Scintillation of liquid helium for low-energy nuclear recoils

Abstract

The scintillation properties of liquid helium upon the recoil of a low energy helium atom are discussed in the context of the possible use of this medium as a detector of dark matter. It 1s found that the prompt scintillation yield in the range of recoil energies from a few keV to 100 keV is somewhat higher than that obtained by a linear extrapolation from the measured yield for an 5 MeV alpha particle. A comparison is made of both the scintillation yield and the charge separation by an electric field for nuclear recoils and for electrons stopped in helium.

Direct detection of sub-GeV dark matter using a superfluid He4 target

“…The relative fraction of energy appearing in each Lindhard channel is the ratio of ν to η, and we assume the fraction of energy deposited in the detector through nuclear stopping can be detected as quasiparticle excitations. The ionization and excitation production ratio, which has been described and modeled for helium-helium collisions by Guo & McKinsey [29] and Ito & Seidel [30], can be derived from measured cross sections. As in Guo & McKinsey, we have neglected secondary electron effects in our calculation of the electronic stopping power since we are concerned with recoils of energies well below 100 keV.…”

“…Light dark matter may also be detected through its coupling to optical phonons in polar materials [25]. Superfluid 4 He has been previously considered for WIMP detection in [26] as part of the HERON project [27,28], and has recently gained attention in the context of low-mass dark matter detection [29][30][31]. Advantages of superfluid 4 He include a) Low target arXiv:1810.06283v1 [physics.ins-det] 15 Oct 2018 mass, allowing relatively good kinematic matching to low-mass dark matter particles; b) Multiple observable and distinguishable signal channels summing to the total recoil energy, including phonons and rotons (commonly referred to collectively as 'quasiparticles'), substantial scintillation light, and triplet helium excimers; c) Inhibited vibrational coupling of the target mass to the environment (the container walls), due to the distinct superfluid phonon/roton dispersion relation; d) High radiopurity, as helium has no long-lived isotopes, may be purified using getters or cold traps, and impurities freeze out of the bulk; d) A large band gap energy of 19.77 eV (the energy needed to excite atomic helium to an n = 2 state), inhibiting all electronic excitation backgrounds below this energy; e) Quasiparticle excitations which are long-lived and ballistic, thereby preserving recoil information encoded in their production; and f) A liquid state down to zero K, enabling mK-temperature calorimetric readout of an easily-scalable liquid target mass.…”

Quantum Monte Carlo calculations of dark matter scattering off light nuclei

“…2 we present the results for isoscalar terms in Eq. (16). For each nucleus, we compare the results for LO and NLO contributions.…”

“…where F (0+1) is (q 2 ) is defined by the sum of the three isoscalar terms on the right-hand side of Eq. (16). Working at NLO and expanding for small order (ν = 1) corrections, this expression reduces to…”

Design of the multi-reflection time-of-flight mass spectrometer for the RAON facility

“…However, PTMS is not suitable for very short-lived nuclei [7,8], since PTMS requires measurement times in excess of 100 ms. For the fast, high precision mass measurements, we will develop another device, a multi-reflection time-of-flight mass spectrometer (MR-TOF-MS), which allows to achieve a very high mass resolving power (> 10 5 ) with extremely short measurement times (several ms) in a compact device. MR-TOF-MS has been proposed by Wollnik in 1990 [9] and developed at RIBF/RIKEN [7,8], at SHIPTRAP/GSI [10][11][12], and at ISOLTRAP/CERN [13][14][15][16][17][18], etc. Recently, MR-TOF-MS has been commissioned online at ISOLTRAP/CERN for the first time [15][16][17][18].…”