Preliminary experimental study and simulation of an energy-tunable quasi-monochromatic laser-Compton X/γ-ray source

We propose a slanting collision scheme for Compton scattering of a laser light against a relativistic electron beam. This scheme is suitable to generate an energy-tunable X/γ-ray source. In this paper, we present theoretical study and simulation of the spectral, spatial and temporal characteristics of such a source. We also describe two terms laser-Compton scattering (LCS) experiments at the 100 MeV Linac of Shanghai Institute of Applied Physics, where quasi-monochromatic LCS X-ray energy spectra with peak energies of ～30 keV are observed successfully. These preliminary investigations are carried out to understand the feasibility of developing an energy-tunable quasi-monochromatic X/γ-ray source, the future Shanghai Laser Electron Gamma Source.     

On the surface brightness radial profile of the extendedγ-ray sources

The morphology of the extendedγ-ray source is governed by the propagation process of parent relativistic particles.In this paper,we investigate the surface brightness radial profile of extendedγ-ray sources illuminated by cosmic ray protons and electrons,considering the radiation mechanisms,projection effects,and the response of instruments.We find that the parent particle species and the propagation process can cause considerable differences in the observed radial profiles.Thus,the surface brightness profile can be used as a unique tool to identify the radiation mechanism and the propagation process of the parent particles.In addition,we also discuss the possible implications regarding the latest discoveries from very/ultra-high energyγ-ray instruments like LHAASO and HAWC.     

Study of Neutron-Rich Hypernuclei by the (π −, K +) Reaction at J-PARC

We are planning to perform an experiment at J-PARC and produce new neutron-rich Λ hypernuclei by using the (π ^?, K ⁺) reaction (J-PARC E10). As the first step, we are planning to produce ${^6_{\Lambda}{\rm H}}$ hypernuclei with a ⁶Li target. To conduct this experiment, we are developing new detectors, those are scintillating fiber tracker, and silicon strip detector, for high rate operation to aim at increasing beam intensity up to 10⁷/spill. As a result of beam test in Jun 2012, we are going to use high-rate beam at least 10⁷/spill.     

An approach to evaluate the efficiency of γ-ray detectors to determine the radioactivity in environmental samples

This work provides an approach to determine the efficiency of γ-ray detectors with a good accuracy in order to determine the concentrations of either naturally occurring or artificially prepared radionuclides. This approach is based on the efficiency transfer formula(ET), the effective solid angles, the self- absorptions of the source matrix, the attenuation by the source container and the detector housing materials on the detector efficiency. The experimental calibration process was done using radioactive(Cylindrical Marinelli) sources, in different dimensions,that contain aqueous152 Eu radionuclide. The comparison point to a fine agreement between the experimental measured and calculated efficiencies for the(NaI HPGe) detectors using volumetric radioactive sources.     

The effects of ⁶⁰Co γ-ray irradiation on the DC characteristics of enhancement-mode AlGaN/GaN high-electron-mobility transistors

The effects of 60Co γ-ray irradiation on the DC characteristics of AlGaN/GaN enhancement-mode high-electron-mobility transistors (E-mode HEMTs) are investigated. The results show that having been irradiated by 60Co γ-rays at a dose of 3 Mrad (Si), the E-mode HEMT reduces its saturation drain current and maximal transconductance by 6% and 5%, respectively, and significantly increases both forward and reverse gate currents, while its threshold voltage is affected only slightly. The obvious performance degradation of E-mode AlGaN/GaN HEMTs is consistent with the creation of electronegative surface state charges in the source-gate spacer and gate-drain spacer after being irradiated.     

