Experiments with pure electron plasmas

Malmberg, J. H.; Driscoll, C. F.; Beck, B.; Eggleston, D. L.; Fajans, J.; Fine, K. S.; Huang, X.‐P.; Hyatt, A.W.

doi:10.1063/1.37613

“…To measure D from n(r, t), we manipulate the diffusion equation to give, D= dN/dt 27trodn/drlr=jo 0 ' (6) where N(t) = fo"n(r,t)27trdr. We measure the slope dn/dr from a single image with n(r) = 2,f6 n(rO)dO.…”

Section: Transportmentioning

confidence: 99%

Quadrupole-Induced Resonant-Particle Transport in a Pure Electron Plasma

Gilson

¹

,

Fajans

²

2003

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Abstract. We performed experiments that explore the effects of a quadrupole magnetic field on a pure electron plasma confined in a Malinberg-Penning trap. This work is important both as an example of resonant particle transport and for antihydrogen (R). The R experiments plan to use magnetic quadrupole neutral atom traps to confine R atoms created in double-well positron/antiproton Malmberg-Penning traps. Our results show that a quadrupole field of only 0.020 G/cm can cause significant transport when applied to a I cm radius plasma confined by an axial field of 100 G. Our model describes the shape of the plasma and shows that resonant electrons follow trajectories that take them on large radial excursions, leading to enhanced transport. If the electrons are off resonance, then diffusion will not be greatly enhanced. The measured diffusion scales like the square of the quadrupole field strength, inversely like the square of the axial magnetic field and, below resonance, like the square of the E x B rotation frequency. The location of the resonance in parameter space scales accordingly as we vary the length and temperature of the plasma. However, the temperature used in fitting the data differs from the independently measured temperature by a factor of four, suggesting that our description of the effect as purely diffusive is not correct.

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“…Removing these complexities allows the electric field to be known at all points within the apparatus allowing for greatly simplified diagnostics. While such an approach has not been documented in Hall thruster studies, an examination of non-neutral plasma has proven to be useful for numerous types of charged particle transport studies, 7,8 examples being the Electron Diffusion Gauge (EDG) experiments of Chao and Davidson, 9 the measurement of neo-classic mobility by Robertson,10,11,12 and numerous other related work involving positrons and ions. 13 Without plasma fluctuations or wall-interactions, mobility in such Hall thruster fields can be studied in its purest sense and a comparison with classical and experimental mobility can be made.…”

Section: Introductionmentioning

confidence: 99%

Mobility Studies of a Pure Electron Plasma in Hall Thruster Fields

Fossum

¹

,

King

²

,

Makela

³

2006

42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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An electron trapping apparatus was constructed in order to study electron dynamics in the defining electric and magnetic fields of a Hall-effect thruster. The approach presented here decouples the cross-field mobility from plasma effects by conducting measurements on a pure electron plasma in a highly controlled environment. Dielectric walls are removed completely eliminating all wall effects; thus, electrons are confined solely by a radial magnetic field and a crossed, independently-controlled, axial electric field that induces the closed-drift azimuthal Hall current. Electron trajectories and cross-field mobility were examined in response to electric and magnetic field strength and background neutral density. Without wall effects or neutral plasma effects mobility is presumed to follow the classical mobility model. In the present research, measurement techniques are investigated, and results are verified against the classical model. Preliminary findings suggest that that the apparatus and techniques used will be valid for mobility studies in more complex field environments. Nomenclature

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“…DN(03) has a maximum, Dmax, at Ores = x/2th. Therefore, Dmax scales like 0 2 exp(-w0 2 /2o0)I2es (6) where N(t) = fo"n(r,t)27trdr. We measure the slope dn/dr from a single image with n(r) = 2,f6 n(rO)dO.…”

Section: Transportmentioning

confidence: 99%

Quadrupole induced resonant particle transport in a pure electron plasma

Gilson

¹

,

Fajans

²

1999

AIP Conference Proceedings

Self Cite

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Abstract. We performed experiments that explore the effects of a quadrupole magnetic field on a pure electron plasma confined in a Malinberg-Penning trap. This work is important both as an example of resonant particle transport and for antihydrogen (R). The R experiments plan to use magnetic quadrupole neutral atom traps to confine R atoms created in double-well positron/antiproton Malmberg-Penning traps. Our results show that a quadrupole field of only 0.020 G/cm can cause significant transport when applied to a I cm radius plasma confined by an axial field of 100 G. Our model describes the shape of the plasma and shows that resonant electrons follow trajectories that take them on large radial excursions, leading to enhanced transport. If the electrons are off resonance, then diffusion will not be greatly enhanced. The measured diffusion scales like the square of the quadrupole field strength, inversely like the square of the axial magnetic field and, below resonance, like the square of the E x B rotation frequency. The location of the resonance in parameter space scales accordingly as we vary the length and temperature of the plasma. However, the temperature used in fitting the data differs from the independently measured temperature by a factor of four, suggesting that our description of the effect as purely diffusive is not correct.

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Experiments with pure electron plasmas

Cited by 31 publications

References 1 publication

Quadrupole-Induced Resonant-Particle Transport in a Pure Electron Plasma

Quadrupole-Induced Resonant-Particle Transport in a Pure Electron Plasma

Mobility Studies of a Pure Electron Plasma in Hall Thruster Fields

Quadrupole induced resonant particle transport in a pure electron plasma

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