Characteristics of the nitrogen ion beam produced in a plasma focus device

Abstract

Summary form only given, as follows. The characteristics of the nitrogen ion beam produced in a plasma focus device have been studied experimentally to apply the beam to material processing. In this application, the purity of the ion beam is very important. To clarify the mechanism of the production of impurity ions, 2-types of anode (tip type and hollow type) were used. In the experiment, a Mather type plasma focus device was used with a capacitor bank of 43.2 /spl mu/F. To produce nitrogen ions, the device was pre-filled with N/sub 2/ at 5.5 Pa. The bank was charged to 30 kV giving a peak discharge current of 600 kA and the current rise time was 1.5 /spl mu/s. The ion current density was measured with a biased ion collector (BIC). In the BIC measurement, the ion beam of current density of 1500 A/cm/sup 2/, duration of 50 ns (FWHM) was obtained at z=250 mm downstream from the top of the anode. Ion species and their energy spectra were evaluated using a Thomson parabola spectrometer (TPS). N/sup +/, N/sup 2+/ and N/sup 3+/ ions of energy from 0.15 MeV to 1 MeV were observed by a TPS with impurity ions (Cu/sup +/, Cu/sup 2+/, O/sup +/, O/sup 2+/, C/sup +/) in both type of anode. Comparing both type of the anode, the percentage of impurity ions was lower for the hollow type anode.