Recoil Cross Section Research Articles

Determination of hydrogen concentration in solids by transmission ERDA under nuclear-elastically enhanced recoiling of H by 8 and 9 MeV He

Hydrogen concentrations in thin self-supporting samples of polyphenylene sulfide (PPS) and muscovite have been determined by nuclear-elastic recoil detection analysis (ERDA) of transmission layout. The analysis procedure is based only on the database of stopping power and recoil cross section for material analysis, without using any reference sample of known H content. For the PPS sample, the determined value of H cm−3 is in good agreement with the calculated value of H cm−3. For the muscovite sample, the H concentration originating each from bound water and absorbed water is uniform over the entire thickness of the sample. The determined concentration H cm−3 of the muscovite agrees excellently with the value of H cm−3 obtained from other quantitative analyses typically applied for minerals. The present results demonstrate the capability of accurate determination of H contents in materials and minerals by transmission ERDA.

Sensitive multi-element profiling with high depth resolution enabled by time-of-flight recoil detection in transmission using pulsed keV ion beams

The potential of time-of-flight recoil detection for sensitive multi-element profiling of thin membranes and quasi-2D systems in transmission geometry using pulsed keV ion beams is assessed. While the time-of-flight approach allows for simultaneous detection of multiple elements, to the largest extent irrespective of recoil charge states, the keV projectile energies guarantee high recoil-cross sections yielding high sensitivity at low dose. We demonstrate the capabilities of the approach using 22Ne and 40Ar as projectiles transmitted through thin carbon foils featuring optional LiF-coatings and single-crystalline silicon membranes for different sample preparation routines and crystal orientations.Using a large position-sensitive detector (0.13 sr), a depth resolution below 6 nm and sensitivity below 1014 atoms/cm2 was achieved for H in a 50 nm thick silicon membrane. For crystalline targets, we show how the probability of creation and detection of recoils and their observed angular distribution depend on sample orientation.

DARWIN: direct dark matter search with the ultimate detector

DARk matter WImp search with liquid xenoN (DARWIN) is a future experiment for the direct detection of dark matter based on a multi-ton liquid xenon time projection chamber. The main goal of DARWIN is to reach an unprecedented sensitivity to WIMP (Weakly Interacting Massive Particle)-nuclear recoil cross sections for a large WIMP mass range, down to the level where the irreducible background from neutrino interactions with the target is dominant. This ultra-low background experiment will also have competitive sensitivity to test other dark matter hypotheses such as dark photons and superWIMPs and to detect other rare events like solar neutrinos, neutrinoless double-beta decay of 136Xe, solar axions and neutrinos from galactic supernovae. In this paper we present the design of the DARWIN detector and the estimated WIMP sensitivity based on the expected backgrounds. Other rare event searches are also discussed.

Microscopic 3-dimensional mapping of hydrogen bubbles in polycrystalline Al by elastic recoil detection analysis under transmission geometry

We have measured microscopic 3-dimensional distribution of plasma-charged hydrogen in polycrystalline Al. The measurements have been carried out nondestructively by using elastic recoil detection analysis under transmission geometry of a collimated 8 MeV 4He2+ beam. The recoil cross section as large as 2 × 103 mb/sr due to the nuclear elastic collision allowed observation of the spatial distribution of hydrogen in the Al sample of 80 μm thickness. The distribution maps of hydrogen clearly visualize hydrogen bubbles of 10–20 μm diameter in the surface layer of about 12 μm thickness. The critical concentration of hydrogen minimally needed for growth of the hydrogen bubble of ten-μm size has been determined to be 1.6 × 1020 cm−3.

The shadow of dark matter as a shadow of string theory

We point out that string theory can solve the conundrum to explain the emergence of an electroweak dipole moment from electroweak singlets through induction of those dipole moments through a Kalb–Ramond dipole coupling. This can generate a U_Y(1) portal to dark matter and entails the possibility that the U_Y(1) gauge field is related to a fundamental vector field for open string interactions. The requirement to explain the observed dark matter abundance relates the coupling scale M in the corresponding low-energy effective U_Y(1) portal to the dark matter mass m_chi . The corresponding electron recoil cross sections for a single dipole coupled dark matter species are generically below the current limits from XENON, SuperCDMS and SENSEI, except in the GeV mass range if the electric dipole coupling becomes stronger than the magnetic coupling, a_e^2ge a_m^2. Furthermore, the recoil cross sections are above the neutrino floor, and the U_Y(1) portal can be tested with longer exposure or larger detectors. Discovery of electroweak dipole dark matter would therefore open an interesting window into string phenomenology.

