<i>miniPixD</i>: a compact sample analysis system which combines X-ray imaging and diffraction

This paper introduces miniPixD: a new, compact system that utilises transmission X-ray imaging and X-ray diffraction (XRD) to locate and identify materials of interest within an otherwise opaque volume. The system and the embodied techniques have utility in security screening, medical diagnostics, non-destructive testing (NDT) and quality assurance (QA). This paper outlines the design of the system including discussion on the choice of components and presents some data from relevant samples which are compared to other energy dispersive and angular dispersive XRD techniques

Precision scans of the pixel cell response of double sided 3D pixel detectors to pion and x-ray beams

hree-dimensional (3D) silicon sensors offer potential advantages over standard planar sensors for radiation hardness in future high energy physics experiments and reduced charge-sharing for X-ray applications, but may introduce inefficiencies due to the columnar electrodes. These inefficiencies are probed by studying variations in response across a unit pixel cell in a 55μm pitch double-sided 3D pixel sensor bump bonded to TimePix and Medipix2 readout ASICs. Two complementary characterisation techniques are discussed: the first uses a custom built telescope and a 120GeV pion beam from the Super Proton Synchrotron (SPS) at CERN; the second employs a novel technique to illuminate the sensor with a micro-focused synchrotron X-ray beam at the Diamond Light Source, UK. For a pion beam incident perpendicular to the sensor plane an overall pixel efficiency of 93.0±0.5% is measured. After a 10o rotation of the device the effect of the columnar region becomes negligible and the overall efficiency rises to 99.8±0.5%. The double-sided 3D sensor shows significantly reduced charge sharing to neighbouring pixels compared to the planar device. The charge sharing results obtained from the X-ray beam study of the 3D sensor are shown to agree with a simple simulation in which charge diffusion is neglected. The devices tested are found to be compatible with having a region in which no charge is collected centred on the electrode columns and of radius 7.6±0.6μm. Charge collection above and below the columnar electrodes in the double-sided 3D sensor is observed

First demonstration of 3D optical readout of a TPC using a single photon sensitive Timepix3 based camera

The ARIADNE project is developing innovative optical readout technologies for two-phase liquid Argon time projection chambers (LArTPCs). Optical readout presents an exciting alternative to the current paradigm of charge readout. Optical readout is simple, scalable and cost effective. This paper presents first demonstration of 3D optical readout of TPC, using CF4 gas as a proof of principle. Both cosmic rays and an Americium-241 alpha source have been imaged in 100 mbar CF4. A single-photon sensitive camera was developed by combining a Timepix3 (TPX3) based camera with an image intensifier. When a pixel of TPX3 is hit, a packet containing all information about the hit is produced. This packet contains the x,y coordinates of the pixel, time of arrival (ToA) and time over threshold (ToT) information. The z position of the hit in the TPC is determined by combining drift velocity with ToA information. 3D event reconstruction is performed by combining the pixels x,y location with this calculated z position. Calorimetry is performed using time over threshold, a measure of the intensity of the hit

Review of hybrid pixel detector readout ASICs for spectroscopic X-ray imaging

Semiconductor detector readout chips with pulse processing electronics have made possible spectroscopic X-ray imaging, bringing an improvement in the overall image quality and, in the case of medical imaging, a reduction in the X-ray dose delivered to the patient. In this contribution we review the state of the art in semiconductor-detector readout ASICs for spectroscopic X-ray imaging with emphasis on hybrid pixel detector technology. We discuss how some of the key challenges of the technology (such as dealing with high fluxes, maintaining spectral fidelity, power consumption density) are addressed by the various ASICs. In order to understand the fundamental limits of the technology, the physics of the interaction of radiation with the semiconductor detector and the process of signal induction in the input electrodes of the readout circuit are described. Simulations of the process of signal induction are presented that reveal the importance of making use of the small pixel effect to minimize the impact of the slow motion of holes and hole trapping in the induced signal in high-Z sensor materials. This can contribute to preserve fidelity in the measured spectrum with relatively short values of the shaper peaking time. Simulations also show, on the other hand, the distortion in the energy spectrum due to charge sharing and fluorescence photons when the pixel pitch is decreased. However, using recent measurements from the Medipix3 ASIC, we demonstrate that the spectroscopic information contained in the incoming photon beam can be recovered by the implementation in hardware of an algorithm whereby the signal from a single photon is reconstructed and allocated to the pixel with the largest deposition