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A galaxy has been seen producing strong, regular bursts of X-rays that recur on timescales of hours. The eruptions imply that the matter flowing onto the galaxy's central black hole undergoes repeated restructuring. Evidence of possible rapid restructuring of an accretion disk., Author(s): Bozena Czerny Author Affiliations: Spectacularly rapid and regular X-ray eruptions observed from an active galaxy https://www.nature.com/articles/s41586-019-1556-x , Miniutti et al .[sup.1] report a stunning phenomenon unlike anything observed before [...]

Modulated differential scanning calorimetry (MDSC), optical, and X-ray diffraction measurements are carried out in order to completely characterize the 70CB + 80CB two-component system. The experimental results confirm the existence of a monotropic reentrant nematic phase.

Conventional microstrip gas chambers (MSGCs) have encountered many difficulties, such as limited gas gain and sparking damages. We propose a new multigrid-type MSGC (M-MSGC) to overcome some of these difficulties. Additional grid strips are inserted between the anode and the cathode in this new type of MSGC. Gaps between these strips are chosen to be as small as 10 [micro]m where one can expect an efficient removal of the surface charge. With the existence of other strips with lower potentials than the anode, the field strength around the neighboring grid to the anode strip is not as high as the conventional small-gap MSGCs. The contribution of the surface streamer to the damage is greatly suppressed because the electric field parallel to the surface is screened by the intermediate grid electrodes. However, additional electrodes also screen all the electric field of the upper part of the substrate, and we cannot observe induced signals from the backside of the substrate. To overcome that difficulty, we propose another signal readout method using a patterning approach. Floating pads are placed close to the cathode strip on the surface of the M-MSGC, and the induced charges are read out via the pads. If the area of the pads is sufficiently large and the positive charges are moving toward the pads, the backside electrodes can sense the induced charge. Collected charges on the pads are leaked through the surface resistance. The backside signal through 2.3-mm-thick glass readout of the position along the cathode strips is successfully confirmed through experimental results. Index Terms--Gas counter, neutron, position-sensitive detector, X-ray.

The use of a thin metal blade to generate controlled electron multiplication in gas proportional mode has been studied. Measurements with x-rays have been made on assemblies of an anode blade and two adjacent cathodes in a test chamber. Systematic studies of various detector parameters and their influences on the multiplication process have been carried out. Devices constructed using this technique are very rugged and can be tailored to a curved geometry for the purposes of eliminating parallax error for small and large angle x-ray scattering experiments. Experimental results of a curved, one-dimensional position sensitive detector for synchrotron radiation, with an arc length of 20cm and a 45 [degrees] coverage, will be discussed.

New third generation x-ray sources such as the Advanced Photon Source have created a need for a detector that can provide multiple frames of detailed x-ray images on the millisecond time scale. Such detectors will prove invaluable in applications such as time-resolved x-ray diffraction, x-ray microtomography, as well as materials science applications like polymer processing. Currently, detectors capable of acquiring high resolution x-ray images at such high speed do not exist, thus limiting progress in many of these important areas of research. To address these needs we have developed a prototype fast x-ray imaging system, using a structured CsI(Tl) scintillator coupled to a fast-frame 1K x 1K CCD. The system has been successfully employed to capture 1024 x 64 pixel x-ray images at a rate of 1000 frames per second (fps) with a 12 bit dynamic range. The system exceeds the capabilities of the current high speed x-ray imaging systems which typically operate at the rate of 30 fps. Fabrication of a large area detector is currently underway, using a microstructured CsI(Tl) scintillator coupled to a fast-frame CCD with a 3:1 fiberoptic taper. The camera will operate in a burst mode, acquiring 8 1K x 1K images at rates up to 1000 frames per second with 12 bit dynamic range. Higher image capture speeds can be accomplished by reducing the image area. This paper will discuss the specific characteristics of the CsI(Tl) screens, experimental details of the prototype and the new design for the large area detector being developed specifically for time-resolved x-ray diffraction experiments in structural biology.

