Strain Effects of Absorbing Layer on Superconducting Properties of a High-Flux Neutron Detector

An increasingly unstable supply of ³He in the past decade along with growing demands for detectors from the large-scale neutron facilities have led to a higher focus on developing neutron detectors not relying on ³He. In this study a superconducting transition edge sensor (TES) based on a stack of thin films is combined with a neutron absorbing layer of ¹⁰B₄C to build a sensitive and robust neutron detector. The difference in lattice structure causes tensile strain in the thin, stacked, structure, which results in changes in the superconducting parameters. The strain was measured along with its effect on the superconducting transition and thereby the sensitivity of the detector. A decrease in T_c of a few percent and in the range of 0.3 to 2.2 K was found from two different samples with varying boron coverage for a calculated strain of < 0.07%. A change in sensitivity due to strain was found to be from -58% to -15%, depending on deposition coverage and the deposition process. Effects on the superconducting properties were found to be within a range that can be compensated by design and setup considerations and these are therefore not expected to pose problems for the future detectors build on this principle.