Digital Pulse Processors
PulseTor designed the first DPP optimized for high rate analysis of spectra with a substantial low energy X-Ray component: TORRENT.
One of the dramatic advantages of Silicon Drift Detectors is the high count rates that are achievable. The Torrent digital pulse processor is the industry leader in terms of accurate processing of high rate spectra from SDDs, particularly when low energy peaks are present at high intensities, as is often the case in SEM spectra. The unique Torrent technology has been awarded five patents, most of which involve techniques to improve coincidence detection and accurate measurement of X-ray events very closely spaced in time. This advanced technology leads to better sum peak rejection and more accurate analysis.
In the spectra shown below, the PulseTor Torrent was connected to an EDS system by splitting its SDD preamplifier output so that it fed the Torrent and the original system simultaneously. The specimen is Corundum (a.k.a. ruby, Al2O3). Corundum is an interesting case, because Al + O sum peak is within 2 eV of the Phosphorus K-alpha and cannot be separated from a real P peak by fitting. The upper spectrum is from the original system; the lower spectrum is the same detector and preamplifier connected to the PulseTor Torrent DPP.
The only difference between the spectra is the pulse processing. The dead time recorded by the PulseTor Torrent is 6% lower and throughput is 5% higher, yet the fitted resolution of the Al peak is slightly better on the Torrent (94.8 eV vs. 95.5 eV). The sum peaks are visibly smaller relative to background for the Torrent.
A quantitative measure of pile-up detection efficiency is a number called Pulse Pair Resolving Time (PPRT). It is the minimum average time between any two X-rays which allows them to be recognized as separate events. It is valuable as a measure of processor performance because it is mostly independent of count rate, low-energy efficiency, and compositional differences.
PulseTor offers free, open-source software which allows you to measure PPRT from any EMSA-format spectrum: EMSAviewer.
The Torrent DPP may be readily customized to your specific application. Both a configurable digital I/O port and TCP/IP data-streaming mode are provided, with the ability to insert custom timing packets based on arbitrary input signals with 10-nS precision. Please contact PulseTor with your interfacing needs for a quotation.