Field-reversed configuration formed by in-vessel <i>θ</i>-pinch in a tandem mirror device

Lin, Min; Liu, Ming; Zhu, Guangyan; Shi, Peiyun; Zheng, Jian; Lu, Quanming; Sun, Xuan

doi:10.1063/1.5001313

Cited by 18 publications

(11 citation statements)

References 26 publications

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“…The field reversed configuration (FRC) is a compact toroid that is dominated by the poloidal magnetic field [1]. The advantages of FRC as a magnetic confinement of hightemperature plasma include the high averaged beta [2], the linear device geometry, the stability exceeding expectations from the magnetohydrodynamics (MHD) theory [3,4], and the natural divertor structure [5]. Besides these, an FRC plasma can maintain its magnetic structure during the supersonic translation [6,7] and survive the violent collision and merging process [8,9].…”

Section: Introductionmentioning

confidence: 99%

MHD simulation on magnetic compression of field reversed configurations with NIMROD

Zhu²,

Ren³

et al. 2023

Nucl. Fusion

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Magnetic compression has long been proposed a promising method for plasma heating in a field reversed configuration (FRC). However, it remains a challenge to fully understand the physical mechanisms underlying the compression process, due to its highly dynamic nature beyond the one-dimensional (1D) adiabatic theory model [R. L. Spencer et al., Phys. Fluids 26, 1564 (1983)]. In this work, magnetohydrodynamics (MHD) simulations on the magnetic compression of FRCs using the NIMROD code [C. R. Sovinec et al., J. Comput. Phys. 195, 355 (2004)] and their comparisons with the 1D theory have been performed. The effects of the assumptions of the theory on the compression process have been explored, and the detailed profiles of the FRC during compression have been investigated. The pressure evolution agrees with the theoretical prediction under various initial conditions. The axial contraction of the FRC can be affected by the initial density profile and the ramping rate of the compression magnetic field, but the theoretical predictions on the FRC's length in general and the relation r s=√2 r o in particular hold approximately well during the whole compression process, where r s is the major radius of FRC separatrix and r o is that of the magnetic axis. The evolutions of the density and temperature can be affected significantly by the initial equilibrium profile and the ramping rate of the compression magnetic field. During the compression, the major radius of the FRC is another parameter that is susceptible to the ramping rate of the compression field. Basically, for the same magnetic compression ratio, the peak density is higher and the FRC's radius r s is smaller than the theoretical predictions.

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Section: Introductionmentioning

confidence: 99%

MHD simulation on magnetic compression of field reversed configurations with NIMROD

Zhu²,

Ren³

et al. 2023

Nucl. Fusion

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“…A high current with a fast rise time in the scale of microsecond and a long pulse duration is needed in plasma physics research, such as field-reversed configuration (FRC) [1][2][3], magnetized target fusion (MTF) [2,[4][5][6], and tokamak [7]. To obtain a high current with a fast front edge, a method of discharging the charge of energy storage capacitors into an inductive load is generally adopted.…”

Section: Introductionmentioning

confidence: 99%

“…A so-called "crowbar" technique [8][9][10][11][12] for preventing the oscillation of circuit and energy re-storage in the capacitors was proposed, that is, the energy storage capacitors are short-circuited at about current maximum. Crowbar system mainly consists of low inductance capacitors, main and crowbar switches for the capacitors, and an inductive load [3,13]. When all of the energy from the charged capacitors is transferred to inductive load and converted to magnetic energy, i.e.…”

Section: Introductionmentioning

confidence: 99%

High-voltage and high-current crowbar system based on pseudospark switches: from system design to verification

et al. 2020

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This paper presents a high-voltage and high-current crowbar system using pseudospark switches to produce a fast front edge and prolonged pulse current with low ripple amplitude. The crowbar system mainly consists of a main switch, a crowbar switch, an energy storage capacitor, and an inductive load. The basic parameters of the pseudospark switch crowbar system: the storage capacitance is 5 µF, the typical operation voltage is 30 kV, the peak discharge current is about 46.2 kA, the rise time is 4.3 µs, and the pulse duration time is approximately 109 µs, which is nearly 25 times of the rise time. In this paper, we report the timing setting for crowbar system. Experimental results show that crowbar timing should be set slightly after first current maximum, which has a great advantage of increasing the time scale without any reduction in the loss-free peak current. In addition, the pulse current characteristics are also studied. In the research, crowbar inductance L c and crowbar resistance R c have significant effects on the ripple amplitude and load current amplitude of pulse current. The experimental results also show that the crowbar current I c can reach nearly twice of the coil load current I load with low crowbar inductance L c . The over-current capacity of the crowbar switch needs to be greater than that of the main switch. The experimental results in this paper can be used to optimize the inductive load current in high-voltage and high-current crowbar system. K: Pulsed power; Plasma generation (laser-produced, RF, x ray-produced)1Corresponding author.

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“…For collision-merging FRCs, the kinetic energy can be transferred to the thermal energy through a magnetic reconnection process. As demonstrated in the C2-U (C2-Upgrade), the world's largest CT, after merging two FRCs with speeds of more than 200 km s −1 , the merged FRC typically had an electron density of ñe -´- The experiments reported in this paper were conducted on the KMAX (Keda Mirror with AXisymmetricity) mirror machine, and the FRCs were formed by conical θ-pinch placed inside the central cell near two mirror throats [12]. Similar to other translated FRC experiments, the FRC was ejected into a uniform magnetic field region.…”

Section: Introductionmentioning

confidence: 99%

Translation speed measurements of hydrogen, helium, and argon field-reversed configurations in the central cell of a KMAX mirror device

Liao¹,

Lin²,

Liu³

et al. 2019

Plasma Sci. Technol.

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A series of experimental results of field-reversed configurations (FRCs) on a KMAX (Keda Mirror with AXisymmetricity) tandem mirror machine are reported. Single-side FRC translation processes with three different gas species were measured by avalanche photodiodes. Consistent with the theoretical prediction, the measured FRC speeds were inversely proportional to the square root of the ion mass. However, the speeds of the hydrogen FRC increased even in a uniform magnetic field region while the speeds of the helium and argon FRCs decreased. Possible mechanisms are discussed. The speed of the second pass due to the reflection of the mirror fields was found to be ∼1/3 of the first pass speed. The internal magnetic fields were measured for a colliding-merging argon FRC, and the results show that, even for very slowmoving FRCs, merging can occur.

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Field-reversed configuration formed by in-vessel θ-pinch in a tandem mirror device

Cited by 18 publications

References 26 publications

MHD simulation on magnetic compression of field reversed configurations with NIMROD

MHD simulation on magnetic compression of field reversed configurations with NIMROD

High-voltage and high-current crowbar system based on pseudospark switches: from system design to verification

Translation speed measurements of hydrogen, helium, and argon field-reversed configurations in the central cell of a KMAX mirror device

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