Stability of the Dense Plasma Focus

Mather, J. W.; Bottoms, P.J.; Carpenter, J. P.; Williams, A. H.; Ware, K.

doi:10.1063/1.1692352

Cited by 32 publications

(12 citation statements)

References 1 publication

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“…INTRODUCTION I N z-PINCH and plasma focus discharges, the presence of deuterium in the load is accompanied by the production of neutrons from D-D fusion reaction according to the beam-target principle [1]- [10]. The evolution of the pinched column and neutron production can be influenced by external magnetic fields [1], [11]- [14]. In these experiments, the stabilization influence of the axial magnetic field upon the plasma column, the decrease of neutron yield, and the increase of its anisotropy (the ratio of its axial and radial signals) have all been found.…”

Section: Puffing Deuterium Compressed By a Neon Plasmamentioning

confidence: 99%

Puffing Deuterium Compressed by a Neon Plasma Sheath at the Initial Poloidal Magnetic Field in Plasma Focus Discharge

Kubeš

Paduch

Cikhardt

et al. 2015

IEEE Trans. Plasma Sci.

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This paper presents the results of the experimental study of the influence of the applied poloidal magnetic field on the transformation of the plasma column formed by the compression of (10 ± 3)-µg/cm deuterium injected by the gas-puff nozzle in front of the anode axis by the neon plasma sheath of (50 ± 10) µg/cm at a current of 2 MA. The permanent magnet with an initial induction of 20-40 mT placed inside the anode: 1) increased the diameter of the pinch and of the stagnation; 2) depressed the evolution of instabilities and formation of the dense structures in the column; 3) delayed the dip of the current derivative in time (and start of the hard X-ray and neutron emission) 200-300 ns after the first peak of the soft X-ray emission (and the pinch with a minimal diameter near the anode); and 4) decreased the total neutron yield to 10-20%. These results were interpreted in terms of the increase in the repulsive pressure of the compressed poloidal magnetic field, which increases the stabilizing helicity of the discharge current. The transformations are independent of the polarity of the magnet.Index Terms-Dense plasma focus, fusion neutron sources, interferometry diagnostics, stabilization of pinched plasma.

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Section: Puffing Deuterium Compressed By a Neon Plasmamentioning

confidence: 99%

Puffing Deuterium Compressed by a Neon Plasma Sheath at the Initial Poloidal Magnetic Field in Plasma Focus Discharge

Kubeš

Paduch

Cikhardt

et al. 2015

IEEE Trans. Plasma Sci.

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“…21 On one hand, the accelerated plasma will now lose energy on its way due to collision processes with the neutral gas, 13 but on the other hand, there is no deposited energy inside a pinch at the end of the electrodes, like it is the case in a DPF. 8 In summary, the presented work seizes the advantages of both technologies the Marshall-type plasma gun and the DPF to generate an optimized ambient for the examination of the colliding plasmas.…”

Section: Introductionmentioning

confidence: 98%

“…1,2 Still there are several groups performing collision experiments, where the plasma is generated using either pulsed plasma accelerators 3 or laser target interaction. 4 Coaxial plasma accelerators are well known as coaxial plasma guns, [5][6][7] dense plasma focus (DPF), 8 and plasma thruster. 9 Further applications for single plasma accelerators include x-ray lithography, laboratory modeling of astrophysical jets, and thruster for the propulsion in space and plasma refueling for fusion reactors.…”

Section: Introductionmentioning

confidence: 99%

Experimental characterization of a coaxial plasma accelerator for a colliding plasma experiment

et al. 2015

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We report experimental results of a single coaxial plasma accelerator in preparation for a colliding plasma experiment. The utilized device consisted of a coaxial pair of electrodes, accelerating the plasma due to J Â B forces. A pulse forming network, composed of three capacitors connected in parallel, with a total capacitance of 27 lF was set up. A thyratron allowed to switch the maximum applied voltage of 9 kV. Under these conditions, the pulsed currents reached peak values of about 103 kA. The measurements were performed in a small vacuum chamber with a neutral-gas prefill at gas pressures between 10 Pa and 14 000 Pa. A gas mixture of ArH 2 with 2.8% H 2 served as the discharge medium. H 2 was chosen in order to observe the broadening of the H b emission line and thus estimate the electron density. The electron density for a single plasma accelerator reached peak values on the order of 10 16 cm À3 . Electrical parameters, inter alia inductance and resistance, were determined for the LCR circuit during the plasma acceleration as well as in a short circuit case. Depending on the applied voltage, the inductance and resistance reached values ranging from 194 nH to 216 nH and 13 mX to 23 mX, respectively. Furthermore, the plasma velocity was measured using a fast CCD camera. Plasma velocities of 2 km/s up to 17 km/s were observed, the magnitude being highly correlated with gas pressure and applied voltage. V C 2015 AIP Publishing LLC.

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“…Some examples for coaxial plasma accelerators are plasma thruster, dense plasma focus (DPF), plasma refueling and high current switches. 3,[9][10][11][12] While there is also a long history of experiments with colliding plasmas there are still new approaches to study colliding plasmas. Some examples for colliding plasmas based on pulsed power driven accelerators (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…It was mentioned that the used coaxial plasma accelerators are a compromise between a Marshall gun 2 and a dense plasma focus (DPF) 3 with the goal to seize the advantages of both technologies in order to generate an optimized ambient for the examination of the colliding plasmas. In addition the prefilled gas environment should allow for a more precise and synchronized ignition of the plasma guns than the implementation of gas puff valves.…”

Section: Introductionmentioning

confidence: 99%

Electron density and plasma dynamics of a colliding plasma experiment

et al. 2016

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We present experimental results of two head-on colliding plasma sheaths accelerated by pulsed-power-driven coaxial plasma accelerators. The measurements have been performed in a small vacuum chamber with a neutral-gas prefill of ArH2 at gas pressures between 17 Pa and 400 Pa and load voltages between 4 kV and 9 kV. As the plasma sheaths collide, the electron density is significantly increased. The electron density reaches maximum values of ≈8 ⋅ 1015 cm−3 for a single accelerated plasma and a maximum value of ≈2.6 ⋅ 1016 cm−3 for the plasma collision. Overall a raise of the plasma density by a factor of 1.3 to 3.8 has been achieved. A scaling behavior has been derived from the values of the electron density which shows a disproportionately high increase of the electron density of the collisional case for higher applied voltages in comparison to a single accelerated plasma. Sequences of the plasma collision have been taken, using a fast framing camera to study the plasma dynamics. These sequences indicate a maximum collision velocity of 34 km/s.

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Stability of the Dense Plasma Focus

Cited by 32 publications

References 1 publication

Puffing Deuterium Compressed by a Neon Plasma Sheath at the Initial Poloidal Magnetic Field in Plasma Focus Discharge

Puffing Deuterium Compressed by a Neon Plasma Sheath at the Initial Poloidal Magnetic Field in Plasma Focus Discharge

Experimental characterization of a coaxial plasma accelerator for a colliding plasma experiment

Electron density and plasma dynamics of a colliding plasma experiment

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