Modeling and Proof-of-Concept of a Blackbody-Based Calibration Method in the InfraBREAD Detector

Abstract

The Broadband Reflector Experiment for Axion Detection (BREAD) is an ongoing collaboration searching for the conversion of yet undiscovered axion-like dark matter particles to photons in the presence of a magnetic field. InfraBREAD, a pilot experiment realization of BREAD, uses a superconducting nanowire single photon detector (SNSPD), a high-efficiency and low-noise device, to specifically detect infrared-range photons produced by O(eV) axion-like particles. The unique BREAD coaxial reflector setup allows for the focusing of converted signal photons to a 1mm × 1mm SNSPD. However, when the detector is cooled to cryogenic temperatures during operation, uneven thermal contraction of reflector components may lead to a small shift in the location of the focal spot. A novel calibration method using blackbody radiation is proposed to locate the true focal spot of the detector in situ. Through ray tracing simulations done in FRED Optical Engineering Software, this method is demonstrated to locate the focus to within 50 μm in the axial dimension. Additionally, it is demonstrated that the blackbody photon source used in this calibration must be at a temperature of at least 15K to 40K, depending on the sensitivity of the SNSPD.