Monte Carlo Simulation of Massive Absorbers for Cryogenic Calorimeters

Abstract

There is a growing interest in cryogenic calorimeters with macroscopic absorbers for applications such as dark matter direct detection and rare event search experiments. The physics of energy transport in calorimeters with absorber masses exceeding several grams is made complex by the anisotropic nature of the absorber crystals as well as the changing mean free paths as phonons decay to progressively lower energies. We present a Monte Carlo model capable of simulating anisotropic phonon transport in cryogenic crystals. We have initiated the validation process and discuss the level of agreement between our simulation and experimental results reported in the literature, focusing on heat pulse propagation in germanium. The simulation framework is implemented using Geant4, a toolkit originally developed for high-energy physics Monte Carlo simulations. Geant4 has also been used for nuclear and accelerator physics, and applications in medical and space sciences. We believe that our current work may open up new avenues for applications in material science and condensed matter physics.

Invited Review Article: Physics and Monte Carlo techniques as relevant to cryogenic, phonon, and ionization readout of Cryogenic Dark Matter Search radiation detectors

“…The GEANT4 collaboration is beginning to implement phonon and charge transport modules into the GEANT4 toolkit and will expand the benefits of this research to others outside the cryogenic detector community [69].…”

Optimizing the design and analysis of cryogenic semiconductor dark matter detectors for maximum sensitivity

“…Though incredibly valuable for it's time, it has now been greatly improved upon and superseded by the work of Kevin McCarthy and Steve Leman at MIT. Consequently, only a qualitative outline of the phonon, charge, and sensor dynamics vi will be discussed here (my largest contribution), and the more quantitative results of the CDMS detector monte carlo can be found [4], [5] and eventually in the not to be missed thesis of Kevin. …”

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“…Qualitatively, this is due to the fact that the probability of interaction scales as the square of the baryon density and thus the probability of incomplete nucleosynthesis (and thus larger relic amounts of 2 H and 3 He) is much more likely for small baryon densities [35]. Unfortunately, observation of the relative relic abundances of 4 He and 3 He today has been made enormously more complicated by the fact that these elements are also byproducts in stellar nucleosynthesis and thus the only precise measure of the baryon density is the relic abundance of 2 H (due to its fragility, it can not be produced in stars). This measurement alone, though, strongly constrains dark matter properties.…”