1301.4290 (S. Sangiorgio et al.)

First demonstration of a sub-keV electron recoil energy threshold in a
liquid argon ionization chamber    [PDF]

S. Sangiorgio, A. Bernstein, J. Coleman, M. Foxe, C. Hagmann, T. H. Joshi, I. Jovanovic, K. Kazkaz, K. Mavrokoridis, V. Mozin, S. Pereverzev, P. Sorensen

We make a first demonstration of a sub-keV electron recoil energy threshold in a dual-phase liquid argon time-projection chamber. This is an important step in a program to build a detector capable of identifying the ionization signal resulting from nuclear recoils at a few keV and below. We obtained this result by observing the peaks in the energy spectrum at 2.82 keV and 0.27 keV, following the K- and L-shell electron capture decay of Ar-37. We describe the details of the Ar-37 source preparation, as this calibration technique may prove useful, e.g. for dark matter direct detection experiments. A Fe-55 internal x-ray source was also measured simultaneously and provided another calibration point at 5.9 keV. We discuss the ionization yield and electron recombination in liquid argon at the three calibration energies.

View original: http://arxiv.org/abs/1301.4290