First results from dark matter search experiment in the Nokogiriyama underground cell

An experiment to search for hypothetical particle dark matter using cryogenic thermal detector, or bolometer is ongoing. The bolometer consists of eight pieces of 21 g LiF absorbers and sensitive NTD germanium thermistors attached to them and is installed in the Nokogiriyama underground cell which is a shallow depth site (∼15 m w.e.). We report on the results from the first running for about ten days using this arrayed bolometer system together with appropriate shieldings and muon veto counters. From the obtained energy spectra the exclusion limits for the cross section of the elastic neutralino-proton scattering are derived under commonly accepted astrophysical assumptions. The sensitivity for the light neutralino with a mass below 5 GeV is improved by this work.     

Effective atomic numbers for CoCuNi alloys using transmission experiments

Effective atomic numbers for CuCoNi alloys against changing Ni contents were measured in the X-ray energy range from 15.746 to 40.930 keV. The gamma rays emitted a ²⁴¹Am point source have been send on absorbers to be used transmission arrangement. The X-rays were counted by a Si(Li) detector with a resolution of 160 eV at 5.9 keV. The compositions of the Ni films were determined to be 0.03, 0.47, 0.62, 1.23, 1.22 and 1.6 by a scanning electron microscopy in CuCoNi alloys prepared against changing Ni contents. CoCuNi alloy films were prepared with an electrodeposition technique. Also, the total effective atomic numbers of each alloy were estimated using mixture rule. The measured values were compared with estimated values for alloys.     

Measurement of mass attenuation coefficients for undoped and boron nitride–doped magnesium diboride superconductors in the x-ray region 8.04–59.5 keV

In this study, mass attenuation coefficients of the undoped and 2% boron nitride–doped magnesium diboride superconductor samples were investigated. Mass attenuation coefficients were measured at 8.04–59.5?keV x-ray energies by using a high-purity germanium detector with a resolution of 182?eV at 5.9?keV. It is observed that mass attenuation coefficients in undoped and doped magnesium diboride samples decrease with increasing photon energy, and doping with the boron nitride leads to increase the absorption of the electromagnetic radiation.     

The extensive air shower muon number spectrum beyond the knee in the cosmic-ray energy spectrum

The extensive air shower (EAS) muon number spectrum is obtained with increased statistics using the central muon detector of the EAS MSU array, which records muons with energies above 10 GeV. The dependence of the mass composition of primary cosmic rays on the energy is considered. The conclusion is confirmed that for energies from 3 × 10¹⁵ eV (the primary energy spectrum knee) up to 10¹⁷ eV a change in the composition associated with an increase in the proportion of heavy nuclei occurs; however, after the energy of 10¹⁷ eV, the proportion of heavy nuclei begins to decrease and the composition becomes lighter. A comparison with similar data from other experiments is conducted. The existence of an additional component of cosmic rays is confirmed; earlier an indication of its presence was derived from data on the EAS electron number spectrum.     

Superconducting tunnel junctions as detectors for high‐resolution x‐ray spectroscopy

Superconducting tunnel junctions (STJs) are a type of cryogenic detector with a working temperature of about 100 mK. They allow the combination of low energy threshold, high quantum efficiency and good count rate capability with an excellent energy resolution; at an x‐ray energy of 5.9 keV an energy resolution of 10.8 eV (FWHM) has been achieved. The detector system described is based on STJs which consist of two superconducting Al electrodes separated by a thin dielectric tunnel barrier. The tunneling process of quasi‐particles created by deposition of energy in the electrodes leads to a detectable current signal. The STJ is equipped with a superconducting Pb absorber which is read out via phonons. The Pb absorber increases absorption efficiency (～50% at 6 keV) and suppresses detector artefacts. The degeneration of Pb, most probably due to oxidation, is overcome by the introduction of a protective SiO layer on top of the absorber. This layer leads to a slight reduction of energy resolution. Nevertheless, a resolution of 9.7 eV at 1.7 keV and of ～20 eV at 5.9 keV could be realized with a prototype detector. Currently this STJ‐based detector system is being incorporated into a prototype cryogenic spectrometer for XRF analysis. Copyright © 2004 John Wiley & Sons, Ltd.     

