Deuterium gas-puff Z-pinch implosions on the Z accelerator

Abstract

Experiments on the Z accelerator with deuterium gas-puff implosions have produced up to 3.7×1013 (±20%) neutrons at 2.34MeV (±0.10MeV). Although the mechanism for generating these neutrons was not definitively identified, this neutron output is 100 times more than previously observed from neutron-producing experiments at Z. Dopant gases in the deuterium (argon and chlorine) were used to study implosion characteristics and stagnated plasma conditions through x-ray yield measurements and spectroscopy. Magnetohydrodynamic (MHD) calculations have suggested that the dopants improved the neutron output through better plasma compression, which has been studied in experiments increasing the dopant fraction. Scaling these experiments, and additional MHD calculations, suggest that ∼5×1014 deuterium-deuterium (DD) neutrons could be generated at the 26-MA refurbished Z facility.

Experimental Demonstration of Fusion-Relevant Conditions in Magnetized Liner Inertial Fusion

“…This is consistent with expectations since the implosion velocity (70 km/s) is too low to generate such high temperatures in a non-magnetized, non-preheated target. The isotropic, near-Gaussian DD NTOF spectra, DD yield isotropy, high ion and electron temperatures (with T i ≈ T e ), and the large secondary DT yield provide evidence for a thermonuclear origin of the yield rather than beam-target reactions, which have been suggested as a significant source of yield in other magnetically-driven implosions [32][33][34]. The range of measured DD yields (5e11-2e12) is encompassed by the 2e11-6e13 thermonuclear yield range estimated based on the 0.2-0.6 g/cm 3 fuel density (from x-ray yield), 2-3.1 keV temperature (from NTOF and x-ray spectra), 0.02-0.05 mm 3 volume (from x-ray imaging), and 1-2 ns duration (from x-ray emission history).…”

Neutron spectra from beam-target reactions in dense Z-pinches

“…No measurable yield was recorded, suggesting that the yield of secondary neutrons was below this value. 30 In our simulations, we model secondary neutron production by producing 1.01 MeV triton particles from DD TN fusion reactions. These triton particles are then tracked in the same way as the accelerated deuterons, and their reactivity with the background plasma is recorded.…”

“…15 MA gas puff Deuterium gas puff experiments on the Z machine produced 3 Â 10 13 neutrons. 4,30 The gas puff consisted of two annular shells of deuterium, spanning radii of 1-2 cm and 3-4 cm, approximately 2 cm in height and with a total linear mass of 405 lg cm À1 . The maximum current in the experiments was 15.4 MA.…”

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

“…Plasma liners along with the classic pinches and plasma foci can serve as sources of intense neutron radiation with a neutron yield in the range 10 9 -4×10 13 neutrons per pulse [5]. The highest neutron yield for pinches (~ 4×10 13 ) was received at the Z-machine (SNL, USA) in experiments on the compression of deuterium liners [5].…”