Pulse shapes in single photon, single particle calorimeters

Abstract

Single photon or single particle calorimeters with energy resolutions of order 1 eV fwhm have recently been proposed as detectors for X-ray astronomy and many other applications. Such devices consist, essentially, of an absorber (linked to a heat bath at ∼ 0.1 K) and one or more thermistors The temperature rise induced in the former element by the absorption of a single photon or particle produces voltage waveforms at the ouput of the latter from which energy information may be abstracted. In this paper, we consider the practical limits to the energy resolution which arise from the “thermal nonuniformity” of the absorber mass. The variation in thermistor pulse shape with position of photon absorption is estimated from solutions of the heat conduction equation, for a number of linear calorimeter designs. An assessment is made of the position-sensing properties of a calorimeter with two line-end thermistors.