<title>Thermoelectrically cooled semiconductor detectors for portable energy-dispersive x-ray fluorescence equipment</title>

Abstract

Thermoelectrically cooled semiconductor detectors, such as Si-PIN, Si-strip and Hg12, coupled to miniaturized low-power Xray tubes, are well suited for constructing portable systems for energy-dispersive X-ray fluorescence analysis (EDXRF) of samples of archaeological interest. The Si-PIN detector is characterized by a thickness of about 3OOim, an area of about 2x3 mm2, an energy resolution of about 250-300 eV at 5.9 keV and an entrance window of75 jim. The Si-strip detector has approximate the same area and thickness, but an energy resolution of 145 eV at 5.9keV. The efficiency of these detectors is around 100% from 4 to 10 keV, and then decreases versus energy, reaching 10% at 30 keV. Coupled to a miniaturized 10 kV, 0. 1 mA, Ca-anode or to a miniaturized 30 kV, 0. 1 mA, W-anode X-ray tubes, completely portable systems can be constructed, which are able to analyze K-lines of elements up to about silver, and L-lines of heavy elements. The Hg12 detector has an efficiency of about 100% in the whole range of X-rays, and an energy resolution of about 200 eV at 5.9 keV. Coupled to a small 50 kV, 1 mA, W-anode X-ray tube, a portable system can be constructed, for analysis of practically all elements. These equipments were applied to analysis in the field of archaeometry and in all applications for which portable systems are needed or at least usefiui (for example X-ray transmission measurements, X-ray microtomography and so on). More specifically, concerning EDXRF analysis, ancient gold samples were analyzed in Rome, in Mexico City and in Milan, nuragic bronzes in Sassari, ceramics of various origin in Merida, La Habana and Sassari, and sulfur (due to pollution) in an old roman fresco in S.Stefano Rotondo (Rome).Concerning transmission measurements, ancient copper coins and wood samples were analyzed, and microtomographic measurements are in progress to improve the quality of the image.

Characterization of Surface Coats of Bacterial Spores with Atomic Force Microscopy and Wavelets

“…The surface of bacteria, bacterial spores, and viruses can be probed by many techniques, including transmission electron microscopy (TEM), − photoemission (PE) near edge X-ray absorption fine structure (NEXAFS) spectroscopy, microelectrophoresis, and scanning probe microscopy (SPM) such as atomic force microscopy (AFM). − AFM is particularly useful because it can provide information about surface architecture of bacteria and viruses on the nanometer scale. For the rapid measurement and characterization of samples, such as chemicals, toxins, bacteria, viruses, and physical properties of samples, there have been a number of reports on the development and use of portable instruments that can be easily moved from one to another location to make measurements in the field. − There is interest in developing portable detection devices, such as AFM, for field-usable detection of bacteria and viruses . Coupled to use of sensitive detection using a portable AFM in the field for bacteria and virus identification, there would be an urgent need to conduct rapid image analysis of the obtained data in the field, which could then be used to rapidly identify bacteria and viruses.…”

“…For the rapid measurement and characterization of samples, such as chemicals, toxins, bacteria, viruses, and physical properties of samples, there have been a number of reports on the development and use of portable instruments that can be easily moved from one to another location to make measurements in the field. [21][22][23][24][25][26][27][28][29][30][31] There is interest in developing portable detection devices, such as AFM, for field-usable detection of bacteria and viruses. 23 Coupled to use of sensitive detection using a portable AFM in the field for bacteria and virus identification, there would be an urgent need to conduct rapid image analysis of the obtained data in the field, which could then be used to rapidly identify bacteria and viruses.…”