In line-focused laser-produced plasma experiments on planar and cylindrical targets, we have obse... more In line-focused laser-produced plasma experiments on planar and cylindrical targets, we have observed the line-focused laser beam breakup into filaments as well as small-scale plasma jet-like structures. These phenomena might become obstacles in achieving optimum X-ray lasing in the type of experiments using line-focused laser-produced plasmas as a gain medium.
Time integrated optical and X-ray observations recorded on 0.35 nm laser irradiated thin foil tar... more Time integrated optical and X-ray observations recorded on 0.35 nm laser irradiated thin foil targets show the production of non-uniform and non-planar shock waves, caused by hot spots on the ablation surface. Optical striations seen on the rear side of the target correspond to spots in the X-ray image. The optical emission can be described by a model of shock wave unloading from a free surface.
We review results from an experimental investigation to examine the characteristics of x-ray gene... more We review results from an experimental investigation to examine the characteristics of x-ray generation from subpicosecond UV laser irradiation of collisionless gas targets under conditions such that the optical field strength is larger than an atomic unit. The purpose of the experiment was to test the conjecture that multiphoton-induced inner-shell excitation occurs at large laser irradiance. We found no evidence to support the validity of the conjecture at I 3 X 1017 W/cm 2. We did, however, detect delayed x rays, which were generated for unexpectedly long times following laser irradiation of the target. We present numerical simulations describing the processes that give rise to this signal. Earlier experiments 1 on collision-free multiphoton ioniza
IEE Proceedings - Radar, Sonar and Navigation, 1996
Investigating the performance of the optimum radar signal processor cipcraling in a gaussian dist... more Investigating the performance of the optimum radar signal processor cipcraling in a gaussian distributed interference environment, it has been often assumed that the clutter has a gaussian Doppler spectrum. The a uthors predict the clutter cancellation by making use of experimental Doppler frequency spectra for low grazing angles.
In laser-produced plasmas, the laser energy is absorbed only below and up to the critical density... more In laser-produced plasmas, the laser energy is absorbed only below and up to the critical density. For laser fusion applications, this energy must be transported beyond the corona via electron thermal conduction towards colder, higher density regions of the target to heat up material and cause ablation, which in turn generates an inward pressure to compress the fusion fuel. If the heat conduction is inhibited, the consequences are a weaker ablation and therefore a weaker implosion. For many years now, the inhibition of heat conduction, i.e., the reduction of heat conduction relative to classical conduction, in laser-produced plasmas at relevant irradiances was apparent from the large body of experimental evidence. Many mechanisms, such as dc magnetic fields, ion acoustic turbulence, and Weibel instabilities, were proposed to be the cause of inhibition of heat conduction. Even improved calculations of the classical heat flux were carried out to solve this problem. Nevertheless, no single one of the above mentioned mechanisms explains the large inhibition observed in the experiments.
We report on the first ohservatlons of periodic structures caused by the filamentation instabilit... more We report on the first ohservatlons of periodic structures caused by the filamentation instability. These structures were observed on 0.35 pm laser irradiated planar target experiments. Comparison of these observations with self-focucing theory indicates that rwn though thermal filamentation may initiate the instability. ponderomotive force effects eventually dominate the actual filamentatlon process. * This is achieved by using four dielectric mirrors coated for 0.35 pm radiation following the conversion crystals and by chromatic aberrations in the focusing lens.
In line-focused laser-produced plasma experiments on planar and cylindrical targets, we have obse... more In line-focused laser-produced plasma experiments on planar and cylindrical targets, we have observed the line-focused laser beam breakup into filaments as well as small-scale plasma jet-like structures. These phenomena might become obstacles in achieving optimum X-ray lasing in the type of experiments using line-focused laser-produced plasmas as a gain medium.
Time integrated optical and X-ray observations recorded on 0.35 nm laser irradiated thin foil tar... more Time integrated optical and X-ray observations recorded on 0.35 nm laser irradiated thin foil targets show the production of non-uniform and non-planar shock waves, caused by hot spots on the ablation surface. Optical striations seen on the rear side of the target correspond to spots in the X-ray image. The optical emission can be described by a model of shock wave unloading from a free surface.
We review results from an experimental investigation to examine the characteristics of x-ray gene... more We review results from an experimental investigation to examine the characteristics of x-ray generation from subpicosecond UV laser irradiation of collisionless gas targets under conditions such that the optical field strength is larger than an atomic unit. The purpose of the experiment was to test the conjecture that multiphoton-induced inner-shell excitation occurs at large laser irradiance. We found no evidence to support the validity of the conjecture at I 3 X 1017 W/cm 2. We did, however, detect delayed x rays, which were generated for unexpectedly long times following laser irradiation of the target. We present numerical simulations describing the processes that give rise to this signal. Earlier experiments 1 on collision-free multiphoton ioniza
IEE Proceedings - Radar, Sonar and Navigation, 1996
Investigating the performance of the optimum radar signal processor cipcraling in a gaussian dist... more Investigating the performance of the optimum radar signal processor cipcraling in a gaussian distributed interference environment, it has been often assumed that the clutter has a gaussian Doppler spectrum. The a uthors predict the clutter cancellation by making use of experimental Doppler frequency spectra for low grazing angles.
In laser-produced plasmas, the laser energy is absorbed only below and up to the critical density... more In laser-produced plasmas, the laser energy is absorbed only below and up to the critical density. For laser fusion applications, this energy must be transported beyond the corona via electron thermal conduction towards colder, higher density regions of the target to heat up material and cause ablation, which in turn generates an inward pressure to compress the fusion fuel. If the heat conduction is inhibited, the consequences are a weaker ablation and therefore a weaker implosion. For many years now, the inhibition of heat conduction, i.e., the reduction of heat conduction relative to classical conduction, in laser-produced plasmas at relevant irradiances was apparent from the large body of experimental evidence. Many mechanisms, such as dc magnetic fields, ion acoustic turbulence, and Weibel instabilities, were proposed to be the cause of inhibition of heat conduction. Even improved calculations of the classical heat flux were carried out to solve this problem. Nevertheless, no single one of the above mentioned mechanisms explains the large inhibition observed in the experiments.
We report on the first ohservatlons of periodic structures caused by the filamentation instabilit... more We report on the first ohservatlons of periodic structures caused by the filamentation instability. These structures were observed on 0.35 pm laser irradiated planar target experiments. Comparison of these observations with self-focucing theory indicates that rwn though thermal filamentation may initiate the instability. ponderomotive force effects eventually dominate the actual filamentatlon process. * This is achieved by using four dielectric mirrors coated for 0.35 pm radiation following the conversion crystals and by chromatic aberrations in the focusing lens.
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