Zhu An

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.

Study of cross-sections for the K-shell ionization of atoms by electron and positron impact

Abstract In this paper, the K-shell ionization cross-sections of some atoms by electron impact in the energy region less than several ten keV recently measured by our group and by other groups have been compared with the theoretical results of plane-wave Born approximation (PWBA) with Coulomb, relativistic, and exchange corrections as well as the Luo and Joys theory. These experimental data have also been compared with Casnati et al.s empirical formula and Deutsch-Margreiter-Mark (DMM) semi-empirical formula, which is modified by us based upon the most recently precisely measured K-shell ionization cross-sections of Cr, Ni, Cu elements of Llovet et al. Moreover, the experimental K-shell ionization cross-section ratios of electron and positron impact have been re-analyzed using the PWBA with Coulomb, relativistic, and exchange corrections. It is found that for most of the elements analyzed in this paper the experimental data are in good or acceptable agreement with the PWBA theoretical results and Luo and Joys theory and that our modified DMM semi-empirical formula can also provide a good or better description to the experimental data of K-shell ionization cross-section by electron impact.

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.

Measurement of scandium and vanadium K-shell ionization cross sections by electron impact

Electron impact Sc and V K-shell ionization cross sections have been measured for the first time in the incident energy region from near threshold to 45 keV. Thin targets with thick substrates are used in the experiments. The influence of the substrate on measured data has been corrected by a method based upon an electron transport calculation. For Sc and V elements, the experimental data are compared with some empirical formulae and theoretical results. It is found that the experimental data for Sc and V and most of the other elements measured before (i.e. Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb and Mo) with the same method as presented in this paper, can be reasonably described by both Luos theoretical results and Casnatis empirical formula.

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 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.

Bremsstrahlung spectrum data for thick Al, Ti, Zr, Mo, and W targets by keV electron impact

The data presented in this paper are related to the research paper entitled “Bremsstrahlung spectra produced by kilovolt electron impact on thick targets” [1]. The dataset includes our measured bremsstrahlung spectra on Al, Ti, Zr, Mo, and W thick targets at 5, 10, 15, 20, and 25u202fkeV electron impact. In this paper we present the experimental method and make the dataset publicly available to enable extended analyses or reuse. The dataset is available on mendeley data public repository at http://dx.doi.org/10.17632/5zx3459bj3.1