Following neutron capture in a material there will be prompt nuclear recoils in addition to the gamma cascade. The nuclear recoils that are left behind in materials are generally below 1\,keV and therefore in the range of interest for dark matter experiments and CE$ν$NS studies--both as backgrounds and calibration opportunities. Here we obtain the spectrum of prompt nuclear recoils following neutron capture for silicon.
Low-energy nuclear recoils (NRs) are hard to measure because they produce few e$^{-}$/h$^+$ pairs in solids -- i.e. they have low "ionization yield". A silicon detector was exposed to thermal neutrons over 2.5\,live-days, probing NRs down to 450\,eV. The observation of a neutron capture-induced component of NRs at low energies is supported by the much-improved fit upon inclusion of a capture NR model. This result shows that thermal neutron calibration of very low recoil energy NRs is promising for dark matter searches, coherent neutrino experiments, and improving understanding of ionization dy…
Anisotropic scintillators can offer a unique possibility to exploit the so-called directionality approach in order to investigate the presence of those Dark Matter (DM) candidates inducing nuclear recoils. In fact, their use can overcome the difficulty of detecting extremely short nuclear recoil traces. In this paper we present recent measurements performed on the anisotropic response of a ZnWO$_4$ crystal scintillator to nuclear recoils, in the framework of the ADAMO project. The anisotropic features of the ZnWO$_4$ crystal scintillators were initially measured with $α$ particles; those resul…
Neutron capture-induced nuclear recoils have emerged as an important tool for detector calibrations in direct dark matter detection and coherent elastic neutrino-nucleus scattering (CE$ν$NS). $\texttt{nrCascadeSim}$ is a command-line tool for generating simulation data for energy deposits resulting from neutron capture on pure materials. Presently, silicon, germanium, neon, and argon are supported. While the software was developed for solid state detector calibration, it can be used for any application which requires simulated neutron capture-induced nuclear recoil data.
Nuclear recoils in crystal detectors generate radiation damage in the form of crystal defects that can be measured in scientific-grade CCDs as local hot spots of leakage current stimulated by temperature increases in the devices. In this proceeding, we use a neutron source to generate defects in DAMIC-M CCDs, and using increases in leakage current at different temperatures, we demonstrate a procedure for identifying crystal defects in the CCDs of the DAMIC-M experiment. This is the first time that individual defects generated from nuclear recoils have been studied. This technique could be used…
Nuclear recoils in germanium and silicon are shown to have much larger variance in electron-hole production than their electron-recoil counterparts for recoil energies between 10 and 200\,keV. This effect--owing primarily to deviations in the amount of energy given to the crystal lattice in response to a nuclear recoil of a given energy--has been predicted by the Lindhard model. We parameterize the variance in terms of an intrinsic nuclear recoil Fano factor which is 24.3$\pm$0.2 and 26$\pm$8 at around 25\,keV for silicon and germanium respectively. The variance has important effects on the ex…
Germanium is the detector material of choice in many rare-event searches looking for low-energy nuclear recoils induced by dark matter particles or neutrinos. We perform a systematic exploration of its quenching factor for sub-keV nuclear recoils, using multiple techniques: photo-neutron sources, recoils from gamma-emission following thermal neutron capture, and a monochromatic filtered neutron beam. Our results point to a marked deviation from the predictions of the Lindhard model in this mostly unexplored energy range. We comment on the compatibility of our data with low-energy processes suc…
The bright scintillation of pure CsI operated at liquid-nitrogen temperature makes of this material a promising dark matter and neutrino detector. We present the first measurement of its quenching factor for nuclear recoils. Our findings indicate it is indistinguishable from that for sodium-doped CsI at room temperature. Additional properties such as light yield, afterglow, scintillation decay properties for electron and nuclear recoils, and energy proportionality are studied over the \mbox{108-165 K} temperature range, confirming the vast potential of this medium for rare-event searches.
The development of single charge resolving, macroscopic silicon detectors has opened a window into rare processes at the O(eV) scale. In order to reconstruct the energy of a given event, or model the charge signal obtained for a given amount of energy absorbed by the electrons in a detector, an accurate charge yield model is needed. In this paper we review existing measurements of charge yield in Silicon, focusing in particular on the region below 1 keV. We highlight a calibration gap between 12-50 eV (referred to as the "UV-gap") and employ a phenomenological model of impact ionization to exp…
The PALEOCCENE concept offers the potential for room-temperature, passive and robust detectors in the gram to kilogram range for the detection of low-energy nuclear recoil events. Nuclear recoil events can be caused by neutron scattering, coherent elastic neutrino nucleus scattering (CEvNS) or dark matter scattering and therefore, PALEOCCENE could find applications in all three areas. In this white paper we present current and planned R&D efforts to study the feasibility of this technique.
