Kinetic simulations of gas breakdown in the dense plasma focus

Bennett, Nichelle; Blasco, Michael; Breeding, K.; DiPuccio, V.; Gall, B.; Garcia, M. R.; Gardner, Steven D.; Gatling, James; Hagen, E. C.; Luttman, Aaron; Meehan, B. T.; Molnar, S.; O’Brien, Robert; Ormond, Eugene C.; Robbins, Laurence L.; Savage, M. E.; Sipe, Nathan; Welch, D. R.

doi:10.1063/1.4985313

Cited by 7 publications

(1 citation statement)

References 43 publications

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“…These phenomena may be important for the described Y n vs p 0 dependency, as some authors have already suggested, e.g. Milanese et al [41], Kubes et al [42], Bennett et al [43] and Hahn et al [44]. On the other hand, the influence of filamentation on a PF discharge during axial and radial phases prior to the plasma pinch formation may already be approximately included through the Lee model code parameters.…”

Section: Discussionmentioning

confidence: 92%

Numerical experiments on the total D–D fusion neutron yield versus deuterium pressure for different energy plasma focus devices using the Lee model code

Wahbe¹,

Abou-Ali²,

Akel³

et al. 2023

Plasma Phys. Control. Fusion

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Numerical experiments using the Lee model code were carried out to compute the total D-D fusion neutron yield versus initial deuterium pressure for nine different plasma focus devices [PF50, AACS, PF400J, PF2.2, UNU-ICTP, PFZ200, PF24, PF78, Poseidon]. The computed data were compared with the published experimental results. In addition, the maximum discharge current, the pinch current and the pinch ion number density as a function of initial deuterium pressure were discussed as well as their effect on the neutron yield. The optimum pressures that correspond to the maximum neutron yield Yn were obtained for all considered devices, with reference to the specific plasma focus properties. The scaling laws for the D-D fusion neutron production, in terms of storage energies E0 and pinch current Ipinch were derived. The scaling of Yn with Ipinch and E0 over the whole range of investigated energies up to 300 kJ has been obtained as follows: (Y_n~I_pinch^5 ,Y_n~E_0^1.95 ). These laws are important for planning and designing a plasma focus as a potentially powerful pulse neutron source.

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Section: Discussionmentioning

confidence: 92%

Numerical experiments on the total D–D fusion neutron yield versus deuterium pressure for different energy plasma focus devices using the Lee model code

Wahbe¹,

Abou-Ali²,

Akel³

et al. 2023

Plasma Phys. Control. Fusion

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Magnetohydrodynamic simulations of a megaampere-class Kr-doped deuterium dense plasma focus

Narkis

Hahn

Lowe³

et al. 2021

Physics of Plasmas

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The addition of Kr dopant to a deuterium or deuterium–tritium dense plasma focus (DPF) is conventionally thought to enhance radiative cooling of the imploding sheath, resulting in a tighter pinch and, under optimized conditions, increased neutron yield [M. Krishnan, IEEE Trans. Plasma Sci. 40, 3189 (2012)]. In this work, 2D radiation magnetohydrodynamic (MHD) simulations are conducted of a DPF at peak current levels in the 2–3 MA range with Kr dopant concentrations of 0%, 0.1%, and 1.0% (by volume). Fully kinetic simulations are required to accurately model the pinch stagnation and accurately predict total neutron yield (thermonuclear + beam target), as MHD simulations cannot capture kinetic effects or beam-target neutron production. However, insights can be gained from following the evolution of the bulk dynamics of the sheath. The results show that sheath width narrows with increasing dopant concentration due to increased radiation. Thermonuclear neutron yields of ∼109−1010 are observed, which is in good agreement with experimental data [E. N. Hahn et al., J. Appl. Phys. 128, 143302 (2020)] and simulations [N. Bennett et al., Phys. Plasmas 24, 021702 (2017)] that measure yields of ∼1011 at ∼2 MA with ∼1% of that yield having thermonuclear origin. Scaling in excess of the conventional ∝I4 scaling is observed, though this should be confirmed with 3D and/or fully kinetic simulations of Kr-doped DPFs.

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Effect of insulator length and fill pressure on filamentation and neutron production in a 4.6 kJ dense plasma focus

et al. 2022

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Optimization of neutron yields from dense plasma focus devices is a complex multi-faceted challenge that necessitates the prudent selection of mechanical constraints such as the electrode and insulator geometries. Here, the neutron yield is found to significantly depend on the insulator length. As the length of the insulator increases, the exposed anode length traveled by the sheath during the run-down phase decreases. This suggests an increase in the optimal fill pressure with increasing insulator length to maintain the pinch time near peak current. However, in the present study, the opposite trend is observed—the optimal fill pressure for neutron production decreases with increasing insulator length. Optical probing of the sheath from run-down to the pinch reveals significant plasma filamentation with increasing pressure and a dependence of insulator length on filamentation onset. A direct consequence of increased filamentation is a reduction in mass sweeping efficiency, directly quantified as a function of fill pressure for the first time.

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Kinetic simulations of gas breakdown in the dense plasma focus

Cited by 7 publications

References 43 publications

Numerical experiments on the total D–D fusion neutron yield versus deuterium pressure for different energy plasma focus devices using the Lee model code

Numerical experiments on the total D–D fusion neutron yield versus deuterium pressure for different energy plasma focus devices using the Lee model code

Magnetohydrodynamic simulations of a megaampere-class Kr-doped deuterium dense plasma focus

Effect of insulator length and fill pressure on filamentation and neutron production in a 4.6 kJ dense plasma focus

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