Xiaoan Zhang

Trends in heavy ion interaction with plasma

In this work, we review current trends in China to investigate beam plasma interaction phenomena. Recent progresses in China on low energy heavy ions and plasma interaction, ion beam-plasma interactions under the influences of magnetic fields, high energy heavy ion radiography through marginal range method, energy deposition of highly charged ions on surfaces and Raman spectroscopy of surfaces after irradiation of highly charged ions are presented.

X-ray emission of Xe 30+ ion beam impacting on Au target

X-ray emission from Xe 30+ ions at 350–600 keV impacting on an Au target was investigated at the Heavy Ion Research Facility at Lanzhou. Characteristic X-rays of Xe ions at energy of about 1.65 keV were observed. This X-ray emission is induced by the decay of very high Rydberg states of Xe ions. It was also found that the yield of such characteristic X-rays is decreasing with increasing the projectile kinetic energy. Simultaneously, the yield of the characteristic Au X-rays from the M shell increases also. These phenomena are qualitatively analyzed with the classical Coulomb over the Barrier Mode (COBM) for highly charged ions interacting with solid state surfaces.

X-ray emission induced by 1.2-3.6 MeV Kr13+ ions

X-ray emission from Kr13+ ions in the energy range 1.2-3.6 MeV in steps of 0.6 MeV impacting on an Au target was investigated on electron cyclotron resonance ion source at the Heavy Ion Research Facility in Lanzhou. It was found that a shift of the X-ray lines to the higher energy side occurred. We measured the relationship between the characteristic of X-ray yield of Au M X-rays and Kr L X-rays as a function of incident energy. Furthermore, M-shell X-ray production cross-section of Au induced by Kr13+ was measured. The measured cross-section of target is compared to the classical binary-encounter approximation and plane-wave-born approximation theoretical model, which is a significant different between experimental and theoretical model.

K-shell ionization of Al induced by ions near the threshold energy

The K-shell ionization cross sections of Al induced by H+ and Ne7+ were studied. The ionization cross sections obtained are compared with the predictions of ECPSSR theory (based on the perturbed-stationary-state approach including Coulomb deflection, energy loss and relativistic corrections), BEA (binary encounter approximation) and 1sσ molecular-orbital ionization. It is found that the ECPSSR theoretical results agree with the experimental data very well for proton impact, while the BEA model with correction of Coulomb deflection shows good agreement with experimental results.

Target Z dependence of Xe L x-ray emission in heavy ion–atom collision near the Bohr velocity: influence of level matching

X-ray yields for the projectile L-shell have been measured for collisions between Xe20+ and thick solid targets throughout the periodic table with incident energies near the Bohr velocity. The yields show a very pronounced cyclic dependence on the target atomic number. This result indicates that Xe L x-ray emission intensity is greatly enhanced either in near-symmetric collisions or if the binding energy of the Xe M-shell matches the L- or N-shell binding energy of the target.

Temperature and energy effects on secondary electron emission from SiC ceramics induced by Xe 17+ ions

Secondary electron emission yield from the surface of SiC ceramics induced by Xe17+ ions has been measured as a function of target temperature and incident energy. In the temperature range of 463–659 K, the total yield gradually decreases with increasing target temperature. The decrease is about 57% for 3.2 MeV Xe17+ impact, and about 62% for 4.0 MeV Xe17+ impact, which is much larger than the decrease observed previously for ion impact at low charged states. The yield dependence on the temperature is discussed in terms of work function, because both kinetic electron emission and potential electron emission are influenced by work function. In addition, our experimental data show that the total electron yield gradually increases with the kinetic energy of projectile, when the target is at a constant temperature higher than room temperature. This result can be explained by electronic stopping power which plays an important role in kinetic electron emission.

X-ray emission from 424-MeV/u C ions impacting on selected target*

The K-shell x-rays of Ti, V, Fe, Co, Ni, Cu, and Zn induced by 424-MeV/u C6+ ion impact are measured. It is found that the K x-ray shifts to the high energy side and the intensity ratio of K beta/K alpha is larger than the atomic data, owing to the L-shell multiple-ionization. The x-ray production cross sections are deduced from the experimental counts and compared with the binary encounter approximation (BEA), plane wave approximation (PWBA) and energy-loss Coulomb-repulsion perturbed-stationary-state relativistic (ECPSSR) theoretical predictions. The BEA model with considering the multipleionization fluorescence yield is in better consistence with the experimental results. In addition, the cross section as a function of target atomic K-shell binding energy is presented.

Study on the electron configuration and the average equilibrium charge-state of highly charged Kr13+ ion

The Kr L X-ray induced by Kr13+ in the energy of 1.8-3.6 MeV impacting on Au was measured. It was found that a shift of Kr Lα X-ray lines to the higher energy side occurred. The electron configuration and the average equilibrium charge-state of Kr13+ are calculated.

INTERACTION OF HIGHLY CHARGED Xeq+ (q = 26, 27, 30) IONS WITH MOLYBDENUM SURFACE

Experimental investigation of Molybdenum L-shell X-ray emission is reported in the collision of highly charged Xeq+ (q = 26,27,30) ions with Molybdenum surface in the energy range 400 to 600 keV. Based on the X-ray spectra obtained and by the extrapolation of experimental data to the lower incident energy range, a limit was found for the energy of the incident ions. The influence of initial charge state on X-ray emission from the target L-shell was observed. The difference of the initial charge state and electron configuration of the incident ions may lead to observably different contribution to the target atom vacancy production and L-shell X-rays emission. Based on COB model, a simple explanation was presented to interpret the features of the experimental results.