| The experiment system for studying the interaction of high intensity ultrashort pulse laser with solid targets, the facilities and methods for measuring ultrafast hard X-ray have been built. The hard X-ray continuum was measured by a single photon incident method based on a HPGe X-ray spectrometer with very low background. To avoid the overlap of photon in the detector, the detected efficiency was kept below 0.17/shot. The method was examined by filter method.The reflected light spectrum from interaction of UV laser with solid plasma was measured to investigate the frequency shift due to Doppler effect of expanding critical density. The spectrum data improved that the ponder-motive force can compete with thermal pressure significantly, and the thermal expanding velocity was reduced in the experiment. This data was used to deduce the plasma density scale length in the UV experiment.The hard X-ray (>30keV) continuum from the interaction of IR (744nm),ultrashort pulse (120fs), moderated intensity (10 W/cm ) laser with solid target wasmeasured. When P-polarized light irradiated 5mm Cu slab with 45? the hard X-ray with energy of 400keV was detected. The spectrum can be fitted by Maxwellian distribution, the hot electron temperature given by the slope is 85keV. The low pre-pulses of Ti:Sapphire laser have no affect on laser plasma interaction. The plasma density scale length decided by main laser pulse in the experiment is suitable for Vacuum Heating, and it is the dominant process for hot electron generation. From the scaling law about hot electron temperature given by VH model, the hot electron measured by experiment was reasonable, the temperature was higher than the temperature given by Resonant Absorption scaling law. But the detail explanation forexperiment results requires 2D PIC simulation with the experiment condition. The X-ray is isotropic measured by PIN detector, the hard X-ray (>30keV) production become smaller with the reduction of the incident laser intensity, when the intensity is lower than 1014W/cm2, there is no hard X-ray. At the intensity of 10l6W/cm2, the hard X-ray (>30keV) production is 1.4x 107/shot. As our best known, this is the first experimental measurement of so high hot electron temperature at moderated intensity, pre-pulse free condition.And then the hard X-ray (>30keV) continuum from the interaction of high intensity(1017W/cm2), UV(248nm), ultrashort pulse (440fs) laser with solid target was measured. When P-polarized light irradiated 5mm Cu slab with 45? the hard X-ray with energy above 200keV was detected. The spectrum can be fitted by Maxwellian distribution, the hot electron temperature given by the slope is 67keV. The low pre-pulses of Ti:Sapphire/KrF laser have no affect on laser plasma interaction. In this experiment the ponder-motive force can compete with plasma thermal pressure, which is estimated by theory and confirmed by frequency shift measured in reflected light of UV laser. The plasma density scale length given by combination of ponder-motive force and thermal pressure is suitable for VH. Considering the spatial intensity distribution in focal spot, the RA may give some contribution in some place. So the hot electron was generated by combination of VH and RA. The RA can explain the lower energy part of the spectrum. From the scaling law about hot electron temperature given by VH model, the hot electron measured by experiment was reasonable, the temperature was higher than the temperature given by Resonant Absorption scaling law. But the detail explanation for experiment results requires 2D hydrodynamic and PIC simulation with the experiment condition. The X-ray is isotropic measured by PIN detector, the hard X-ray (>30keV) production become smaller with the reduction of the incident laser intensity, when the intensity is lower than 101?W/cm2, there is no hard X-ray generation. This is the first time experimentalmeasurement of the hard X-ray continuum from high intensity ultrashort KrF laser with solid plasma. The data is useful to un...
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