Emission Characteristics of a High-energy Pulsed-ion-beam Produced in a Dense Plasma Focus Device

Abstract

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/cm with a pulse width of 60 ns was obtained 110 mm downstream from the top of the anode on the axis. In order to evaluate the angular distribution of the ion current density and the ion energy spectrum, we arrayed the biased ion collectors and the incident angle resolved energy spectrometers simultaneously at nine different angular positions (−80◦, −60◦, −40◦, −20◦, 0◦, 30◦, 50◦, 70◦, and 90◦) on a circumference of 110 mm in radius, centered at the focus. From measurements with the BIC, we found that the angular distribution of the ion current density was axially symmetric and that the ion current density decreased with increasing emission angle. Experimental results for the energy spectrum showed that the proton beam energy was distributed from 0.1 MeV to 1.4 MeV and that ions with energies lower than 300 keV were distributed widely over emission angles ranging from −80◦ to 90◦, with higher-energy ions (>1 MeV) being confined to emission angles of −20◦ ∼ 30◦. In addition, the ion energy and the track density were found to decrease rapidly with increasing emission angle.