Helium Afterglow and the Decay of the Electron Energy

Ingraham, J. C.; Brown, Sanborn C.

doi:10.1103/physrev.138.a1015

Cited by 55 publications

(6 citation statements)

References 13 publications

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“…The experimental results given below establish definitely that cumulative pro- cesses involving 2 3 S X atoms are major contributors to ionization in a helium discharge over the range of pressures studied. This is consistent with the conclusions of previous work 5 " 7 ; in particular, the metastable-metastable reactions He(2 3 S 1 ) + He(2 3 S 1 )^He(l 1 S 0 ) + He + + ^-,…”

supporting

confidence: 93%

Intense Polarized Electron Beams from Optically Pumped Helium Discharges

1969

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Spin conservation in ionizing reactions involving optically oriented 2 3 S 1 metastable helium atoms in a helium discharge has been exploited to produce a continous beam of polarized electrons. A beam polarization of (10±0.5)% is measured, with beam current 0.2 /iA. Electrons extracted from the pulsed discharge afterglow have polarization (14 ±0.7)%. The apparatus is simple and versatile, and should be readily adaptable to atomic and nuclear scattering experiments.

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supporting

confidence: 93%

Intense Polarized Electron Beams from Optically Pumped Helium Discharges

1969

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“…A time-resolving 2.8 GHz radiometer described here is an extension of the type first developed by Ingraham and Brown (1965) and has been described in detail elsewhere (Sugawara et af 1970). A block diagram of this device is given in figure 7 .…”

Section: Radiometer Measurementsmentioning

confidence: 99%

Decay processes of atomic ions in low-pressure argon afterglows

Sugawara

Okada

Kobayashi

1986

J. Phys. D: Appl. Phys.

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A microwave-cavity technique has been used to measure the time dependence of electron density in decaying plasmas. Applying the sawtooth voltage to the radially-movable probe and sampling the corresponding probe current, the authors have measured the radial density distribution of electrons at various stages of the afterglows within the range of 1 ms to 10 ms. The present measurements constitute the first observation of the radial density distribution of electrons in afterglows. From the observations, the characteristic diffusion lengths have been determined. A 2.8 GHz microwave radiometer was used to measure the electron temperature in the afterglows in order to confirm that electrons reach thermal equilibrium with neutral gas. The value of the mobility of atomic argon ions in argon gas, mu 01=1.67+or-0.13 cm2 V-1 s-1, calculated from the rate of electron loss by ambipolar diffusion, compares well with previously published data obtained using the mass spectrometric method and also is compared with those measured with the drift-tube technique. The conversion rate constant of atomic argon ions to molecular argon ions in a three-body reaction with two neutral argon atoms k=2.06+or-0.2 cm6 s-1, analysed from the variation of the measured decay rate of electrons with pressure, is compared with values obtained by other workers and a comparison is also made with the existing theoretical estimate.

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“…The existence of these metastables greatly influences the properties of discharge plasmas: additional ionization channels like step-wise ionization and chemo-ionization influence the ionization balance and thus, e.g., electric fields in the positive column [1] as in the cathode fall and the negative glow of dc discharges [2] as well as in parallel plate discharges [3]. In afterglow plasmas even the electron distribution function (EDF) is strongly influenced as chemo-ionization constitutes a source of high-energy electrons [4][5][6][7][8]. For the case of the positive column, i.e.…”

Section: Introductionmentioning

confidence: 99%

Metastable atoms and the electron distribution function in a helium discharge positive column

Alexandrov

Flender

Kolokolov

et al. 1996

Plasma Sources Sci. Technol.

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The influence of chemo-ionization processes on the shape of the electron distribution function (EDF) is investigated both by solving the Boltzmann equation and by measurements in a dc low-pressure (0.3 Torr) low-current (i = 10-80 mA) helium discharge. Probes were used to measure EDFs, electron densities and the axial and radial electric field strengths. The concentrations of metastable helium atoms in triplet and singlet states were measured using an optical absorption method. For calculating distribution functions the kinetic equation was solved analytically in local and nonlocal approximations. Good agreement is achieved between experiment and the nonlocal approximation for electron energies above 5 eV. Chemo-ionization is found to influence the high-energy tail of the EDF and thus the rates of electron impact excitation and ionization.

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Helium Afterglow and the Decay of the Electron Energy

Cited by 55 publications

References 13 publications

Intense Polarized Electron Beams from Optically Pumped Helium Discharges

Intense Polarized Electron Beams from Optically Pumped Helium Discharges

Decay processes of atomic ions in low-pressure argon afterglows

Metastable atoms and the electron distribution function in a helium discharge positive column

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