Development Of X-ray Detectors Research Articles

Numerical modeling of defects induced dark current in halide perovskite X-ray detectors

Metal halide perovskites have been widely used in x-ray detection due to their outstanding optoelectronic properties. However, the dark current of perovskite x-ray detectors is not appreciably low for integration on thin-film transistors pixel circuits and thus limits their applications in X-ray imaging. Based on numerical models, we investigate the correlation between the dark current and defects of perovskite x-ray detectors. The deep-level defects are the major factor to induce dark current, which has a proportional relation to the defect density. Compared to deep-level defects, the dark current induced by shallow-level defects depends on both of defect energy level and defect density. At last, simulation results present a guidance to engineer defects with suitable values of density and energy level, which yields desirably low dark current. This work provides implications and theoretical guidance for the optimization of defects in halide perovskites, which is believed to assist the further development of x-ray detectors with a low dark current density.

Facile preparation of fully amorphous bulk PbO-Ga2O3 system for direct photon-charge conversion X-ray detector with low dark current and high photocurrent

An amorphous state makes the material free of interface and ensures the overall uniformity of the material and device, to the benefit of large-area electronic devices, such as amorphous silicon and indium gallium zinc oxide display devices and amorphous selenium flat panel detectors. Elements with high atomic number endow the PbO-Ga2O3 system materials with high X-ray absorption coefficients, and wide band gap leading to a low dark current and high signal-to-noise ratio. These advantages are in line with the criteria for a practical X-ray detector development. Herein, the direct photon-charge conversion X-ray detectors based on fully amorphous bulk PbO-Ga2O3 system [(PbO)x(Ga2O3)1-x (x = 0.698, 0.747, 0.761, 0.789)] was fabricated by using high-temperature melt quenching method. Under a fixed electric field of 100 V/mm and X-ray irradiation dose rate of 0.57 μGy ms−1, the dark current as low as 1.1 pA mm−2, photocurrent up to 1600 pA mm−2, signal-to-noise ratio up to 800, comparable sensitivity as 2.02 μC Gy−1 cm−2 of the as fabricated X-ray detector were obtained. All the results suggest that amorphous bulk PbO-Ga2O3 system materials are potential candidates for developing of direct photon-charge conversion X-ray detectors.

SRS-based Timepix3 readout system

With the combination of the highly granular pixel ASIC Timepix3 by the Medipix3 collaboration and several technologies we are developing a range of detectors. These technologies are bump bonded sensors, microchannel plates (MCP) and photolithographically postprocessed gas amplification stages (InGrid). For example, we are using the combination of the ASIC and an InGrid for the development of X-ray detectors for X-ray polarimetry and for axion search at IAXO. Based on the combination of the ASIC and silicon sensors we are developing a tracker or respectively a beam telescope. The combination of the ASIC and a microchannel plate will be used for neutron detectors. As this range of detectors has several requirements towards the readout and control system and a wide range of designs from low- to high-rate (Hz to MHz) and from single- to multichip, a versatile readout system is needed which adapts these applications without producing too much overhead for the others. To fulfil these requirements, we are developing a modular and scalable readout and control system based on the basil framework — a modular data acquisition system and system testing framework. The fully open-source implementation uses Verilog for the firmware and Python for the software. The system supports several FPGA boards to offer different applications a range of capabilities. One of these FPGA boards is the Scalable Readout System (SRS) by RD51 which offers scalability in low to medium rate applications. For high-rate applications we are working towards the firmware implementation on Xilinx adaptive compute acceleration platform. Besides the scalability, the system offers an optional monitoring interface via a microcontroller for monitoring chip temperatures and power supply voltages. Additionally, further external sensors could be connected to the monitoring system for example via I2C or SPI. For controlling the full system, the software offers a command line interface and a graphical user interface. Both interfaces also include an online event display to monitor the raw data. Additional meta data and data of the monitoring system is stored in a database and can be visualised with a monitoring dashboard.

