Liang Tianjiao

Double Jet Emission of Hot Electrons from a Micro-droplet Spray

Spatial distribution of hot electrons with energies above 50 keV are investigated by an ethanol micro-droplet spray irradiated by linearly and elliptically polarized 150 fs laser pulses at an intensity of 1016W/cm2. Two symmetric hot electron jets with respect to the laser propagation direction are observed in the polarization plane for a linearly polarized laser field and in the plane of the long electric vector for an elliptically polarized laser field, respectively. Particle-in-cell simulations suggest that the resonance absorption on the spherical surface of the droplets is mainly responsible for the generation of the double-jet emission of hot electrons.

Effects of Polarization on Super-hot Electron Generation in Femtosecond Laser-Plasma Interaction

The effects of laser polarization on super-hot electron (> 100 keV) generation have been studied in the interaction of femtosecond laser light (800 nm, 150 fs, 6 x 10(15) W(.)cm(-2)) with a pre-formed plasma from a slab Cu target. For p-polarized laser pulses, high-energy gamma -rays of the energy similar to 400keV were detected. The electron temperatures deduced from the gamma -ray spectra were 66 and 52 ke V, respectively, in normal and reflective directions of the solid target, and hot electrons were emitted out of the plasma mainly in the normal direction. In contrast, there were nearly no gamma -rays > 100keV found for s-polarized laser pulses. The hot electron temperature was 26 keV and the emission of hot electrons was parallel to the laser field. The superposition of resonant field with electrostatic field excited by escaping electrons may contribute to the high-energy gamma -ray or super-hot electron (> 100keV) generation.

Study of neutron activation yields in spallation reaction of 400 MeV/u carbon on a thick lead target

The spallation-neutron yield was studied experimentally by bombarding a thick lead target with 400 MeV/u carbon beam. The data were obtained with the activation analysis method using foils of Au, Mn, Al, Fe and In. The yields of produced isotopes were deduced by analyzing the measured γ spectra of irradiated foils. According to the isotopes yields, the spatial and energy distributions of the neutron field were discussed. The experimental results were compared with Monte Carlo simulations performed by the GEANT4 + FLUKA code.The spallation-neutron yield was studied experimentally by bombarding a thick lead target with 400 MeV/u carbon beam. The data were obtained with the activation analysis method using foils of Au, Mn, Al, Fe and In. The yields of produced isotopes were deduced by analyzing the measured gamma spectra of the irradiated foils. According to the isotopes yields, the spatial and energy distributions of the neutron field were discussed. The experimental results were compared with Monte Carlo simulations performed by the GEANT4+FLUKA code.

Calculations of radioactivity and afterheat in the components of the CSNS target station

This paper shows the calculations of radioactivity and afterheat in the components of the China Spallation Neutron Source (CSNS) target station, with the Monte Carlo codes LAHET, MCNP4C and the multigroup code CINDER’90. These calculations provide essential data for the detailed design and maintenance of the CSNS target station.

Ion Acceleration by an Electrostatic Field in the Interaction Between Femtosecond Laser Pulses and Solid Targets

We have studied the ion emission in the interaction between femtosecond laser pulses and solid targets by experiments and particle-in-cell (PIC) simulations. We found experimentally that almost all of the fast ions are confined within a cone symmetrically around the normal direction of targets. The PIC simulation results demonstrate that the fast ion beam can be accelerated by the laser-induced electrostatic field in front of solid targets.