Tang Xiao-Wei

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.

LOSS OF LIGHT YIELD OF DOPED LEAD TUNGSTATE CRYSTALS AFTER IRRADIATION

Loss of light yield of doped lead tungstate crystals after irradiation with a low dose rate has been observed. The La, Pr, and Y doping may improve radiation hardness, whereas Bi or Mo doping is harmful.

Short-Term Memory and Its Biophysical Model

The capacity of short-term memory has been studied using an integrate-and-fire neuronal network model. It is found that the storage of events depend on the manner of the correlation between the events, and the capacity is dominated by the value of after-depolarization potential. There is a monotonic increasing relationship between the value of after-depolarization potential and the memory numbers. The biophysics relevance of the network model is discussed and different kinds of the information processes are studied too.

Great Scintillating Properties of a YAlO3:Ce Crystal

We study the decay time constants and light output of an 18×18×1 mm3 YAlO3 crystal doped with cerium. The result shows that the light pulse is composed of fast and slow components. The fast component has a decay time constant of 24.05±0.15 ns with an intensity of 81.57±0.97% and the slow component has a decay time constant of 87.67±2.49 ns with an intensity of 18.51±1.34%. The measured light output is 3608±80 photoelectrons/MeV without the correction for the quantum efficiency of the photomultiplier tube XP2262B.

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.

Gamma-rays generated from plasmas in the interaction of solid targets with femtosecond laser pulses

The gamma-rays with energies up to 300 keV have been observed from:plasmas produced by femtosecond laser pulses at a focused intensity of 5 x 10(15) W.cm(-2).mu m(2) irradiating Ta, Mo, and Cu targets. By introducing an 8% prepulse of 70 ps before the main pulse, the fraction of high energy gamma-ray photons (hv >100 keV) was significantly enhanced relative to low energy photons (hv <100 keV).

HYPOTHESIS OF INTRACELLULAR SIGNALING BASED ON THE CYTOSKELETON NETWORK

In order to explain the direction, speed and specificity of cell signaling a dual pathway hypothesis is proposed. In this hypothesis the physical pathway is coupled to the biochemical pathway. As an example, the propagation of a mechanical wave along the cytoskeleton components is discussed.