By using a convex-curved mica crystal spectrometer, detailed spectral distributions of soft x-ray (<19.84Å) from the laser induced plasmas generated from the target materials C (Z=6), Al (Z=13), Ti (Z=22), Fe (Z=26), Cu (Z=29), Mo (Z=42) are investigated.
The size of the laser plasma is measured by using a pin-hole camera and x-ray film. It is found to be 570㎛.
In the present work, the electron temperatures are obtained for the laser induced plasma. It is found there exist two electron groups having low (slow electron group) and high (fast electron group) electron temperatures.
The temperatures obtained from the slope of soft x-ray intensity versus photon energy curve are 55,61,79,80,92,99eV in slow electron group and 2.9, 7.1, 7.9, 9.3, 8.5, 8.7 KeV in fast electron group for the target elements C, Al, Ti, Fe, Cu, Mo, respectively.
The existence of fast electron group is explained by parametric instability with the positive growth rate, and the slow electron group is explained by inverse Bremsstrahlung absorption.
