Isobar Attenuation Using Anion–Gas Reactions for Accelerator Mass Spectrometry and Application to <sup>36</sup>Cl
Bibliographic record
Abstract
Preliminary tests of a prototype radio‐frequency quadrupole (RFQ) collision cell system, known as an isobar separator for anions (ISA), for the removal of isobaric interferences for accelerator mass spectrometry (AMS) and for studies of anion–gas interactions are reported. The ISA decelerated a mass‐analysed beam of anions from an energy (∼ 20 keV) typically generated by an AMS ion source to < 10 eV. RFQs and electrostatic lenses then guided the ions through the collision cell where ion‐gas collisions reduced both the energy and energy spread of the ion beam (cooled the ions) and ion‐gas reactions attenuated most of the unwanted isobars. The anions were then re‐accelerated to their original energy for injection into the rest of the AMS system. With the ISA installed on a full 3 MV AMS system, attenuations of 32 S ‐ , 12 C 3 ‐ and 39 K ‐ by six, seven and greater than ten orders of magnitude, respectively were achieved using 0.7–1 Pa NO 2 gas in the collision cell, while maintaining approximately 10–30% of the chlorine anion transmission. A further measurement of a 36 Cl/Cl = 4.1 × 10 ‐11 RM is also described. The results suggest that the 36 Cl/Cl lower detection limit of the current system was 10 ‐14 –10 ‐15 for samples that could be prepared with S/Cl ratios below 10 μg g ‐1 .
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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 | 0.001 | 0.001 |
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 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".