Construction and properties of a gamma-ray detector based on D(γ, n)H neutron counting

The photodisintegration of deuterium with subsequent neutron counting has been used in a system to detect high-energy γ-rays. The system consists of a cylindrical tank filled with 242 l of heavy water and surrounded by 30 ³He-filled proportional counters. Details of the construction, specifications and characteristics of the detector are described. The detector has been used to measure the hexadecapole strength of the 2506 (J^π = 4⁺) → 0 (J^π = 0⁺) keV γ-ray transition in ⁶⁰Ni (E4 = 78 nuclear physics applications, it is proposed that the detector be used for studies relevant to nuclear astrophysics, in particular for the study of capture reactions induced on highly radioactive targets (up to about 1 Ci). The detector is also useful for neutron work (18% neutron efficiency).     

Measurements of (n,γ) neutron capture cross-sections with liquid scintillator detectors

A method for measuring (n,γ) neutron capture cross-sections using liquid scintillator detectors has been investigated. If the response function of the detector is known, and the efficiency as a function of energy is low and approximately constant, then gamma cascades can be counted via a method that is independent of the cascade path provided the detector response is manipulated to allow detection efficiency to be proportional to emitted gamma-ray energy.In this paper, we demonstrate the measurement of efficiency and response functions for a C₆D₆ liquid scintillator using gamma-ray sources and (p,γ) reactions on light nuclei. Methods to reproduce the detector response and efficiency data successfully using simulations are presented and discussed. An entire response matrix for the detector has been constructed using a new interpolation technique, allowing weighting functions that force the detector efficiency to be proportional to gamma-ray energy to be calculated. An analysis of the sources of error involved in making (n,γ) cross-section measurements with this method has been undertaken using Monte-Carlo simulation techniques.     

An optimized C6D6 detector for studies of resonance-dominated (n,γ) cross-sections

Hydrogen-free scintillators are indispensable for determining the small, resonance-dominated neutron capture cross-sections of light and neutron magic nuclei, data which are needed for advanced reactor concepts, for transmutation of radioactive wastes as well as for astrophysical scenarios of neutron capture nucleosynthesis. A critical comparison of the existing detector concepts by means of detailed GEANT simulations revealed large differences in neutron sensitivity. Based on these simulations, an optimized detector was developed and successfully tested. Compared to a commercial detector, the neutron sensitivity of this solution is more than an order of magnitude lower, thus allowing even extremely small capture/scattering ratios to be measured reliably.     

A neutron polarimeter for the (p,n) reaction at Ep=50–80 MeV

A conventional type of neutron polarimeter consisting of three 12.5 × 12.5 cm cylindrical liquid scintillators and two 12.5 × 12.5 cm cylindrical plastic scintillators has been used to measure the transverse polarization transfer coefficient K_y^y in the (p, n) reaction in the energy range 50 < E_{p < 80 MeV}. The effective analyzing powers of this polarimeter have been obtained empirically by observing neutrons from the ⁶Li(p, n)⁶Be reaction at θ = 0° and E_p = 50,65 and 80 MeV whose polarizations are deduced from the K_y^y values of the ⁶Li(p,p′)⁶Be¹ (0⁺ reaction by utilizing the analogue relation. Observed effective analyzing powers are significantly reduced particularly at high energy, most likely due to the ¹²C(n,np)¹¹B reaction process. The double scattering efficiencies are 6 × 10⁻⁴ and 3 × 10⁻⁴ with effective analyzing powers of 0.14 and 0.11 at E_{n = 45} and 75 MeV, respectively.     

测量(n,γ)混合场中子吸收剂量用的电离室的光子刻度

本文讨论用已定度过的次级标准照射量仪对用于(n,γ)混合场快中子吸收剂量测量的电离室进行光子定度的方法,并给出组织等效电离室(IC-17A)、碳电离室(IC-17G)和镁电离室(IC-17M)在~(60)Co和~(137)Cs两种光子束中的定度因子R/Q和灵敏度KQ’/D_(TE,λ)。     

X-ray Spectrometric Determination of Thorium in Soil Samples Using the (γ,n) Reaction

A highly sensitive (detection limit 3 ×10^-7 g g^-1) procedure was developed for determination of Th in samples of soils and environmental objects. The method is based on the reaction ²³²Th(,n)²³¹Th (T1/2 = 25.5 h). The samples were -irradiated for 4 h at an average electron current of 15 A and electron energy E _e = 24.5 MeV. The Th content was estimated by recording X-ray emission of ²³¹Th with E = 25.65 keV. The X-ray spectra of the irradiated samples were recorded on an X-ray spectrometer with an Si(Li) semiconductor detector [30 mm² area; resolution at the FeK line (6.4 keV) 200 eV].     

