A transport model for alcator scaling in tokamaks

A theoretical model is proposed to explain the tokamak energy confinement time. With no adjustable numerical coefficients, the model predicts experimentally observed values to within a level of uncertainty consistent with the intrinsic spread of the experimental data and the necessity of calculating the confinement time without precise knowledge of the temperature profile.     

A study of the radiation from Am241

The radiation from the alpha decay of Am²⁴¹ has been investigated by studying the fine structure of the alpha spectrum and by performing alpha-gamma and gamma-gamma coincidence measurements. For the daughter nucleus Np²³⁷ a level scheme is proposed which comprises 21 excited states and 39 gamma transitions. Evidence was found for the existence of previously unknown gamma rays at (80), 82, 88, (90), 100, 150 (two transitions), 170, (~210), 295, (300), 360, 420, 460 and 690 keV, as well as for the probable occurrence of a new fine structure alpha group at 4754 keV corresponding to a level at 804 keV. For the alpha groups and for most of the gamma rays absolute intensities are given. For some transitions theK-conversion coefficients and multipolarities were determined. The results are discussed within the framework of the unified model. The level density agrees well with the predictions of the superfluid model and is approximately twice the density yielded fromNilsson's theory.     

A study of radiation from circular groove guide horn

A novel horn antenna for millimeter waves based on circular groove guide is presented and investigated in this paper. Its radiation patterns are calculated by employing the aperture field method. The patterns obtained by experiment show agreement with calculated results.     

Study of molybdenum K-series line radiation emission from a low energy plasma focus

K-series line radiation emission of Mo and Cu from a low energy Mather-type plasma focus is investigated. Quantrad Si pin diodes are employed as time resolved X-ray detectors, where as a pin hole camera is used for time integrated analysis. The measurable X-ray flux for hydrogen is observed in the pressure range of 0.5–3.5 mbar. Mo and Cu K-line radiation emission in this geometry has the highest values of about 0.05 J/sr and 0.17 J/sr, respectively at a filling pressure of 2.0 mbar. The corresponding efficiencies are 0.03% and 0.09%, respectively. Total X-ray emission and efficiency in 4π-geometry are also obtained with values 4.12 J and 0.18% at 2.0 mbar. The Mo K-line radiation emission may result due to interaction of energetic electron beam emitted from the focus region with the molybdenum insert.     

A spectropolarimetric study of theH α radiation from ellerman bombs

Polarization data are given for three whiskers recorded with the large solar vacuum telescope at the Baikal Observatory, Institute of Solar-Terrestrial Physics, Russian Academy of Sciences. The observed degree of polarization varies from 2 to 13%. The direction of the polarization plane for the mediumintensity whisker was tangential, while that for the weakest one was radial. The brightest whisker had the polarization plane direction close to radial at the center of the line but tangential at the flanks. It is assumed that the polarization is due to impact excitation of a hydrogen-atom ensemble in the solar chromosphere by an electron beam, and estimates are made of the beam energy. St. Petersburg Fine Mechanics and Optics Institute, St. Petersburg. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 41, No. 12, pp. 85–89, December 1998.     

Crystalline silicon films sputtered on molybdenum: A study of the silicon–molybdenum interface

Polycrystalline silicon films were grown on molybdenum (Mo)-coated substrates at high deposition rate using the pulsed magnetron sputtering technique. Our study investigates the silicon–molybdenum interface of these films to elucidate stimulating mechanisms for an ordered crystalline silicon thin film growth. Both Auger electron spectroscopy and Rutherford backscattering reveal that at a substrate temperature as low as T_S=450 °C during the deposition process intermixing of Si and Mo at the Si–Mo interface takes place leading to a compositional ratio Mo:Si of about 1:2. By Raman spectroscopy hexagonal β-MoSi₂ could be identified as the dominant phase in this intermixed region. The dependence of the resulting thickness of the reacted interface layer on the deposition conditions is not fully understood yet.     

Comparison of radiation shielding ratios of nano-sized bismuth trioxide and molybdenum

In this study, radiation shielding fibers using non-hazardous nano-sized bismuth trioxide and molybdenum instead of lead were developed and evaluated. Among the elements with high densities and atomic numbers, non-hazardous elements such as bismuth trioxide and molybdenum were chosen as a shielding element. Then, bismuth trioxide (Bi₂O₃) with average particle size 1–500?µm was ball milled for 10?min to produce a powdered form of nanoparticles with average particle size of 10–100?nm. Bismuth trioxide nanoparticles were dispersed to make a colloidal suspension, followed by spreading and hardening onto one or two sides of fabric, to create the radiation shielding fabric. The thicknesses of the shielding sheets using nano-sized bismuth and molybdenum were 0.4 and 0.7?mm. According to the lead equivalent test of X-ray shielding products suggested by KS, the equivalent dose was measured, followed by calculation of the shielding rate. The shielding rate of bismuth with 0.4?mm thickness and at 50?kVp was 90.5%, which is comparable to lead of 0.082?mm thickness. The shielding rate of molybdenum was 51.89%%, which is comparable to lead of 0.034?mm. At a thickness of 0.7?mm, the shielding rate of bismuth was 98.73%, equivalent to 0.101?mm Pb, whereas the shielding rate of molybdenum was 74.68%, equivalent to 0.045?mm?Pb. In conclusion, the radiation shielding fibers using nano-sized bismuth developed in this study are capable of reducing radiation exposure by X-ray and its low-dose scatter ray.     

