Operation of a 0.2–1.1 keV ion source within a magnetized laboratory plasma

Boehmer, H.; Edrich, D.; Heidbrink, W. W.; McWilliams, R.; Zhao, L.; Leneman, D.

doi:10.1063/1.1646766

Cited by 13 publications

(20 citation statements)

References 5 publications

(3 reference statements)

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“…Classically, energy diffusion is very small for a fast-ion beam that slows down primarily on electrons ͑Ͻ0.1 eV͒. Changes of this magnitude are much smaller than the ϳ10 eV energy spread 24 of the source and are undetectable experimentally. The experimental observations are consistent with this expectation.…”

Section: -7mentioning

confidence: 99%

“…A 3-cm diameter rf ion beam source 24 is modified to produce a pulsed ribbon shaped ͑3 cmϫ 0.5 cm͒ argon ion beam in the parallel direction or with 15°to the magnetic field in the LAPD. The energy of the beam is the sum of the screen grid bias, the plasma potential of background plasma, and the plasma potential of the plasma inside the ion source, which is dependent on the rf power and the gas flow rate.…”

Section: Methodsmentioning

confidence: 99%

“…The resolution of the energy analyzer is calibrated by laser-induced fluorescence ͑LIF͒. 24 The first ͑outer͒ grid of the energy analyzer is grounded to the vessel potential. The second grid is biased 60 V negatively to the vessel.…”

Section: Methodsmentioning

confidence: 99%

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Measurements of classical transport of fast ions

et al. 2005

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To study the fast-ion transport in a well controlled background plasma, a 3-cm diameter rf ion gun launches a pulsed, ϳ300 eV ribbon shaped argon ion beam parallel to or at 15°to the magnetic field in the Large Plasma Device ͑LAPD͒ ͓W. Gekelman, H. Pfister, Z. Lucky, J. Bamber, D. Leneman, and J. Maggs, Rev. Sci. Instrum. 62, 2875 ͑1991͔͒ at UCLA. The parallel energy of the beam is measured by a two-grid energy analyzer at two axial locations ͑z = 0.32 m and z = 6.4 m͒ from the ion gun in LAPD. The calculated ion beam slowing-down time is consistent to within 10% with the prediction of classical Coulomb collision theory using the LAPD plasma parameters measured by a Langmuir probe. To measure cross-field transport, the beam is launched at 15°to the magnetic field. The beam then is focused periodically by the magnetic field to avoid geometrical spreading. The radial beam profile measurements are performed at different axial locations where the ion beam is periodically focused. The measured cross-field transport is in agreement to within 15% with the analytical classical collision theory and the solution to the Fokker-Planck kinetic equation. Collisions with neutrals have a negligible effect on the beam transport measurement but do attenuate the beam current.

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Section: -7mentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Measurements of classical transport of fast ions

et al. 2005

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“…The lithium ion gun 22,23 is inserted into the LAPD plasma at port 35 with variable pitch angle to the axial magnetic field. The initial width of the lithium ion beam is limited by the exit aperture of the gun ($5 mm), while the beam energy is set by the biasing voltage between the lithium emitter and the molybdenum grid on the aperture.…”

Section: A Overviewmentioning

confidence: 99%

Dependence of fast-ion transport on the nature of the turbulence in the Large Plasma Device

et al. 2011

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Strong turbulent waves (dn=n $0.5, f $5-40 kHz) are observed in the upgraded Large Plasma Device [W. Gekelman, H. Pfister, Z. Lucky, J. Bamber, D. Leneman, and J. Maggs, Rev. Sci. Instrum. 62, 2875] on density gradients produced by an annular obstacle. Energetic lithium ions (E fast = T i ! 300, q fast =q s $ 10) orbit through the turbulent region. Scans with a collimated analyzer and with probes give detailed profiles of the fast ion spatial distribution and of the fluctuating wave fields. The characteristics of the fluctuations are modified by changing the plasma species from helium to neon and by modifying the bias on the obstacle. Different spatial structure sizes (L s ) and correlation lengths (L corr ) of the wave potential fields alter the fast ion transport. The effects of electrostatic fluctuations are reduced due to gyro-averaging, which explains the difference in the fast-ion transport. A transition from super-diffusive to sub-diffusive transport is observed when the fast ion interacts with the waves for most of a wave period, which agrees with theoretical predictions.

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“…LIF with diode lasers [4] can characterize the ion beam [5] and the beam source plasma. In addition, background neutrals through which the beam propagates may be ionized, causing a low temperature non-beam plasma [6].…”

Section: Kaufman-type Ion Beam Sourcesmentioning

confidence: 99%