On the plasma quasineutrality under oscillatory confinement based on a nanosecond vacuum discharge

Abstract

One of the main problems for inertial electrostatic confinement devices with electron injection is the space charge neutralization. This work is devoted to the analysis of the problem of plasma quasineutrality in the scheme of plasma oscillatory confinement based on nanosecond vacuum discharge (NVD). Electrodynamics modeling of the processes of aneutronic fusion of proton–boron showed that the plasma in the NVD, and especially on the discharge axis, really corresponds to a quasineutral regime, which is rather different from the well-known scheme of periodically oscillating plasma spheres (POPS). In this case, small oscillations in the NVD are a mechanism of resonant ion heating, unlike coherent compressions in the original POPS model. The scaling of the fusion power turns out to be close to the fusion scheme with POPS, but differs significantly in the values of the parameter of quasineutrality and the compression ratio.

Oscillating Plasmas for Proton- Boron Fusion in Miniature Vacuum Discharge

“…In fact, oscillatory confnement in NVD also uses small POPS-type oscillations to heat the plasma [20,41]. Present PiC simulations (as well as preliminary ones [42]) are showing that the oscillating plasma in the NVD near and on the discharge axis represents a rather quasineutral mode (Figure 4(d)), where the value of the parameter η can reach ∼100. Also, we can estimate the compression ratio value as just θ < 10 if comparing charge densities on the discharge axis (Figure 4(b)) and far from the axis (Figure 3).…”

“…So we see that the plasma in the close vicinity of the discharge axis is almost a quasineutral one n i (t) ≈ n e (t) not only at individual moments of time but also during almost the entire time of simulation t = 20 ns (Figure 4(d)). Similar quasineutrality is available also for slower voltage rise ∆t f = 5 ns [42]. Remark, in the region of the anode space r ≈ 0.1 cm, electrons, decelerating and unfolding, form a VC with a large electron density (Figure 1), and the deviation from quasineutrality there naturally should be maximal (Figure 4(c)).…”

“…Note that, fast boron ions appear for the voltage front ∆t f ≈ 2 ns only in the time interval 4-5 ns (Figure 2(b)), while for the voltage front ∆t f = 1 ns they will appear already at 2-3 ns (not shown here), and also earlier than for ∆t f ≈ 2 ns the frst α particles will appear here (Section 4). For a voltage front ∆t f = 5 ns, fast boron ions and α particles will appear as in the frst case at interval 4-5 ns (the results of 2D PiC simulations for the case of slower voltage rise ∆t f = 5 are presented in [42]).…”

“…In particular, the type of DF and the specifcs of the oscillations and confnement of boron ions are afected, for example, by the rate ∆t f in increase of the high voltage applied. In fact, with a slower voltage increase such as ∆t f = 5 ns [42], it is possible to obtain a "more Maxwellian" type of DF and a more stable acceleration and confnement of ions during their oscillations in potential well (Figure 2(b) in [42]) in comparison with the case ∆t f = 1 ns (not shown here), where the part of boron ions can leave rather deep PW (Figure 2(a)) along the axis Z.…”

“…Tis paper discusses and compares the features and capabilities of oscillating plasmas for nuclear fusion both in the POPS scheme [29,31,34] and the OSCO regime based on NVD [20,[35][36][37][38][39][40][41]. Te study of a fundamental issue for IEC devices with electron injection as neutralization of the spatial charge started for NVD recently [42] and is developing further. Some prehistory and specifcs of DD and pB nuclear synthesis study based on NVD are given in Section 2.…”