Stimulated Brillouin scattering spectral profiles and gain coefficients for laser fusion optical drivers
Bibliographic record
Abstract
Several architectural concepts of petawatt optical drivers required for the commercialization of electrical power generated by laser fusion rely on the temporal compression of ultraviolet laser pulses by stimulated Brillouin scattering (SBS). For the design of SBS pulse compressors, precise measurements of the SBS gain spectrum and the strength of coupling between the pump and seed laser pulses are critical but not available. To that end, high-resolution measurements of the SBS gain spectral profiles and absolute coupling coefficients for Ar, Kr, and N2 in the ultraviolet are reported here. The SBS spectra recorded at 266 nm with <90 MHz resolution are in general agreement with the predictions of kinetic theory (Boltzmann–BGK model) over the entire 1–6 atm pressure range investigated, whereas hydrodynamic theory (Navier–Stokes model) describes neither the observed spectral profiles nor the coupling coefficients. At one atmosphere, the peak coupling coefficients predicted by the hydrodynamic theory for the rare gases Kr, Ar, and Ne are factors of 5–13 lower than those predicted by the kinetic theory. The success of kinetic theory models in accurately predicting SBS gain spectra opens a new parameter space for the design of high-energy Brillouin amplifiers for laser fusion drivers.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| 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".