Effect of electrons produced by ionization on calculated electron-energy distributions

Yoshida, Shintaro; Phelps, A. V.; Pitchford, L. C.

doi:10.1103/physreva.27.2858

Cited by 113 publications

(72 citation statements)

References 39 publications

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“…Secondary electrons from ionisation are initialised with a random energy chosen by the experimental distribution in reference [11]. Other distributions such as uniform (E sec = RE primary with R a pseudorandom number uniformly distributed in [0 − 1]) or 'equally shared energy' (50%-50%) have been tested with little variation of the results.…”

Section: Numerical Modelmentioning

confidence: 99%

Modelling and optimisation of ionisation gauges for magnetic nuclear devices

Scarabosio

Sauter

Haas

2010

Nuclear Instruments and Methods in Physics Research Section A:

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We have developed a numerical tool that simulates the operation of an ionisation-based pressure gauge in the presence of magnetic field. In this paper we describe the physical model, the numerical implementation and the validation of the code against laboratory experiments using the so called ASDEX pressure gauge. We then show how this modelling has led to a deeper understanding of processes associated with the presence of magnetic field in this type of gauge: sensitivity enhancement, sensitivity dependence on primary electron current and output saturation at high gas pressure. The combined electric and magnetic fields may trap electrons long enough so that they can spend all their energy in collisions with the neutral gas, thus increasing the sensitivity and leading to early saturation (with respect to the no B-field case). Although it seems difficult to avoid particle trapping with strong B-field, the fraction of trapped electrons and the trapping time can be limited by careful tailoring of the electric potential in the gauge and thus creating E × B drifts. This results in a modified sensitivity and saturation characteristic. Finally we show an example of a modified gauge which has an improved upper pressure limit in view of the next generation nuclear fusion experiment such as ITER.

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Section: Numerical Modelmentioning

confidence: 99%

Modelling and optimisation of ionisation gauges for magnetic nuclear devices

Scarabosio

Sauter

Haas

2010

Nuclear Instruments and Methods in Physics Research Section A:

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“…Details of the energy spectrum of secondary electrons, described by differential ionization cross sections, and the effect of that spectrum on electron energy distribution, excitation, and ionization rates, have been studied elsewhere. [11][12][13]15,16 The nascent spectrum of secondary electrons has a sharp maximum at about 5 eV, which is substantially lower than the ionization energy, and the probability for the secondary electron to immediately ionize a molecule is quite small. [11][12][13]15,16 At pressures of hundreds of Torr, secondary electrons will rapidly lose the memory of their nascent distribution and form the energy distribution function corresponding to the local value of E/N.…”

Section: ͑1͒mentioning

confidence: 99%

“…[11][12][13]15,16 The nascent spectrum of secondary electrons has a sharp maximum at about 5 eV, which is substantially lower than the ionization energy, and the probability for the secondary electron to immediately ionize a molecule is quite small. [11][12][13]15,16 At pressures of hundreds of Torr, secondary electrons will rapidly lose the memory of their nascent distribution and form the energy distribution function corresponding to the local value of E/N. [11][12][13]15,16 Because of this, details of the nascent spectrum were found to be unimportant, [11][12][13]15 and simply assuming that new electrons are produced with either zero energy or with a mean energy corresponding to the local plasma electron temperature, T e (x), turned out to yield reasonably accurate energy distribution functions and kinetic rates.…”

Section: ͑1͒mentioning

confidence: 99%

“…[11][12][13]15,16 At pressures of hundreds of Torr, secondary electrons will rapidly lose the memory of their nascent distribution and form the energy distribution function corresponding to the local value of E/N. [11][12][13]15,16 Because of this, details of the nascent spectrum were found to be unimportant, [11][12][13]15 and simply assuming that new electrons are produced with either zero energy or with a mean energy corresponding to the local plasma electron temperature, T e (x), turned out to yield reasonably accurate energy distribution functions and kinetic rates. [11][12][13]15,16 The contribution of secondary ͑plasma͒ electrons to the total ionization rate is, therefore, determined by the electron temperature, or, more exactly, by the value E/N ͓see Eqs.…”

Section: ͑1͒mentioning

confidence: 99%

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Modeling of discharges generated by electron beams in dense gases: Fountain and thunderstorm regimes

2001

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In this paper we present an analysis of the predicted dynamics of plasmas generated in air and other gases by injecting beams of high-energy electrons. Two distinct regimes are found, differing in the way that the excess negative charge brought in by the ionizing electron beam is removed. In the first regime, called a fountain, the charge is removed by the back current of plasma electrons toward the injection foil. In the second, called a thunderstorm, a substantial cloud of negative charge accumulates, and the increased electric field near the cloud causes a streamer to strike between the cloud and a positive or grounded electrode, or between two clouds created by two different beams. A quantitative analysis, including electron beam propagation, electrodynamics, charge particle kinetics, and a simplified heat balance, is performed in a one-dimensional approximation.

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“…[18]. We define q as the cross-section for producing secondary or scattered electrons of particular energies.…”

Section: Aiaa-2001-3326mentioning

confidence: 99%

Electron energy distribution function in a Hall discharge plasma

Meezan

Cappelli

2001

37th Joint Propulsion Conference and Exhibit

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The role of inelastic collisions in Hall thruster operation is studied through simulation of the electron energy distribution function (EEDF) inside the thruster channel. The electron Boltzmann equation is solved using the Lorentz approximation (two-term expansion) and the "local-field" approximation. The resultant zero-dimensional Boltzmann equation takes into account inelastic losses due to ionizing collisions and wall-collisions. Secondary electrons from ionization and wall-collisions are also included in the model. Electron continuity is used to calculate the sheath potential at the insulator walls. Results show an EEDF cut off at high energy due to electron loss to the walls. Secondary and scattered electrons from ionization provide a large population of low-energy electrons. The calculated EEDFs agree well with experimental electron temperature data when an experimentally-determined effective collision frequency is used for electron momentum transport. Predicted values for the wall-sheath potential agree with results from a charge-balance model, except where said model predicts sheath collapse.

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Effect of electrons produced by ionization on calculated electron-energy distributions

Cited by 113 publications

References 39 publications

Modelling and optimisation of ionisation gauges for magnetic nuclear devices

Modelling and optimisation of ionisation gauges for magnetic nuclear devices

Modeling of discharges generated by electron beams in dense gases: Fountain and thunderstorm regimes

Electron energy distribution function in a Hall discharge plasma

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