高时间分辨X射线探测器的研制

高时间分辨X射线探测器的研制

Proton radiation damage experiment for X-ray SOI pixel detectors

In low earth orbit, there are many cosmic rays composed primarily of high energy protons. These cosmic rays cause surface and bulk radiation effects, resulting in degradation of detector performance. Quantitative evaluation of radiation hardness is essential in development of X-ray detectors for astronomical satellites. We performed proton irradiation experiments on newly developed X-ray detectors called XRPIX based on silicon-on-insulator technology at HIMAC in National Institute of Radiological Sciences. We irradiated 6 MeV protons with a total dose of 0.5 krad, equivalent to 6 years irradiation in orbit. As a result, the gain increases by 0.2% and the energy resolution degrades by 0.5%. Finally we irradiated protons up to 20 krad and found that detector performance degraded significantly at 5 krad. With 5 krad irradiation corresponding to 60 years in orbit, the gain increases by 0.7% and the energy resolution worsens by 10%. By decomposing into noise components, we found that the increase of the circuit noise is dominant in the degradation of the energy resolution.

Soft X-ray detectors for pulsar navigation

This paper summarizes the requirement of X-ray pulsar navigation and the development of X-ray detector. The difficulties of pulsar navigation in space environment are pointed out. The lack of detectors in terms of detection efficiency, time resolution and load is discussed. Finally, some suggestions are given for future research in X-ray pulsar navigation.

ソフトマターを対象とした時間分割小角X線散乱測定技術

Soft matter generally shows a hierarchical structure both spatially and temporally. Time-resolved small-angle X-ray scattering is effective in revealing this spatio-temporal hierarchical structure of soft matters. Increase in X-ray brilliance and developments of X-ray detectors have contributed to improve the technique. Here recent progress in time-resolved small-angle X-ray scattering including X-ray photon correlation spectroscopy is briefly described.

SynchLink: an iOS app for ISPyB.

The macromolecular crystallography (MX) user experience at synchrotron radiation facilities continues to evolve, with the impact of developments in X-ray detectors, computer hardware and automation methods making it possible for complete data sets to be collected on timescales of tens of seconds. Data can be reduced in a couple of minutes and in favourable cases structures solved and refined shortly after. The information-rich database ISPyB, automatically populated by data acquisition software, data processing and structure solution pipelines at the Diamond Light Source beamlines, allows users to automatically track MX experiments in real time. In order to improve the synchrotron users' experience, efficient access to the data contained in ISPyB is now provided via an iOS 6.0+ app for iPhones and iPads. This provides users, both local and remote, with a succinct summary of data collection, visualization of diffraction images and crystals, and key metrics for data quality in real time.

X-Ray Fibre Diffraction Analysis of 6 MV Photon-Induced Mimosa pudica

Mimosa pudica L (M. pudica) fibre is a natural fibre with electrically conductive in nature. Because of it”s electro-active sensing nature, it found very interesting among physicists, chemists, biologists, material scientists and technologists. The M. pudica fibre was extracted from the stem of the herb by sinking the stem in 10% NaOH solution for one week. The processed fibre was irradiated with 6MV X-ray photon beam with a dose of 20Gy using a medical linear accelerator (LINAC).The effect of fibre structure due to irradiation was investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. In the present report, the structure of M. pudica fibre was observed as celluloseII and is monoclinic in nature. Improvement of fibre orientation due to irradiation was confirmed from both XRD and SEM analysis. The irradiated M. pudica fibre shows improved percent of crystallinity along with two new sharp diffraction peaks due to high flux irradiation. In the present work, high energy X-ray photon induced effect and defects on M. pudica fibre have been investigated for its implementation in the field of X-ray detector development. Keywards: MV X-ray photon, LINAC, Mimosa pudica fibre, X-ray diffraction, SEM, irradiation