紫外光诱导光电子发射负离子源的阈值光电子成像仪设计 (cited: 2)

设计了一套紧凑的光电子成像装置,它包括解离式光电子贴附负离子源、垂直安装的高分辨阈值光电子速度成像装置和线性飞行时间质谱仪．紫外光辐射金属表面诱导低能光电子发射,再通过低能电子贴附超声分子束产生高强度和冷的负离子源．结合这种负离子源和飞行时间质谱-光电子成像仪装置,仪器的质量分辨能达到200左右,能量分辨优于3%(即对1 eV动能的电子,分辨达到30 meV)．此外,使用该实验装置获得了CH₃S^-和S₂^-在611.46 nm下的低能阈值光电子成像结果．同时得到了CH₃S和S₂的更精确的电子亲和势分别为1.8626±0.0020和1.6744±0.0035 eV．初步的结果证明了该装置对研究阈值光电子成像精确测量光电子亲和势非常有效     

Design of an Auger Electron Mössbauer Spectrometer (AEMS) using a modified cylindrical mirror analyzer

We have designed and built an Auger Electron Mössbauer Spectrometer (AEMS) for the detection of resonant ⁵⁷Fe Auger electrons using a modified commercial cylindrical mirror analyzer (CMA). The CMA final aperture was modified intentionally in order to increase electron transmission at the expense of reducing its energy resolution, from an original value of 0.5 % to a value of 11 % after the modification. The Channeltron detector electronics and the pre-amplifier were also modified in order to increase the counting efficiency. The electron energy analyzer is selective in energy in the 30 eV–3000 eV range, so the spectrometer can be used to detect MNN (45 eV) and LMM (600–700 eV) Fe Auger signals, what gives it a high surface sensitivity for Fe containing samples. We have used it to acquire the Fe LMM Auger signals generated from the de-excitation process after γ-Ray resonant nuclear absorption. The spectrometer can be used to study samples non-enriched in ⁵⁷Fe, with acquisition times from 5 to 7 days, what is a big advantage. From electron trajectory Monte Carlo simulations in metallic iron, the mean-escape-depth of the detected Auger signals has been estimated in approximately 1 nm. Fe K conversion electrons and KLL Auger electrons with mean escape depths of 129 nm and 78 nm respectively also contribute to the detected signal although in a lesser proportion.     

Performances of a metallic magnetic calorimeter for the measurement of hard X‐ray emission intensities

The energy spectrum analysis of X‐ray intensities with semiconductor detectors is often difficult because their energy resolution is usually not good enough to separate the different X‐ray lines. Metallic magnetic calorimeters (MMCs) can be an alternative; they can offer both high energy resolution and high intrinsic detection efficiency from 0 to 100 keV. MMCs are thermal detectors; that is to say, the energy of each absorbed photon is measured as a temperature elevation. At very low temperature, typically few tens of mK, a very large pulse height‐to‐noise ratio can be obtained that is an essential condition for high energy resolution. We are involved in the development of MMCs for metrology applications such as the determination of hard X‐ray emission intensities. For that purpose, we conceived an MMC with an energy resolution of 57 eV around 30 keV. The absorber is made of gold providing high intrinsic detection efficiency even for a small volume, greater than 90% below 60 keV. We will describe the physical principle and the practical realisation of this detector and discuss its performances by analysing the energy spectrum obtained from a ¹³³Ba source. Preliminary outcomes of relative emission intensities of the K X‐ray of cesium are presented and compared with other experimental data and theoretical calculations. Copyright © 2012 John Wiley & Sons, Ltd.     

Fundamental parameter approach to XRF spectroscopy measurements of arsenic in polyester resin skin phantoms

A fundamental parameter (FP) approach that explicitly incorporates the energy‐broadening response of the detector was developed. The ratio between Kα fluorescence peak area and the sum of coherently and incoherently scattered peak areas was used as an indicator of trace element concentration. The peak ratio was theoretically calculated using the FP method. The energy‐broadening response curve of the Si(Li) detector was estimated by matching the theoretical and experimental values of this ratio. The method was implemented for the analysis of the K‐shell x‐ray fluorescence (K‐XRF) spectra of six polyester resin samples corresponding to six different arsenic concentrations. A ¹⁰⁹Cd radioactive source provided the excitation radiation for spectra acquisition. The predicted detector energy resolution expressed as full width at half‐maximum (FWHM) for Fe Kα fluorescence peak (208 ± 5 eV at 6.4 keV) and As Kα fluorescence peak (222 ± 5 eV at 10.5 keV) were in agreement with the experimental measurements. Copyright © 2008 John Wiley & Sons, Ltd.     