The NaI(Tl) scintillation response has been studied for over four decades. Two of the significant conclusions that have been made from these studies (with respect to using NaI(Tl) to detect gamma rays and X rays) are: 1) the NaI(Tl) scintillation response is nearly linear (especially over limited energy ranges) and 2) the NaI(Tl) scintillation response has significant nonproportionalities. While these conclusions may at first appear to be inconsistent with each other, upon further consideration these conclusions are not mutually exclusive. In fact, these conclusions are fully consistent with each other. Published results typically confirm only one of these conclusions (as it was likely the intention to study either linearity or proportionality, but not both) and are not always presented such that direct comparisons can be made with other results. Consequently, it is critical that both the intent of the study and the means with which the results are presented be appropriately considered. Otherwise, it is possible to make inaccurate conclusions about both linearity and proportionality. To facilitate accurate conclusions and meaningful comparisons, this study defines a fully consistent nomenclature, examines some of the subtleties which must be considered when comparing scintillation response results, and uses a review of the literature to demonstrate both the definitions and the subtleties.

We describe a new system of incoherent scatter computed tomography (ISCT) using monochromatic synchrotron X rays, and we discuss its potential to be used in in vivo imaging for medical use. The system operates on the basis of computed tomography (CT) of the first generation. The reconstruction method for ISCT uses the least squares method with singular value decomposition. The research was carried out at the BLNE5A bending magnet beam line of the Tristan Accumulation Ring in KEK, Japan. An acrylic cylindrical phantom of 20mm diameter containing a cross-shaped channel was imaged. The channel was filled with a diluted iodine solution with a concentration of 200 [[micro]gram]I/ml. Spectra obtained with the system's high purity germanium (HPGe) detector separated the incoherent X-ray line from the other notable peaks, i.e., the [K.sub.[Alpha]] and [K.sub.[[Beta].sub.1] X-ray fluorescent lines and the coherent scattering peak. CT images were reconstructed from projections generated by integrating the counts in the energy window centering around the incoherent scattering peak and whose width was approximately 2 keV. The reconstruction routine employed an X-ray attenuation correction algorithm. The resulting image showed more homogeneity than one without the attenuation correction. Index Terms - Computed tomography, incoherent scatter, least squares method, Monte Carlo simulation, singular value decomposition, synchrotron radiation.

In this paper we present the working principle and the design criteria of the Controlled-Drift Detector, a novel device suitable for the simultaneous measurement of energy and two-dimensional position of X rays. In the Controlled-Drift Detector the pixel structure typical of a charge-coupled device and the fast readout typical of a silicon drift detector are joined. When the radiation is to be detected, suitable potential barriers are generated to prevent the drift of the signal electrons that are confined within a matrix of integration wells. The potential barrier which prevents the drift is selectively removable to allow the fast transport of the confined signal electrons to the readout electrodes by means of a static drift field. In principle such a device can achieve excellent energy resolution and readout times of some tens of microseconds. Three different confining mechanisms that allow control of the drift of the stored electrons are studied, and their advantages and drawbacks are discussed. First prototypes of the Controlled-Drift Detector are currently in production. Index Terms - Fast read-out, high-energy resolution, silicon detector, X-ray imaging.

An X-ray spectrometer has been developed for high energy resolution and high efficiency X-ray detection. The spectrometer consists of Nb-Ta-Al-Al2O3-Al superconducting tunnel junction structures and a separate superconductor-insulator-superconductor readout. It also features a tantalum X-ray absorber for improved charge collection. The spectrometer has an absorption efficiency of more than 35% and optimum thermal stability.

We have designed and built a modified Positron Emission Tomography (PET) imaging system for monitoring the dose delivered by proton and [Gamma]-ray radiotherapy beams. By measuring the amount and ratio of the beam-induced positron-emitting activity, the dose distribution and tissue composition may be determined. The system utilizes fast LeCroy ECLine electronics and a VME multinode transputer based frontend. Utilizing a transputer based filter, positron annihilation events containing timing, energy, and position information will be filtered in real-time at event rates of up to 40 kHz. This will result in only valid events being transmitted back to the host for further analysis and display, reducing both storage media requirements and image reconstruction time. At these rates proton radiotherapy beams may be monitored between beam pulses for on-line range verification. It will also be possible to perform bloodflow studies on tumors using the activity induced by a [Gamma]-ray radiotherapy beam. Future electronic developments will allow event rates up to roughly 80 kHz. For both treatment modalities, determination of the composition of tumors will directly affect treatment planning through compensation for oxygen enhancement effects to the dose.

