High-current space-charge-limited pulses using ultrashort laser pulses
Bibliographic record
Abstract
The maximum current that can be delivered by a 1-D vacuum diode is limited due to the space-charge reduction of the accelerating field. For a steady-state operation, this is given by the Child-Langmuir space-charge limit. However, for pulsed diode sources, the instantaneous current can be much higher than this limit, as long as the pulse length is much less than the transit time across the diode gap. This enables the generation of high current pulses with pulse durations of the order of tens of picoseconds using photocathodes driven by ultrashort laser pulses. The generation of such short and powerful electromagnetic pulses is important for numerous applications such as ultrawideband radar or as photocathode sources for accelerators. In this work, the limiting current pulse is investigated in the case of a very short, square-top initial pulse and it is found that these pulses propagate in a self-similar manner, remaining as a square-top charge cloud in space throughout their acceleration and propagation. The resultant current and pulse duration turn out to be dependent on only three parameters, which are the applied voltage, the vacuum transit time, and the fraction of the saturation charge density in the initial charge cloud. The resultant scaling of the resultant peak current and pulse duration are calculated numerically as a function of starting sheet-charge density, allowing the calculation of the resultant pulses for any ultrashort, pulse-driven vacuum photodiode design.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 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".