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This paper describes an innovative X-ray Fluorescence spectrometer specifically designed to reach high performances in terms of energy resolution, position resolution and detection rate in elemental mapping applications. The spectrometer is characterized by several novelty contents. In particular, it is based on a ring-shaped monolithic array of Silicon Drift Detectors with a hole cut in its center. In this way a coaxial X-ray excitation beam can reach the sample, allowing to obtain a particular geometry that optimizes the solid angle for the collection of the X-ray fluorescence. Moreover, the X-ray beam is collimated on the sample by means of capillary optics in order to obtain high photon density in a small excitation spot. Detector, optics and generator are assembled in a compact vacuum tightened unit. The paper describes the structure of this spectrometer and presents the first experimental results obtained with the XRF spectrometer.

In the miniature scintillation camera that is composed of a position-sensitive photomultiplier tube (PSPMT) and a scintillation crystal, a computer simulation of maximum-likelihood position estimation (MLPE) for better correction of image than that by a conventional algorithm has been studied. So far MLPE has been proposed in several papers, and mostly experiments finding look-up table (LUT) is necessary to apply this method. In this paper, the MLPE using a simulation method instead of experiments, which can consider all stochastic processes of converting the location of gamma-ray interaction with scintillator into position signals, has been proposed, implemented, and compared to conventional algorithm. From the analysis and comparison of images, the quality of image was better than that of resulting from the conventional algorithm. We verified this simulation method through comparison this simulation images with experimental images using small gamma camera of a NaI(Tl) and a PSPMT. From the result, it is proposed that this simulation method could be applied for all PSPMT with only one simulation instead of every tedious experiment to obtain the LUT for different PSPMT even with the same specification.

We present some additional results obtained with the BETAview system, a digital system for real time /spl beta/-imaging based on semiconductor pixel detectors and on a single photon counting read-out chip. In this paper, we describe the system assembled with a Si detector, 300 /spl mu/m thick, segmented into 64/spl times/64 square pixels with 170 /spl mu/m pitch. The solid state pixel array detector is bump-bonded pixel by pixel to a low threshold, single particle counting electronics, the photon counting chip (PCC) developed by the Medipix1Collaboration for biomedical applications. Each cell (corresponding to a detector pixel) of the front-end chip has a maximum count rate of 2 MHz, a minimum nominal threshold of 1400 e~ (corresponding to about 5 keV in Si) and contains a 15-bit counter. The detector sensitive area is about 1 cm/sup 2/, but several detectors could be assembled in arrays. The measured background counts were about 3.5/spl middot/10/sup -2/ cps/cm/sup 2/, which implies a very high sensitivity of the device. The detection threshold used in this experiment was 15 keV. In this paper we show the results obtained in the real time monitoring of two biological dynamic processes: an amino acid uptake and the thermal denaturation process of oligonucleotides. Specifically, we have followed over time the accumulation of a marked amino acid ([/sup 14/C]L-Leucine) into Octopus vulgaris eggs cells. After about 20 min from the beginning of the uptake process, the radioactively marked eggs become clearly visible over the background culture radioactive medium. We also describe the successful performance of the /spl beta/-imaging system in genetic studies involving the real time reconstruction of denaturation and kinetics curves for two different /sup 32/P-radiolabeled nucleotides.