Efficient generation of fast neutrons by magnetized deuterons in an optimized deuterium gas-puff z-pinch

Z-pinch experiments with deuterium gas puffs have been carried out on the GIT-12 generator at 3 MA currents. Recently, a novel configuration of a deuterium gas-puff z-pinch was used to accelerate deuterons and to generate fast neutrons. In order to form a homogeneous, uniformly conducting layer at a large initial radius, an inner deuterium gas puff was surrounded by an outer hollow cylindrical plasma shell. The plasma shell consisting of hydrogen and carbon ions was formed at the diameter of 350 mm by 48 plasma guns. A linear mass of the plasma shell was about 5 μg cm^-1 whereas a total linear mass of deuterium gas in single or double shell gas puffs was about 100 μg cm^-1. The implosion lasted 700 ns and seemed to be stable up to a 5 mm radius. During stagnation, m = 0 instabilities became more pronounced. When a disruption of necks occurred, the plasma impedance reached 0.4 Ω and high energy (>2 MeV) bremsstrahlung radiation together with high energy deuterons were produced. Maximum neutron energies of 33 MeV were observed by axial time-of-flight detectors. The observed neutron spectra could be explained by a suprathermal distribution of deuterons with a high energy tail f(E<inf>d</inf>) ∝ E<inf>d</inf>^-(1.8±0.2). Neutron yields reached 3.6 × 10¹² at a 2.7 MA current. A high neutron production efficiency of 6 × 10⁷ neutrons per one joule of plasma energy resulted from the generation of high energy deuterons and from their magnetization inside plasmas.