Beam heating explains critical current suppression measured during ion irradiation of REBCO tapes
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_Devitre_2024__Beam_heating_explains_critical_current_suppression_measured_during_ion_irradiation_of_REBCO_tapes.pdf
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Author(s)
Devitre, Alexis
Fischer, David
Riva, N.
Rae, M.
Kortman, Lauryn
Woller, Kevin
Fisher, Zoe
Short, Michael
Whyte, Dennis
Hartwig, Zachary
Date Issued
December 2, 2024
Journal
Superconductor Science and Technology
Publisher
IOP Publishing
Citation
A R Devitre et al 2025 Supercond. Sci. Technol. 38 015005
Version
Author's final manuscript
Abstract
Reports of critical current (Ic) suppression during cryogenic ion
irradiation of REBCO tapes have raised concerns for the operational margins
of fusion power plant (FPP) magnets. However, the data remain inconclusive
regarding beam heating due to the difficulty of measuring local temperatures
with contact probes. This leaves a critical knowledge gap concerning the
mechanism behind Ic suppression, and whether the so-called beam on effect is
to be expected under neutron irradiation during FPP operation. In this paper,
we show that Ic suppression is independent of atomic displacement rate in the
REBCO layer, the latter of which increases twelve-fold as we reduce the beam
energy from 2400 to 800 keV. At fixed power, we observe statistically identical
suppression with 150 keV protons, which do not have enough energy to reach
the REBCO layer, refuting hypotheses about beam on effects being caused by
nuclear displacements or direct ion-Cooper pair interactions. These results show
that REBCO temperature rise alone can explain Ic suppression, leaving little to no
margin for alternative mechanisms. With this insight, we developed a method to
measure beam spot temperature that does not depend on the specific installation
of our temperature sensor. With this new method, we measured the temperature
gradient across the tape during irradiation and found that thermal resistance at
the tape/target interface is the controlling variable in Ic suppression. As such,
accelerator-based facilities aiming to reproduce the operation of REBCO magnets
in a nuclear fusion environment should find strategies to minimize interface
thermal resistance. Most importantly, we find that the dose rates expected
in a FPP will not change Ic due to ballistic radiation damage or ion-Cooper
pair interactions, allowing us to safely ignore these effects when designing FPP
magnets.
MIT Department
Massachusetts Institute of Technology. Plasma Science and Fusion Center
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
Massachusetts Institute of Technology. Department of Materials Science and Engineering
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DOI of Published Version
https://doi.org/10.1088/1361-6668/ad95c2
