SEMIANALYTICAL SCALING LAWS FOR NE-LIKE SLAB TARGET XUV LASERS

We investigate the scaling properties of the Ne-like collisional laser through a semi-analytic scaling model. The model is found to reproduc e the temporal development of the electron density profile and tempera ture remarkably well, although some aspects of the driving laser wavel ength dependences are not completely satisfactory. The model is useful as a means to calculate approximate plasma conditions when detailed h ydrodynamic calculations are inappropriate. We use the scaling laws to identify the existence of two threshold incident intensity conditions for lasing. The first of these is straightforwardly that the absorbed energy is sufficient to generate the required electron temperature. T his constraint reproduces the threshold intensities for the elements w hich have been modelled in detail. The second constraint is that the d ensity gradients are low enough to allow propagation of the lasing lig ht, leading to a minimum energy required to produce a plasma of adequa te scale length. At low Z the second constraint is found to completely dominate the energy requirements (an important consideration as inter est is developing in these elements as a means to reduce the required driving power). This is true even for the J = 0-1 transition which has the shortest wavelength of the lasing lines in low-Z ions. In calcium (Z = 20), in which the refraction constraint defines the threshold, c omparable incident intensities to germanium (Z = 32) are required, in which the temperature constraint is applicable. We conclude that eleme nts in the vicinity of iron (Z = 26) are likely to be the most efficie nt low-Z schemes.