Nuclear Recoil Research Articles

Collision Cascade in a Silicon-Based Device under Energetic Ar Ions Irradiation

Silicon, as the basic material of biochips and electronic devices, is often exposed to irradiation environments, and its radiation resistance has attracted much attention in recent decades. We calculated collision cascade in a silicon-based device under energetic Ar ions irradiation by using Monte Carlo and molecular dynamics simulations. The difference in vacancy probability density under different energetic incident ion irradiation is caused by the penetrating power and the straggling power of incident ions. The kinetic energy of an incident ion determines the size of local collision cascade density; a high energy incident ion can induce greater local collision cascade density. The efficiency of transferring energy from incident ions to target electrons at the silicon surface is more than in silicon, and the recoil atoms dissipate most of their energy at the lattice sites where they are stopping. These results provide more insight into the radiation resistance of silicon-based devices.

A 50 l Cygno prototype overground characterization

The nature of dark matter is still unknown and an experimental program to look for dark matter particles in our Galaxy should extend its sensitivity to light particles in the GeV mass range and exploit the directional information of the DM particle motion (Vahsen et al. in CYGNUS: feasibility of a nuclear recoil observatory with directional sensitivity to dark matter and neutrinos, arXiv:2008.12587, 2020). The Cygno project is studying a gaseous time projection chamber operated at atmospheric pressure with a Gas Electron Multiplier (Sauli in Nucl Instrum Meth A 386:531, https://doi.org/10.1016/S0168-9002(96)01172-2, 1997) amplification and with an optical readout as a promising technology for light dark matter and directional searches. In this paper we describe the operation of a 50 l prototype named LIME (Long Imaging ModulE) in an overground location at Laboratori Nazionali di Frascati (LNF) of INFN. This prototype employs the technology under study for the 1 cubic meter Cygno demonstrator to be installed at the Laboratori Nazionali del Gran Sasso (LNGS) (Amaro et al. in Instruments 2022, 6(1), https://www.mdpi.com/2410-390X/6/1/6, 2022). We report the characterization of LIME with photon sources in the energy range from few keV to several tens of keV to understand the performance of the energy reconstruction of the emitted electron. We achieved a low energy threshold of few keV and an energy resolution over the whole energy range of 10–20%, while operating the detector for several weeks continuously with very high operational efficiency. The energy spectrum of the reconstructed electrons is then reported and will be the basis to identify radio-contaminants of the LIME materials to be removed for future Cygno detectors.

A refined numerical simulation approach to assess the neutron irradiation effect on the mechanical behavior of wurtzite GaN

Neutron irradiation often produces distinct types of damage or defects in gallium nitride (GaN) materials, which could alter the mechanical properties of GaN. This work develops a numerical approach utilizing molecular dynamics (MD) simulation to capture the structural changes and defect evolution characteristics of wurtzite GaN under long-term low-dose neutron irradiation, and to evaluate the variations in fundamental mechanical properties. By comparing different types of potential functions available for describing GaN materials, the Tersoff/ZBL potential energy function is found to be more suitable for describing the irradiation effects of GaN. A method of using multiple recoil atoms to trigger cascade collision together with a three-stage irradiation process description is proposed to achieve an effective distribution of irradiation defects, as well as to improve computational efficiency. To simulate the irradiation damage accumulation due to successive cascade collisions, it is applicable to apply an iterative process for the simulation model. Using these approaches, uniaxial tension simulations for irradiated wurtzite GaN are performed to analyze the variations in its fundamental mechanical properties along [1 0 1¯ 0] crystalline direction. The results indicate that low-dose irradiation tends to decrease the Young's modulus and tensile strength of wurtzite GaN material, and could alter its deformation mechanisms to some extent.

