Engineering, dependence of neutron fluence anisotropy on the source axial extension in plasma focus device IPF-2/20

Since the measurement of the dependence of neutron fluence anisotropy (A(θΠ/90o)) relies on a ratio of the neutron fluences at different angles θΠ over the fluence at 90o on the source axial dimension, a screening disk of 45 mm diameter was placed axially at the following distances from the anode: 3, 5, 7, 9, and 13.6 cm. The neutron detection system consists of 7 channels of silver activation counters (in situ calibrated) placed at the angles 0o, 26o, 60o, 90o, 123o, 152o, and 180o. The axial extension of the neutron source Z≅ 15 cm (Z axis is at θΠ = 0o) greatly exceeds the axial dimension of the pinch Z≅ 2 cm. The neutron emission from the pinch zone is practically isotropic (A(θΠ/90o)≅ 1), while the emissive zones further in front of the pinch present a strong anisotropy (A(0o/90o) > 2 for Z = 7 - 13.6 cm). A stronger dependence of the anisotropy on the source axial dimension was observed for smaller angles (θΠ ≤). (Author)