YIELD OPTIMIZATION OF THE LYMAN-ALPHA EMISSION IN PINCH PLASMAS

The scaling of the x-ray yield into a single K-shell line per pulse is discussed for pinch plasma devices. The determining parameters are the current I-0 through the plasma, the number density n(0), the atomic number Z of the working gas and the radius a of the electrode. Special interest is devoted to the question of how to choose these parameters in order to optimize the emission in the Lyman-alpha line of hydrogen-like ions. The scaling of relevant properties like lifetime, plasma size or plasma temperature is deduced by similarity considerations of the plasma dynamics. The plasma dynamics is discussed in terms of a simple model including the relevant processes to deduce optimization criteria for the Lyman-alpha emission. Experimental data for proper matching of current and number density in order to achieve maximum Lyman-alpha emission are known for nitrogen and compared with the theoretical considerations. The theoretical discussion shows that a minimum number density is required to achieve efficient hydrogen-like emission. At too low number densities the processes of the plasma dynamics are too slow compared to the lifetime of the plasma. This minimum density is approximately given by n(i)(min) approximate to 2 x 10(17) cm(-2) x Z(2)/a. If this minimum density is exceeded, the optimized energy input per ion for Lyman-alpha emission scales with Z(3).