In this paper we report quantitative measurements of the imaging performance for the current generation of hybrid pixel detector, Medipix3, used as a direct electron detector. We have measured the modulation transfer function and detective quantum efficiency at beam energies of 60 and 80keV. In single pixel mode, energy threshold values can be chosen to maximize either the modulation transfer function or the detective quantum efficiency, obtaining values near to, or exceeding those for a theoretical detector with square pixels. The Medipix3 charge summing mode delivers simultaneous, high values of both modulation transfer function and detective quantum efficiency. We have also characterized the detector response to single electron events and describe an empirical model that predicts the detector modulation transfer function and detective quantum efficiency based on energy threshold. Exemplifying our findings we demonstrate the Medipix3 imaging performance recording a fully exposed electron diffraction pattern at 24-bit depth together with images in single pixel and charge summing modes. Our findings highlight that for transmission electron microscopy performed at low energies (energies <100keV) thick hybrid pixel detectors provide an advantageous architecture for direct electron imaging.

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A single photon counting x-ray imaging system based on a MicroHole and Strip Plate (MHSP) using a resistive charge division method was implemented. The MHSP is a hybrid microstructure that combines within the same device the features of the Gas Electron Multiplier (GEM) and the Micro-strip Gas Chamber (MSGC). The MHSP presents two multiplication stages thus allowing reaching high gains. Two thin orthogonal resistive lines of about 100 between each strip (top side) and between each anode strip (bottom side) allows us to obtain the actual position in both x and y directions. The readout electronics use only two charge preamplifiers in each dimension and a TNT module with four independent ADCs controlled through FPGAs that allow converting and registering the four signals through the USB port of a computer. Position resolution in both dimensions as a function of the detector parameters are presented for a 30 keV copper-target x-ray tube. Detector position resolution of x =130 m and y =250 m were achieved for 8keV, making it suitable for many applications in single photon x-ray imaging. The first x-ray images produced by the system are also presented together with a discussion of the image quality and the future prospects.

We introduce the microhole and strip plate (MHSP) detector as a micropattern detector for the detection of thermal and epithermal neutrons. Detection sensitivity is obtained by filling these detectors with 3 He at high pressures. We propose the use of argon-xenon penning mixtures as the stopping gas as opposed to the usual carbon based stopping gases. These argon-xenon mixtures provide suitable gas gains for the high pressure/high resolution neutron detector applications. With these mixtures it is possible to obtain a sealed detector with only rare-gas filling which is simple to purify and not subject to ageing. An MHSP gas detector filled with a 3-bar argon/50-mbar xenon/6-bar helium mixture can achieve gains above 2 10 3. This mixture allows neutron detection efficiencies of about 70% at 1 A for a 2.5-cm thick absorption region and intrinsic position resolution (full-width at half-maximum) of about 1.8 mm. The sensitivity to-rays of the present mixture will be the same when compared to that of 2.6-bar CF 4 I. INTRODUCTION A NEW generation of neutron gas-detectors to meet the requirements of new neutron spallation sources [1]-[8] is under development. Neutron applications include the use in 2-D position sensitive beam monitors, reflectometers, and single crystal diffractometers. Typical requirements for the future detectors include: i) neutron detection efficiency of 70% at 1 ; ii) position resolution of about 1 mm 1 mm; iii) time resolution in the s range; iv) large area, larger than 200 mm 200 mm sensitive area; v) count rates up to 1 MHz/mm ; vi) low-sensitivity. With the introduction of the microstrip gas chamber (MSGC) by Oed [9], applications to neutron detection have been carried out with success [3], [5]. Additionally, other micropattern detectors such as microgap chambers [10], pin-pixel detectors [2], and detectors based on the gas electron multiplier (GEM) [4], [6] have been investigated.

A: We have developed an imaging detector based on a non-standard GEM, made from a 100 µm thick kapton foil (2-fold thicker than standard GEM's). The 100 micron thick GEM is produced using the same wet etching technique as the standard GEM and is less prone to the damage caused by discharges, creating a robust detector that can safely operate at high gain.In this work we present the results obtained with a cascaded gaseous electron multiplier composed by two 100 micron thick GEM and a 10 × 10 cm 2 bi-dimensional readout electrode with resistive charge division. We have recorded energy resolution of 21% and charge gains above 10 4 when the detector was irradiated with 5.9 keV X-rays emitted by a 55 Fe radioactive source. We also present 10 × 10 cm 2 images acquired with the detector when irradiated with X-rays. The minimum position resolution recorded was 1.7 mm.