Study of magnetic fields and current in the Z pinch at stagnation

Иванов, В. В.; Anderson, Andrew A.; Papp, Dóra; Astanovitskiy, A. L.; Nalajala, V.; Dmitriev, O.

doi:10.1063/1.4931079

Cited by 15 publications

(8 citation statements)

References 30 publications

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“…We note that previous measurements in classical Zpinches have indicated that during the stagnation some of the current is carried by an imploding trailing plasma [25,31]. However, here we show a completely different phenomenon that is directly related to the presence of an applied B z .…”

supporting

confidence: 49%

“…However, reliable experimental data on the B-field distribution in Z-pinches are scarce due to the high electron densities, high ion velocities, and transient nature of the plasma, which make measurements of B-fields in such plasmas rather difficult. We note a few examples of such spectroscopic measurements in gas-puff Z-pinches [22][23][24], and measurements based on Faraday rotation in wire-array Z-pinches [25].…”

mentioning

confidence: 99%

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Effects of a Preembedded Axial Magnetic Field on the Current Distribution in a Z -Pinch Implosion

et al. 2019

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supporting

confidence: 49%

mentioning

confidence: 99%

Effects of a Preembedded Axial Magnetic Field on the Current Distribution in a Z -Pinch Implosion

et al. 2019

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“…Specifically, we measure that during stagnation the current transitions out of the SP and into a low density plasma (LDP), residing at much larger radii, while the SP continues to implode. This phenomenon might be connected to the previous observations of low current in the SP of Zpinches [11,20,[24][25][26], and might be common to various pulsed-power systems, including those of lower density plasmas [11], such as plasma switches [12][13][14] and high power transmission lines [15,16].…”

Section: Introduction -supporting

confidence: 66%

“…Note that applying the same analysis for locations farther away from the cathode, a gradually changing behavior is found: at distances of 3 mm and 5 mm from the cathode, the discharge current is never observed to flow at small radii [30], consistent with the absence of significant current in the stagnating plasma seen in previous experiments [11,20,[24][25][26].…”

Section: Introduction -supporting

confidence: 56%

“…A few experimental studies have measured the timedependent magnetic field radial distribution in the imploding Z-pinch plasma [22][23][24][25]; those that were performed at the time of stagnation [24][25][26], outside the SP but close enough to it, confirmed the flow of only a small fraction of the current in this plasma. However, in the present work, the temporal evolution of the current density radial distribution was determined down to the small radius of the SP and, in particular, with a high spatial resolution.…”

Section: Introduction -mentioning

confidence: 99%

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Observation of fast current redistribution in an imploding plasma column

Stollberg¹,

Kroupp²,

Mikitchuk³

et al. 2021

Preprint

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Spectroscopic measurements of the magnetic field evolution in a Z-pinch throughout stagnation and with particularly high spatial resolution reveal a sudden current redistribution from the stagnating plasma (SP) to a low density plasma (LDP) at larger radii, while the SP continues to implode. Based on the plasma parameters it is shown that the current is transferred to an increasingconductance LDP outside the stagnation, a process likely to be induced by the increasing impedance of the SP. Since an LDP often exists around imploding plasmas and in various pulsed-power systems, such a fast current redistribution may dramatically affect the behavior and achievable parameters in these systems.

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Coulomb explosion of “hot spot”

Oreshkin

Chaikovsky

et al. 2016

Physics of Plasmas

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The study presented in this paper has shown that the generation of hard x rays and highenergy ions, which are detected in pinch implosion experiments, may be associated with the Coulomb explosion of the hot spot that is formed due to the outflow of the material from the pinch cross point. During the process of material outflow, the temperature of the hot spot plasma increases, and conditions arise for the plasma electrons to become continuously accelerated. The runaway of electrons from the hot spot region results in the buildup of positive space charge in this region followed by a Coulomb explosion. The conditions for the hot spot plasma electrons to become continuously accelerated have been revealed and estimates have been obtained for the kinetic energy of the ions generated by the Coulomb explosion.A Z pinch is an electrical discharge in plasma, which is compressed under the action of the magnetic pressure produced by the intrinsic discharge current [1][2][3][4][5][6][7]. Typical of Z pinches is the formation of hot spots due to the development of large-scale MHD instabilities [1,2,8-10].The discharge plasma column is deformed during compression, which is accompanied by the formation of necks smaller in radius than the main column. The magnetic pressure in the neck region increases, resulting, first, in faster compression and, second, in material outflow from the neck region in the axial direction. The final stage of the necking is a hot spot.Apparently, the axial jets were first detected in an experimental study [11] where the process of compression of deuterium pinches was investigated. As these jets were accounted for by an increase in neutron yield, the authors of Ref.[11] proposed a "noncylindrical Z pinch" in which the formation of the hot spot was predetermined by the geometry of the discharge.Subsequently, this configuration was called a plasma focus [12,13]. In subsequent experiments on a deuterium plasma focus at currents of about 1 MA, electron beams, hard x rays, and "epithermal" deuterons with energies up to 8 MeV were detected [14]. Even more energetic deuterons with energies of several tens of megaelectron-volts were detected in experiments with deuterium liners imploded at a current of 2.7 MA [15]. To explain the generation of high-energy ions and hard x rays, the so-called "target" mechanism was proposed [16]. It is assumed that in the final stage of formation of the hot spot, displacement currents occur that generate strong electric fields in which charged particles are accelerated.

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Study of magnetic fields and current in the Z pinch at stagnation

Abstract: Magnetic field measurements via visible spectroscopy on the Z machine Review of Scientific Instruments 85, 11E609 (2014);

Cited by 15 publications

References 30 publications

Effects of a Preembedded Axial Magnetic Field on the Current Distribution in a Z -Pinch Implosion

Effects of a Preembedded Axial Magnetic Field on the Current Distribution in a Z -Pinch Implosion

Observation of fast current redistribution in an imploding plasma column

Coulomb explosion of “hot spot”

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