Current collection by a cylindrical probe in a partly ionized, collisional plasma
Bibliographic record
Abstract
A numerical calculation of ion and electron current collection by a cylindrical Langmuir probe in a partly ionized plasma has been done. The effect of electron and ion collisions with neutrals on the current collected by the probe has been investigated. The validity of the collisionless theory of Laframboise [J. G. Laframboise, University of Toronto, Institute for Aerospace Studies, UTIAS Report No. 100 (1966)] has been studied. The iterative scheme of Laframboise has been combined with Monte Carlo solution of the Boltzmann equation to provide self-consistent steady-state electron and ion density and electric potential distributions as functions of radius. Our model includes elastic ion-neutral and electron-neutral collisions, ionization of neutrals by electron impact, energy loss of electrons due to excitation and ionization of neutrals, and charge-exchange collisions. Our model has been demonstrated by calculating the current collection by a probe in a nitrogen plasma, but it can be applied in other cases because we avoided adjustable parameters. Our results confirm published experimental data which indicate that Laframboise’s theory can be applied when the attracted particles are electrons and ionization processes do not play an important part. When the attracted particles are ions, it is found that charge-exchange collisions in the sheath produce by far the largest contribution to the increase in their collection current. For this situation, collisionless theory can be applied only when the mean distance traveled by ions inside the sheath is much less than the mean free path. The condition that the sheath size is much smaller than the mean free path does not guarantee a collisionless sheath near a cylindrical probe. This condition is in good agreement with experimental results in the literature.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".