The charge-collection efficiency of beveled-edge-type silicon avalanche photodiodes has been determined for soft x rays in the 50-300-eV range. An efficiency of greater than 80% is measured for energies below the Si L absorption edge. The measured efficiency is well described by a model that accounts for absorption in an oxide overlayer and recombination at the front surface of the diode. The avalanche photodiodes are shown to be significantly more sensitive compared with other detectors for pulsed sources such as a laser-produced plasma source. These results are also very encouraging for soft-x-ray/extreme-UV applications involving synchrotron radiation. PACS numbers: 29.40.Wk, 07.85 + n, 85.60.Dw.

The simple structure of CdTe semiconductor detectors facilitates their downsizing, and their possible application to radiographic sensors has been studied. The escape of K X-rays from these detectors increases with reduction of their dimensions and affects the measurements of X- and gamma-ray spectra. K X-rays also produce crosstalk in multi-channel detectors with adjacent channels. Therefore, K X-rays which escape from the detector elements degrade both the precision of energy spectra and spatial resolution. The ratios of escape peak integrated counts to total photon counts for various sizes of CdTe single detectors were calculated for gamma rays using the Monte Carlo method. Also, escape and crosstalk ratios were simulated for the CdTe multi-channel detectors. The theoretical results were tested experimentally for 59.54-keV gamma rays from a 241 Am radioactive source. Results showed that escape ratios for single detectors were strongly dependent on element size and thickness. The escape and crosstalk ratios increased with closer channel pitch. Our calculated results showed a good agreement with the experimental data. The calculations made it clear that K X-rays which escaped to neighboring channels induced crosstalk more frequently at smaller channel pitch in multi-channel detectors. A radiation shielding grid which blocked incident photons between the boundary channels was also tested by experiment and by calculation. It was effective in reducing the probability of escape and crosstalk.

We describe a novel, lightweight x-ray burst detector that can be embedded in a satellite structure, thus forming a 'smart skin,' which has minimal impact on the host satellite. The design is based on two types of optical fibers coupled to photodiodes. The first is a scintillating fiber, which gives a fast signal for timing. The second is a germanium-doped silica fiber, which darkens for a few milliseconds when irradiated with a burst of x rays. The resulting slow signal is used to discriminate against electrostatic discharges. The coincidence of a fast signal from the scintillating fiber with a slow signal from the darkening fiber is the signature of an x-ray burst. The response is linear at low doses and becomes nonlinear at high doses. We have two techniques to test the instrument in a space experiment scheduled for 1994. First, a small, space-qualified flash x-ray unit can illuminate the fibers. Second, we can detect space background radiation. The cumulative dose will be monitored by RADFET dosimeters. Future work on embedding the fibers and the electronics as Application Specific Integrated Circuits (ASICs) in the spacecraft skin could lead to use of these detectors on many satellites.

A prototype detection system has been built for single photon X-ray detection which provides precise position and good energy measurements. The detecting element is a silicon microstrip detector, originally developed for high-energy physics. The readout is provided by a 16 channel prototype VLSI circuit, each channel consisting of a low-noise preamplifier followed by an RC-CR shaper (shaping time of 1500 ns) and a discriminator. The self-triggering property of the chip allows efficient X-ray detection. Two readout chips have been connected to the p-side of a FOXFET biased double-sided AC-coupled microstrip detector. The system has been tested with a multi-energy X ray source and at an X-ray diffractometer. Energy calibration is shown together with a few images, proving the good performances of the system for X-ray imaging. A Debye-Scherrer diagram has been recorded.

High resistivity CdZnTe is a very promising material for X-ray detection at room temperature or slightly below. Cooling a [Cd.sub.0.8][Zn.sub.0.2]Te crystal down to -30 [degrees] C reduces the leakage current to the picoamp level, which enables the use of low-noise pulsed optical feedback instead of noisier resistive feedback preamplifiers. Also, longer shaping time constants at the linear amplifier can be used for the optimum resolution. We have obtained resolutions of 240 eV (FWHM) for the 5.9-keV 55Fe line at -40 [degrees] C and of 282 eV at -30 [degrees] C. The Fano factor for the material at -40 [degrees] C was calculated to be 0.14. These results compare well with the results obtained with peltier-cooled Hg[I.sub.2] detectors.

