The scattering suppression of X-rays with energy of 20–200 keV in spectrometers with Barkla polarizers

The method is proposed for estimating the polarization parameters and the scattering suppression coefficients in energy dispersive X-ray spectrometers with Barkla polarizers (EDPXRS) for X-ray fluorescence (XRF) analysis. The scatter suppression coefficients are estimated accounting primary beam polarization, secondary beams yields, detectors response function, and partial factors. Estimations of scatter suppression coefficients due to polarization do not require the use of Stokes parameters and matrices. The method gives the possibility to make polarization-related corrections in calculations by XRF theory based on scattering cross sections of unpolarized beams. Calculations clarify early estimations of EDPXRS parameters with Barkla polarizers in the 20–200 keV range. The polarizing ability at δ = 7° deviations varies from 0.973 at 20 keV to 0.863 at 200 keV. The analyzing ability of registration system is about the same. In a simple XRF version on a synchrotron radiation with Barkla polarizer, the scattering can be decreased 60 times at 20 keV and 11 times at 80 keV with δ_s = 3°. In EDPXRS, the scatter suppression factor varies within 10–4.2 at deviations δ = 10° and within 20–4.8 at δ = 7°. The scatter suppression at low energies is determined by angular factor and background and at high energies is limited by energetic factors.     

Measurement of attenuation cross-sections of some fatty acids in the energy range 122–1330 keV

The mass attenuation coefficients (μ_m) have been measured for undecylic acid (C₁₁H₂₂O₂), lauric acid (C₁₂H₂₄O₂), tridecylic acid (C₁₃H₂₆O₂), myristic acid (C₁₄H₂₈O₂), pentadecylic acid (C₁₅H₃₀O₂) and palmitic acid (C₁₆H₃₂O₂) using ⁵⁷Co, ¹³³Ba, ¹³⁷Cs, ⁶⁰Co and ²²Na emitted γ radiation with energies 122, 356, 511, 662, 1170, 1275 and 1330 keV, respectively. The accurate values of the effective atomic number (Z_eff), atomic cross-section (σ_t,), electronic cross-section (σ_e) and the effective electron density (N_eff) have great significance in radiation protection and dosimetry. These quantities were obtained by utilizing experimentally measured values of mass attenuation coefficients (μ_m). A NaI(Tl) scintillation detector with 8.2% (at 662 keV) resolution was used for detecting of attenuated γ-photons. The variation in Z_eff and N_eff of fatty acids with energy is discussed. The experimental and theoretical results are in good agreement within 2% deviation.     

Calibrated binding energies of some core levels in the energy range between 1.5–4 keV

A commercial photoelectron spectrometer equipped with four interchangeable anodes (Mg, Al, Ag, Ti) has been utilized after careful calibration for accurately measuring binding energies of several deep core levels in the energy range between 1.5–4 keV.     

Induced fractional zero-point angular momentum for charged particles of the Bohm–Aharonov system by means of a “spectator” magnetic field

An induced fractional zero-point angular momentum of charged particles by the Bohm–Aharonov (BA) vector potential is realized via a modified combined trap. It explores a “spectator” mechanism in this type of quantum effects: In the limit of the kinetic energy approaching one of its eigenvalues the BA vector potential alone cannot induce a fractional zero-point angular momentum at quantum mechanical level in the BA magnetic field-free region; But when there is a “spectator” magnetic field the BA vector potential induces a fractional zero-point angular momentum. The “spectator” does not contribute to such a fractional angular momentum, but plays essential role in guaranteeing non-trivial dynamics at quantum mechanical level in the required limit. This “spectator” mechanism is significant in investigating the BA effects and related topics in both aspects of theory and experiment.     

Ionization of M subshells of Pb atoms by electron impact in an energy range of 5–30 keV

The relative intensities of the M ₅ N and M ₄ N satellites of Pb under electron bombardment of thick targets in the range of accelerating voltages U = 5?30 kV are experimentally investigated. Based on the previously proposed model of M X-ray emission, the relative intensities of these satellites are calculated using the total ionization cross sections of M subshells under electron impact found in different approximations. It is established that, among the models yielding analytical expressions for calculating total ionization cross sections, the model of classical binary collisions provides the best agreement with experimental data in the electron energy range under study. The parameters of the semiempirical Bethe formula for calculating the ionization cross sections of Pb M subshells under electron impact are determined.     

