Photoacoustic Spectroscopy Dual-Gas Sensor for CH <sub>4</sub> and NH <sub>3</sub> Based on Dual-Path Dense Spot Multipass Cell and Dual-Frequency Photoacoustic Cell
Bibliographic record
Abstract
In this paper, a highly sensitive methane (CH 4 ) and ammonia (NH 3 ) dual-gas photoacoustic spectroscopy (PAS) gas sensor based on a dual-path high-spot-density multipass cell (MPC) and dual-frequency photoacoustic cell (PAC) was demonstrated for the first time. A dual-path MPC mathematical model was established to achieve multiple independent rings and 223 excitations of dual gases. In order to integrate with the MPC more conveniently, the designed dual-frequency PAC was used to excite the Helmholtz resonance mode. A Raman fiber amplifier (RFA) and an erbium-doped fiber amplifier (EDFA) were employed to amplify the output power of the two diode lasers to enhance the excitation intensity. The experimental results indicated that when the output power was set as 50 and 300 mW, respectively, the 2 f signals for CH 4 and NH 3 detection with the high-spot-density MPC showed 41.91-fold and 41.30-fold enhancements compared to the system without MPC, demonstrating significant performance improvement. The minimum detection limits (MDLs) of CH 4 and NH 3 were found to be 65 and 374 ppb, respectively, when the average time of the CH 4 /NH 3 –PAS dual-gas sensor was 1000 s.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".