A Capillary Discharge Experiment For The Investigation Of Possible Gain in the Ha Line of CVI

Evidence for gain in the H α (ls-2p) line of CVI at 182.1A has been seen recently in a capillary discharge experiment at the Ruhr University of Bochum. Previously, gain on this transition and those of similar energies had only been seen in high-power laser plasma experiments. The object of this experiment is to produce similar discharge conditions to those in Bochum and to obtain more evidence for gain on the same transition with a slightly different measurement technique. The circuit consists of two parallel 0.05 μF, 20 nH HV capacitors, with flat copper/brass transmission lines leading to graphite electrodes at either end of the capillary. The capacitors are charged from 10 to 20 kV and the discharge is initiated by a -22 kV pulse on a graphite trigger pin axially mounted behind the cathode. The discharge current is measured using a Rogowski coil. We employ a McPig 1m grazing incidence XUV spectrograph with a variety of diffraction gratings and a grazing incidence cylindrical mirror to image the discharge on the entrance slit. Time integrated and time gated spectra have been recorded for a variety of discharge conditions in delrin and polyethelene capillaries with diameters of 1/2 to 1 mm. These have revealed the presence of OV and OVI in the delrin discharges and CIV, CV, CVI, OV and OVI in the polyethelene discharges. In the case of the delrin discharges emission was observed in the first current half cycle only, with the intensity approximately following the current.