Electron excitation of hydrogen atom by ions impact in the energy range 20–1000 keV/amu

We have calculated the electron excitation cross sections of hydrogen atom by the impact of protons, alpha particles and He⁺ ions using the boundary corrected continuum intermediate state approximation in the intermediate and high energies. The calculated results are compared with other theoretical and experimental results. The angular influence of excitation to the H atom at the intermediate energy is also discussed. The distortion effects due to the projectile charges in reactions of electron excitation to bound states of the target H atom are shown in the intermediate and high collision energy.     

Measurement of the deflection of cosmic-ray electrons in the energy range 75–250 GeV by the Earth’s magnetic field with the PAMELA experiment

The deflection of electrons in the Earth’s magnetic field in the energy range 75–250 GeV (the so-called east-west effect) has been measured with the PAMELA satellite-borne experiment. The results are presented for various L-shells. The data obtained can be used to construct mathematical models that describe the structure of the Earth’s magnetic field and to refine the already existing models. These data can also be directly applied to estimate the positron fraction in cosmic-ray electron fluxes both in the PAMELA experiment and in other satellite-borne experiments.     

Optimum condition of efficiency functions for HPGe γ-ray detectors in the 121-1408 keV energy range

The optimum condition of three commonly used functions in the Genie 2000 γ spectra analysis software have been studied in the 121-1408 keV energy range. The three functions are applied for fitting the full-energy peak efficiency of the HPGe gamma-ray detector. A detailed procedure to obtain the optimum condition is described. The HPGe detector is calibrated at 11 cm by three radioactive sources of point form （^152Eu, ^137Cs, ^60Co） providing 11 energy peaks. After data processing, results shows that the three functions used in the Genie 2000 gamma spectra analysis software fit best at orders 3-5. Lastly the standard radioactive source 133Ba is chosen to validate the results. Differences between the standard activity of 133Ba and the result obtained from the fitting functions are below 1.5%. Therefore the optimum orders of the three functions used in the Genie 2000 3, spectra analysis software are 3-5 with the 11 energy peaks.     

Optimum condition of efficiency functions for HPGe γ-ray detectors in the 121-1408 keV energy range

The optimum condition of three commonly used functions in the Genie 2000 γ spectra analysis software have been studied in the 121-1408 keV energy range.The three functions are applied for fitting the full-energy peak effciency of the HPGe gammaray detector.A detailed procedure to obtain the optimum condition is described.The HPGe detector is calibrated at 11 cm by three radioactive sources of point form(152Eu,137Cs,60Co) providing 11 energy peaks.After data processing,results shows that the three functions used in the Genie 2000 gamma spectra analysis software fit best at orders 3-5.Lastly the standard radioactive source 133Ba is chosen to validate the results.Differences between the standard activity of 133Ba and the result obtained from the fitting functions are below 1.5%.Therefore the optimum orders of the three functions used in the Genie 2000 γ spectra analysis software are 3-5 with the 11 energy peaks.     

A new method for detection of alpha particles in 1 mm thick polycarbonate detectors using 50 Hz – HV ECE method

Recent studies in our laboratory have proved that electrochemical etching (ECE) of polycarbonate track detectors (PCTD) under 50 Hz – high voltage (HV) field conditions has potentials for time-integrated heavy charged particle detection and dosimetry applications. The rationale in the study is the ECE process of alpha particle tracks in 1 mm thick PCTDs by a 50 Hz – HV generator at optimized ECE conditions. Tracks of 3.2 MeV alpha particles from a collimated beam of an ²⁴¹Am source degraded in air and background tracks were registered. The effects of HV and ECE duration on alpha track registration efficiency and track diameters were studied for 3 sets of 50 Hz – 4, 5 and 6 kV field conditions in a PEW solution (potassium hydroxide, ethanol and water) at 26 °C. The optimized ECE conditions obtained at this stage of development for 1 mm thick PCTDs are 50 Hz – 4 kV in PEW solution at 26 °C for 10 h. Alpha track registration efficiency at 3.2 MeV is about 30% with 37 ± 6 μm mean track diameter. The mean background track density at the above stated optimized conditions is about 571 ± 16 tracks.cm⁻² with a mean diameter of 65 ± 5 μm. All tracks are observable by the unaided eyes. The mean background track diameter is near two times larger than that of alpha particle tracks at the optimum conditions applied; they are easily distinguished against each other. This high background track density while at this stage of development seems a drawback for low dose and low fluence particle applications, it has minimal effects on high fluence ion detection applications. The simple 50 Hz – HV generator used proved to be convenient for efficient alpha track amplifications. Studies are underway for improvement of the method in particular for reducing background track density.     