MC design and FIB preparation of a YSZ biochemical material microstructure

Aiming at the difficulty of traditional machining of Y2O3–ZrO2 (YSZ) inert ceramic materials, a different method using focused ion beam to selectively create nanoscale microscale structures on the surface of materials was proposed. The sputtering yield, surface damage, and the energy loss of YSZ materials was investigated using the SRIM software using the Monte Carlo method. It is shown that the sputtering yield increases with ion energy in the range 0–30 keV, reaching a maximum of 9.4 atoms/ion at 30 keV. At an ion beam voltage of 30 keV, the most severe damage to the material is 8 mm on the surface. At the same time, the main forms of energy loss in the treatment are phonon energy loss and ionization energy loss, of which phonon energy loss due to the recoil atoms is the largest. In addition, we continue to perform focused ion beam processing experiments on YSZ materials, combining previous MC modeling to optimize different operating conditions such as ion beam, voltage and processing mode. The optimized processing parameters are 30 keV and 2.5 nA. It is shown that the quality of the deep grooves gradually improves with decreasing ion beam current at the same ion beam voltage. However, an excessively small ion beam current leads to an excessively large depth of the deep grooves and lengthy processing times.

Detection and Calibration of Low-Energy Nuclear Recoils for Dark Matter and Neutrino Scattering Experiments

Detection of low-energy nuclear recoil events plays a central role in searches for particle dark matter interactions with atomic matter and studies of coherent neutrino scatters. Precise nuclear recoil calibration data allow the responses of these dark matter and neutrino detectors to be characterized and enable in situ evaluation of an experiment's sensitivity to anticipated signals. This article reviews the common methods for detection of nuclear recoil events and the wide variety of techniques that have been developed to calibrate detector response to nuclear recoils. We summarize the main experimental factors that are critical for accurate nuclear recoil calibrations, investigate mitigation strategies for different backgrounds and biases, and discuss how the presentation of calibration results can facilitate comparison between experiments. Lastly, we discuss the challenges for future nuclear recoil calibration efforts and the physics opportunities they may enable.

Clustering in gallium ion beam sputtered compound materials driven by bond strength and interstitial/vacancy reaction

The investigation of chemical reactions during ion irradiation is a frontier for the study of the ion–material interaction. In order to probe the chemistry of ion produced nanoclusters, valence electron energy loss spectroscopy (VEELS) was exploited to investigate Ga+ ion damage in Al2O3, InP, and InGaAs, where each target material has been shown to react differently to the interaction between impinging ions, recoil atoms, and vacancies: metallic Ga, ternary InGaP clusters, and metallic In clusters are formed in Al2O3, InP, and InGaAs, respectively. Supporting simulations based on Monte Carlo and crystal orbital Hamiltonian calculations indicate that the chemical constitution of cascade induced nano-precipitates is a result of a competition between interstitial/vacancy consumption rates and preferential bond formation due to differing bond strengths.

Directionality for nuclear recoils in a Liquid Argon TPC

Directional sensitivity to nuclear recoils would provide a smoking gun for a possible discovery of dark matter in the form of WIMPs (Weakly Interacting Massive Particles). A hint of directional dependence of the response of a dual-phase argon Time Projection Chamber (TPC) was found in the SCENE experiment. Given the potential importance of such a capability in the framework of dark matter searches, a new dedicated experiment, ReD (Recoil Directionality), was designed by the Global Argon Dark Matter Collaboration, in order to scrutinise this hint. A small dual-phase argon TPC was irradiated with neutrons produced by the p(7Li,7Be)n reaction using the 15 MV TANDEM accelerator of the INFN - Laboratori Nazionali del Sud, Catania, Italy, so as to produce argon nuclear recoils in the range (20 - 100) keV of interest for dark matter searches. Energy and direction of nuclear recoils are inferred by the detection of the elastically-scattered neutron by a set of scintillation detectors. Events were selected by gating of the associated 7Be, which is detected by a telescope of Si detectors.

