Measurement of the electron drift velocity for directional dark matter detectors

F Mayet,D Santos,D Maire,G Bosson,L Lebreton,J P Richer,O Guillaudin,J Billard,J Lamblin,F J Iguaz,Q Riffard,O Bourrion

doi:10.1088/1742-6596/469/1/012006

Abstract

Three-dimensional track reconstruction is a key issue for directional Dark Matter detection. It requires a precise knowledge of the electron drift velocity. Magboltz simulations are known to give a good evaluation of this parameter. However, large TPC operated underground on long time scale may be characterized by an effective electron drift velocity that may differ from the value evaluated by simulation. In situ measurement of this key parameter is hence a way to avoid bias in the 3D track reconstruction. We present a dedicated method for the measurement of the electron drift velocity with the MIMAC detector. It is tested on two gas mixtures : CF4 and CF4 + CHF3. We also show that adding CHF3 allows us to lower the electron drift velocity while keeping almost the same Fluorine content of the gas mixture.

Highlights

Directional detection of galactic Dark Matter offers a unique opportunity to identify Weakly Interacting Massive Particle (WIMP) events as such [1,2,3,4,5,6,7,8,9,10,11,12,13]
Large TPC operated underground on long time scale may be characterized by an effective electron drift velocity that may differ from the value evaluated by Magboltz simulation [23], due to e.g. impurities, field inhomogeneities, long drift distances
We present a dedicated method for an in situ measurement of electron drift velocity with the MIMAC detector [19], using a collimated α source, together with a maximum likelihood method associated to a modelisation of the signal induced on the grid

Summary

Introduction

Directional detection of galactic Dark Matter offers a unique opportunity to identify Weakly Interacting Massive Particle (WIMP) events as such [1,2,3,4,5,6,7,8,9,10,11,12,13]. This new search strategy requires the simultaneous measurement of the recoil energy and the direction of the 3D track of low energy recoils. In situ measurement of this key parameter is a way to avoid bias in the 3D track reconstruction

Methods

Results

Conclusion