L Feng

Vortex: a new high performance silicon multicathode detector for XRD and XRF applications

VortexTM, a high performance Silicon Multi-Cathode Detector (SMCD), has been developed and extensively tested for potential X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) applications. As a type of Silicon Drift Detector (SEE), it utilizes our patented structure design and has achieved very low capacitance and very low leakage current with a relatively large active area (~50 mm2). Results will be presented to demonstrate its superior performance over the conventional cryogenic Si(Li) detectors, especially in the resolution and throughput at short peaking times. The detector operates at near room temperature and is thus very compact in size. These features make it idea for XRD and XRF applications.

High throughput high resolution Vortex/spl trade/ detector for X-ray diffraction

Vortex/spl trade/ is a multicathode drift-type X-ray detector produced from high-purity silicon using state-of-the-art CMOS production technology . Based on the Vortex/spl trade/ detector, we have developed a compact detector package for X-ray diffraction applications. The spectrometric package contains a 50 mm/sup 2/ detector cooled using a small Peltier element. The detector package was interfaced with a digital pulse processor, and its performance was tested as a function of the input count rate and pulse peaking time. A pure Cu sample was irradiated with varying flux from an X-ray generator, and the output count rate and energy resolution were measured. The system was able to operate at very high rate (>1 Mcps) with virtually zero loss in resolution and no peak shift. Finally, the performance of the Vortex/spl trade/ system was tested on a Philips (Model PW 1835) powder diffractometer, replacing the sealed tube proportional counter and the graphite monochromator with the silicon detector. The elimination of the graphite monochromator resulted in improvement of the detection efficiency by a factor of 2.5 and improvement in the detection limits due to the low background of the semiconductor detector.

A very large area (100 mm 2 ) silicon drift detector for EXAFS applications

A 100 mm2 silicon drift detector (SDD) has been developed in an effort to improve the solid angle of our Vortex® SDD. The 100 mm2 SDD features the same basic structure as our smaller area (50 mm2) devices and possesses the same advantages, including low noise, high count rates, and excellent energy resolution with thermoelectric cooling. The 100 mm2 SDD is ideal for low or high count rate applications in which the x-rays of interest are occurring over a large solid angle, such as are encountered in TXRF (total reflection x-ray ray fluorescence), EXAFS (extended x-ray absorption fine structure) and other synchrotron applications. The new 100 mm2 SDD has been evaluated in an EXAFS experiment at the National Synchrotron Light Source at Brookhaven National Laboratory, which investigated the local atomic structure surrounding Mn in a LaMnO3/SrMnO3 superlattice. Results show that the new large area SDD delivers excellent energy resolution, high peak-to-background and significantly reduces the data collection time for these types of sensitive EXAFS measurements.

Large Solid Angle 50 mm 2 SDD for TEM Applications

Concomitant with this high spatial resolution capability is the need to optimize ancilliary detector systems to maximize the information collected during any microanalytical investigation. While SDDs have shown their remarkable high count rate performance, there remains a second and equally important advantage to these detectors. The new generation of SDDs offers a range of alternate geometries, which are particularly useful in electron-optical beam-lines. A customized SDD can significantly increase the collection efficiency over that of traditional Si(Li) systems, and also over an SDD which is attached to the EM column in the common up-angle geometry. Typical solid angles for many beam-lines with traditional Si(Li) detectors, with areas 10 -100 mm, are in the range of 0.01-0.1 sR [2].

Low Energy X-Ray Detection with a Silicon Multi-Cathode Detector for Microanalysis

This paper presents several aspects of our design efforts toward the development of a large-area, high energy resolution analytical x-ray spectrometry system for x-ray microanalysis and x-ray spectrum imaging [1]. The spectrometer achieves excellent energy resolution and is capable of operating at very high counting rates (up to 600,000 cps throughput). The Vortex-EM spectrometer is based on a thermoelectrically-cooled silicon multi-cathode detector (SMCD), which is a type of “drift” detector [2-3]. The detector is specifically designed for optimal performance in the 0.2 40 keV range. Recent advancements in the detector design enhance the low energy x-ray performance. The spectrometer utilizes a non-cryogenic design, operating with thermoelectric cooling and passive heat transfer to the ambient without using any moving parts; a photograph of the spectrometer is shown in Figure 1.

A Silicon Multi-Cathode Detector For Microanalysis Applications

Microanalysis Applications Shaul Barkan and Liangyuan Feng Radiant Detector Technologies, LLC Jan S. Iwanczyk, Bradley E. Patt and Caroiyn R, Tull Photon Imaging, Inc. Dale E. Newburyand John A. Small National Institute of Standards & Technology Introduction Anew class of silicon multi-cathode detector (SMCD) has been developed for microanaiysis spectrometry applications. The detector has excellent energy resolution (< 150 eV FWHM) and high count rate capability (>1 Mcps). An energy resolution of 143 eV FWHM at 5.9 keV was measured with the SMCD at 6 us peaking time. At a