A new pulse shape description for $\alpha$ particle pulses in a highly-sensitive sub-Kelvin bolometer

TL;DR

This paper introduces a novel pulse shape description method for alpha particle signals in highly-sensitive sub-Kelvin bolometers, improving physical understanding and modeling of energy propagation mechanisms.

Contribution

It presents a new fitting approach that replaces non-physical parameters with a physically motivated convolution model, enhancing pulse analysis accuracy.

Findings

Eliminated the need for a quadratic nonlinearity factor

Achieved pulse forms consistent with thermal physics principles

Improved understanding of energy propagation in bolometer detectors

Abstract

The next generation of cosmology space missions will be sensitive to parasitic signals arising from cosmic rays. Using a composite bolometer, we have investigated pulses produced by $\alpha$ particles in order to understand the movement of energy produced by ionising radiation. Using a series of measurements at 100 mK, we have compared the typical fitting algorithm (a mathematical model) with a second method of pulse interpretation by convolving the detector's thermal response function with a starting profile of thermalised athermal phonons, taking into account the effects of heat propagation. Using this new fitting method, we have eliminated the need for a non-physical quadratic nonlinearity factor produced using more common methods, and we find a pulse form in good agreement with known aspects of thermal physics. This work is carried forward in the effort to produce a physical model for energy deposition in this detector. The modelling is motivated by the reproduction of statistical features in the experimental dataset, and the new interpretation of $\alpha$ pulse shapes represents an improvement in the current understanding of the energy propagation mechanisms in this detector.