Effect of (n, γ) and (n, α) reactions of framework atoms on the (n, γ) recoils in Ba and Cs cations in high-silica zeolites

The effects of (n, γ) and (n, α) reactions of framework atoms on the fate of (n, γ) recoil species ¹³¹Ba²⁺ and ¹³⁴Cs⁺ from Ba²⁺ and Cs⁺ loaded in high-silica aluminosilicate and borosilicate zeolites (boron-zeotypes) have been studied. Studies were made of the recoil from “open to locked-in” and “locked-in to open” sites. In open to locked-in recoil, target ions were eluted with efficiencies of 90% where only (n, γ) processes were in operation, but in the presence of (n, γ) and (n, α) reactions, the efficiency fell to 80%. For locked-in to open site recoil, the corresponding efficiencies were in the ranges 50–60% and 40–50%. The effect of calcination temperature on the exchange of cations present was also ascertained. The high-silica zeolites used were synthesized according to published methods and were characterized by XRD, i.r., SEM, and t.g.-d.t.g./d.s.c. techniques, and all were found to be crystalline. In boron-zeotype materials, the magnitude of (n, α) damage was increased by the use of ¹⁰B isotope.     

Exchange Interactions and Ferromagnetism of Pr_(n+1)Co_(3n+5)B_(2n)-type Compounds

In present investigation exchange interactions of Pr_(n+1)Co_(3n+5)B_(2n)-type compounds have been evalu-ated in the light of molecular-field theory. The exchange interactions and ferromagnetism in thesecompounds are discussed in terms of lattice parameters and interatomic distance between Co atom.     

Quantum Tunneling of D(H) Atoms and 2 – in Solid Hydrogen

This paper contains three results. First, the rate constants for the tunneling reaction HD + D H + D ₂ in solid HD increase steeply with increasing temperature above 5 K, while they are almost independent of temperature below 5 K. A mechanism of a vacancy–assisted tunneling reaction is proposed to account for this temperature dependence. Second, a hydrogen atom and a hydrogen molecule form a van der Waals complex in the Ar matrix at 20 K, where the tunneling reaction HD + D H + D ₂ takes place in this complex. The analysis of well–resolved ESR spectra of the complex determined the distance between a hydrogen atom and a hydrogen molecule as 2.3 – 2.5 Å. Third, the decay rate constants of anions in solid parahydrogen decrease with decreasing temperature below 6.6 K, attain the minimum value at 5 K, and then increase with decreasing temperature in the range of 5 2.7 K. The abnormal temperature dependence of the decay rate constants below 5 K is ascribed to a phonon–scattering process of quantum diffusion.     

Synthesis and properties of poly (organophosphazenes) ionomers [NP(HNC6H5)2−(x+y)(HNC6H4SO3H) x (HNC6H4SO3Li) y ] n

Poly(anilino sulphamicphosphazenes) such as [NP(HNC₆H₅)_2–x (HNC₆H₄SO₃H) _x ] _n for polymer (I) x=0.3 and for polymer (II) x=0.8 were prepared by the reaction of poly(anilinophosphazene) [NP(HNC₆H₅)₂] _n and sulphonic chloride HSO₃Cl in tetrachloroethane solvent several timeS. Also, H protons in the polymer (I) and (II) were prepared from lithum hydroxide in aqueous solution. It was found, by chemical analysis, that the product prepared with (I) and (II) had compositions such as [NP(HNC₆H₅)_1.7 (HNC₆H₄SO₃H)_0.1(HNC₆H₄SO₃Li)_0.2] _n (III) and [NP(HNC₆H₅)_1.2(HN-C₆H₄SO₃Li)_0.8] _n (IV). Also, the resistivity of products (III) and (IV) were determined and found to be 3.3×10⁷ and 1.5×10⁷ cm^–1, respectively.     

Calculation of Ionization Energy and Electron Affinity of Molecule of Hydro‐ and Fluorinefullerenes C60H(F) n (0 ≤ n ≤ 60)

Abstract

Vertical and adiabatic electron affinities (EA) and ionization energies (IE) of C₆₀H(F) _n (0 ≤ n ≤ 60) have been determined using semiempirical calculations with AM1 Hamiltonian. Comparison of the thermo‐chemical characteristics of the fluorinated and hydrogenated fullerene positive and negative ions has been carried out on the basis of these calculations.     

纳米γ-(Fe,Ni)合金粉开发及应用研究

以五羰基铁和四羰基镍为前驱体，通过高温气相热分解可以获得纳米级γ－（Ｆｅ，Ｎｉ）合金粉，这种纳米合金粉主要为面心立方的γ－（Ｆｅ，Ｎｉ）相，颗粒大小为１０～５０ｎｍ，呈非球形，具有优异的光、电、磁性能，可用于开发具有某些奇特功能的新材料。