Direct signals from electroweak singlets through the Higgs portal

We review predictions and constraints for nuclear recoil signals from Higgs portal dark matter under the assumption of standard thermal creation from freeze-out. Thermally created scalar and vector Higgs portal dark matter masses are constrained to be in the resonance region near half the Higgs mass, [Formula: see text], or above several TeV. The resonance region for these models will be tested by XENONnT and LZ. The full mass range up to the unitarity limit can be tested by DarkSide-20k and DARWIN. Fermionic Higgs portal dark matter with a pure CP odd coupling is constrained by the Higgs decay width, but has strongly suppressed recoil cross sections which cannot be tested with upcoming experiments. Fermionic Higgs portal dark matter with a combination of CP even and odd Higgs couplings can be constrained by the direct search experiments.

Two-dimensional mapping of hydrogen and other elements in materials with microbeam-based transmission ERDA and PIXE

We report on the preliminary studies for two-dimensional (2D) mapping of hydrogen and other elements in materials with transmission ERDA and PIXE using a microbeam of 8 MeV 4He. The extremely enhanced forward recoil cross section of hydrogen in the non-Rutherford scattering allows 2D mapping of hydrogen in the sample. The mapping by PIXE, which provides complementary information to the mapping by ERDA, was obtained simultaneously. The present work probably leads to 3D mapping of hydrogen in bulk materials, i.e., the present spatial 2D plus depth as an additional dimension, since the energy of the outgoing hydrogen corresponds to the depth where the hydrogen is originally located.

Differential dpa calculations with SPECTRA-PKA

The processing code SPECTRA-PKA produces energy spectra of primary atomic recoil events (or primary knock-on atoms, PKAs) for any material composition exposed to an irradiation spectrum. Such evaluations are vital inputs for simulations aimed at understanding the evolution of damage in irradiated material, which is generated in cascade displacement events initiated by PKAs. These PKA spectra present the full complexity of the input (to SPECTRA-PKA) nuclear data-library evaluations of recoil events. However, the commonly used displacements per atom (dpa) measure, which is an integral measure over all possible recoil events of the displacement damage dose, is still widely used and has many useful applications – as both a comparative and correlative quantity. This paper describes the methodology employed that allows the SPECTRA-PKA code to evaluate dpa rates using the energy-dependent recoil (PKA) cross section data used for the PKA distributions. This avoids the need for integral displacement kerma cross sections and also provides new insight into the relative importance of different reaction channels (and associated different daughter residual and emitted particles) to the total integrated dpa damage dose. Results are presented for Fe, Ni, W, and SS316. Fusion dpa rates are compared to those in fission, highlighting the increased contribution to damage creation in the former from high-energy threshold reactions.

Projected sensitivity of the SuperCDMS SNOLAB experiment

SuperCDMS SNOLAB will be a next-generation experiment aimed at directly detecting low-mass (< 10 GeV/c$^2$) particles that may constitute dark matter by using cryogenic detectors of two types (HV and iZIP) and two target materials (germanium and silicon). The experiment is being designed with an initial sensitivity to nuclear recoil cross sections ~ 1 x 10$^{-43}$ cm$^2$ for a dark matter particle mass of 1 GeV/c$^2$, and with capacity to continue exploration to both smaller masses and better sensitivities. The phonon sensitivity of the HV detectors will be sufficient to detect nuclear recoils from sub-GeV dark matter. A detailed calibration of the detector response to low energy recoils will be needed to optimize running conditions of the HV detectors and to interpret their data for dark matter searches. Low-activity shielding, and the depth of SNOLAB, will reduce most backgrounds, but cosmogenically produced $^{3}$H and naturally occurring $^{32}$Si will be present in the detectors at some level. Even if these backgrounds are x10 higher than expected, the science reach of the HV detectors would be over three orders of magnitude beyond current results for a dark matter mass of 1 GeV/c$^2$. The iZIP detectors are relatively insensitive to variations in detector response and backgrounds, and will provide better sensitivity for dark matter particle masses (> 5 GeV/c$^2$). The mix of detector types (HV and iZIP), and targets (germanium and silicon), planned for the experiment, as well as flexibility in how the detectors are operated, will allow us to maximize the low-mass reach, and understand the backgrounds that the experiment will encounter. Upgrades to the experiment, perhaps with a variety of ultra-low-background cryogenic detectors, will extend dark matter sensitivity down to the "neutrino floor", where coherent scatters of solar neutrinos become a limiting background.

