In order to improve the heat transfer from accelerator superconducting cables to surroundings during ramping rate or beam losses, a ceramic insulation with high porosity was tested. Two experimental mock-ups with different values of compressive load 10 MPa and 20 MPa for reproducing the mechanical and thermal conditions of the superconducting cables were used. The experiments were performed at normal (T=4.23 K and p=1 bar) and supercritical helium conditions (T=4.23 K and p=2.0 to 3.75 bar). The volume dissipated heat in the conductor was changed in a wide range from 0.1 W/m to about 5 W/m of conductor length. The paper shows the first results of the temperature difference within the stack of cables as a function of heat load for the different thermodynamic helium conditions and the two different compressive loads. Results are also compared with previous results obtained with an all-polyimide insulation.
A high magnetic field accelerator magnet of 13 T is being developed in Work Package 7 of the European Union FP7 project EuCARD. The application is to enable higher luminosities and energies for accelerators such as the LHC. The high magnetic field demands superconductors that require a heat treatment step such as Nb 3 Sn. This paper reports thermal tests on conventional composite electrical insulation with pressurized superfluid helium at atmospheric pressure as a coolant. Two composite insulation systems composed of cyanate ester epoxy mix or a tri-functional epoxy (TGPAP-DETDA) with Sglass fiber, have been chosen as candidate materials. The knowledge of their thermal properties is necessary for the thermal design and therefore samples have been tested in pressurized He II where heat is applied perpendicularly to the fibers between 1.6 K and 2.0 K. Overall thermal resistance is determined as a function of temperature and the results are compared with other electrical insulation systems used for accelerator magnets.
Abstract. To investigate the unsteady heat dissipation in accelerator superconducting coils insulated with porous ceramic insulation, two experimental mock-ups reproducing the thermal and the mechanical conditions of a superconducting coils were produced. The mock-ups with compressive load of 10 MPa and 20 MPa were tested at normal (T = 4.23 K and p = 1 bar) and supercritical helium conditions (T = 4.23 K and p = 2.0 to 3.75 bar) during unsteady heat dissipation. The paper presents the experimental results of temperature rise in both superconducting coils as a function of time for a wide range of a localized heat load varying from 0.1 kJ/m 3 up to 12.8 MJ m -3 per pulse. A numerical model of the transient process in these coils has been developed and the computations are compared with the experimental results.
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