Radiation emission characteristics in the X-ray/EUV from spherically pinched and vacuum spark sources

Abstract

Summary form only given. Soft X-ray and ultraviolet (UV) microlithography technologies call for compact, cost-effective radiation sources other than the conventional, expensive synchrotron machines. To this end, extensive research and development have been pursued worldwide on various schemes of plasma radiation sources, such as the laser-plasma X-ray source, the dense plasma focus, and the spherical pinch. At Advanced Laser and Fusion Technology (ALFT), a prototype spherical pinch X-ray source, SPX II, and a commercial machine, SPX III, have been developed as broadband radiation sources. More recently, an alternative and complementary X-ray device, the vacuum spark VSX I, has been developed. The spherical pinch is a novel concept based on the principle of strong spherically convergent shock waves compressing a preformed plasma in the center of a spherical vessel. The preformed central plasma is generated by a discharge in a noble gas between two electrodes located near the center of the spherical vessel. Then an imploding shock wave is launched inductively by discharging a condenser bank into a spherically shaped coil. As a result of the strong wave compression a high temperature plasma can be generated in the center of the spherical vessel, with a size smaller than 1 mm. Our work on the spherical pinch sources, SPX II and SPX III, is described in terms of their specifications and radiation output, and on the vacuum spark source, VSX I, is presented in terms of its setup and experimental results.