Figure 1: Orbis Micro-XRF analyzer with optional viewport.
Improvements in speed and sensitivity of analysis can be achieved with detectors and associated signal processing electronics
by improving spectral resolution, enhancing signal collection by size and positioning of the detector or increasing signal
processing speed, also referred to as "throughput." The general goal in optimizing and improving these detector parameters
is to avoid augmenting one at the sacrifice of the others. For example, it would do little good to increase the detector size
while making significant sacrifices in detector resolution or throughput. Such a detector could collect more signal but would
be unable to provide a high resolution spectrum or process the additional signal collected. This application note will explain
the benefits of the new 50 mm2 Apollo XRF-ML50 detector and describe in which analytical situations increased speed and sensitivity can be realized.
Improvements in speed and sensitivity begin with the amount of sample X-ray signal collected by the detector, which is referred
to as the "solid angle" by system designers. Detector solid angle is proportional to the signal collection area of the detector,
known as active area, and inversely proportional to the square of the distance between sample and detector as shown in equation
1.
Table I: Comparison of Orbis detector structural and performance parameters
In general, augmenting active area leads to larger solid angles and increased X-ray signal collection as long as the distance
between sample and detector can be optimized. In Table I, a comparison of performance parameters is made between the three
detectors which are available on the Orbis system. The structural and performance characteristics of the 30 mm2 and 50 mm2 SDD detectors are very similar except for the active area while the throughput of the Si{Li} detector is limited.
