Table 1. Estimated attenuation contributions by the background absorbers using FFAST theoretical data of X-ray mass attenuation coefficients, and the geometry of the experimental setup.
For fluorescence geometry one needs to separate the incident flux at incident energy through the upstream path lengths, from the fluorescent emission path lengths, hence the parameters displayed in the table. The path lengths were determined from the measured geometry of the experimental set-up.
| Background absorber | Chemical formula | Density (g cm−3) | Path length (cm) | (ρt)nominal (g cm−2) | (μ/ρ)FFAST (cm2 g−1) | (μ/ρ)(ρt)FFAST |
|---|---|---|---|---|---|---|
| Upstream, incident E, e.g. 8.45 keV | ||||||
| Air | N2 (78%) + O2 (21%) + Ar (0.93%) | 0.0011 | 28.9 (6) | 0.03179 | 7.696 | 0.2447 |
| Detector gas | N2 | 0.0012 | 19.0 (1) | 0.02280 | 6.171 | 0.1407 |
| Kapton (polymide) | C12H10N2O5 | 1.42 | 0.010 (1) | 0.0142 | 5.610 | 0.0797 |
| Silicone (adhesive) | CH3—Si2O2—C4H9 | 0.968 | 0.0060 (6) | 0.00581 | 22.29 | 0.1295 |
| He gas (cryostat) | He | 0.0001785 | 1.1 (1) | 0.000196 | 0.2633 | 0.0000516 |
| Downstream, fluorescent E, Ni Kα 7.39 keV | ||||||
| Air | N2 (78%) + O2 (21%) + Ar (0.93%) | 0.0011 | 8.2 (1) | 0.00902 | 11.47 | 0.1035 |
| Kapton (polymide) | C12H10N2O5 | 1.42 | 0.0060 (6) | 0.00852 | 8.305 | 0.0708 |
| Silicone (adhesive) | CH3—Si2O2—C4H9 | 0.968 | 0.0060 (6) | 0.00581 | 32.59 | 0.1893 |
| He gas (cryostat) | He | 0.0001785 | 1.1 (1) | 0.000196 | 0.2932 | 0.0000575 |