Ion-Beam Induced Current in High-Resistance Materials

The peculiarities of electric current in high-resistance materials, such as semiconductors or semimetals, irradiated by ion beams are considered. It is shown that after ion--beam irradiation an unusual electric current may arise directed against the applied voltage. Such a negative current is a transient effect appearing at the initial stage of the process. The possibility of using this effect for studying the characteristics of irradiated materials is discussed. A new method for defining the mean projected range of ions is suggested.Comment: 1 file, 7 pages, RevTex, no figure

Longitudinal Schottky spectra of a bunched Ne10+ ion beam at the CSRe

The longitudinal Schottky spectra of a radio-frequency (RF) bunched and electron cooled 22Ne10+ ion beam at 70 MeV/u have been studied by a newly installed resonant Schottky pick-up at the experimental cooler storage ring (CSRe), at IMP. For an RF-bunched ion beam, a longitudinal momentum spread of has been reached with less than 107 stored ions. The reduction of momentum spread compared with coasting ion beam was observed from Schottky noise signal of the bunched ion beam. In order to prepare the future laser cooling experiment at the CSRe, the RF-bunching power was modulated at 25th, 50th and 75th harmonic of the revolution frequency, effective bunching amplitudes were extracted from the Schottky spectrum analysis. Applications of Schottky noise for measuring beam lifetime with ultra-low intensity of ion beams are presented, and it is relevant to upcoming experiments on laser cooling of relativistic heavy ion beams and nuclear physics at the CSRe.Comment: to be published in Chinese Physics

Genome‐wide association study identifies three novel susceptibility loci for systemic lupus erythematosus in Han Chinese

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145580/1/bjd16500_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145580/2/bjd16500.pd

Pressure Effect on the superconducting properties of LaO_{1-x}F_{x}FeAs(x=0.11) superconductor

Diamagnetic susceptibility measurements under high hydrostatic pressure (up to 1.03 GPa) were carried out on the newly discovered Fe-based superconductor LaO_{1-x}F_{x}FeAs(x=0.11). The transition temperature T_c, defined as the point at the maximum slope of superconducting transition, was enhanced almost linearly by hydrostatic pressure, yielding a dT_c/dP of about 1.2 K/GPa. Differential diamagnetic susceptibility curves indicate that the underlying superconducting state is complicated. It is suggested that pressure plays an important role on pushing low T_c superconducting phase toward the main (optimal) superconducting phase.Comment: 7 pages, 4 figure

Safety evaluations of a large-scale facility under blast loading

In this work, the safety performance and loading behavior of a large-scale facility were studied using experimental observations, numerical simulations and theoretical calculations. Furthermore, the effects of concentration, pressure relief and volume on the shock wave loadings were investigated. In particular, based on the dimensional theoretical analysis, a model for the analysis of overpressure peak and impulse for such facilities was proposed. The results showed that if concentration was larger than 10.5 %, the peak overpressure and the maximum overpressure rate were decreased; if the ignition mode was chemical, the propagation speed of flame was increased. In addition, it was found that the overpressure was the largest if the concentration was 9.5 %, and with the increase of the distance from the ignition source, the overpressure peak decreased first and then increased. The present study and results can therefore provide the loading information to enhance the antiexplosion performance of such facilities, which is very promising for the future safety evaluations and fault diagnosis of buildings, and constructions in various fields, especially, for nuclear power stations

Electron Spin Dephasing and Optical Pumping of Nuclear Spins in GaN

We have measured the donor-bound electron spin dynamics in cubic GaN by time-resolved Kerr rotation experiments. The ensemble electron spin dephasing time in this quantum dot like system characterized by a Bohr radius of 2.5 nm is of the order of 1.5 ns as a result of the interaction with the fluctuating nuclear spins. It increases drastically when an external magnetic field as small as 10 mT is applied. We extract a dispersion of the nuclear hyperfine field {\delta}Bn $\sim$ 4 mT, in agreement with calculations. We also demonstrate for the first time in GaN based systems the optical pumping of nuclear spin yielding the build-up of a significant nuclear polarization