Nanoscale evidence of zircon-coffinite-xenotime solid solution observed by atom probe tomography

Ion probe zircon U-Pb dating has been widely used in earth and planetary sciences research. Previous studies found that ion probes have problems in the U-Pb dating of zircon with high U content. When the U content of zircon reaches a high threshold, the apparent age of U-Pb will become scattered and mostly older, which is called the “high U effect”. Based on micron-scale observations, predecessors have proposed that the spontaneous alpha decay of high content of radioactive element U and its daughter nuclear recoil will damage the zircon lattice, resulting in an increased yield of Pb+ in SIMS analyses and therefore an older 206Pb/238U age. However, there are also studies showing that zircons that have not been damaged also show a “high U effect”. In this contribution, scanning electron microscopy, ion probe and atom probe tomography research were carried out on high U content zircon grains (3.0 ± 0.1 Ma) in a highly fractionated leucogranites from the Himalayas to study the microcosmic occurrence state of zirconium constituent elements. Results show that these zircon grains have extremely high U contents ranging from 4271 to 95,176 μg/g. The distribution of U, P and Y in zircon is inhomogeneous, with enrichment features in local nanoscale regions. Zr constituent elements mainly exist in two states: (1) lamellar enrichment region, which corresponds to the compositional oscillation ring of zircon. The lamellar high U region is nearly parallel distributed. Its composition is in the transition between zircon, coffinite (USiO4) and xenotime; (2) The agglomerated high U region, which appears as isolated particles in zircon with a composition close to coffinite. The composition of the observed highest U region is Zr2.7Si12.2O61.8U19.8P1.4Y1.2Yb0.6Hf0.3, and the particle size is ∼8 nm. Nanoscale coffinites and xenotimes in high U zircons result in obvious differences between the matrix with the ion probe zircon standard reference materials, which resulted in the “high U effect”.

Mineral detection of neutrinos and dark matter. A whitepaper

Minerals are solid state nuclear track detectors - nuclear recoils in a mineral leave latent damage to the crystal structure. Depending on the mineral and its temperature, the damage features are retained in the material from minutes (in low-melting point materials such as salts at a few hundred degrees C) to timescales much larger than the 4.5 Gyr-age of the Solar System (in refractory materials at room temperature). The damage features from the $O(50)$ MeV fission fragments left by spontaneous fission of $^{238}$U and other heavy unstable isotopes have long been used for fission track dating of geological samples. Laboratory studies have demonstrated the readout of defects caused by nuclear recoils with energies as small as $O(1)$ keV. This whitepaper discusses a wide range of possible applications of minerals as detectors for $E_R \gtrsim O(1)$ keV nuclear recoils: Using natural minerals, one could use the damage features accumulated over $O(10)$ Myr$-O(1)$ Gyr to measure astrophysical neutrino fluxes (from the Sun, supernovae, or cosmic rays interacting with the atmosphere) as well as search for Dark Matter. Using signals accumulated over months to few-years timescales in laboratory-manufactured minerals, one could measure reactor neutrinos or use them as Dark Matter detectors, potentially with directional sensitivity. Research groups in Europe, Asia, and America have started developing microscopy techniques to read out the $O(1) - O(100)$ nm damage features in crystals left by $O(0.1) - O(100)$ keV nuclear recoils. We report on the status and plans of these programs. The research program towards the realization of such detectors is highly interdisciplinary, combining geoscience, material science, applied and fundamental physics with techniques from quantum information and Artificial Intelligence.

MD Simulations of Collision Cascades in α-Ti. The Residual Number of Radiation Defects, Cascade Relaxation Time and Displacement Cascade Region Morphology

Molecular dynamics (MD) simulations were applied to study radiation damage formation in collision cascades created by the recoil of primary knock-on atoms (PKA) with PKA energies Epka = 5, 10, 15, 20 and 25 keV in α-Ti at temperatures T = 100, 300, 600 and 900 K. A series of 24 collision cascades with the same set of (Epka, T) parameters has been simulated to generate representative sampling. Sapling size was justified a posteriori. The number of Frenkel pairs Nfp and cascade relaxation time were obtained as functions of (Epka, T). It was shown that the average ⟨Nfp(Epka,T)⟩ fits within 0.3NRT, provided the threshold displacement energy is chosen in 28-40 eV range depending on the irradiation temperature. Under high PKA energy/low irradiation temperature conditions, displacement cascade region splits into subcascades expended along high-energy recoil trajectories. Cascade relaxation time does not depend on Epka in this case. Contrary, under low PKA energy/ high temperature simulation conditions, most of collision cascades possess equiaxial shape, and their relaxation time grows with PKA energy increase.