Measurement of radiation energy by spectrometric systems based on uncooled silicon detectors

The results of measurements of radiation energy for single-channel detection systems based on uncooled silicon planar detectors and spectrometric readout electronics, developed at the Kharkiv Institute of Physics and Technology National Scientific Center, are presented. Radiation sources of ⁵⁵Fe, ²⁴¹Am, ⁵⁷Co, ¹³⁷Cs, and ^99MTc and characteristic X-ray radiation (CXR) are used in the experiments. The radiation energy in the range of E _γ = 3–140 keV is measured by a spectrometer based on a Si PIN detector. The energy resolution (full width at half maximum, FWHM) in this energy range changes with increasing photon energy from 0.97 to 1.3 keV. The CXR of calcium (K _α = 3.69 keV) is measured by a Si planar detector with an input aluminum foil. Emission lines in the energy range of E _γ = 0.04–0.662 MeV are measured by a CsI(Tl) scintillator-silicon PIN-photodiode detection system. The energy resolution of the spectrometer changes with quantum energy increasing from 22 to 70 keV. The CXR from cesium and iodine with K _α 31 and 28.6 keV, respectively, is recorded.     

A three‐crystal spectrometer for high‐energy resolution fluorescence‐detected X‐ray absorption spectroscopy and X‐ray emission spectroscopy at SSRF

A Johann‐type spectrometer for the study of high‐energy resolution fluorescence‐detected X‐ray absorption spectroscopy, X‐ray emission spectroscopy and resonant inelastic X‐ray scattering has been developed at BL14W1 X‐ray absorption fine structure spectroscopy beamline of Shanghai Synchrotron Radiation Facility. The spectrometer consists of three crystal analyzers mounted on a vertical motion stage. The instrument is scanned vertically and covers the Bragg angle range of 71.5–88°. The energy resolution of the spectrometer ranges from sub‐eV to a few eV. The spectrometer has a solid angle of about 1.87 × 0^?3 of 4π sr, and the overall photons acquired by the detector could be 10⁵ counts per second for the standard sample. The performances of the spectrometer are illustrated by the three experiments that are difficult to perform with the conventional absorption or emission spectroscopy. Copyright © 2016 John Wiley & Sons, Ltd.     

A VUV isochromat spectrometer for surface analysis

A vacuum ultraviolet isochromat spectrometer employing an energy selective Geiger-Müller photon counter is described. The mean energy of the spectrometer is 9.7 eV with a standard deviation of ±0.23 eV. Together with the thermal energy distribution of the electrons emitted from a directly heated tungsten cathode, an overall resolution of ±0.33 eV is obtained. Pulsed operation of the x-ray tube avoids additional broadening due to the voltage drop across the filament. Further, pulsed operation of the accelerating voltage is employed to avoid counting losses due to the relatively large dead time of the radiation detector. Operating frequencies of up to 2 kHz are possible. With sensitivities of typically 10⁷ pulses per Coulomb, the anode currents are in the range of 100–200 μA. These attractive properties suggest to employ the method to study surface electronic properties of solids.     

Time-resolved luminescence spectroscopy of pure and doped with Ce3+ ions SrAlF5 crystals

The results of a study of time-resolved photoluminescence (PL) and energy transfer in both pure and doped with Ce³⁺ ions SrAlF₅ (SAF) single crystals are presented. The time-resolved and steady-state PL spectra in the energy range of 1.5–6.0 eV, the PL excitation spectra and the reflectivity in the energy range of 3.7–21 eV, as well as the PL decay kinetics were measured at 8.8 and 295 K. The lattice defects were revealed in the low temperature PL spectra (emission bands at 2.9 and 4.5 eV) in the undoped SAF crystals. The luminescence spectra of the doped Ce³⁺:SAF crystals demonstrate a new selective emission bands in the range of 3.7–4.5 eV with the exponential decay kinetics (τ ≈ 60 ns at X-ray excitation). These bands correspond to the d-f transitions in Ce³⁺ ions, which occupy nonequivalent sites in the crystal lattice.     

Messung der Energieverlustspektren von Aluminium- und Silberfolien mit hoher Auflösung

The energy loss spectra of polycrystalline aluminium and silver foils have been measured with high resolution. For the plasmon energy of aluminium 14.97 eV is obtained. The half width of the plasmon peak is 0.60 eV corresponding to a relaxation time τ=1.1×10^?15 sec in fair agreement with optical data. In silver films of certain thicknesses the surface plasmon peak and the plasmon peak can be separated in the energy loss spectrum. The values of the energy losses are 3.64 and 3.78 eV respectively.     

