Electrical and Mechanical Performance of an Enhanced Cable Insulation Scheme for Superconducting Magnets

Abstract

Abstract-New polyimide cable insulation schemes improving the cooling of Nb-Ti superconducting coils were recently developed to face the severe heat loads at which the next generation of superconducting accelerator magnets will work.In order to qualify the new insulation, a test campaign was realized to assess both its electrical and mechanical features with respect to the standard LHC insulation. The electrical tests assessed the dielectric strength and inter-turn leakage current to be satisfactory. The mechanical tests investigated the insulation thickness under load and the stress relaxation at ambient temperature, thus providing essential information for the magnetic and mechanical design of the final focusing magnets for the LHC upgrade phase I.Index Terms-LHC upgrade, mechanical and electrical tests, stress relaxation, superconducting magnets cable insulation.

Heat Transfer in an Enhanced Cable Insulation Scheme for the Superconducting Magnets of the LHC Luminosity Upgrade

“…The difference with the previous measurement was not significant, meaning that the creep effect in this time scale has no impact on heat transfer. This is probably due to the fact that the creep effect is more evident during the first 3-4 days [6], which is the time the sample usually remains under pressure before being measured.…”

“…This paper reports on the results of heat transfer measurements performed in He-II, aiming at verifying the enhanced thermal properties under the mechanical stress typical for magnet operation. The electrical and mechanical performance was also assessed to be satisfactory, as described in a separate paper [6].…”

Finite Element Modeling in 3D of the Impact of Superfluid Helium Filled Micro-Channels on the Heat Transfer through LHC Type Cable Insulation

“…The new insulation consists of three layers as well, but each layer incorporates helium channels due to spacing of the polyimide (Kapton) ribbons. In both cases, dielectric protection is guaranteed [12] and mechanical protection is provided by the outer layer. Here the focus is on the complex network of the EI insulation scheme.…”

“…The thickness of the insulation layer Finite Element Modeling in 3D of the impact of superfluid helium filled micro-channels on the heat transfer through LHC type cable insulation Erwin Bielert, Arjan Verweij, and Herman ten Kate S EDMS No : 1167417 1HP2-6 2 depends on the transversally applied pressure. The effective cooling channel cross-section is decreased by some 31% at 130 MPa and 29% at 80 MPa [12]. Consequently a higher pressure will decrease the tolerable heat deposition to reach the same temperature.…”

A 120 mm Bore Quadrupole for the Phase I LHC Upgrade

“…In order to improve the coil transparency to helium a new insulation scheme has been proposed and is being tested [6], [7]. The new insulation provides enhanced heat transfer capacity with respect to the standard LHC insulation through channels that are created between the three polyimide layers.…”