Plasma pinch EUV source with particle injection

Pinch discharge EUV sources tend to produce 13.5nm radiation from an elongated plasma, decreasing the possible collection efficiency for the lowest etendue collector designs. As a means to concentrate EUV emission we have investigated particle injection to locate the radiating species in a small volume at the center of the pinch. We have considered theoretically the rate of ionization and expansion of a small tin droplet in a buffer gas pinch plasma of argon or helium. The particle becomes negatively charged, with consequences for the electron and ion heat fluxes onto its surface. Photo-emission can reduce this negative potential and enhance the electron heat flux. We estimate that the 30 μm diameter tin particle that contains the minimum, or 'mass limited' number of atoms for a 5J EUV-emitting plasma, will fully ionize in less than 100nsec in a typical Star Pinch [1] plasma at the relevant electron density of 2x10 19 cm -3 and temperature of 30eV. We report on the generation of high velocity, on-demand, accurately positioned tin droplets suitable for the injection pinch, and on limitations to the system reliability.