The electrical properties of sulfur-implanted cubic boron nitride thin films

Cubic boron nitride (c-BN) thin films are deposited on p-type Si wafers using radio frequency (RF) sputtering and then doped by implanting S ions. The implantation energy of the ions is 19 keV, and the implantation dose is between 10 15 ions/cm 2 and 10 16 ions/cm 2 . The doped c-BN thin films are then annealed at a temperature between 400°C and 800 C. The results show that the surface resistivity of doped and annealed c-BN thin films is lowered by two to three orders, and the activation energy of c-BN thin films is 0.18 eV.     

The extrapolation of NEMO techniques to future generation 2<Emphasis Type="Italic">β</Emphasis>-decay experiments

The possibilities of using NEMO techniques for future neutrinoless double-beta decay experiments are discussed. The main idea is to have a realistic program with planned sensitivity for half-life measurement on the level of ～(1.5–2)×10²⁶ yr (sensitivity to neutrino mass ～0.04–0.1 eV). It is argued that this can be achieved using the improved NEMO technique to study 100 kg of ⁸²Se. A possible scheme for a future SUPERNEMO detector and its main characteristics are presented. Such a detector can also be used to investigate 0νββ decay in ¹⁰⁰Mo, ¹³⁰Te, and ¹¹⁶Cd with a sensitivity of up to ～(2–5)×10²⁵ yr or with a sensitivity to neutrino mass of ～0.04–0.26 eV.     

Hybrid density functional study of optically active Er3+ centers in GaN

Understanding the luminescence of GaN doped with erbium (Er) requires a detailed knowledge of the interaction between the rare‐earth dopant and the nitride host, including intrinsic defects and other impurities that may be present in the host material. We address this problem through a first‐principles hybrid density functional study of the structure, energetics, and transition levels of the Er impurity and its complexes with N and Ga vacancies, substitutional C and O impurities, and H interstitials in wurtzite GaN. We find that, in the interior of the material, Er_Ga is the dominant Er³⁺ center with a formation energy of 1.55 eV, Er_Ga–V_N possesses a deep donor level at 0.61 eV which can assist in the transfer of energy to the 4f ‐electron core. Multiple optically active Er³⁺ centers are possible in Er‐doped GaN. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

On the possibility of application of superconducting tunnel-junction detectors in Mössbauer spectroscopy

It is shown that a Nb-based superconducting tunnel-junction detector can be used to record γ radiation in the energy range from 1 to 15 keV. The possibility of application of such detectors in Mössbauer spectroscopy is discussed. Prospects of application of tantalum absorbers are considered, in particular, the possibility of developing a cryogenic resonant detector for ¹⁸¹Ta.     

Design and performance evaluation of SDD based X-ray spectrometer for future planetary exploration

Silicon Drift Detector (SDD) based X-ray spectrometer has been developed for obtaining the elemental composition of unknown samples by detecting fluorescent X-rays in the energy region 1–25 keV by a non-destructive process. The use of new technology X-ray detector provides good energy resolution for detecting the elements separated with ～150 eV apart. Here we present the design of a complete X-ray spectrometer intended for use in the future space-born experiment. The low energy threshold of <1 keV and the energy resolution of ～150 eV at 5.9 keV, as measured from the system is comparable to the standard spectrometers available off-the-shelf. We evaluated the system performance for different signal peaking time, as well as for different input count rates and show that the performance remains stable for incident count rate up to 20,000 counts per second. We have also carried out a ‘proof of concept’ experiment of measuring fluorescent X-ray spectrum from various standard XRF samples from the USGS catalog irradiated by the laboratory X-ray source ²⁴¹Am with 1 mCi activity. It is shown that intensities of various characteristic X-ray lines are well correlated with the respective elemental concentrations. A specific effort has been made while designing the developed X-ray spectrometer to use electronic components which are available in space grade so that the same electronic design can be used in the upcoming planetary missions with appropriate mechanical packaging.     

Chemical effect on the K shell fluorescence yield of Fe, Mn, Co, Cr and Cu compounds

Chemical effects on the K shell fluorescence yields of Fe, Mn, Co, Cr and Cu compounds were investigated. Samples were excited using 59.5 keV energy photons from a²⁴¹ Am radioisotope source. K X-rays emitted by samples were counted by a Si(Li) detector with a resolution 160 eV at 5.9 keV. Chemical effects on the K shell fluorescence yields (ωk) for Fe, Mn, Co, Cr and Cu compounds were observed. The values are compared with theoretical, semiempirical fit and experimental ones for the pure elements.