Mantian Liu

Cross sections for K-shell ionization by electron impact☆

Cross sections for K-shell ionization by electron impact derived from experimental measurements are tabulated according to target atomic number and incident electron energy. Data are presented for elements C through U.

Measurements of L-shell x-ray production cross-sections of Au and Ag by low energy electron impact

Lα, Lβ x-ray production cross-sections for Gd (Z = 64) and W (Z = 74) by electron impact up to 40 keV have been measured. Thin films with thick carbon substrates were used as targets in the experiments. The effects of multiple scattering of electrons when penetrating the target film, of electrons reflected from the thick pure carbon substrate and of bremsstrahlung photons produced by the impact of incident electrons on the target were corrected by means of Monte Carlo simulation. For Gd L-shell x-ray characteristic peaks, the spectra were fitted by using spectrum-fitting program ALLFIT to extract more accurately the Lα and Lβ peak counts. The experimental data are compared with the DWBA theory and the PWBA–C–Ex theory and available experimental data from the literature.

Some recent progress on the measurement of K-shell ionization cross-sections of atoms by electron impact: Application to Ti and Cr elements

In this paper, we have taken some measures to improve the accuracy of our experimental data for K-shell ionization cross-sections by electron impact. These measures include (1) measurement of the thin target thickness with Rutherford backscattering spectroscopy and (2) detection efficiency calibration in the lower energy region using thick carbon target bremsstrahlung by electron impact and (3) electron reflection correction and electron mean track length correction based upon Monte Carlo method. These measures are applied to the measurement of K-shell ionization cross-sections of Ti and Cr elements from the threshold energies up to 26 keV. From the comparison with some theoretical models, empirical formulae and some previous experimental data, it is concluded that these measures taken in this paper are effective in the improvement of accuracy of experimental data. The present experimental data for Ti and Cr elements also clarify the discrepancies among some experimental data sets. In addition, these measures will also be very helpful in the measurement of K-shell ionization cross-sections for lower Z elements and in the measurement of L, M-shell ionization cross-sections for medium and higher Z elements.

Production of cadmium-107 and cadmium-109 by deuteron bombardment of silver

Abstract 107Cd and 109Cd have been produced by 13.4 MeV deuteron bombardment of a natural silver target in a cyclotron. The activities of the reaction products are measured with a well-calibrated HPGe detector. The excitation functions for 107Ag(d, 2n)107Cd and 109Ag(d, 2n)109Cd reactions up to the deuteron energy of 13.4 MeV are determined by using the stacked foil technique. The calculation of thick-target yields for these reactions is performed from these excitation functions. The experimental results for the 109Ag(d, 2n)109Cd reactions are compared with previous works.

Excitation functions for 107Ag(d, 2n)107Cd, 109Ag(d, 2n)109Cd and 109Ag(d, p) 110mAg reactions

Abstract The excitation functions for the 107 Ag(d, 2n) 107 Cd, 109 Ag(d, 2n) 109 Cd and 109 Ag(d, p) 110m Ag reactions were determined by irradiation of a natural silver target with a 13.4 MeV deuteron beam and by the stacked-foil technique. The measurement of γ-ray spectra for radioactive products was carried out by using a well calibrated HPGe detector and a low background chamber. A computer system was employed to acquire and analyse datta. The present result for the 109 Ag(d, 2n) 109 Cd reaction was compared with those of other authors. The statistical model was applied to calculate the excitation functions for these reactions. The agreement between measured and calculated values is quite good.

On the efficiency calibration of Si(Li) detector in the low-energy region using thick-target bremsstrahlung

Abstract In this paper, the efficiency calibration of a Si(Li) detector in the low-energy region down to 0.58 keV has been performed using thick-carbon-target bremsstrahlung by 19 keV electron impact. The shape of the efficiency calibration curve was determined from the thick-carbon-target bremsstrahlung spectrum, and the absolute value for the efficiency calibration was obtained from the use of 241Am radioactive standard source. The modified Wentzels formula for thick-target bremsstrahlung was employed and it was also compared with the most recently developed theoretical model based upon the doubly differential cross-sections for bremsstrahlung of Kissel, Quarles and Pratt. In the present calculation of theoretical bremsstrahlung, the self-absorption correction and the convolution of detectors response function with the bremsstrahlung spectrum have simultaneously been taken into account. The accuracy for the efficiency calibration in the low-energy region with the method described here was estimated to be about 6%. Moreover, the self-absorption correction calculation based upon the prescription of Wolters et al. has also been presented as an analytical factor with the accuracy of ∼1%.

Measurements of germanium K-shell ionization cross sections and tin L-shell x-ray production cross sections by electron impact

This article reports experimental measurements of germanium K-shell ionization cross sections and tin L-shell x-ray production cross sections by electron impact. In order to avoid the difficulty of preparing thin and uniform self-supporting targets, thin targets with thick substrates are used in the experiments. Since electrons reflected by the substrate can induce additional ionization of target atoms, we developed a method to correct the measured x-ray intensities and eliminated the influence of the substrate on measured data. Our measured cross sections are in good agreement with previous measurements. The present results are also compared with the predictions of theories and semiempirical and empirical formulas. It is found that the K-shell ionization cross sections of Ge at energies from near threshold to 40 keV can be reasonably described by the semiempirical formula of Green and Cosslett. Experimental absolute L-shell x-ray production cross sections of Sn are presented. It seems that, so far, none ...

The hydrogen concentration of diamondlike amorphous carbon films by elastic recoil detection analysis

Abstract By using elastic recoil detection analysis, the hydrogen concentration of amorphous carbon films prepared by ion beam deposition was determined. The dependence of the hydrogen concentration on the deposition parameters (energy of ion beam, beam current density, and ratio of hydrogen to methane in gas mixture) was observed for these films. It seems clear that the diamond cubic structure in a-C:H films increases monotonically with decreasing hydrogen concentration.

Measurements of the K-shell ionization cross sections of Si by 3―25-keV electron impact using the thick-target method

In this paper, the K-shell ionization cross sections of Si element in the threshold energy region of 3-25 keV have been measured by using the thick-target method. With the Monte Carlo simulations, the effects of multiple scattering of incident electrons and from the bremsstrahlung photons and other secondary particles in the thick-target method have been discussed. The detection efficiency calibration in the lower-energy region has been performed by using the bremsstrahlung spectra of thick carbon target by electron impact in combination with the use of standard x-ray sources, and the detector thickness parameters have also been determined by a nonlinear least-squares fit. The ill-posed inverse problem involved in the thick-target method has been dealt with by the Tikhonov regularization method. The experimental K-shell ionization cross sections for Si element obtained in this paper have also been compared with some theoretical models, and it has been observed that the experimental data in this paper are in good agreement with the theoretical values based on the distorted-wave Born approximation model developed most recently.

Amorphous composition in Gd–Co–Al system extracted from bulk metallic glass matrix composite

Multiphase structure including the metallic glass matrix and the primary crystalline phase(s) was found in the Gd55Co15Al30−xGex (0≤x≤10) alloys. It was confirmed by x-ray diffraction and energy dispersive spectroscopy that the primary crystalline phase was Gd5Ge3 when x≥5. Based on these results, ternary bulk metallic glasses with composition of Gd52.5–53.8Co16.5–20.5Al25.7–31.0, which exhibit good glass forming ability and high thermal stability, were discovered.