Abstract

A repetitively pulsed fast plasma pinch has been used to generate strong emission on a number of transitions in highly ionized carbon, nitrogen, oxygen and neon, at a range of wavelengths between 95 and 350 Angstroms. The transitions are all fed by recombination during the expansion phase of the pinch. A typical starting geometry for the pinch is a helium-filled cylinder of diameter 2.5 cm and length 4 - 8 cm, containing approx 4 % propane, at a total pressure of 1 torr. The outside surface of the pinch cylinder is preionized using RF power before a longitudinal current of 200kA is initiated. The pinch reaches maximum compression and temperature after 150 nsec. The plasma column reaches a diameter of less than 400 microns. Its energy is 150 J and its temperature is estimated to be >100eV. Spectral lines are recorded axially on a 0.5 meter grazing incidence spectrometer. The strongest observed recombination line is from C V (1s2p - ls5d) at 175.67 Angstroms. It has a time-integrated intensity up to 11 times that of the helium II resonance line at 303.78 Angstroms. The latter line is radiatively trapped, representing the maximum brightness that the source can emit other than by the recombination mechanism. Other very strong lines include C VI (2p - 4d) at 134.99 Angstroms, of interest for EUV lithography. The identity of the strong spectral lines, their narrow width and their intensity are indicative of X-ray amplification. Preliminary length scaling shows an increase in intensity of 4x when the pinch length is doubled, from 4 cm to 8 cm.

© 1996 Optical Society of America