Bayesian inference of spectrometric data and validation with numerical simulations of plasma sheath diagnostics of a plasma focus discharge

Avaria, Gonzalo; Clausse, Alejandro; Davis, Sergio; Pavez, Cristian; Villalba, Nelson; Cuadrado, Osvaldo; Moreno, José; Ruiz, H. M.; Soto, Leopoldo

doi:10.1038/s41598-022-19764-7

Cited by 4 publications

(2 citation statements)

References 48 publications

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“…In addition, a high-density toroidal structure (curly type) is observed, which surrounds the plasma sheet in an intermediate section. This toroidal structure has been identified with interferometry in the PF-50J generator [36] and with spectroscopic techniques [37] and interferometry [18] in the PF-400J generator. This toroidal structure has its origin in the lower part of the anode, next to the upper edge of the insulator.…”

Section: Resultsmentioning

confidence: 97%

New evidence about the nature of plasma filaments in plasma accelerators of type plasma-focus

Pavez¹,

Zorondo²,

Pedreros³

et al. 2022

Plasma Phys. Control. Fusion

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In this work, new evidence and information about both the origin and evolution of filamentary structures observed in the current sheath of a small plasma focus discharge are reported. The experiments were carried out in a small generator of low energy (multipurpose generator MPG), at the plasma focus configuration, under different operation conditions. These include different anode and insulator geometries, without return bars and a high-performance regime of the generator at high pressures (> 10 mbar). The evolution of the plasma structures is characterized by mean of refractive optical techniques. The electrical behavior of the discharge, as well as its performance, are monitored with conventional electrical diagnostics and neutron and X-ray detectors, respectively. Plasma filaments of the same species are present in all tested configurations, however, in those with a large effective anode length (and smaller anode radius), the plasma region containing the filaments moves away from the anode surface and it is confined in a region of the plasma sheath, such as a toroidal plasma belt, without reaching the anode top nor participating in the radial compression phase. According to images of the plasma sheath in its early phase, the filaments originate and evolve from a precursor annular plasma formed in the lower part of the anode next to the insulator, in the process of electrical breakdown. The local character that these dense-filamentary structures acquire in the evolution of the plasma sheath would discard the current-filament hypothesis. On the other hand, in experiments in deuterium gas with a large effective anode length and without filaments in the radial compression phase, a high performance at the neutron and X-rays production were obtained.

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Section: Resultsmentioning

confidence: 97%

New evidence about the nature of plasma filaments in plasma accelerators of type plasma-focus

Pavez¹,

Zorondo²,

Pedreros³

et al. 2022

Plasma Phys. Control. Fusion

Self Cite

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“…The characteristics required for pulsedpower drivers include fast rise time (~100-ns), high current (>1-MA), high voltage (>1-MV), high efficiency (>85%), and repeatability (>0.1-Hz) 12 . While conventional fast discharge capacitor banks have been used in devices that drive dense plasma focuses and Z-pinches [13][14][15][16][17][18][19] , they have limitations in achieving the high voltage and short rise time necessary for pulsed fusion approaches and NGPP facilities. Recent Marx generator technologies have been able to produce higher voltages with a faster rise time than conventional capacitor banks, however, the high voltages present in the latest stages (peaking/steepening switches) of the generators result in short switch lifetimes 20 .…”

Section: Introductionmentioning

confidence: 99%

Experimental results of a 330 GW impedance-matched Marx generator

Damideh,

Btaiche,

et al. 2024

Preprint

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Impedance-Matched Marx Generators (IMGs) are considered next generation pulsed-power drivers because of their long lifetime (> 10,000 shots), repeatability (> 0.1-Hz), fast rise time (~ 100-ns), and high-energy-delivery efficiency (~ 90%). “TITAN” is a 14-stage IMG designed to deliver 1-TW to a 2-Ω matched load. In this paper, design, simulation, and experimental results for six stages of TITAN including its triggering system, air delivery system, and pulse shaping are presented. To achieve efficiency over 85% and maximize the capability of an IMG, synchronized triggering, reduced pre-fire rate, and pulse shaping ability are crucial. In this paper, novel engineering solutions are introduced, tested, and proven to overcome those challenges. 6-stage TITAN, powered by 102 identical bricks and 102 field-distortion-triggered gas switches, could generate ~ 600-kA and ~ 700-kV across a ~ 0.9-Ω matched load when fully charged to +/- 100-kV. In these experiments, 6-stage TITAN is tested up to +/- 70-kV charge voltage which delivers a peak power of 330-GW to a 1.2-Ω resistive load.

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Bayesian inference of plasma parameters from collective Thomson scattering technique on a gas-puff near stagnation

Escalona,

Valenzuela,

Avaria

et al. 2023

Sci Rep

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The Collective Thomson scattering technique has been implemented to study the stagnation of a single liner gas-puff. The plasma parameters are determined by theoretically modelling the scattering form factor in combination with Bayesian inference to provide the set of the most probable parameters that describe the experimental data. Analysis of the data reveal that incoming flows are able to interpenetrate partially. Estimation of the mean free path shows a gradual transition from a weakly collisional to a collisional regime as the plasma gets to the axis. Furthermore, we find that the ion energy at $$\mathrm{r}=2.5\,\mathrm{mm}$$ r = 2.5 mm is $${13.6}_{-0.9}^{+1.0}\,\mathrm{keV}$$ 13.6 - 0.9 + 1.0 keV and is mostly kinetic in nature and represents $${98}_{-9}^{+10} \%$$ 98 - 9 + 10 % of the total energy. This kinetic energy is far greater than the value on axis of $${3.7}_{-0.5}^{+0.4}\,\mathrm{keV}$$ 3.7 - 0.5 + 0.4 keV which is $${84}_{-14}^{+15} \%$$ 84 - 14 + 15 % of the total energy. Energy transfer to the electrons and radiation losses are found to be negligible by this time. A possible explanation for this energy imbalance is the presence of an azimuthal magnetic field larger than $$\sim 4.7\,\mathrm{T}$$ ∼ 4.7 T that deflect the ions vertically. The uncertainties quoted represent 68% credible intervals.

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Bayesian inference of spectrometric data and validation with numerical simulations of plasma sheath diagnostics of a plasma focus discharge

Cited by 4 publications

References 48 publications

New evidence about the nature of plasma filaments in plasma accelerators of type plasma-focus

New evidence about the nature of plasma filaments in plasma accelerators of type plasma-focus

Experimental results of a 330 GW impedance-matched Marx generator

Bayesian inference of plasma parameters from collective Thomson scattering technique on a gas-puff near stagnation

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