Mirror ratio scaling of axial confinement of a mirror-trapped collisional plasma

Lam, Kwok L.; Leikind, B.; Wong, A. Y.; Dimonte, Guy; Kuthi, A.; Olson, Lynn; Zwi, H.

doi:10.1063/1.865859

Cited by 10 publications

(9 citation statements)

References 7 publications

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“…42), where Λ m is the primary mirror ratio. This estimate is expected to hold when the pitch angle scattering time of mirror-trapped ions exceeds the collisional parallel mirror confinement time43 τ ∥c = L SOL Λ m /2(0.3 c s )∼0.5 ms. Here, L SOL is the distance from the FRC midplane to the axial endplates.…”

Section: Resultsmentioning

confidence: 96%

Suppressed ion-scale turbulence in a hot high-β plasma

et al. 2016

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An economic magnetic fusion reactor favours a high ratio of plasma kinetic pressure to magnetic pressure in a well-confined, hot plasma with low thermal losses across the confining magnetic field. Field-reversed configuration (FRC) plasmas are potentially attractive as a reactor concept, achieving high plasma pressure in a simple axisymmetric geometry. Here, we show that FRC plasmas have unique, beneficial microstability properties that differ from typical regimes in toroidal confinement devices. Ion-scale fluctuations are found to be absent or strongly suppressed in the plasma core, mainly due to the large FRC ion orbits, resulting in near-classical thermal ion confinement. In the surrounding boundary layer plasma, ion- and electron-scale turbulence is observed once a critical pressure gradient is exceeded. The critical gradient increases in the presence of sheared plasma flow induced via electrostatic biasing, opening the prospect of active boundary and transport control in view of reactor requirements.

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Section: Resultsmentioning

confidence: 96%

Suppressed ion-scale turbulence in a hot high-β plasma

et al. 2016

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“…The total number of particles in the device N R is governed by the simple differential equation shown in equation (34), where G is the fueling rate and τ c is the particle confinement time which represents the mean time to empty all the particles inside the volume of plasma. In the simple case of an isotropic plasma, usually a good approximation for a low temperature helicon plasma, the particle confinement time is given by equation ( 35) [59] where R is the mirror ratio, L is the mirror-to-mirror length and C s is the ion sound speed. This expression is only valid for plasmas which have a fully populated loss-cone distribution.…”

Section: Mpex: Helicon-only Dischargesmentioning

confidence: 99%

Parallel transport modeling of linear divertor simulators with fundamental ion cyclotron heating ^*

et al. 2023

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The Material Plasma Exposure eXperiment (MPEX) is a steady state linear device with the goal to perform plasma material interaction (PMI) studies at future fusion reactor relevant conditions. A prototype of MPEX referred as ‘Proto-MPEX’ is designed to carry out research and development related to source, heating and transport concepts on the planned full MPEX device. The auxiliary heating schemes in MPEX are based on cyclotron resonance heating with radio frequency (RF) waves. Ion cyclotron heating (ICH) and electron cyclotron heating (ECH) in MPEX are used to independently heat the ions and electrons and provide fusion divertor conditions ranging from sheath-limited to fully detached divertor regimes at a material target. A Hybrid Particle-In-Cell code- PICOS++ is developed and applied to understand the plasma parallel transport during ICH in MPEX/Proto-MPEX to the target. With this tool, evolution of the distribution function of MPEX/Proto-MPEX ions is modeled in the presence of (1) Coulomb collisions, (2) volumetric particle sources and (3) quasi-linear RF-based ICH. The code is benchmarked against experimental data from Proto-MPEX and simulation data from B2.5 EIRENE. The experimental observation of “density-drop” near the target in Proto-MPEX and MPEX during ICH is demonstrated and explained via physics-based arguments using PICOS++ modeling. In fact, the density drops at the target during ICH in Proto-MPEX/MPEX to conserve the flux and to compensate for the increased flow during ICH. Furthermore, sensitivity scans of various plasma parameters with respect to ICH power are performed for MPEX to investigate its role on plasma transport and particle and energy fluxes at the target.

