Impact of 440 GeV Proton beams on Superconductors in a Cryogenic Environment

A Will,J Schubert,A Bernhard,C Senatore,M Mentink,A Verweij,A.-S Mueller,D Wollmann,A Oslandsbotn,A Siemko,M Bonura,B Bordini,R Schmidt

doi:10.1088/1742-6596/1559/1/012060

Abstract

The superconducting magnets used in high energy particle accelerators such as CERN’s LHC can be impacted by the circulating beam in case of specific failures. This leads to interaction of the beam particles with the magnet components, like the superconducting coils, through direct beam impact or via secondary particle showers. The interaction causes energy deposition in the timescale of microseconds and induces large thermal gradients within the superconductors, which are in the order of 100 K/mm. To investigate the effect on the superconductors, an experiment at CERN’s HiRadMat facility was designed and executed, exposing short samples of Nb-Ti and Nb3Sn strands in a cryogenic environment to microsecond 440 GeV proton beams. The irradiated samples were extracted and analyzed for their critical transport current I c. This paper describes the results and analysis of the measurements of I c as well as thermo-mechanical simulations of the Nb3Sn strands to evaluate the degradation of I c as a function of the mechanical strain present during and after the beam impact.

Highlights

In order to understand the damage limits of superconducting accelerator magnets due to direct beam impact, an experiment was performed in 2018 at CERN’s HiRadMat facility [1]
No significant reduction in critical transport current was observed in any of the examined samples. This is coherent with previous beam impact experiments on Nb-Ti strands at room temperature [7], where the critical current density was derived from magnetization measurements
With increasing hot spot temperature the critical currents could only be measured at increasing external fields

Summary

Introduction

In order to understand the damage limits of superconducting accelerator magnets due to direct beam impact, an experiment was performed in 2018 at CERN’s HiRadMat facility [1]. In this experiment, short samples of superconducting Nb3Sn and Nb-Ti strands were impacted by 440 GeV proton bunches, while being in a cryogenic environment close to 4 K. The energy deposition in the copper sample holder was calculated with FLUKA [4, 5] as a function of the parameters of the impacting beam. The temperature in the samples was scaled using the heat capacity of copper

Findings

Published under licence by IOP Publishing Ltd

The absolute pinning force