An x-ray detector system, based on a silicon strip detector wire-bonded to a low noise charge-sensitive amplifier integrated circuit, has been developed for synchrotron radiation experiments which require very high count rates and good energy resolution. Noise measurements and x-ray spectra were taken using a 6 mm long, 55 [[micro]meter] pitch strip detector in conjunction with a prototype 16-channel charge-sensitive preamplifier, both fabricated using standard 1.2 [[micro]meter] CMOS technology. The detector system currently achieves an energy resolution of 350 eV FWHM at 5.9 keV, 2 [[micro]second] peaking time, when cooled to -5 [degrees] C.

Experimental measurements of the spectral distribution of keV x-ray energy conversion of the M-shell emission from gold plasma produced by a 4 GW, 5 nS Nd:glass laser are presented. At a laser intensity of 2 X 10 to the thirteenth power W/cm squared, the overall x-ray yield for 2.0 less than or equal to h-Nu less than or equal to 3.6 keV is determined to be 0.1% of the laser energy. The effect of the keV x-ray spectral distribution on radiation preheat is discussed.

Parameters are identified by a new method in the grazing incidence X-ray reflectometry, based on a nonlinear least-squares approach with on-line low-pass filtering, which also suits the measured reflectivity curve as a function of the incidence angle. The filter is applied in the angular frequency domain. The global solution is determined by the automatic restarting. The data having large scattering vectors is assessed using the roughness model's generalization. An accuracy of 0.2 nanometers is determined with the thickness.

A multichannel detector was fabricated with 32 elements, each 1 mm wide x 0.25 mm long x 0.3 mm thick on a single CdTe crystal wafer whose overall size was 1 x 8 x 0.3 mm. One of the elements was subjected to an energy analysis using diagnostic wavelength X-rays. We note that the energy spectrum was distorted because of the small size of the element. Errors caused by the X-ray escape and by the energy dependency of the photoelectric absorption process were appreciable; however, these errors are specific to narrow energy ranges and can be corrected. The response function of the detector to monochromatic 59.54 keV to the 241 power Am gamma-rays was measured and by fitting the results to a calibration curve, this small size CdTe detector was able to detect X-ray spectra reliably.

The capability to measure bursts of neutron fluences and gamma/x-ray fluxes directly with charge coupled device (CCD) cameras while being able to distinguish between the video signals produced by these two types of radiation, even when they occur simultaneously, has been demonstrated. Volume and area measurements of transient radiation-induced pixel charge in English Electric Valve (EEV) Frame Transfer (FT) charge coupled devices (CCDs) from irradiation with pulsed neutrons (14 MeV) add Bremsstrahlung photons (4-12 MeV endpoint) are utilized to calibrate the devices as radiometric imaging sensors capable of distinguishing between the two types of ionizing radiation. Measurements indicate [is nearly equal to] 0.5 V/rad responsivity with [greater than or equal to] 1 rad required for saturation from photon irradiation. Neutron-generated localized charge centers or 'peaks' binned by area and amplitude as functions of fluence in the [10.sup.5] to [10.sup.7] n/[cm.sup.2] range indicate smearing over [is nearly equal to] to 10% of CCD array with charge per pixel ranging between noise and saturation levels.

ABSTRACT--The technique of zero degree electron spectroscopy, first developed in studies involving ion-atom collisions, have been applied to study the energy distribution of electrons inelastically scattered to the K-shell ionization [...]

A single-crystal silicon carbide (SiC) detector is used for measuring soft x rays, electrons, and ion emission from laser-generated plasma obtained with the use of the Prague Asterix Laser System (PALS). The detector is used by inserting absorber films of different thickness in front of the SiC surface in order to determine the mean energy of the soft x-ray emission from the plasma.