Directional dark matter readout with a novel multi-mesh ThGEM for SF6 negative ion operation

Abstract Direct searches for Weakly Interacting Massive Particle (WIMP) dark matter could greatly benefit from directional measurement of the expected induced nuclear recoils. Gas-based Time Projection Chambers (TPCs) offer potential for this, opening the possibility of measuring WIMP signals below the so-called neutrino floor but also of directional measurement of recoils induced by neutrinos from the Sun, for instance as proposed by the CYGNUS collaboration. Presented here for the first time are results from a Multi-Mesh Thick Gas Electron Multiplier (MM-ThGEM) using negative ion gases for operation with such a directional dark matter TPC. Negative ion drift gases are favoured for directionality due to their low diffusion characteristics. The multiple internal mesh structure is designed to provide a high gain amplification stage when coupled to future large area Micromegas, strip or pixel charge readout planes. Experimental results and simulations are presented of MM-ThGEM gain and functionality using low pressure pure CF4, SF6 and SF6:CF4 mixtures irradiated with alpha particles and 55Fe x-rays. The concept is found to work well, providing stable operation with gains over 103 in pure SF6.

First Dark Matter Search with Nuclear Recoils from the XENONnT Experiment.

We report on the first search for nuclear recoils from dark matter in the form of weakly interacting massive particles (WIMPs) with the XENONnT experiment, which is based on a two-phase time projection chamber with a sensitive liquid xenon mass of 5.9ton. During the (1.09±0.03) ton yr exposure used for this search, the intrinsic ^{85}Kr and ^{222}Rn concentrations in the liquid target are reduced to unprecedentedly low levels, giving an electronic recoil background rate of (15.8±1.3) events/ton yr keV in the region of interest. A blind analysis of nuclear recoil events with energies between 3.3 and 60.5keV finds no significant excess. This leads to a minimum upper limit on the spin-independent WIMP-nucleon cross section of 2.58×10^{-47} cm^{2} for a WIMP mass of 28 GeV/c^{2} at 90% confidence level. Limits for spin-dependent interactions are also provided. Both the limit and the sensitivity for the full range of WIMP masses analyzed here improve on previous results obtained with the XENON1T experiment for the same exposure.

Scintillating Bubble Chambers for Rare Event Searches

The Scintillating Bubble Chamber (SBC) collaboration is developing liquid-noble bubble chambers for the detection of sub-keV nuclear recoils. These detectors benefit from the electron recoil rejection inherent in moderately-superheated bubble chambers with the addition of energy reconstruction provided from the scintillation signal. The ability to measure low-energy nuclear recoils allows the search for GeV-scale dark matter and the measurement of coherent elastic neutrino-nucleus scattering on argon from MeV-scale reactor antineutrinos. The first physics-scale detector, SBC-LAr10, is in the commissioning phase at Fermilab, where extensive engineering and calibration studies will be performed. In parallel, a functionally identical low-background version, SBC-SNOLAB, is being built for a dark matter search underground at SNOLAB. SBC-SNOLAB, with a 10 kg-yr exposure, will have sensitivity to a dark matter–nucleon cross section of 2×10−42 cm2 at 1 GeV/c2 dark matter mass, and future detectors could reach the boundary of the argon neutrino fog with a tonne-yr exposure. In addition, the deployment of an SBC detector at a nuclear reactor could enable neutrino physics investigations including measurements of the weak mixing angle and searches for sterile neutrinos, the neutrino magnetic moment, and the light Z’ gauge boson.