This article reports the measurement of the ionization quenching factor in germanium for nuclear recoil energies between 0.4 and 6.3 keV$_{nr}$. Precise knowledge of this factor in this energy range is relevant for coherent elastic neutrino-nucleus scattering and low mass dark matter searches with germanium-based detectors. Nuclear recoils were produced in a thin high-purity germanium target with a very low energy threshold via irradiation with monoenergetic neutron beams. The energy dependence of the ionization quenching factor was directly measured via kinematically constrained coincidences …
The Cryogenic Dark Matter Search (CDMS II) experiment aims to detect dark matter particles that elastically scatter from nuclei in semiconductor detectors. The resulting nuclear-recoil energy depositions are detected by ionization and phonon sensors. Neutrons produce a similar spectrum of low-energy nuclear recoils in such detectors, while most other backgrounds produce electron recoils. The absolute energy scale for nuclear recoils is necessary to interpret results correctly. The energy scale can be determined in CDMS II silicon detectors using neutrons incident from a broad-spectrum $^{252}$…
A two-phase argon detector has high discrimination power between electron recoil and nuclear recoil events based on the pulse shape discrimination and the ionization/scintillation ratio (S2/S1). This character is very suitable for the dark matter search to establish the low background experiment. However, the basic properties of S2/S1 of argon are not well known, as compared with xenon. We report the evaluation of S2/S1 properties with a two-phase detector at drift-fields of 0.2-3.0 kV/cm. Finally, the discrimination power against electron recoil background of S2/S1 is discussed.
A new measurement of the quenching factor for low-energy nuclear recoils in CsI[Na] is presented. Past measurements are revisited, identifying and correcting several systematic effects. The resulting global data are well-described by a physics-based model for the generation of scintillation by ions in this material, in agreement with phenomenological considerations. The uncertainty in the new model is reduced by a factor of four with respect to an energy-independent quenching factor initially adopted as a compromise by the COHERENT collaboration. A significantly improved agreement with Standar…
Nuclear Recoil Migdal Effect in Liquid Xenon Dark Matter Experiments
Lawrence Livermore National Laboratory (LLNL)（劳伦斯利弗莫尔国家实验室）；University of California, Santa Barbara（加州大学圣塔芭芭拉分校）；C.N. Yang Institute for Theoretical Physics, Stony Brook University（纽约州立大学石溪分校陈省身理论物理研究所）；SLAC National Accelerator Laboratory（斯坦福直线加速器中心）
The electronic energy deposited on nuclear emulsions due to C ions of 5 -- 200~keV and Kr ions of 5 -- 600~keV are evaluated and compared with those due to fast ions for design and construction of fine grain nuclear emulsion for directional dark matter searches. Nuclear quenching factors and the electronic LET (linear energy transfer), the specific electronic energy deposited along the ion track, are evaluated. The so-called core and penumbra of heavy-ion track structure is modified for understanding the track due to recoil ions produced by dark matter candidate, WIMPs, striking nucleus in the…
The feasibility of an ultra-low energy nuclear-recoil measurement in liquid xenon using neutron capture is investigated for a small (sub-kilogram) liquid xenon detector that is optimized for a high scintillation gain, and a pulsed neutron source. The measurement uses the recoil energies imparted to xenon nuclei during the de-excitation process following neutron capture, where promptly emitted $γ$ cascades can provide the nuclei with up to $0.3$ keV$_\text{nr}$ of recoil energy due to conservation of momentum. A successful calibration of scintillation photon and ionization electron yields below…
Measuring the scintillation and ionization yields of liquid xenon in response to ultra-low energy nuclear recoil events is necessary to increase the sensitivity of liquid xenon experiments to light dark matter. Neutron capture on xenon can be used to produce nuclear recoil events with energies below $0.3$ keV$_\text{NR}$ via the asymmetric emission of $γ$ rays during nuclear de-excitation. The feasibility of an ultra-low energy nuclear recoil measurement using neutron capture was investigated for the Michigan Xenon (MiX) detector, a small dual-phase xenon time projection chamber that is optimi…
