Space charge saturation of Faraday cup detectors used in laser-produced plasmas studies
Bibliographic record
Abstract
Summary form only given, as follows. Faraday cups are commonly used to measure plasma expansion characteristics in laser-produced plasmas. In its simplest design a Faraday cup consists of a grounded entrance grid and a biased collector plate. As an expanding laser plasma flows into the Faraday cup, the entrance grid, with a mesh size smaller than the local Debye screening length, separates electrons from the ions to be measured and the transmitted ion flux is subsequently collected by the collector plate. When large signals are measured, space charge effects can significantly distort the signals. Such distortion may still lead to apparently reasonable looking ion signal waveforms which are, however, limited in amplitude or truncated from the full correct signal. Thus, the design of Faraday cups should include a consideration of the space charge saturation effects. An analytic approach in one dimension (1D) for calculation of the self consistent fields and effect on the streaming ions in the space charge limited regime is developed to model this process. Based on this approach the ion current modification due to a longitudinal space charge field is investigated theoretically and compared experimentally to measurements for a simple two-electrode ion detector system. The measurements were carried out with carbon plasmas produced by 25 ns KrF laser pulses. In order to maintain the 1D geometry, the size of the gap between the two electrodes in the ion detector is kept small compared to the size of the entrance aperture. The experimental results and comparison to theory will be presented.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".