Pinch plasma EUV source with particle injection

Injection of tin droplets into an argon or helium pinch discharge can provide high extreme ultraviolet (EUV) generation efficiency together with small plasma size. We estimate the rates of evaporation, ionization and expansion of a spherical solid density target in a gas pinch discharge. It is found that an initial tendency for the particle to become negatively charged reduces electron heat transport from the plasma. Negative charging is counteracted, and electron heat flux enhanced, by the generation of secondary electrons by ion impact on the surface and by photoemission dependent on the plasma radiation spectrum. When the heat flux exceeds 1 GW cm(-2) the particle can ionize and expand very rapidly to a diameter comparable to that of the pinch plasma. The time required for ionization and the final radius are each estimated as a function of particle size, plasma density and temperature. It is demonstrated that the plasma conditions in the Star Pinch EUV source are suitable for high brightness EUV generation via particle injection.