Electrical discharge radiation source for the wavelength region below 10 nm

The results of the experiments with potentially “clean” electrical discharge source of extreme ultraviolet (EUV) radiation with wavelength below 10 nm are presented. The operation of the source is based upon the use of the early stage of vacuum discharge with external triggering. The main feature of the stage under consideration is the presence of the voltage across the discharge gap. The phenomenon involves the acceleration of the electrons, emitted by trigger plasma under the action of the applied electrical field, evaporation, and finally, ionization of the anode material driven by the accelerated electrons. No plasma pinching and electrode melting take place. The operation of such a discharge as an EUV source was demonstrated in the spectral range 10–20 nm for 10 kV. A more advanced discharge circuit proposed in the present work made it possible to increase the working voltage from 10 to 34 kV. This step has allowed to operate at shorter wavelength regions. The use of rare earth metals (Nd, Sm, Tb) as anode materials allowed us to get radiation with spectral maxima at 8.3, 7.5, and 6.8 nm, respectively.