Molecular dynamics simulations of bubble nucleation in dark matter detectors

Abstract

Bubble chambers and droplet detectors used in dosimetry and dark matter particle search experiments use a superheated metastable liquid in which nuclear recoils trigger bubble nucleation. This process is described by the classical heat spike model of F. Seitz [Phys. Fluids (1958-1988) 1, 2 (1958)], which uses classical nucleation theory to estimate the amount and the localization of the deposited energy required for bubble formation. Here we report on direct molecular dynamics simulations of heat-spike-induced bubble formation. They allow us to test the nanoscale process described in the classical heat spike model. 40 simulations were performed, each containing about 20 million atoms, which interact by a truncated force-shifted Lennard-Jones potential. We find that the energy per length unit needed for bubble nucleation agrees quite well with theoretical predictions, but the allowed spike length and the required total energy are about twice as large as predicted. This could be explained by the rapid energy diffusion measured in the simulation: contrary to the assumption in the classical model, we observe significantly faster heat diffusion than the bubble formation time scale. Finally we examine α-particle tracks, which are much longer than those of neutrons and potential dark matter particles. Empirically, α events were recently found to result in louder acoustic signals than neutron events. This distinction is crucial for the background rejection in dark matter searches. We show that a large number of individual bubbles can form along an α track, which explains the observed larger acoustic amplitudes.

7 pages, 5 figures, accepted for publication in Phys. Rev. E, matches published version

References in corpus (11)

• First dark matter search results from a 4-kg CF${}_3$I bubble chamber operated in a deep underground site
• Dark Matter Search Results from the PICO-2L C${}_3$F${}_8$ Bubble Chamber
• Constraints on Low-Mass WIMP Interactions on 19F from PICASSO
• Results on low mass WIMPs using an upgraded CRESST-II detector
• Large Scale Molecular Dynamics Simulations of Homogeneous Nucleation
• Discrimination of nuclear recoils from alpha particles with superheated liquids
• First Results of the Phase II SIMPLE Dark Matter Search
• Direct Simulations of Homogeneous Bubble Nucleation: Agreement with CNT and no Local Hot Spots
• The SIMPLE Phase II Dark Matter Search
• Cumulative distribution functions associated with bubble-nucleation processes in cavitation
• Bubble Evolution and Properties in Homogeneous Nucleation Simulations

Cited by in corpus (5)

• First Demonstration of a Scintillating Xenon Bubble Chamber for Detecting Dark Matter and Coherent Elastic Neutrino-Nucleus Scattering
• Modeling emission of acoustic energy during bubble expansion in PICO bubble chambers
• On the critical energy required for homogeneous nucleation in bubble chambers employed in dark matter searches
• Low-threshold response of a scintillating xenon bubble chamber to nuclear and electronic recoils
• Model for bubble nucleation efficiency of low-energy nuclear recoils in bubble chambers for dark matter detection