Recent Experimental Results of HL-1M Tokamak and Progress of HL-2A Project

Recent experimental results of HL-1M tokamak and progress of HL-2A project are presented. Strong fishbone instability was observed during off-axis ECRH. This is first observation of the fishbone instability purely driven by energetic electrons produced by ECRH. The MBI was first proposed and demonstrated on HL-1M. Recently new results of MBI experiment were obtained by increasing the pressure of gas. A stair-shape density increment was obtained with high-pressure multi-pulse MBI just like the density evolution behavior during the multipellet injection. It is shown     

A mini transmissionγ-ray Compton polarimeter and measurements of the sign of magnetic moments of radioactive nuclei

A mini transmission-ray Compton polarimeter was developed for the measurement of the sign of magnetic moments of radioactive nuclei with low-temperature nuclear orientation. The signs of the magnetic moments of the following isotopes were determined:¹⁹³Os [=+0.7297(16) _N];^191m Ir [=+6.20(9) _N];¹⁹²Ir [=+1.924(10) _N];¹⁹⁴Ir [=+0.39(1) _N];^195m Pt [=–0.605(15) _N].Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday     

Spectroscopy of Ly-α Lines at Storage Rings by Crystal Spectrometry and Absorption Edge Technique

Crystal spectrometry and absorption edge technique have the capability to overcome the gap in accuracy between experiment and theory in the strong field domain of QED. New results are presented which indicate the capacity of these methods to measure the energies of X-rays emitted by highly charged heavy ions at modern storage rings with a precision sensitive to second order corrections to the Lambshift in H-like very heavy ions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chinese Journal of Spectroscopy Laboratory,Vol.20,2003,Index in the Alphabetic Order of the Primary Author Surname and Name

BBAIH ong- Mei　 et.al(白红梅　杨继红　尹家元 ) (1- 0 6 9)………………………………………………………………………………BAIXiao- H ua　 et.al(白晓华　杨旗风　代丽萍　张玉青 ) (4 - 5 79)……………………………………………………………………BAIXiao- H ua　 et.a     

Tunable Diode Laser Absorption Spectroscopy Detection of N2O at 2.1μm Using Antimonide Laser and InGaAs Photodiode

Tunable diode laser absorption spectroscopy detection of N2 0 around 2.1 μm is demonstrated by using a homemade InGaAsSb/AlGaAsSb MQW laser diode and an InGaAs wavelength extended photodiode. Details of the devices and the detection system are described. In the system, the laser is driven by low frequency pulses with long duration to form a wavelength scan around 4741 cm^-1; the absorption information is obtained from the detected signal of the photodiode. By using a gas cell with 15cm path length, a detection limit is estimated to be smaller than 0.2 Torr.     

Results from the irradiation of stainless steel and copper by 23 MeV γ-quanta in the atmosphere of molecular deuterium at a pressure of 2 kbar

Metal samples were arranged inside a “finger-type” high-pressure chamber (DHPC-FT) filled by deuterium. They were two aluminum rods, a copper rod, two specimens of homogeneous YMn₂ alloy, and a stainless steel wire. The pressure of molecular deuterium in DHPC-FT was about 2 kbar. The samples were irradiated by braking γ-quanta at a threshold energy of 23 MeV. All the samples were studied using scanning electron microscopy (SEM) and X-ray (roentgen) microelement probe analysis (RMPA). Considerable changes in the surface structure and elemental composition were found for the samples of copper, aluminum, YMn₂ alloy, and stainless steel. Unusual results were analyzed in detail and compared with the earlier data.     

Applications of Spectroscopy in the Study of Glassy Solids Part I. Introduction, γ-Ray Spectroscopy (Mössbauer Effect), X-Ray Absorption Fine Structure,UV Absorption,and Visible Spectra

Abstract

Interest in glasses and the amorphous solid state in general, having for a long time been limited t o the separate camps of silicate glass technology and polymer science, has in the last few years become very general. This growth and diversification in scientific interest originates jointly in the discovery and utilization of glasses of quite new types e.g., the chalcogenide glasses, and the recognition by chemists and physicists alike that the glassy state is of very general occurrence in nature, with examples now being known from every class of chemical substance, whether metallic, vander Waals, covalent, or ionic in the interparticle bond character.     

