Timescale Analysis of Spectral Lags

A technique for timescale analysis of spectral lags performed directly in the time domain is developed. Simulation studies are made to compare the time domain technique with the Fourier frequency analysis for spectral time lags. The time domain technique is applied to studying rapid variabilities of X-ray binaries and γ-ray bursts. The results indicate that in comparison with the Fourier analysis the timescale analysis technique is more powerful for the study of spectral lags in rapid variabilities on short time scales and short duration flaring phenomena.

Effect of lanthanum ion implantation on oxidation behavior of zircaloy

In order to investigate the effect of lanthanum ion implantation on theoxidation behavior of zircaloy at 500℃, Zircaloy specimens were implanted by lanthanum ions with adose range from 5xl0^(16) to 2xl0^(17) ions/cm^2 at room temperature, and then oxidized at 500℃ for100 min. The valence of the oxides in the scale was analyzed by X-ray Photoelectron Spectroscopy(XPS). The phase structures of the oxides in the scale were examined by Glancing Angle X-rayDiffraction (GAXRD). With the increase of implanted lanthanum ions dose, the phase structures in theoxide scale are transformed from monoclinic zirconia to hexagonal one and then to monoclinic oneagain. The measurement of weight gain showed that a similar change from the decreased gain toincreased one again is achieved in the oxidation behavior of lanthanum ion implanted zircaloycompared with that of as-received zircaloy.

Tuning Effect on the Electron Energy Distribution Function of an Inert Gas Mixture in nitrogen Inductively Coupled Plasma Discharges

By using a Langmuir probe, the electron energy distribution function (EEDF) is measured in inductively coupled plasma discharges in N2/Ar mixtures at 200W rf powers. In pure N2 discharges a Maxwellian EEDF is observed.When the mixing ratio of Ar increases, the distribution of high-energy electrons evolves with a different trend from that of low-energy electrons, resulting in an apparent “two temperature structure” of the EEDF. We discuss this non-Maxwellian EEDF and its effect on the measurement and the interpretation of “electron temperature”by both the probe and line ratio technique.

Possibility of rapidly reporting ^(226)Ra activity in ^(226)Ra-^(222)Rn samples with unknown equilibrium factor by γ spectrometer

This paper reports the observed changes for equilibrium factors between 226Ra and 222Rn with sealing time of the samples. The samples include soil, raw coal, mineral water, cement, rock, etc. Especially the conceptions of “pre-equilibrium time” and “pre-equilibrium factor” have been put forward and methods of measuring and proc- essing data have been given which can be used for rapidly reporting activity of 226 Ra in samples with unknown equi- librium factor. It is definitely concluded that, using methods given in the paper, a test report will be completed in 3~7 days, instead of one month, after receiving the sample whose activity is not lower than LLD of the spectrometer.

A general fan-beam reconstruction algorithm for free-form trajectories

In this paper we develop a general exact fan-beam reconstruction algorithm for free-form trajectories not only closed but also unclosed,based on the fan-beam reconstruction formula recently developed by Noo et al.. A mathematical proof is then provided with the geometrical explanation of equi-spatial detectors. With this algorithm we can obtain exact region of interest (ROI) reconstruction if and only if every projecting line passing through the ROI intersects the free-form source trajectory,when the projections are not truncated. Furthermore,under the condi- tion that the source-to-detectors distance changes slowly enough relative to the length itself,we obtain a very good approximate reconstruction algorithm,which is the same as the algorithm of the circular trajectory except that the source-to-detectors distance is a function of the rotation angle. Then the algorithms are tested using the Shepp-Logan phantom and the experiment shows that the algorithms can get perfect numerical results.

Measurements of ^(222) Rn and ^(220)Rn with a Large Size Collector of Radon Progeny

Radon concentrations in high background radiation areas in the south are higher than those of others in China, especially 220 Rn concentration is significantly high. Therefore, measurements of 222 Rn and 220 Rn concentrations should be carried out there. This paper introduces a large size collector of radon progeny and its applications. The collector is a sheet of polyvinyl chloride fiber with electrostatics of (-500 V)-(-700 V). Its size (60 mm in diameter) is larger than those of others (26 mm in diameter) that work with the same principle. The collector is more effective to adsorb radon progeny than most of others. The equipment of ZnS(Ag) Scintillation Counting System is available for large size collectors to detect radon progeny. Therefore, its sensitivity of measurement is higher than that of others. According to the different half lives of radon progeny, and based on both theory and experiments, a formula for discrimination and calculation of 222 Rn and 220 Rn concentrations is deduced. The 222 Rn and 220 Rn concentrations were surveyed with electrostatic collectors of radon progeny on the campus of commercial school and some other areas in Hainan, southern China. Neither 222 Rn nor 220 Rn concentration was found significantly high. However, several faults underground were delineated. The collector is also used to study radon transportation. Results indicate that radon changes regularly with date when it has transported for a certain distance. Velocities of radon migration in the four media are quite different. Radon migrates more quickly in vertical tube than in the horizontal tube.

Study on Limited Projections in Micro—focus X—ray Swing Laminography

This paper resents a new X-ray imaging method swing Laminography(SL) that is suitalble to perform non-destructive testing on the slender-shaped multi-layer samples.Computer simulations are made to compare the limited projections in SL and the principle of choosing Optimal Projection Angular Region(OPAR) is discussed.The experiment on a two-layer Printed Circuits Board shows that SL with 120° swing angles distributed in OPAR can get the separated images of each layer.