What does a 150 mm2 detector do better than a smaller detector?
Take an example. At 20 kV a 150 mm2 detector requires less than 2 nA to generate 200,000 counts per second. In contrast, a 10 mm2 detector requires nearly 20 nA
The graph below shows typical count rate at different beam currents, when analysing Pure-Mn at 20 kV using a detector with 30° take off angle and 45 mm sample to crystal distance. Using a larger sensor, count rates are increased without increasing beam current. This means productive count rates are achieved under conditions where spatial resolution is maximised and beam damage minimised. The images to the left show the potential effects of increasing beam current on image quality.
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The effect of beam current on nanoscale analytical capability
When using smaller detectors, the high beam current required to achieve usable count rate leads to poor spatial resolution. The X-MaxN 150 Very Large Area detector acquires high count rates at excellent spatial resolution, for successful analysis of the smallest nanostructures.
Right: X-ray mapping of fragile nanostructures at 5 kV. For the same count rate, a 150 mm2 detector requires much lower beam current, meaning that the spatial resolution is good enough to clearly show nanoscale variations and minimise specimen damage. In contrast, higher beam current required for 10 mm2 results in loss of nanoscale resolution and significant damage during the map collection.
Right: X-ray maps collected at 0.2 nA, 3 kV using 150 mm2 X-MaxN detector to investigate nanostructures in a memory alloy. Variations in Fe La, Ni La and Cu La clearly demonstrate chemical differences on a scale down to at least 20 nm.