Filamentary structure of the pinch column in plasma focus discharges

Sadowski, M.; Herold, H.; Schmidt, H.; Shakhatre, M.

doi:10.1016/0375-9601(84)90650-9

Cited by 64 publications

(46 citation statements)

References 5 publications

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“…In almost all shots with the deuterium gas-puffi ng and pure neon as working gas it was found that X-rays are emitted mostly from the injected gas. The appearance of distinct plasma fi laments even during the maximum compression of the PF pinch column was for the fi rst time observed in the POSEIDON facility [3]. In the past years the formation of such fi laments has had been observed in many Z-pinch type experiments [5].…”

Section: Experimental Results: Time-integrated Imagesmentioning

confidence: 93%

“…(about 1 cm 3 , at the pressure of 1500 Torr) along the anode axis. That gas injection was usually performed about 1.5-2 ms before the main discharge triggering.…”

Section: Figmentioning

confidence: 99%

“…Moreover, with this technique it is possible to observe such phenomena as 'hot-spots' and 'fi lament' appearing in particular during the phase of maximum compression [3].…”

Section: Introductionmentioning

confidence: 99%

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Recent measurements of soft X-ray emission from the DPF-1000U facility

et al. 2015

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Abstract. Soft X-ray imaging is a very useful diagnostic technique in plasma-focus (PF) experiments. This paper reports results of four experimental sessions which were carried out at the DPF-1000U plasma-focus facility in 2013 and 2014. Over 200 discharges were performed at various experimental conditions. Measurements were taken using two X-ray pinhole cameras with a line of sight perpendicular to the z-axis, at different azimuthal angles (about 20° and 200°), and looking towards the centre of the PF-pinch column. They were equipped with diaphragms 1000 m or 200-300 m in diameter and coated with fi lters of 500 m Al foil and 10 m Be foil, respectively. Data on the neutron emission were collected with silver activation counters. For time-resolved measurements the use was made of four PIN diodes equipped with various fi lters and oriented towards the centre of the PF-column, in the direction perpendicular to the electrode axis. The recorded X-ray images revealed that when the additional gas-puff system is activated during the discharge, the stability of the discharge is improved. The data collected in these experiments confi rmed the appearance of a fi lamentary fi ne structure in the PF discharges. In the past years the formation of such fi laments was observed in many Z-pinch type experiments. Some of the recorded X-ray images have also revealed the appearance of the so-called hot--spots, i.e. small plasma regions of a very intense X-ray emission. Such a phenomenon was observed before in many PF experiments, e.g. in the MAJA-PF device, but it has not been investigated so far in a large facility such as the DPF-1000U. The time-resolved measurements provided the evidence of a time lapse between the X-ray emission from plasma regions located at different distance from the anode surface. The formation of distinct 'hot-spots' in different instants of the DPF-1000U discharge was also observed.

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Section: Experimental Results: Time-integrated Imagesmentioning

confidence: 93%

“…(about 1 cm 3 , at the pressure of 1500 Torr) along the anode axis. That gas injection was usually performed about 1.5-2 ms before the main discharge triggering.…”

Section: Figmentioning

confidence: 99%

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Recent measurements of soft X-ray emission from the DPF-1000U facility

et al. 2015

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“…Experimental research on X-rays and electron beams, as well as ion beams and fusion products that are emitted from PF-type discharges has been carried out with different PF facilities in various laboratories for many years [1][2][3][4][5][6][7][8], but there are still some unsolved questions concerning mechanisms and characteristics of these electromagnetic and corpuscular emissions.…”

Section: Introductionmentioning

confidence: 99%

“…One of possible explanations is a hypothesis that some electrons are accelerated inside miniature plasma diodes, which can be formed due to magnetohydrodynamic (MHD) instabilities of current fi laments observed in PF discharges, and particularly inside pinch columns [1,4]. This hypothesis has been partially confi rmed by experimental observations of current fi laments and Measurements of fast electron beams and soft X-ray emission from plasma-focus experiments so-called hot spots (i.e., microregions of an increased X-ray emission) observed on soft X-ray pinhole images, but there is no theoretical model that might be used to compute dimensions and characteristics of such fi laments and hot spots [9,10].…”

Section: Introductionmentioning

confidence: 99%

Measurements of fast electron beams and soft X-ray emission from plasma-focus experiments

et al. 2016

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Abstract. The paper reports results of the recent experimental studies of pulsed electron beams and soft X-rays in plasma-focus (PF) experiments carried out within a modifi ed PF-360U facility at the NCBJ, Poland. Particular attention was focused on time-resolved measurements of the fast electron beams by means of two different magnetic analyzers, which could record electrons of energy ranging from about 41 keV to about 715 keV in several (6 or 8) measuring channels. For discharges performed with the pure deuterium fi lling, many strong electron signals were recorded in all the measuring channels. Those signals were well correlated with the fi rst hard X-ray pulse detected by an external scintillation neutron-counter. In some of the analyzer channels, electron spikes (lasting about dozens of nanoseconds) and appearing in different instants after the current peculiarity (so-called current dip) were also recorded. For several discharges, fast ion beams, which were emitted along the z-axis and recorded with nuclear track detectors, were also investigated. Those measurements confi rmed a multibeam character of the ion emission. The time-integrated soft X-ray images, which were taken side-on by means of a pinhole camera and sensitive X-ray fi lms, showed the appearance of some fi lamentary structures and so-called hot spots. The application of small amounts of admixtures of different heavy noble gases, i.e. of argon (4.8% volumetric), krypton (1.6% volumetric), or xenon (0.8% volumetric), decreased intensity of the recorded electron beams, but increased intensity of the soft X-ray emission and showed more distinct and numerous hot spots. The recorded electron spikes have been explained as signals produced by quasi-mono-energetic microbeams emitted from tiny sources (probably plasma diodes), which can be formed near the observed hot spots.

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3D modelling of ion motion within dynamic filamentary PF-pinch column

2000

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The paper reports on the results of a 3-D modelling of ion motion within the plasma focus (PF) pinch column, which is treated as a filamentary, non-stationary system. Besides magnetic fields, also the induced electrical fields as well as the ion-ion and ion-electron collisions have been included in the equations of ion (deuteron) motion. The results obtained show that the filamentary structure influences the 3-D ion trajectories and 2-D angular distribution of ions. It has been confirmed that 3-D flower-like filaments can explain some important characteristics of the ion emission from PF discharges.

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Filamentary structure of the pinch column in plasma focus discharges

Cited by 64 publications

References 5 publications

Recent measurements of soft X-ray emission from the DPF-1000U facility

Recent measurements of soft X-ray emission from the DPF-1000U facility

Measurements of fast electron beams and soft X-ray emission from plasma-focus experiments

3D modelling of ion motion within dynamic filamentary PF-pinch column

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