Simultaneous two-dimensional laser-induced-fluorescence measurements of argon ions

Hansen, Alex; Galante, Matthew; McCarren, Dustin; Sears, Stephanie; Scime, Earl

doi:10.1063/1.3460630

Cited by 14 publications

(9 citation statements)

References 18 publications

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“…Detailed descriptions of the full LIF system are available elsewhere. 31 For these experiments, the laser light injection and the fluorescent emission collection are accomplished with an in situ, scanning, mechanical probe. The probe includes options for simultaneous parallel and perpendicular light injection and moves the measurement location throughout a plane intersecting the plasma source axis and spans the region downstream of the junction between the plasma source and the expansion chamber (see Fig.…”

Section: Experimental Apparatusmentioning

confidence: 99%

“…We measured the perpendicular IVDFs at the same locations as the parallel IVDFs and under the same conditions. While simultaneous parallel and perpendicular IVDF measurements using multiplexing with the scanning LIF probe are possible, 31 the parallel and perpendicular LIF measurements were obtained sequentially in these experiments. Switching from parallel to perpendicular measurements is accomplished by moving the injection fiber to a different fitting on the external interface of the probe.…”

Section: B Perpendicular Ivdf Measurementsmentioning

confidence: 99%

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Spatial structure of ion beams in an expanding plasma

et al. 2017

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We report spatially resolved perpendicular and parallel, to the magnetic field, ion velocity distribution function (IVDF) measurements in an expanding argon helicon plasma. The parallel IVDFs, obtained through laser induced fluorescence (LIF), show an ion beam with v ≈ 8000 m/s flowing downstream and confined to the center of the discharge. The ion beam is measurable for tens of centimeters along the expansion axis before the LIF signal fades, likely a result of metastable quenching of the beam ions. The parallel ion beam velocity slows in agreement with expectations for the measured parallel electric field. The perpendicular IVDFs show an ion population with a radially outward flow that increases with distance from the plasma axis. Structures aligned to the expanding magnetic field appear in the DC electric field, the electron temperature, and the plasma density in the plasma plume. These measurements demonstrate that at least two-dimensional and perhaps fully three-dimensional models are needed to accurately describe the spontaneous acceleration of ion beams in expanding plasmas.

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Section: Experimental Apparatusmentioning

confidence: 99%

Section: B Perpendicular Ivdf Measurementsmentioning

confidence: 99%

Spatial structure of ion beams in an expanding plasma

et al. 2017

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“…Each LIF measurement (see Ref. 12 for a complete description of the diagnostic system) consists of sweeping the frequency of the very narrow bandwidth laser through the thermally broadened ion velocity distribution function. Measurement of the intensity of the photon emission from the excited state as a function of laser frequency provides a direct measurement of the ivdf.…”

Section: Experimental Apparatusmentioning

confidence: 99%

Spontaneous ion beam formation in the laboratory, space, and simulation

et al. 2013

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We present experimental evidence for the spontaneous formation of multiple double layers within a single divergent magnetic field structure. Downstream of the divergent magnetic field, multiple accelerated ion populations are observed. The similarity of the accelerated ion populations observed in these laboratory experiments to ion populations observed in the magnetosphere and in numerical simulations suggests that the observation of a complex ion velocity distribution alone is insufficient to distinguish between simple plasma expansion and magnetic reconnection. Further, the effective temperature of the aggregate ion population is significantly larger than the temperatures of the individual ion population components, suggesting that insufficiently resolved measurements could misidentify multiple beam creation as ion heating. Ions accelerated in randomly oriented electric fields that mimic heating would have an ion heating rate dependent on the ion charge and mass that is qualitatively consistent with recent experimental observations of ion heating during magnetic reconnection. V C 2013 AIP Publishing LLC. [http://dx

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“…Detailed descriptions of the full LIF system are available elsewhere. 25 For these experiments, the laser light injection and the fluorescent emission collection are accomplished with an in-situ, scanning, mechanical probe. The probe includes options for simultaneous parallel and perpendicular light injection and moves the measurement location throughout a plane intersecting the plasma source axis and spans the region downstream of the junction between the plasma source and the expansion chamber (see Fig.…”

Section: Experimental Apparatusmentioning

confidence: 99%

Ion beams in multi-species plasmas

2018

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Argon and xenon ion velocity distribution functions are measured in Ar-He, Ar-Xe, and Xe-He expanding helicon plasmas to determine if ion beam velocity is enhanced by the presence of lighter ions. Contrary to observations in mixed gas sheath experiments, we find that adding a lighter ion does not increase the ion beam speed. The predominant effect is a reduction of ion beam velocity consistent with increased drag arising from increased gas pressure under all conditions: constant total gas pressure, equal plasma densities of different ions, and very different plasma densities of different ions. These results suggest that the physics responsible for the acceleration of multiple ion species in simple sheaths is not responsible for the ion acceleration observed in expanding helicon plasmas.

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Simultaneous two-dimensional laser-induced-fluorescence measurements of argon ions

Cited by 14 publications

References 18 publications

Spatial structure of ion beams in an expanding plasma

Spatial structure of ion beams in an expanding plasma

Spontaneous ion beam formation in the laboratory, space, and simulation

Ion beams in multi-species plasmas

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