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.     

Fundamental absorption of calcium,magnesium, and lithium fluorides in the range of 8–12 μm

The fundamental absorption of calcium, magnesium, and lithium fluorides in the range of 8–12 μm has been studied experimentally by the spectrophotometric method. The known and experimentally obtained values of the absorption coefficients of these materials have been analyzed. It has been shown that the values experimentally measured in the range of 8–12 μm obey the Uhrbach rule and the multiphoton absorption determines the long-wavelength transmission cutoff of pure optical materials. The results presented make it possible to suggest that plates made of LiF and CaF₂ crystals and of optical ceramics based on MgF₂ can be used to fabricate calibrated radiation attenuators in the spectral range of 8–12 μm.     

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.     

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 total spectrum of electrons and positrons in the energy range of 300–1500 GeV in the PAMELA experiment with the aid of a sampling calorimeter and a neutron detector

A method based on the use of a sampling calorimeter was developed for measuring the total energy spectrum of electrons and positrons from high-energy cosmic rays in the PAMELA satellite-borne experiment. This made it possible to extend the range of energies accessible to measurements by the magnetic system of the PAMELA spectrometer. Themethod involves a procedure for selecting electrons on the basis of features of a secondary-particle shower in the calorimeter. The results obtained by measuring the total spectrum of cosmic-ray electrons and positrons in the energy range of 300–1500 GeV by the method in question are presented on the basis of data accumulated over a period spanning 2006 and 2013.

     

Photofission of 238Pu, 240Pu, and 242Pu in the energy range 5–10 MeV

The cross sections for the photofission of plutonium isotopes ²³⁸Pu, ²⁴⁰Pu, and ²⁴²Pu in the energy range 5–10 MeV have been measured by using a beam of bremsstrahlung photons from the microtron installed at the Institute of Physics and Power Engineering (Obninsk). The energy regions below the fission barrier and above 6 MeV have been scanned with pitches of 0.05 and 0.1 MeV, respectively. In deriving the absolute cross section for ²³⁸Pu photofission, ²³⁸U photofission has been employed as a reference reaction. In measurements involving ²⁴⁰Pu and ²⁴²Pu nuclei, the neptunium isotope ²³⁷Np, which is characterized by a more regular dependence of the photofission cross section on excitation energy than ²³⁸U, has been chosen for the first time as a reference nucleus. The measured cross sections as functions of energy show resonance structures in the vicinity of the fission threshold that are consistent with those previously observed in the energy dependences of fissilities for corresponding direct reactions. The partial-wave cross sections for the J ^π K = 1^?0, 1^?1, and 2⁺0 photofission channels have been determined as functions of energy. At energies below some 5.5 MeV, the total cross section for photofission of each plutonium isotope being studied receives a significant contribution from quadrupole interaction. Within the one-dimensional model of a two-humped fission barrier, the parameters of the barriers for ²³⁸Pu, ²⁴⁰Pu, and ²⁴²Pu have been extracted from data and have then been compared with estimates based on previous measurements.     

Measurement of the total photoabsorption cross section on a proton in the energy range 600–1500 MeV at the GRAAL

The total photoabsorption cross section on a free proton was measured at the GRAAL facility in the energy range E _γ = 600−1500 MeV. The large-aperture LAGRANγE detector and a liquid hydrogen target were used in the experiment performed with a back-scattered Compton gamma beam. To improve the accuracy, two alternative methods were employed. First, a subtraction method of using empty-target measurements allowed the cross section σ _tot to be evaluated directly because of a low level of the electromagnetic background. Second, an algorithm for evaluating σ _tot on the basis of summing the dominating partial cross sections was developed. Experimental results obtained for σ _tot by the two methods are compared with existing data. The article was translated by the authors. Published in Russian in Yadernaya Fizika, 2008, Vol. 71, No. 1, pp. 76–83.     

About the character of the “Knee” at E⋍3×1015 eV in the energy spectrum and the mass composition of primary cosmic rays in the energy range 1015–1017 eV

The method of rescaling from the muon-multiplicity spectrum to the extensive-air-shower spectrum as a function of the total muon number n _μ is presented. The method allows a direct comparison of data obtained in different experiments with muon groups. A direct comparison of data at n _μ>1800 and n _μ=76–660 has been performed. The data in the region n _μ=75–3500 agree better with the assumption that the slope change in the energy spectrum of primary cosmic rays occurs approximately at the same energy per nucleus, E _c=3×10¹⁵ eV, and the mass composition in the energy range 10¹⁵–10¹⁷ eV is close to that observed at 10¹⁴ eV.     

PAMELA spectrum of electrons and positrons of cosmic rays in the energy range of 0.05–1.2 TeV

A proprietary method is used to process measurement data from a high-energy particle (protons, electrons, and positrons with Е ≥ 50 GeV) spectrometer in a near-Earth orbit. The data from three detector systems are used: a tracker in a constant magnetic field (TRK), a calorimeter (CAL), and a neutron detector (ND). A relatively simple and efficient way of isolating electrons and positrons from the total charged particle flux entering the PAMELA spectrometer is proposed. A technique for determining the energy of isolated primary particles and retrieving their energy spectra is described. The composite electron and positron spectrum (below, the total electron and positron flux is referred to simply as the electron flux) for energies up to 1.5 TeV is presented.     