X-ray detectors in medical imaging

Healthcare systems are subject to continuous adaptation, following trends such as the change of demographic structures, the rise of life-style related and chronic diseases, and the need for efficient and outcome-oriented procedures. This also influences the design of new imaging systems as well as their components.The applications of X-ray imaging in the medical field are manifold and have led to dedicated modalities supporting specific imaging requirements, for example in computed tomography (CT), radiography, angiography, surgery or mammography, delivering projection or volumetric imaging data. Depending on the clinical needs, some X-ray systems enable diagnostic imaging while others support interventional procedures. X-ray detector design requirements for the different medical applications can vary strongly with respect to size and shape, spatial resolution, frame rates and X-ray flux, among others.Today, integrating X-ray detectors are in common use. They are predominantly based on scintillators (e.g. CsI or Gd2O2S) and arrays of photodiodes made from crystalline silicon (Si) or amorphous silicon (a-Si) or they employ semiconductors (e.g. Se) with active a-Si readout matrices.Ongoing and future developments of X-ray detectors will include optimization of current state-of-the-art integrating detectors in terms of performance and cost, will enable the usage of large size CMOS-based detectors, and may facilitate photon counting techniques with the potential to further enhance performance characteristics and foster the prospect of new clinical applications.

Developments in X-ray detectors at the Advanced Photon Source

Abstract We present a progress report on some of the X-ray detector developments on-going at the Argonne National Laboratories Advanced Photon Source. We focus on pixel array detector architecture, and emphasize collaborations, particularly with industries and universities. We discuss our progress establishing a silicon-sensor fabrication facility at Northern Illinois University, our application specific integrated circuit design work, X-ray testing and detector calibration, and readout electronics based on a collection of interchangeable digital circuit boards.

Full-Spectrum CT Reconstruction Using a Weighted Least Squares Algorithm With an Energy-Axis Penalty

Recent developments in X-ray detectors have created the potential to perform energy-sensitive X-ray computed tomography (CT); that is, to reconstruct a series of CT images associated with different X-ray energies from a single scan. In this paper we propose a penalized weighted least squares (PWLS) algorithm for reconstruction of polychromatic energy-differentiated X-ray CT data and a unique experimental setup to take energy-differentiated X-ray CT data. The experimental setup is designed to acquire a complete X-ray spectrum for every projection ray. We use these data to estimate the linear attenuation coefficient as a function of energy for every pixel in the reconstructed attenuation map. We use prior knowledge of the properties of attenuation spectra to smooth the reconstructions, significantly reducing the noise and improving the contrast-to-noise ratio (CNR) in the reconstructed images without significantly biasing the data. We conclude that this algorithm is an effective method for reconstructing energy-sensitive CT data and provides justification for further research in energy sensitive CT systems.

Requirements for and development of 2 dimensional X-ray detectors for the European X-ray Free Electron Laser in Hamburg

The source characteristics of the European XFEL and the planned experimental facilities that are relevant for the X-ray detectors are presented, and the requirements for the 2-dimensional X-ray Detectors are stated and explained. It is clear that, although these requirements will evolve with time, they demand new detector concepts to be developed. Three X-ray detector development projects have been initiated by the European XFEL, each using a conceptually different approach to meet the stringent requirements. The basic principles used in the projects are briefly presented.

Picosecond time-resolved laser pump/X-ray probe experiments using a gated single-photon-counting area detector

The recent developments in X-ray detectors have opened new possibilities in the area of time-resolved pump/probe X-ray experiments; this article presents the novel use of a PILATUS detector to achieve X-ray pulse duration limited time-resolution at the Advanced Photon Source (APS), USA. The capability of the gated PILATUS detector to selectively detect the signal from a given X-ray pulse in 24 bunch mode at the APS storage ring is demonstrated. A test experiment performed on polycrystalline organic thin films of alpha-perylene illustrates the possibility of reaching an X-ray pulse duration limited time-resolution of 60 ps using the gated PILATUS detector. This is the first demonstration of X-ray pulse duration limited data recorded using an area detector without the use of a mechanical chopper array at the beamline.

