Effects of high energy irradiation on the properties of the Nb3Sn superconducting magnets in the accelerators HiLumi LHC and FCC

by René Flükiger (University of Geneva)

Thursday 6 Dec 2018, 14:15 → 15:30 Europe/Zurich

30/7-018 - Kjell Johnsen Auditorium (CERN)

The magnets in the accelerators LHC HiLumi and FCC will be submitted to strong irradiation by multiple high energy particles (neutrons, protons, ...). At the same particle fluence ϕt, however, each particle causes a different effect on the superconducting properties. The problem of a correct prediction of the irradiation effects on the properties of Nb3Sn magnets during the accelerator lifetime is solved replacing ϕt by the parameter dpa (displacement per atom), as described in ref [1] . As a result of a collaboration with the Kurchatov Institute (Moscow), it was shown that in contrast to the commonly used fluence ϕt, the dpa can be considered as a universal parameter for describing the variation of Tc after irradiation of Nb3Sn wires by various high energy particles, Tc being uniquely determined by the atomic order parameter in the A15 structure. The variation of Jc in irradiated Nb3Sn wires is more complex and is described by a sum of two contributions: a) from the A15 grain boundaries and b) from the radiation induced point pinning centers.

In this talk, a particular attention is given to the effects of irradiation on Ti ternary alloyed Nb3Sn multifilamentary wires. From a comparison between the present data obtained with E > 0.1 MeV neutrons in collaboration with the ATI in Vienna and earlier data with 14 MeV neutrons, the superconducting parameters Tc and Jc of Nb3Sn magnets are estimated for dpa = 3 x 10-3, the expected value in FCC. After irradiation, Tc is expected to decrease by ~ 1.5 K, while Jc at 4.2K/16T shows an increase ranging between 0 to 60%.

For comparison, the effect of irradiation on the superconducting properties of other superconductors which may be used in future accelerators, e.g. YBCO and Bi-2212 is briefly presented.

[1] CERN-THESIS-2015-086, Proton irradiation effects on Nb3Sn wires and thin platelets in view of High Luminosity LHC upgrade, T. Spina, 167 pages, http://cds.cern.ch/record/2030242?ln=en

ATS Seminars Organisers: H. Burkhardt (BE), M. Modena (ATS), T. Stora (EN)

Coffee / tea will be served after the seminar in room 30/7-012 next to the Auditorium

Flükiger, CERN, presentation 6.12.2018.pdf