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

Abstract

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. Neutron yields reached 3.6 × 10 12 at a 2.7 MA current. A high neutron production efficiency of 6 × 10 7 neutrons per one joule of plasma energy resulted from the generation of high energy deuterons and from their magnetization inside plasmas.

Hybrid MHD/PIC simulation of a deuterium gas puff z pinch

“…Ion-ion Coulomb collision is considered with the use of MC method. In the model simulation, in the configuration close to described in [6], it was obtained the neutron yields up to 1.2×10 12 . Most neutrons are not thermonuclear.…”

“…We present the hybrid MHD/PIC simulations of the time evolution of a deuterium gas puff z pinch. Recent experiments with 3-MA current pinches [6] made in a novel configuration have shown that the neutron yields can reach 3.6×10…”

“…Earlier, this neutron yield could be surpassed only on the 15-MA pinch. Energy neutron spectrum obtained in experiments [6,7] has a high energy non-Maxwellian tail. Possible reasons of this high energy tail origin are discussed, for example, in [8].…”

“…Recent experiments [6,7] made in a novel configuration have shown that the neutron yields can reach 3.6×10 12 at current about of 3 MA. Earlier, this neutron yield could be surpassed only on the 15-MA pinch.…”

“…It was shown that the observed neutron spectra could be explained by a suprathermal distribution of deuterons with a power law fall off in the ion energy distribution function at large energy. These high energy deuterons with energy up to 40 MeV (highest achievement for Z-pinches experiments) were detected in [6,7]. The mechanism of generation of such deuterons is still not clear [8].…”