Comparative study of Monte Carlo particle transport code PHITS and nuclear data processing code NJOY for recoil cross section spectra under neutron irradiation

Because primary knock-on atoms (PKAs) create point defects and clusters in materials that are irradiated with neutrons, it is important to validate the calculations of recoil cross section spectra that are used to estimate radiation damage in materials. Here, the recoil cross section spectra of fission- and fusion-relevant materials were calculated using the Event Generator Mode (EGM) of the Particle and Heavy Ion Transport code System (PHITS) and also using the data processing code NJOY2012 with the nuclear data libraries TENDL2015, ENDF/BVII.1, and JEFF3.2. The heating number, which is the integral of the recoil cross section spectra, was also calculated using PHITS-EGM and compared with data extracted from the ACE files of TENDL2015, ENDF/BVII.1, and JENDL4.0. In general, only a small difference was found between the PKA spectra of PHITS+TENDL2015 and NJOY+TENDL2015. From analyzing the recoil cross section spectra extracted from the nuclear data libraries using NJOY2012, we found that the recoil cross section spectra were incorrect for 72Ge, 75As, 89Y, and 109Ag in the ENDF/B-VII.1 library, and for 90Zr and 55Mn in the JEFF3.2 library. From analyzing the heating number, we found that the data extracted from the ACE file of TENDL2015 for all nuclides were problematic in the neutron capture region because of incorrect data regarding the emitted gamma energy. However, PHITS+TENDL2015 can calculate PKA spectra and heating numbers correctly.

Elastic recoil cross section determination of deuterium by helium-4 ions at 30° with the energy range of 2.6–7.4 MeV

The elastic recoil cross section for D(4He, D) 4He was determined at a recoil angle of 30° over an incident helium energy range from 2.6 to 7.4MeV. A thin solid target Ta/TiDx/Si used for cross section measurement was prepared by direct current magnetron sputtering, and it was so stable to ion beam bombardment that nearly no deuterium loss (less than 0.2%) exists over the whole experiment. A relative determination method is adopted in this measurement. It can avoid the error from the beam dose and the solid angle of the detectors and it is also free to direct measurement of D content in the film. The total uncertainty in the cross section determination is less than 5%.

The finite shelf life of minimal Higgs portal dark matter

We point out that even a very conservative estimate for the uncertainty of the effective Higgs-nucleon coupling yields nuclear recoil cross sections for perturbative Higgs portal dark matter models which will be probed by DEAP-3600 and XENON1T within two years of observations.

Measurements of the elastic recoil cross-section for 1H(12C, 1H)12C

The elastic recoil cross section for 1H(12C, 1H)12C was determined at a recoil angle of 30° over an incident carbon energy range from 4.0 to 8.0MeV. The thin solid film target Pd/TiHx/Si used for cross section measurement was prepared by direct current (DC) magnetron sputtering. The measured cross-section data are compared with records available in literature and a similar trend over the energy range was shown. The total uncertainty in the present cross-section data is less than 7%.

Cross-section measurements of α+ 14N elastic scattering for He beam TOF-ERDA

The elastic scattering cross-sections for α particles from nitrogen at a scattering angle of 83.6° were measured in the energy range of 2.0–5.4MeV, and the nitrogen recoil cross-sections at a recoil angle of 40° were derived from the scattering cross-sections. Simultaneous measurements of scattering cross-sections at a scattering angle of 165° were also performed to validate the measurements. The obtained recoil cross-section data are essential for the quantitative examination of nitrogen through time-of-flight elastic recoil detection analysis with He beams.