A high-resolution spectroscopic study of the gamma radiation from the decay of96Nb

The decay of 24h⁹⁶Nb has been studied with a Ge(Li) spectrometer and with a Ge(Li)-NaI(Tl) coincidence spectrometer. A total of 27 gamma-ray transitions were observed, their energies and intensities measured. All but one of these have been incorporated into the level scheme of⁹⁶Mo. The level at 1,625.9 keV reported recently in (n _th, γ) work on⁹⁵Nb has also been observed through the decay of⁹⁶Nb. No experimental evidence has been found for previously proposed levels at 2,657 and 2,791 keV in⁹⁶Mo.     

Electrochemical study of molybdenum oxide film electrodes

Several different electrochemical techniques were used to study the redox reaction in an aqueous sulphuric acid solution at molybdenum oxide film electrode. It was determined by chronopotentiometry, along with cyclic voltammetry and impedance spectroscopy, that in the redox process, the H⁺ ion combines with an electron from the film to form an intermediate before entering the film, and that the transport of the H atom within the layer of oxide occurs purely by diffusion. The diffusion coefficient of the H atom was deduced from these data (D=10⁻¹² cm² s⁻¹).     

An experimental study of optical radiation from sputtered species

Solids of Li, Be, B, C, Mg, Al, S, Ti, Zn, Cu, Sn, Ag, Cd, Tl, Au, and Bi have been bombarded with 40 and 50 keV Xe⁺ ions. Spectrograms of optical radiation from sputtered species have been recorded in the wavelength interval 200–600 nm. Relative level populations have been measured in Li I, Be I, B I, and Al I. A discussion of the results is given.     

Physical properties of molybdenum monoboride: Ab-initio study

The Ab initio investigations on structural, electronic, optical and thermal properties of MoB have been reported using full potential linearised-augmented plane wave method within the framework of density functional theory. The exchange and correlation potentials were calculated using the Perdew-Burke-Ernzerhof-Sol generalised gradient approximation. The calculated equilibrium lattice constants and cell volume are in excellent agreement with the experimental results as compared to the available theoretical data. Electronic band structure shows that MoB is metallic in nature. From the partial densities of states of MoB it has been found that major contribution on the Fermi level is due to Mo-4d states. Among the reported optical parameters the large value of reflectivity at low energy shows that MoB can be used as a coating material in IR region. Maximum absorption in extreme UV region shows that it can be used in production of electricity through solar power in space vehicles. Various thermal properties have been calculated in a wide temperature range at high pressures. Change in thermal expansion coefficient with respect to temperature shows that anharmonic effect in MoB is very weak at high temperature. The optical and thermal properties of MoB are presented for the first time in this work.     

X-ray spectroscopic study of zirconium and molybdenum diselenides

The K absorption spectra of zirconium, molybdenum and selenium in ZrSe₂ and MoSe₂ have been recorded photographically using a Cauchois type bent crystal (mica) spectrograph. The absorption edge shifts are used along with the data for NbSe₂ (Bhide and Bahl 1971J. Phys. Chem. Solids 32 1001) to propose bond schemes for these compounds.     

等离子体云团宽带电磁辐射源的实验研究

通过工质爆燃,产生了具有很宽频谱的电磁辐射。用4个宽带天线从不同方向对球形工质产生的电磁辐射进行了接收测量,并对信号作了频谱分析。实验结果表明:150 g工质爆炸产生的电磁脉冲持续时间为50 ns,上升沿很陡,频谱连续,频率范围为1~4 GHz,峰值频率为2 GHz,功率为2 W。对爆燃型工质产生电磁辐射的机理进行了初步理论探讨,认为等离子体辐射可能是产生电磁辐射的源。     

等离子体云团宽带电磁辐射源的实验研究

通过工质爆燃,产生了具有很宽频谱的电磁辐射。用4个宽带天线从不同方向对球形工质产生的电磁辐射进行了接收测量,并对信号作了频谱分析。实验结果表明：150 g工质爆炸产生的电磁脉冲持续时间为50 ns,上升沿很陡,频谱连续,频率范围为1～4 GHz,峰值频率为2 GHz,功率为2 W。对爆燃型工质产生电磁辐射的机理进行了初步理论探讨,认为等离子体辐射可能是产生电磁辐射的源。     

A study of radiation damage by elastic scattering experiments

Abstract

Chaneling measurements are used to study the structure and configuration of defects produced in CdS under irradiation by 50–150 KeV Na⁺ ions at room temperature with a current density of 1 μA/cm² and irradiation dose 3.10¹⁵ ion/cm².

The results of studies of 1.8 MeV He⁺ ion dechaneling along the <1120> and <0001> axes are probably indicative of the defect structure extended along the <0001> axis.

For the dependence of the dechaneling cross-section on the ⁴He energy in the energy range 1.2 to 2.4 MeV we found E^?1, which characterizes the produced defects as randomly distributed complexes of interstitial atoms straining the crystal lattice.

The fact that the defects are mostly located along the <0001> direction can possibly be explained by strong anisotropy of CdS therefore the defects form the region of elastic stresses in the crystal which are maximum along the <0001> axis.     

Precision measurements of the wavelengths of emission lines of Na-like and Mg-like Kr in alcator C

The wavelengths of lines from Mg- and Na-like Kr ions were precisely determined by puffing Kr gas into Alcator C tokamak plasmas and observing with a time-resolving spectrograph equipped with a multi-element spectral detector.     

A comparative study of amorphous and crystalline superconducting molybdenum films by ultraviolet photoemission spectroscopy

Ultraviolet photoemission measurements at two photon energies are carried out, to understand the strong enhancement of the superconducting transition temperature T_c in the nitrogen stabilized amorphous molybdenum films. The rise of T_c can be attributed to a 40% increase of the electronic density of states at the Fermi level N(E_F) and a 15% softening of the phonon spectrum.