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High power density laser matter interaction
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Type
Thesis
Author
Wang, Weilong
Supervisor
Lee, Paul Choon Keat
Abstract
High power density laser matter interaction experiments are reported for four target materials (Al, Si, Cu, Au) being irradiated by three different laser energies of 0.2 Joule, 1.0 Joule and 5.0 Joule. This energy range was chosen because it is used in most applications.
The experiments were performed using the high power density laser matter interaction facility at NIE. This facility includes a Nd:YAG laser oscillator and two amplifiers, a vacuum system and electronic synchronization circuits.
Seven diagnostics were used in these experiments. The diagnostics were used together to obtain information like electron temperature, number of ions or expansion velocity.
X-ray diagnostic apparatus include pinhole camera, penumbral imaging system, pinhole transmission grating spectrometer and five channel PIN diode x-ray spectrometer. From the pinhole and penumbral images, we estimated the x-ray source size to be about 60 pm. The x-ray spectra fiom Cu and Au targets were obtained using
the pinhole transmission grating spectrometer. L and N line emissions were obtained for Cu. X-ray spectra were also obtained using five-channel PIN diode x-ray spectrometer. Electron temperatures in the range of 0.7-2.5 keV were calculated using results from the five-channel PIN diode x-ray spectrometer. X-ray conversion efficiency for Cu is about 1.2% at 1.0 Joule laser energy. The results of x-ray measurements obtained by different techniques were consistent.
Shadowgraphy and streak photography were used to diagnose the plasma plume dynamics. The displacements and velocities of dark plume and luminous plume fronts were obtained from these two diagnostics. Expansion velocities of the luminous plume up to several 10' cmd' were measured using streak photography. Ion measurements were performed using Faraday cups. Faraday cup signals were used to obtain the number of ions, ion temperature and ion velocity distribution. Maximum ion temperature obtained is around 320 eV.
Experimental results were then compared with those from the computer simulation (MEDUSA and RATION). The results were found to be consistent with computational results and published results where the experimental conditions overlap.
The experiments were performed using the high power density laser matter interaction facility at NIE. This facility includes a Nd:YAG laser oscillator and two amplifiers, a vacuum system and electronic synchronization circuits.
Seven diagnostics were used in these experiments. The diagnostics were used together to obtain information like electron temperature, number of ions or expansion velocity.
X-ray diagnostic apparatus include pinhole camera, penumbral imaging system, pinhole transmission grating spectrometer and five channel PIN diode x-ray spectrometer. From the pinhole and penumbral images, we estimated the x-ray source size to be about 60 pm. The x-ray spectra fiom Cu and Au targets were obtained using
the pinhole transmission grating spectrometer. L and N line emissions were obtained for Cu. X-ray spectra were also obtained using five-channel PIN diode x-ray spectrometer. Electron temperatures in the range of 0.7-2.5 keV were calculated using results from the five-channel PIN diode x-ray spectrometer. X-ray conversion efficiency for Cu is about 1.2% at 1.0 Joule laser energy. The results of x-ray measurements obtained by different techniques were consistent.
Shadowgraphy and streak photography were used to diagnose the plasma plume dynamics. The displacements and velocities of dark plume and luminous plume fronts were obtained from these two diagnostics. Expansion velocities of the luminous plume up to several 10' cmd' were measured using streak photography. Ion measurements were performed using Faraday cups. Faraday cup signals were used to obtain the number of ions, ion temperature and ion velocity distribution. Maximum ion temperature obtained is around 320 eV.
Experimental results were then compared with those from the computer simulation (MEDUSA and RATION). The results were found to be consistent with computational results and published results where the experimental conditions overlap.
Date Issued
2000
Call Number
QC718.5.P5 Wan
Date Submitted
2000