On the leak width of line- and point-cusp magnetic fields

Kozima, Hideo; Kawamoto, Shinji; Yamagiwa, Kazuaki

doi:10.1016/0375-9601(81)90560-0

Cited by 14 publications

(11 citation statements)

References 4 publications

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“…But the discontinuities in the confining field in the boundary leak the plasma through the cusp regions. The exact scaling for the amount of plasma leaking is not known, though many scaling exists ranging from ion gyro-radius to electron gyro-radius apart from the so-called 'hybrid gyroradius' [10][11][12][13][14]. Also the various fluctuations present in the edge regions (low Beta) and their effect on the central high beta region have not been studied before.…”

Section: Introductionmentioning

confidence: 99%

A new multi-line cusp magnetic field plasma device (MPD) with variable magnetic field

Patel

Sharma

Ramasubramanian

et al. 2018

Review of Scientific Instruments

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A new multi-line cusp magnetic field plasma device consisting of electromagnets with core material has been constructed with a capability to experimentally control the relative volume fractions of magnetized to unmagnetized plasma volume as well as accurate control on the gradient length scales of mean density and temperature profiles. Argon plasma has been produced using a hot tungsten cathode over a wide range of pressures 5 × 10 -1 × 10 mbar, achieving plasma densities ranging from 10 to 10 cm and the electron temperature in the range 1-8 eV. The radial profiles of plasma parameters measured along the non-cusp region (in between two consecutive magnets) show a finite region with uniform and quiescent plasma, where the magnetic field is very low such that the ions are unmagnetized. Beyond that region, both plasma species are magnetized and the profiles show gradients both in temperature and density. The electrostatic fluctuation measured using a Langmuir probe radially along the non-cusp region shows less than 1% (δI/I < 1%). The plasma thus produced will be used to study new and hitherto unexplored physics parameter space relevant to both laboratory multi-scale plasmas and astrophysical plasmas.

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Section: Introductionmentioning

confidence: 99%

A new multi-line cusp magnetic field plasma device (MPD) with variable magnetic field

Patel

Sharma

Ramasubramanian

et al. 2018

Review of Scientific Instruments

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show abstract

“…For plasma density, cusp loss width on the order of 2ðr e r i Þ 1=2 has been reported experimentally, [1][2][3][4] where r e and r i are the electron and ion Larmor radii, respectively. In another experiment, cusp loss width of the order of r i has also been reported.…”

Section: Introductionmentioning

confidence: 85%

Estimation of Width of Electron Energy Loss Region in Cusp Magnetic Field in Negative Ion Sources

Fukano

Hatayama

Ogasawara

2007

jjap

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The loss width of electron energy in the cusp magnetic field in negative ion sources is investigated analytically. Energy equation and continuity equation for electrons are solved with heat flux and particle flux parallel and perpendicular to the magnetic field. Electron energy and density perpendicular to the magnetic field are assumed to decrease exponentially with each decay length and the cusp loss width is defined by the doubling of the decay length. An expression of the ratio of the cusp loss width of electron energy to that of electron density is obtained. The ratio of the cusp loss width depends on electron collision frequencies across the magnetic field and a heat transmission coefficient defined by the ratio of the heat flux to the particle flux multiplied by the electron temperature along the magnetic field. The heat transmission coefficient is related to the sheath potential on the wall surface. Both parameter dependence and the calculated value of the cusp loss width of electron energy derived from our analysis are in good agreement with Horiike et al.'s experimental result for the magnetic multipole ion source.

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“…In the case of cusp magnetic field formed by arrays of permanent magnets, loss width of order of 4͑r Le r Li ͒ 1/2 has been obtained for the line cusp. 4 Bosch and Merlino 5 measured the loss width in a spindle cusp magnetic field and shown that the loss widths of electron and ion are similar and on the order of 2͑r Le r Li ͒ 1/2 in quasineutral plasma, while the loss width of ion is on the order of 2r Li in non-neutral plasma. In other experiment, cusp loss width of order of r Li has been also reported.…”

Section: Introductionmentioning

confidence: 97%

Estimation of the cusp loss width in negative-ion sources

Fukano

Mizuno

Hatayama

et al. 2006

Review of Scientific Instruments

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To estimate loss width in the cusp magnetic field in multicusp negative-ion sources, diffusion of plasma across magnetic field is investigated analytically. The transport process of plasma depends on various plasma conditions. Diffusion coefficients are classified by degrees of plasma ionization. In weakly ionized plasma, where a case of electron-neutral particle collision is dominant as compared with electron-ion collision, there is a possibility that ambipolar diffusion or electron short circuit occurs in plasma. This strongly depends on the conditions of the plasma, the system length, and the wall material. On the other hand, in fully ionized plasma, only ambipolar diffusion occurs automatically due to momentum conservation of electron and ion. In not fully but strongly ionized plasma, plasma diffusion depends on electron-neutral particle collision, ion-neutral particle collision, and electron-ion collision. Being based on the classification of the diffusion coefficients, we derive expressions of loss widths for various plasma conditions.

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On the leak width of line- and point-cusp magnetic fields

Cited by 14 publications

References 4 publications

A new multi-line cusp magnetic field plasma device (MPD) with variable magnetic field

A new multi-line cusp magnetic field plasma device (MPD) with variable magnetic field

Estimation of Width of Electron Energy Loss Region in Cusp Magnetic Field in Negative Ion Sources

Estimation of the cusp loss width in negative-ion sources

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