We report on the design, production, and performance of compact 40-cm$^3$ Time Projection Chambers (TPCs) that detect fast neutrons by measuring the three-dimensional (3D) ionization distribution of nuclear recoils in $^4$He:CO$_2$ gas at atmospheric pressure. We use these detectors to characterize the fast-neutron flux inside the Belle II detector at the SuperKEKB electron-positron collider in Tsukuba, Japan, where the primary design constraint is a small form factor. We find that the TPCs meet or exceed all design specifications, and are capable of measuring the 3D surface shape and charge d…
We examine a recent measurement of the quenching factor (QF) in germanium at 80 K, noticing a number of inconsistencies capable of affecting a claimed agreement with Lindhard's ion-stopping formalism in the sub-keV nuclear recoil energy regime. Namely, an underestimated uncertainty in the energy scale and a missing correction for a large instrumental non-linearity in this scale able to severely distort the QF behavior at low energy, favoring reduced values. The discussion is expanded to inspect the impact of QF model selection on a study of neutrino electromagnetic properties using CE$ν$NS dat…
We present a measurement of scintillation efficiency for a few tens of keV nuclear recoils (NR) with a liquid argon time projection chamber under electric fields ranging from $0$ to $3\ {\rm kV/cm}$. The calibration data are taken with $^{252}{\rm Cf}$ radioactive source. Observed scintillation and electroluminescence spectra are simultaneously fit with spectra derived from Geant4-based Monte Carlo simulation and an NR model. The scintillation efficiency extracted from the fit is reported as a function of recoil energy and electric field. This result can be used for designing the detector and …
Detection of nuclear recoils in prototype dark matter detectors, made from Al, Sn and Zn Superheated Superconducting Granules
这项工作是一个正在进行的项目的一部分，开发一个过热超导颗粒（SSG）探测器的冷暗物质和中微子。用70MeV中子束辐照SSG探测器，研究了SSG器件对核反冲的响应。该实验的目的是测试Sn，Al和Zn SSG探测器对几keV的核反冲能量的灵敏度。该探测器由一个中空的聚四氟乙烯圆柱体（0.1 cm $^3$内容积）组成，填充有嵌入电介质中的微小超导亚稳颗粒。用中子速迹仪测量中子散射角，确定了沉积在SSG中的核反冲能。SSG和速端镜信号之间的时间重合已经清楚地建立。本文讨论了不同SSG本征阈值的中子辐照实验结果，并与蒙特卡罗模拟进行了比较。结果表明，SSG对低至$\sim$ 1keV的反冲能量敏感。有限的角分辨率的中子hodoscope阻止我们测量SSG灵敏度，甚至更低的反冲能量。
We present a comprehensive analysis of electronic recoil vs. nuclear recoil discrimination in liquid/gas xenon time projection chambers, using calibration data from the 2013 and 2014-16 runs of the Large Underground Xenon (LUX) experiment. We observe strong charge-to-light discrimination enhancement with increased event energy. For events with S1 = 120 detected photons, i.e. equivalent to a nuclear recoil energy of $\sim$100 keV, we observe an electronic recoil background acceptance of $<10^{-5}$ at a nuclear recoil signal acceptance of 50%. We also observe modest electric field dependence of …
Large composite dark matter states source a scalar binding field that, when coupled to Standard Model nucleons, provides a potential under which nuclei recoil and accelerate to energies capable of ionization, radiation, and thermonuclear reactions. We show that these dynamics are detectable for nucleon couplings as small as $g_n \sim 10^{-17}$ at dark matter experiments, where the greatest sensitivity is attained by considering the Migdal effect. We also explore Type-Ia supernovae and planetary heating as possible means to discover this type of dark matter.
Quasiparticle and phonon propagation in superheated superconducting granules after nuclear recoils
讨论了Sn和Zn过热超导颗粒内部核反冲产生的过量准粒子和声子的传播。初始扰动向平衡的衰减被假定为一个热扩散过程，描述了一组耦合的热流方程的有效准粒子和声子的温度。对于位于超导颗粒内部任意位置的点源，初始能量分布在准粒子和声子系统中，进行了解析求解。计算出的时间延迟之间的中子相互作用和相变的成核将进行比较，通过照射Zn和Sn SSG探测器与70 Me $\!$ V中子束的时间延迟分布。
Studies of micro time projection chambers using negative ion gas (NI$μ$TPC) are conducted especially for direction-sensitive dark matter searches. A NI$μ$TPC enables to measure the absolute position in the drift direction for self-triggering TPCs. This study provides a development of a NI$μ$TPC using a micro pixel chamber ($μ$-PIC) with dedicated readout electronics, and an evaluation of the capability of three-dimensional absolute position reconstruction of nuclear recoil using a neutron source. The absolute track position was reconstructed throughout the drift volume with an efficiency of 70…
A liquid argon time projection chamber, constructed for the Argon Response to Ionization and Scintillation (ARIS) experiment, has been exposed to the highly collimated and quasi-monoenergetic LICORNE neutron beam at the Institute de Physique Nuclaire Orsay in order to study the scintillation response to nuclear and electronic recoils. An array of liquid scintillator detectors, arranged around the apparatus, tag scattered neutrons and select nuclear recoil energies in the [7, 120] keV energy range. The relative scintillation efficiency of nuclear recoils was measured to high precision at null f…