Nuclear recoil response of liquid xenon and its impact on solar 8B neutrino and dark matter searches

Nuclear recoil response of liquid xenon and its impact on solar 8B neutrino and dark matter searches

Observation of a low energy nuclear recoil peak in the neutron calibration data of the CRESST-III experiment

Observation of a low energy nuclear recoil peak in the neutron calibration data of the CRESST-III experiment

Precision measurement of the specific activity of ^{39}Ar in atmospheric argon with the DEAP-3600 detector

The specific activity of the beta decay of ^{39}Ar in atmospheric argon is measured using the DEAP-3600 detector. DEAP-3600, located 2 km underground at SNOLAB, uses a total of (3269 ± 24) kg of liquid argon distilled from the atmosphere to search for dark matter. This detector is well-suited to measure the decay of ^{39}Ar owing to its very low background levels. This is achieved in two ways: it uses low background construction materials; and it uses pulse-shape discrimination to differentiate between nuclear recoils and electron recoils. With 167 live-days of data, the measured specific activity at the time of atmospheric extraction is (0.964 ± 0.001_textrm{stat} ± 0.024_textrm{sys}) Bq/kg_textrm{atmAr}, which is consistent with results from other experiments. A cross-check analysis using different event selection criteria and a different statistical method confirms the result.

ELOISE - Reliable background simulation at sub-keV energies

CaWO_44 and Al_22O_33 are well-established target materials used by experiments searching for rare events like the elastic scattering off of a hypothetical Dark Matter particle. In recent years, experiments have reached detection thresholds for nuclear recoils at the 10 eV-scale. At this energy scale, a reliable Monte Carlo simulation of the expected background is crucial. However, none of the publicly available general-purpose simulation packages are validated at this energy scale and for these targets. The recently started ELOISE project aims to provide reliable simulations of electromagnetic particle interactions for this use case by obtaining experimental reference data, validating the simulation code against them, and, if needed, calibrating the code to the reference data.

Analysis of radiation damage in silicon charge-coupled devices used for dark matter searches

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 to distinguish nuclear recoils from electron recoils in some energy ranges, which would improve the ability of CCD detectors to search for weakly interacting dark matter.

Quenching Factor estimation of Na recoils in NaI(Tl) crystals using a low-energy pulsed neutron beam measurement

NaI(Tl) based scintillation detectors have become a staple in the field of direct dark matter searches, with the DAMA-LIBRA experiment being the standout for its reported observation of an annually modulating WIMP-like signal which is in direct contrast with other results. In order to accurately calibrate the energies of WIMP-induced nuclear recoil signals, precise measurements of the quenching factor of the NaI crystals are essential for each of these experiments, as it is well established that electron recoils and nuclear recoils have dissimilar scintillation light yields. In this contribution, we present first preliminary results of an ongoing systematic study that has been carried out by the COSINUS collaboration and Duke University to measure the quenching factor of Na recoils. Five ultra-pure NaI crystals, manufactured by the Shanghai Institute for Ceramics, each of which have varying Tl dopant concentrations, were irradiated with a mono-energetic neutron beam at the Triangle Universities National Laboratory, North Carolina, USA to extract the quenching factor values in the low recoil energies of 1-30keV_{nr}nr.

Background suppression in the COSINUS experiment: Active muon veto and radiopure materials selection

For over twenty-five years the DAMA/LIBRA experiment has reported an annual modulation signal that is consistent with a dark matter explanation. This signal is, currently, in tension with the null results observed by other searches that utilize different target detectors. The COSINUS experiment will perform a model-independent cross-check of the DAMA/LIBRA result by using the same target material, NaI crystals, operated as scintillating calorimeters. By measuring both temperature and light the NaI crystals in COSINUS will be able to distinguish between electron and nuclear recoils on an event-by-event basis. However, background events induced by cosmic-rays, environmental radioactivity or the intrinsic contamination of the materials used in the crystal, shielding and infrastructure can pose an issue to any analysis and must be fully understood. We report on the status of the development of the simulation for an active water Cherenkov muon veto, as well as the results of the beginning radiogenic material screening.