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“…For cases where  / l ^L 1, m charged particles are more likely to adiabatically bounce between field ripples; while for  / l ^L 1, m charged particles are more likely to experience randomizing collisions before reflecting from field ripples. For conditions where  / l ^L 1, m adiabatic effects are significantly lessened and plasma transport along field lines behaves 'gas-dynamically' [17][18][19][20].…”

Section: Adiabatic Effects and Coulomb Collisionsmentioning

confidence: 99%

Effect of magnetic field ripple on parallel electron transport during microwave plasma heating in the Proto-MPEX linear plasma device

Caneses

Spong

Lau

et al. 2020

Plasma Phys. Control. Fusion

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The Prototype Material Plasma Exposure eXperiment (Proto-MPEX) is a linear plasma device located at Oak Ridge National Laboratory to develop the plasma source concept for the Materials Plasma Exposure eXperiment (MPEX). Recent experiments have demonstrated the heating of electrons in a high-density deuterium plasma ( ~´n 5 10 m e 193 ) via electron Bernstein waves and source plasma production via helicon waves in this linear configuration. Moreover, experimental observations suggest that the magnetic ripple adversely affects the parallel transport of the heated electrons toward the target where material samples are to be exposed to the plasma. To understand the transport process during microwave application, a test-particle Monte-Carlo (MC) code has been developed that incorporates the effects of Coulomb collisions, magnetic mirror adiabatic trapping and electron cyclotron interaction via a quasilinear RF heating operator. MC calculations indicate that the absence of 2nd turning points along the trajectory of cyclotron heated electrons significantly reduces adiabatic trapping and maximizes power transport to the Target surface. Thermalization of cyclotron heating electrons is analyzed with the MC code and it is found that for conditions relevant to Proto-MPEX, a significant fraction of the absorbed heating power is coupled to the Target surface via ballistic fast electrons; however, under certain conditions, up to 60% of the absorbed RF power can be dissipated via thermalization of the fast electrons on the background plasma. Results are compared with experimental measurements. Finally, the implications of the results are discussed in the context of the upcoming MPEX device.

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Mirror ratio scaling of axial confinement of a mirror-trapped collisional plasma

Abstract: Articles you may be interested inEffect of a plasma sheath and ion injection on axial particle and energy confinement in a collisional mirror plasma Phys. Plasmas 1, 1359 (1994); 10.1063/1.870735Line tying of interchange modes in a nearly collisionless mirrortrapped plasma Phys.

Cited by 10 publications

References 7 publications

Suppressed ion-scale turbulence in a hot high-β plasma

Suppressed ion-scale turbulence in a hot high-β plasma

Parallel transport modeling of linear divertor simulators with fundamental ion cyclotron heating ^*

Effect of magnetic field ripple on parallel electron transport during microwave plasma heating in the Proto-MPEX linear plasma device

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Mirror ratio scaling of axial confinement of a mirror-trapped collisional plasma

Abstract: Articles you may be interested inEffect of a plasma sheath and ion injection on axial particle and energy confinement in a collisional mirror plasma Phys. Plasmas 1, 1359 (1994); 10.1063/1.870735Line tying of interchange modes in a nearly collisionless mirrortrapped plasma Phys.

Cited by 10 publications

References 7 publications

Suppressed ion-scale turbulence in a hot high-β plasma

Suppressed ion-scale turbulence in a hot high-β plasma

Parallel transport modeling of linear divertor simulators with fundamental ion cyclotron heating *

Effect of magnetic field ripple on parallel electron transport during microwave plasma heating in the Proto-MPEX linear plasma device

Contact Info

Product

Resources

About

Parallel transport modeling of linear divertor simulators with fundamental ion cyclotron heating ^*