Multiplicity of charged particles in interactions of neutrons with protons,carbon and neon nuclei in the momentum range (1–200) GeV/c

The data on the multiplicity of charged secondaries produced in inelastic np, n¹²C and n²⁰Ne interactions in the primary momentum range (1–200) GeV/c are presented.     

Study of background processes with the formation of neutrons in nuclear reactions in the energy range of 26–32 kev

The nature of background processes accompanying astrophysical nuclear reactions induced by hydrogen, helium, and neon ions in deuterated targets with small cross sections has been studied in calculations and experiments. The experiments have been performed at a Hall pulsed plasma accelerator in the ion energy range of 26–32 keV. The yield of background neutrons and γ-quanta with energies below 4 MeV in the proton-induced D(p, γ)³He reaction is primarily due to the presence of a natural impurity of gaseous deuterium in gaseous hydrogen and the chain of D(D, ³He)n → (n, γ) or (n, n'γ) reactions. A small contribution comes from the chain of D(¹H, ¹H)D → D(D, ³He)n → (n, γ) or (n, n'γ) reactions. It has been shown that background neutrons and γ-quanta from the D(4He, γ)6Li reaction are entirely due to the chain of D(⁴He, ⁴He)D → D(D, ³He)n → (n, γ) or (n, n'γ) reactions. It has been shown that the yield of neutrons and γ-ray photons detected at the interaction of neon ions with deuterated targets is also entirely due to the chain of elastic- scattering reactions of neon ions on deuterons in the target and to subsequent inelastic processes of interaction of deuterons accelerated at elastic scattering with other deuterons of the target. The main contribution to the yields of background neutrons and γ-quanta comes from doubly charged neon ions. The main conclusion is that the explanation of the yield of neutrons and γ-quanta at the interaction of hydrogen, helium, and neon ions with deuterated targets does not require “exotic” theoretical models.     

Setup for studying quasi-free neutron-neutron scattering in the energy range of 20–60 MeV

A setup installed on the RADEX neutron beam channel (Institute for Nuclear Research, Russian Academy of Sciences) and designed to study quasi-free nn scattering in the n + d → p + n + n reaction is described. The setup is a two-arm time-of-flight spectrometer composed of scintillation neutron hodoscope (in the left arm), a scintillation neutron detector (in the right arm), and an active scintillation deuterated target for detecting protons. Secondary neutrons are detected at angles corresponding to the kinematic conditions of quasi-free nn scattering. Events are selected at low energies of the outgoing proton spectator. It is shown that data on neutron-neutron quasi-free scattering can be obtained in a wide range of primary-neutron energies.     

Study of the stability of charged particle dynamics in a Penning–Malmberg–Surko trap with a rotating field

The solutions of equations characterizing the dynamics of charged particles in electromagnetic Penning–Malmberg traps with a rotating transverse electric field are presented and analyzed. The equations of motion are transformed in a way that makes it possible to distinguish between the motions of magnetron and cyclotron particles, reduce the system of equations to a stationary one, and conclude that asymptotically Lyapunov stable solutions of these equations are lacking in a certain parameter interval. This allows one to optimize the confinement of charged particles in such traps.     

Modelling the directional and energy dependence of 5–10 keV Ar+ ion-induced secondary electron yields from Cu crystals

