plasma (9). The former case (< 1010 w/cm2) is considered here. The reflection coefficient R of the laser light claculated from the inversebremsstrahlung is given by the following equation (2). where Z,HL,K and Te are average ion charge number, scale height of the density gradient (~r/2, r is the laser spot radius and equals about 150 gm), wavelength and the electron temperature, respectively. A is also given by the following equation. where Xe and ne are Debye length and electron density, respectively. The measurement of the reflection coefficient using a TEA CO2 laser which is irradiated on the carbon target has been taken (2). According to these results, the experimental values (/?<0.1) are in good agreement with the value given by Eq. (1) at less than 1010 w/cm2, but it is pointed out that the consideration of nonlinear phenomena should be made to explain the experimental results at larger than 1011 w/cm2. In the PDC it is not necessary to make the plasma with high temperature (i.e., several keV) and high density (1022-1025 cm-3) such as can be produced by laser fusion, but it is important to convert the laser energy to electricity with high efficiency. 3.2 Conversion from Kinetic Energy to Expansion Energy While the laser light is irradiated on the target and just after the irradiation, the produced plasma is of relatively high temperature and high density. The electron temperature Te is nearly equal to the ion temperature T, because collisions are dominant in this condition. During the expansion, the kinetic energy of the high temperature and density plasma is converted mainly to the expansion energy, which directs in one direction and becomes the low temperature and density plasma (7). In this case, the distribution function of the expansion plasma/(v) is given by the following equation. Where, w is the expanding velocity, v, M, T. andA are the thermal velocity, ion mass, ion temperature and the Boltzmann constant, respectively. Tonon et al. (13) have obtained the values of I, ~ 30 eV and u ~ 1.4 x 107 cm/s using a TEA CO2 laser. If the value of u is shown by the equivalent expansion temperature Tu, Tu~ 1.4 keV and ~ 0.02. The velocity distribution v is regarded approximately as the 6 function on the scale of u. 3.3 Conversion from Expansion Energy of the Ions to Electricity As the expansion energy of the electrons is smaller by the mass ratio than that of the ions, it is thought best to convert the expansion energy of the ions to electricity after the separation of the ions and electrons. Although both the electrostatic and magnetic separations are considered to separate the electrons and ions, only the former case is reported here. As shown in Fig. 3, the part of the direct conversion is
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