Are EDS Specifications Still Relevant

The spectral performance of an EDS detector is almost universally described by measuring the Mn kalpha line at an x-ray collection rate of a few thousand counts per second. In many cases, this is the only metric cited in describing detector performance. The rationale is mainly historic and based on the ready availability of Fe 55 as an inexpensive and relatively weak (thereby safe) source of radiation emitted at the Mn-k line. This specification presented a convenient and pragmatic metric for LN-cooled Si(Li)based EDS detectors whose Be window occluded most of the low energy portion of the spectrum. In an era of modern, SDD-based EDS detectors with high count rates and light element windows, the use of this simplified specification warrants examination.