The 2D X-ray detector development program for the European XFEL

The 2D X-ray detector development program for the European XFEL

Two technologies for designing digital X-ray image detectors

The goal of this work was to discuss the problem of replacement of conventional devices for film roentgenography with modern digital X-ray image detectors. Several types of digital detectors are considered. The material presented in this work makes it possible to draw some conclusions on the prospects of development of X-ray detectors and transducers, their advantages and disadvantages.

Stoichiometry, surface and structural characterization of lead iodide thin films

In this work we present the structural properties and stoichiometry analysis of thin films of lead iodide (PbI 2). This material is a very promising semiconductor material for the development of X-ray detectors in digital medical imaging. An alternative deposition method called Spray Pyrolysis was used. We discuss the main advantages and limitations of the deposition process comparing three different starting material powders. Extra iodine atmosphere during deposition and the effect of post-deposition thermal treatment is also discussed. The structural properties were studied by X-ray diffraction, Atomic Force Microscopy (AFM), Scanning Electronic Microscopy (SEM) and stoichiometry analysis were performed using Energy Dispersive Spectroscopy (EDS).

Study of silicon carbide for X-ray detection and spectroscopy

This work presents an analysis of silicon carbide (SiC) as semiconductor for the realization of detectors for soft X-rays (<20 keV). On the basis of experimental data on prototype SiC junctions, the performance in X-ray spectroscopy using planar diode and drift detectors in SiC have been estimated in a wide range of operating temperature (up to 150°C). It has been derived that, due to their extremely low reverse current density (4.7 pA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 300 K and 17 pA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 340 K and at electric field of 100 kV/cm), SiC detectors can potentially reach superior performance with respect to all the other semiconductors presently employed at or above room temperature. In particular, a comparative theoretical analysis, based on experimental data on state-of-the-art silicon and SiC junctions, shows that SiC detectors with areas larger than 1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> have the potentiality to offer higher energy resolution when operating at temperature above 25°C. An energy resolution of about 700 and 1300 eV FWHM have been estimated for 1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 10 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> SiC pad detectors operating at 100°C with a silicon front-end FET. The contribution of a standard silicon front-end electronics on the system performance has been analyzed. The open issues in SiC technology for X-ray detector development are highlighted.

Light elements quantification in stimulated cells cryosections studied by electron probe microanalysis

The quantification of intracellular light elements such as carbon, nitrogen and oxygen may be useful in understanding the biological mechanisms, for example the generation of nitric oxide which is involved in apoptosis and inflammatory reaction. Electron energy loss spectroscopy (EELS) coupled with scanning transmission electron microscopy is a useful method to detect light elements in thin cryosections. Recent developments of X-ray detectors with ultra-thin protection windows allows the detection of such elements by energy dispersive X-ray spectroscopy. In the present study, we have demonstrated using both methods that the stimulation of BV-2 murine microglial cell line by γ-interferon and lipopolysaccharide leads to the increase of intracellular oxygen concentration and no change in the intracellular nitrogen concentration. This indicates the use of exogeneous molecular oxygen in response to the stimulation. But the increase of oxygen concentration detected could not be only due to NO expression because the NO production was 1000 times less than the oxygen concentration increase observed.

Development of X-ray detectors based on Nb/Al/AlO x/Al/Nb superconducting tunnel junctions

X-ray detectors based on Nb/Al/AlO x /Al/Nb superconducting tunnel junctions (STJ) have been fabricated. X-ray responses of the fabricated STJs were measured by illumination with X-rays from a 55 Fe electron capture source. The energy resolution of 41, 58 and 65 eV (FWHM) at 5.9 keV were obtained for 20×20, 100×100, 200×200 μm 2, square-shaped devices, respectively. The X-ray measurements were performed at 0.35 K using a charge-sensitive preamplifier at room temperature. We also discussed the capability to suppress the substrate phonon events using Al 2O 3 insulation layer. An advantage for the combined use of the Al 2O 3 insulation layer and the sapphire substrate was demonstrated.