Calculation of H+-ranges and H+-range stragglings in the energy region 1–1000 keV

The use of various approximations in calculating proton projected ranges has been studied by the analytical and the Monte Carlo methods. A correction is presented for the projected ranges given in the compilation (Andersen and Ziegler: Hydrogen Stopping Powers and Ranges in All Elements). The greatest correction factors at 1, 10, 100 and 1000 keV are 3.5, 2.1, 1.4 and 1.2, respectively. The corrections result from the inclusion of the tabulated electronic stopping power values in the calculation of the projected ránge to the total range ratio and from the estimation of the effect of the reflection. The Monte Carlo calculations show the electronic straggling to be a remarkable factor in the width of the proton range distributions at reduced energies larger than of the order of 100.     

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 broad-band single pulse technique for ultrasound absorption studies of aqueous solutions in the frequency range 200 kHz–1 MHz

A single pulse time-domain technique is described for determining, via Fourier transform methods, the compressional wave ultrasound absorption coefficient in liquids contained in spherical reverberators over a frequency range from ≈ 200 kHz to 1 MHz. Only modest data storage and computational facilities are required. Such a technique offers an advantage over variable continuous frequency methods in that data for a given frequency range can be acquired ‘instantaneously’ and thus it is possible to monitor ultrasound absorption in time-varying systems. The method is illustrated by provision of absorption data in the frequency range 200 kHz–1 MHz for out-gassed water, aqueous solutions of the electrolyte cobaltous sulphate, with and without gas bubbles, and for the protein bovine serum albumin under conditions of acid pH obtained using spherical reverberators of 100 and 250 ml capacity.     

K-shell ionization of Si,Ti, Cu and Ag for incident protons,4He and14N ions in the energy range of 0.17–2.0 MeV/amu

K-shell X-ray production cross sections of Si, Ti, Cu and Ag were measured for incident protons,⁴He and¹⁴N ions in the energy range of 0.17≦E ₁/A ₁≦2 MeV/amu. The experimental ionization cross sections are compared with calculations according to the simple Plane Wave Born Approximation (PWBA) theory as well as the corrected PWBA model (PWBABC). Strong deviations of the experimental cross sections from theZ ₂ ¹ scaling are observed and discussed quantitatively.     

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.     

Calculation of optical conductivity and electron energy loss spectra of YBa2Cu3O7 in the 10–160 eV range

We calculate the high frequency macroscopic dielectric function () of YBaCuO by treating the solid as a dense gas of polarizable cells. The cell polarizability is constructed from independent atomic contributions within a local-density based random phase approximation (LDRPA) and improvements thereof. In this way, interband transitions are treated very schematically but transitions from the core-like Ba 5p ⁶ shell are treated quite well. This is important, because the intense Ba 5p–5d like giant dipole resonance provides about half of the optical conductivity around 20 eV and contributes strongly to the all-valence electron plasma frequency.The calculated conductivity is in quite good agreement with experiment in magnitude and shape above 15–20 eV. The calculated EELS is similar in magnitude and shape to the experimental one but shifted to higher energies: in particular, the valence electron plasmon occurs around 33(26) eV in the calculated (experimental) EELS. This is reasonable, since the real solid involves lowlying charge transfer excitations and interband transitions which are absent in the atomic model of the YBaCuO unit cell. In the atomic model, the corresponding intensity is taken into account by higher frequency atomic transitions.     

Rigidity dependence of cosmic-ray escape length obtained from a comparison of proton and iron spectra in the energy range 3–3000 GeV

A simple leaky-box model of cosmic-ray propagation in the Galaxy is quite suitable for analysis of cosmic-ray nuclei energy spectra and composition at energies under 1 GeV [1, 2]. Within this model the full information about the cosmic-ray propagation in the Galaxy is compressed into a single parameter, viz., escape length, X _e , which characterizes the mean grams of matter that are passed by cosmic-rays from sources to the Earth. In this paper we analyze the worldwide data on proton and iron cosmic-ray spectra that have been collected in experiments and obtain the rigidity dependence of the escape length from the measured rigidity dependence of the proton/iron ratio. This agrees well with the one estimated by a standard manner from the secondary/primary nuclei ratio. However, at R > 300 GV the behavior of X _e (R) distinctly changes, which can point to a change of the proton/iron ratio in cosmic-ray sources.     

Time features of delayed neutrons and partial emissive-fission cross sections for the neutron-induced fission of 232Th nuclei in the energy range 3.2–17.9 MeV

The energy dependence of the relative abundances of delayed neutrons and the energy dependence of the half-lives of their precursors in the neutron-induced fission of ²³²Th nuclei in the energy range 3.2–17.9 MeV were measured for the first time. A systematics of the time features of delayed neutrons is developed. This systematics makes it possible to estimate the half-life of delayed-neutron precursors as a function of the nucleonic composition of fissile nuclei by using a single parameter set for all nuclides. The energy dependence of the partial cross sections for emissive fission in the reaction ²³²Th(n, f) was analyzed on the basis of data obtained for the relative abundances of delayed neutrons and the aforementioned half-lives and on the basis of the created systematics of the time features of delayed neutrons. It was shown experimentally for the first time that the decrease in the cross section after the reaction threshold in the fission of ²³²Th nuclei (it has a pronounced first-chance plateau) is not an exclusion among the already studied uranium, plutonium, and curium isotopes and complies with theoretical predictions obtained for the respective nuclei with allowance for shell, superfluid, and collective effects in the nuclear-level density and with allowance for preequilibrium neutron emission