Elastic recoil cross section determination of 1H by 4He ions at 30° and energy range of 1.6–6.0 MeV

In this paper, the differential cross-section for forward recoiling 1H with 4He ions has been determined in the energy range of 1.6–6.0MeV at a laboratory angle of 30°. A film of ∼54nm TiHx on the Si substrate with an overlayer of ∼7nm Ta on the TiHx foil was used as the target, and hydrogen loss of the target due to ion bombardment can be fully ignored (<0.1%) through the whole measurement. A method of relative determination for the cross-section measurement was employed to be free from absolute determination of hydrogen content in the target as well as absolute measurements of beam dose and solid angles of the detectors. The uncertainty of the determination is less than 5.2%.

Cosmogenic production rates and recoil loss effects in micrometeorites and interplanetary dust particles

AbstractWe present a purely physical model to determine cosmogenic production rates for noble gases and radionuclides in micrometeorites (MMs) and interplanetary dust particles (IDPs) by solar cosmic‐rays (SCR) and galactic cosmic‐rays (GCR) fully considering recoil loss effects. Our model is based on various nuclear model codes to calculate recoil cross sections, recoil ranges, and finally the percentages of the cosmogenic nuclides that are lost as a function of grain size, chemical composition of the grain, and the spectral distribution of the projectiles. The main advantage of our new model compared with earlier approaches is that we consider the entire SCR particle spectrum up to 240 MeV and not only single energy points. Recoil losses for GCR‐produced nuclides are assumed to be equal to recoil losses for SCR‐produced nuclides. Combining the model predictions with Poynting‐Robertson orbital lifetimes, we calculate cosmic‐ray exposure ages for recently studied MMs, cosmic spherules, and IDPs. The ages for MMs and the cosmic‐spherule are in the range &lt;2.2–233 Ma, which corresponds, according to the Poynting‐Robertson drag, to orbital distances in the range 4.0–34 AU. For two IDPs, we determine exposure ages of longer than 900 Ma, which corresponds to orbital distances larger than 150 AU. The orbital distance in the range 4–6 AU for one MM and the cosmic spherule indicate an origin either in the asteroid belt or release from comets coming either from the Kuiper Belt or the Oort Cloud. Three of the studied MMs have orbital distances in the range 23–34 AU, clearly indicating a cometary origin, either from short‐period comets from the Kuiper Belt or from the Oort Cloud. The two IDPs have orbital distances of more than 150 AU, indicating an origin from Oort Cloud comets.

A minimal dark matter interpretation for the CRESST-II signal

AbstractWe report on the possible interpretation of the two proposed dark matter mass values mχ=11.6 GeV and mχ=25.3 GeV from CRESST-II within the framework of the Higgs portal minimal dark matter model. We find that the higher mass value yields a suitable fit with a dark matter-Higgs coupling η/2=0.157 and a recoil cross section which is compatible with contemporary estimates of the effective Higgs–nucleon coupling. On the other hand, the lower mass solution would require a large strangeness component in the nucleon to explain the corresponding nucleon recoil cross section reported by CRESST-II.

Nuclear recoil cross sections from time-dependent studies of two-photon double ionization of helium

We examine the sensitivity of nuclear recoil cross sections produced by two-photon double ionization of helium to the underlying triple differential cross sections (TDCS) used in their computation. We show that this sensitivity is greatest in the energy region just below the threshold for sequential double ionization. Accurate TDCS, extracted from non-perturbative solutions of the time-dependent Schroedinger equation, are used here in new computations of the nuclear recoil cross section.

Triple differential cross sections and nuclear recoil in two-photon double ionization of helium

Triple differential cross sections (TDCS) for two-photon double of helium are calculated using the method of exterior complex scaling both above and below the threshold for sequential (54.4 eV). It is found that sequential produces characteristic behavior in the TDCS that identifies that process when it is in competition with nonsequential ionization. Moreover we see the signature in the TDCS and nuclear recoil cross sections ofvirtual sequential ionization below the threshold for the sequential process.

Decoding sequential versus nonsequential two-photon double ionization of helium using nuclear recoil

Above $54.4\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, two-photon double ionization of helium is dominated by a sequential absorption process, producing characteristic behavior in the single and triple differential cross sections. We show that the signature of this process is visible in the nuclear recoil cross section, integrated over all energy sharings of the ejected electrons, even below the threshold for the sequential process. Since nuclear recoil momentum imaging does not require coincident photoelectron measurement, the predicted images present a viable target for future experiments with new short-pulse vacuum ultraviolet (vuv) and soft x-ray sources.