The primary ion directional effects observed in secondary electron yields induced by ion bombardment [5 keV Ar⁺ → Cu(100)] are simulated using a semi-empirical molecular dynamics model. The directional effects are presumed to arise from inelastic energy transfers that take place in close binary atomic encounters. The latter are estimated using the Oen-Robinson model, in combination with a critical apsidal distance (R_c). The connection between the measured kinetic electron emission (KEE) yields (γ_KEE) and the predicted inelastic energy loss in a binary atomic collision (ΔE_i) is established through a semi-empirical fitting procedure involving R_c and other parameters in the following model: γ_e = γ₀ + γ_KEE = γ₀ + 〈ΔE_i(z)exp(? z/λ)〉, where z is the collision depth. The directional effects are best reproduced by fitting the model to Ar–Cu inelastic collisions for two azimuthal incident directions: R_c is estimated to be 0.47 ± 0.03 Å; the parameter, λ (an effective electron attenuation length), is estimated to be 18 ± 2 Å. The same model also describes the γ_KEE energy dependence for 5–10 keV Ar⁺ normally incident on low-index Cu crystal targets [Phys. Rev. 129 (1963) 2409]. The spatial and temporal distributions of the hard collisions that initiate KEE are discussed on the basis of the model.     

A thermoluminescence study of mineral silicates extracted from herbs in the dose range 0.5–5 Gy

The presence of silicates in many personal objects suggests their potential use at low dose as fortuitous dosimeter in an accidental radiological exposure, when conventional dosimetry is not available. The goal of the present work is the dosimetric characterization of mineral silicates extracted from the plant Hibiscus Sabdariffa L, known as Jamaica flower, in the dose range 0.5–5 Gy. By studying the radiation-induced signal in time, the temperature integration region between 210 °C and 250 °C was found to be the most stable and also reduced the effects of thermal fading in the dose reconstruction process; the dose response curve was linear between 0.5 Gy and 5 Gy. By checking the change in sensitivity after repeated exposures to ionizing radiations and to high temperature heating, no variation in the glow curve shape or peak intensities were detected. To eliminate a pre-existing background signal, all the characterization measurements were performed with aliquots “annealed” by a preliminary readout of the TL.     

Photoelectrical characteristics of the InAsSbP based uncooled photodiodes for the spectral range 1.6–3.5 μm

The electrical characteristics of photodiode structures on the base of InAS/InAsSbP heterojunctions, that have a high room temperature differential resistance and operate in the mid-infrared region over the wavelength range 1.6–3.5 μm are reported. At the difference frequency, C–V measurements are showed that at small biases and temperatures which are higher than 160 K, the measured capacity is increase with decreasing frequency. It is possible to explain by presence the deep recombination centers in space charge region of the investigated structures. Have been studied the avalanche multiplication of the photocurrent and the temperature dependence of the monochromatic power–voltage sensitivity in the temperature range 77–300 K.     

Low-energy relation for the trace of the energy–momentum tensor in QCD and the gluon condensate in a magnetic field

The nonperturbative QCD vacuum in a magnetic field has been studied. A low-energy relation for the trace of the energy–momentum tensor in the magnetic field has been obtained. It has been shown that the derivatives of the quark and gluon contributions to the trace of the energy–momentum tensor with respect to the magnetic field coincide with each other. The magnetic field dependence of the gluon condensate has been calculated in the limits of strong and weak fields.     

The interaction of O2 with the surface of polycrystalline gadolinium at the temperature range 300–670 K

Auger-Electron-Spectroscopy (AES) and Direct-Recoils-Spectrometry (DRS) were applied to study the interaction of O₂ with a polycrystalline gadolinium surface, in the temperature range 300–670 K and oxygen pressure up to 2 × 10^? 6 Torr. It has been found that initial uptake of oxygen, at coverage measurable by the techniques used here, results in rapid oxide island formation. The subsurface is believed to be a mixture of oxide particles and oxygen dissolved in the Gd metal, the latter being the mobile species, even at relatively low temperatures.Enhanced inward diffusion of oxygen starts as early as 420 K and dictates the surface oxygen concentration and effective thickness of the forming oxide. The oxygen accumulation rate at the near-surface region, as measured by the O(KLL) AES signal intensity, goes through a maximum as a function of temperature at 420 K. This is a result of the combination of still efficient oxygen chemisorption that increases surface occupation and slow inward diffusion. The thickest oxide, ~ 1.7 nm, is formed at 300 K and its effective thickness was found to decrease with increasing temperature (due to oxygen dissolution into the metal bulk).Diffusion coefficients of the oxygen dissolution into the bulk were evaluated for various temperatures utilizing models for infinitely thin oxide layer and thick oxide layer, respectively. The best fit under our experimental procedure was obtained by the thick layer model, and the coefficients that were calculated are D₀ = 2.2 × 10^? 16m²s^? 1 and E_a = 46kJ/mol.