Angular distribution measurements of energy spectra of protons emitted from hydrogen plasma focus

The characteristics of ion beams produced in a Mather-type plasma focus device have been studied. When a capacitor bank of 41.6 μF was charged to 30 kV, the discharge current reached a peak current of 450 kA, and after the current dip, an ion current density of 8 kA/cm² with a pulse width of 60 ns was obtained 110 mm downstream from the top of the anode on the axis. The experimental results show that the ion beam was emitted in the half cone angle of 80°. To evaluate the dependence of ion energy spectrum on the emission angle (θ) and the hydrogen gas pressure, we arrayed the incident angle resolved energy spectrometers simultaneously at different angular positions on a circumference of 110 mm in radius, centered at the focus. From the evaluation, we found that at the hydrogen pressure of 300 Pa, the proton beam has an energy range from 100 keV to 2 MeV and that the protons with energies higher than 1 MeV were emitted in the half cone angle of ~30°, while the protons with energies lower than 250 keV were observed at all the emission angles. When the hydrogen gas pressure was set at 250 and 350 Pa, the protons with energies higher than 400 keV were not observed in far off-axis positions.