Table 2.
Characteristics of the NIST LS spectrometers employed in the calibration of 63Ni SRM 4226C
| Characteristic | System B | System P |
|---|---|---|
| LS spectrometer model | Beckman LS7800 | Packard Tri-carb A2500TR |
| Operating mode | Sum-coincidence | Sum-coincidence |
| Photomultiplier tubes | Hamamatsu R331-05 | Hamamatsu R331-08 |
| Operating temperature | Ambient | Ambient |
| Coincidence resolving time | 22 ns | 18 ns |
| Sum-coincident pulse amplification | Logarithmic | Linear |
| Pulse resolving time | 5 μs to 33 μs (variable with pulse height) |
12μs (fixed) |
| Spectral analog-to-digital converter (ADC) capacity | 1000 channels | 2048 channels |
| Nominal conversion gain (energy per channel) | Variable (with logarithmic energy) |
≈1 keV |
| Detection threshold (nominal) | ≤ 1 keV | ≤ 1 keV |
| Live-time determination method (and uncertainty) | Gated oscillator (scaled) (± 0.1 %) |
Gated oscillator (scaled) (± 0.1 %) |
| Quench indicating parameter (QIP) | Horrocks number (H) | Transformed Spectral Index of the External Standard (tSIE) (proprietary) |
| External (-ray source for QIP determination | 137Cs | 133Ba |
| (and location) | (side) | (bottom) |