Anisotropy of the energy spectrum of plasma focus ion beams

The authors determined the energy spectrum Nα/sub (E)dE of the ion beams emitted in different directions (α) with respect to the electrode axis (α = 00,900,1800) of a plasma focus discharge (PF) (≅ 5 kJ at 20 kV), filling pressure 4 Torr of D2/ or of convenient H/sub 2/+D/sub 2/ mixtures. The authors used Thomson spectrometers for ion-energies E ≅ 70 keV-1 MeV (all α) and a high resolution magnetic analyzer with field-edge focusing and ion filtering for E ≅ 0.3-8 MeV (α = 00). The typical spectral amplitude N/sub 180/dE of the ion beam at 1800 (i.e., in the direction in which the PF pinch ejects a collimated ≅ 10 kA beam of ≅ 400 keV electrons) is smaller than N/sub O/dE with typical values N/sub O/(0.3 MeV)/N/sub 180/(0.3 MeV) ≥ 100 but has a relatively-stronger component of high energy ions N/sub 180/(0.8 MeV)/N/sub 180/(0.1 MeV) > 10 N/sub 0/(0.8 MeV)/N(0.1 MeV). The source brightness is reported for different α. The angular spread of the 1800 ion beam decreases for increasing energy values and is << 10 for E ≥0.5 MeV. The spectral resolution δE/E of the magnetic analyzer is better than 1% for 1 MeV ≤ E ≤ 7 MeV and that of the Thomson spectrometer ≅ 10% for E ≅ 0.1 - 0.8 MeV