Observation of keV X-ray emitted from laser produced Au plasmas by using a crystal spectrometer*

X-ray emitted by a laser generated plasma has various applications. Serious issue to be solved is that the energy conversion efficiency from the laser to X-ray is quite low. Recently, it was found that the X-ray emitted by the laser produced Au plasma increases under nitrogen atmospheres. In particular, the intensity of the water window soft X-ray (2.4-4.4 nm) increases approximately ten times. In order to elucidate this enhancement mechanism of X-ray, we have measured soft X-ray spectra from Au plasma in the wavelength of 1-7 nm so far. Recently, we fabricated a TAP crystal spectrometer to observe the photons over 1 keV region (1.0-1.9 eV), which provides useful information of plasma temperature. As a detector, an imaging plate(IP) was used. Titanium filters was also used to block out-of-band emission. As a result, continuum spectra attributed unresolved transition arrays (UTAs) was observed from the Au laser plasma. This spectral profile was compared with the Star2D hydrodynamic code.