconds on Monday, 17 July, the LHC beams had been dumped after solely 9 minutes in collision on account of a radiofrequency interlock brought on by {an electrical} perturbation. Roughly 300 milliseconds after the beams had been cleanly dumped, a number of superconducting magnets across the LHC quenched – i.e. they misplaced their superconducting state. Amongst these magnets had been the interior triplet magnets positioned to the left of Level 8 (LHCb), which play a vital position in focusing the beams for the LHCb experiment.
Whereas this sequence of occasions could not occur fairly often throughout beam operation, it isn’t distinctive for the LHC, as occasional quenches of some superconducting magnets are to be anticipated.
On this explicit case, {the electrical} perturbation prompted the quench safety system (QPS) to set off the quench heaters of the magnets involved. These quench heaters include {an electrical} resistor embedded within the magnet coils; they’re designed to warmth up rapidly when a localised quench happens someplace within the magnet, to be able to successfully convey the entire magnet out of the superconducting state in a managed and homogenous method. Throughout such a quench, the liquid helium within the magnet warms up and turns right into a fuel that’s recovered by the cryogenic system to be re-liquified, prepared to chill down the magnets once more.
Regardless of this being a traditional and anticipated behaviour, the mechanical stresses concerned on this course of are vital and, in very uncommon circumstances, can result in injury. Sadly, within the case of the interior triplet magnet positioned to the left of Level 8, a small leak has appeared between the cryogenic circuit, which incorporates the liquid helium, and the insulation vacuum that separates the chilly magnet from the nice and cozy outer vessel, often known as the cryostat. This vacuum barrier is essential for stopping warmth switch from the encircling LHC tunnel to the inside of the cryostat (that is just like the functioning of a thermos flask). Because of the leak, this insulation was misplaced: the insulation vacuum full of helium fuel, cooling down the cryostat and inflicting condensation to type and freeze on the surface.
As I write, investigations are ongoing to determine the supply of the leak, to permit a restore technique to be elaborated. Nonetheless, it’s clear that an intervention with the interior triplet magnet at room temperature will probably be required. This incident will most likely have a fantastic affect on the LHC schedule, with machine operation unlikely to renew for at the least a number of weeks.