Effect of iron and silicon on structure transformations and on microhardness of Al-30 wt. % Zn alloy aged at 90 °C

The structure transformations during the ageing at 90 C of Al-30 wt. % Zn alloys prepared from Al of 99.7, 99.99 and 99.999 wt. % were studied by X-ray diffraction and by transmission electron microscopy. Simultaneously, the measurement of Vicker's microhardness was carried out. It was found that Fe and Si impurities affect substantially the structure transformations and the microhardness values during the ageing process. These impurities retard the formation of lamellar aggregates of-phase and of impoverished-matrix and thus they slow down the softening of the alloy.In conclusion we would like to express our thanks to Doc. Dr. V.Syneek CSc. for his valuable discussions. We are also indebted to Mr. V.Petr and Mr. Z.iký for their help in the microhardness and X-ray diffraction measurements, and to Mr. P.Vyhlídka for the homogeneity check of the investigated samples.     

Absorption properties of infrared active gases at high pressures—II. N2O and CO

Absorptions of the near infrared N₂O and CO bands were measured at high pressures. The band intensities were found to be 0.153 ± 0.002, 1.14 ± 0.01, 1.67 ± 0.01,0.035 ± 0.002, 3.25 ± 0.02 and 49.9 ± 0.3 cm^-1/(atm-cm)_STP for the 2.0, 2.1, 2.3, 2.5, 2.6 and 2.9 μm N₂O bands, respectively, and 2.07 ± 0.02 cm^-1/(atm-cm)_STP for the first overtone CO band. It was also found for both molecules that the spectra measured under large absorber amounts are smaller in the band wings than those calculated from the Lorentzian line profile. This discrepancy is discussed in terms of non-Lorentzian behavior of the line profile.     

Conformational Studies of 1-(2′-Hydroxythiobenzoyl)piperidine and 4-(2′-Hydroxythiobenzoyl)morpholine by High Resolution N.M.R. Spectroscopy

Abstract

The 220 MHz ¹H nmr spectra of the title compounds (1a) and (2a), respectively, at low temperature in CDCl₃ solution are interpreted in terms of two interconverting chair forms with unequal populations (K_e = 1.17, δG° ～70 cals/mole for 1a and K_e = 1.8, δG° ～0.2 kcal/mole for 2a at ?30°C). A strong intramolecular OH…S hydrogen bond in both compounds reduces the number of degrees of freedom of the bulky N-thiobenzoyl substituent, which nearly eclipses the equatorial α-CH₂ hydrogen atoms in both comformations. Steric interactions between the 6′ phenyl proton and the hetero-ring α-CH₂ protons trans to the thiocarbonyl group are different in the two conformations of la and 2a.     

Estimation of critical grain size at different temperatures and thermodynamic stability of γ→α in NC Fe by QDA and EOS methods

Thermodynamic properties of Nanocrystalline (NC) materials are essentially different from the conventional coarse-grained materials (with the same chemical composition). The role of grain boundary is very important in the characterization of thermodynamic functions and thermal properties of NC materials when the grain size is less than 100 nm. Therefore, the traditional thermodynamics being applied for coarse-grained materials is not applicable for NC materials. In this study, Quasiharmonic Debye Approximation (QDA) and Equation of State (EOS) methods are used to calculate the Gibbs free energy in NC Fe. Since the Gibbs free energy for Fe, predicted by EOS and QDA methods, is inaccurate (especially at temperatures higher than the ambient temperature), a term called as ΔG^Excess is proposed to modify the results. Thus, the Modified QDA (MQDA) and Modified EOS (MEOS) methods are introduced for this purpose. Thereafter, the change in the Gibbs free energy for γ-Fe to α-Fe phase transformation (ΔG^γ→α) via the grain size is calculated by MQDA and MEOS methods. The results obtained by the two methods are also compared and discussed. Finally, the critical grain size, at which ΔG^γ→α=0, can be estimated at different temperatures, is found to increase with increasing temperature.