Thermoluminescent Dosimeters (TLDs) have various applications in nonprimary beam dosimetry. The Monte Carlo simulation of the TLD response was done in low energy beams to improve its clinical use in scattered beam dosimetry. The normalised values of the measured quality dependence factors for different X-ray beams were found to be 1.28, 1.24, 1.16, 1.07 and 1.03 for different beam qualities, respectively. Comparatively, the Monte Carlo for 'n' Particles (MCNP) simulated findings were 1.134, 1.96, 1.139, 1.052 and 1.034. The change of the calibration factor with energy follows the equation CF = B0 + B1E + B2E[sup.2] + B3E[sup.3], where CF and E are the calibration factor and energy (keV), respectively, and B0, B1, B2 and B3 are the constants. Our findings show a significant deviation of the true dose value when the TLDs are calibrated at different beam qualities. The greatest deviation was 19.9 [+ or -] 2.1% with a beam quality of 120 kVp. Obtaining a dose-response curve may be helpful in calculating the calibration factor with more precision.

Byline: Kirsten Bobzin, Erich Lugscheider, Michel Maes, Philipp Immich The process of semisolid metal forming with permanent moulds combines the advantages of the casting and forging process technologies. The processing of steel results in high loads on the surface of the metallic die, such as thermal, mechanical and tribological stresses. To meet this challenge, ceramic-based Physical Vapour Deposition (PVD) hardcoatings are used for tool protection to guarantee high durability of the tool. The first experiments show that especially the high-temperature tetragonal zirconia phase exhibits high strength and toughness. To propose and to examine the appropriate coatings to extend the surface lifetime of the metallic moulds, zirconia coatings were synthesised using pulsed reactive magnetron sputtering. After deposition, these coatings were analysed by common thin film techniques revealing hardness, Young's modulus and x-ray diffraction measurements. The conclusion was that the examination of t-ZrO2 showed the extraordinary potential of these thin films for use as coating for thixoforming dies.

The article explains the magnetic alignment of the various rare-earth-containing liquid crystal complexes. Different crystals are found to exhibit different positive and negative values of magnetic anisotropy.

Various rotational echo adiabatic passage double resonance (REAPDOR) NMR spectroscopic studies are conducted to measure the internuclear spin-1/2 ([super 31]P) and spin-7/2 ([super 51]V) distance in polyoxoanionic solids.

X-ray diffraction (XRD) and resistance measurements are used for examining the sputtered undoped and nitrogen doped [Sb.sub.2][Te.sub.3] (ST and STN) films. The phase separation has made it very difficult for the films to switch reversibly between the crystalline and the amorphous phase.

NIST has recently revised and published a key Measurement Services Guide, NIST Special Publication 250-58, which describes completely the x-ray and gamma-ray calibration services provided at NIST. This publication replaces […]

The paper describes the development of a multi-channel readout system for X-ray measurements using silicon strip detectors. The system comprises two application-specific integrated circuits (ASICs), a front-end chip, and a digital data storage chip. In the front-end ASIC, a binary readout scheme is employed. The binary data are stored in the asynchronous counters and read out serially at the end of the measurement sequence. The front-end circuit is designed such that it can work with direct current coupled detectors with a leakage current up to few nanoamperes. The size of the input device is optimized for a detector capacitance in the range from 2-5 pF per strip. An equivalent noise charge of 110 electrons [micro]s has been achieved for the total strip capacitance of 2.5 pF at the peaking time of 1 [micro]s. Low noise performance and high counting-rate capability have been demonstrated by measurements of X-ray spectra. Index Terms--Front-end electronics, low-noise electronics, silicon strip detectors, X-ray detection.

A charge cloud produced by an X-ray photon in a charge coupled device (CCD) has a finite size. The size can be measured using a mesh experiment: the X-ray interaction position is restricted with subpixel precision by using the small mesh holes. This enables us to measure the charge cloud shape produced by an X-ray photon in the CCD. We measured charge cloud size for A1-K X-rays and for Mo-L X-rays. At both energies, we find the charge cloud shapes to be elongated perpendicular to the charge transfer direction. We confirmed the symmetric shape of the mesh hole both by SEM photography and by an experimental technique, and conclude that the elongation of the charge cloud shape is not an artifact of the experimental setup. We then applied an image restoration technique to directly measure the actual hole shape from the X-ray data. The inferred hole size is bigger than the geometrical shape due to diffraction of the incident X-rays by the mesh holes. We conclude that the distortion of the charge cloud shape is due to the asymmetry of the electric field in the CCD.

The Controlled-Drift Detector is a recently designed position-sensing X-ray detector. It operates by switching between integration and drift mode. The basic idea is to generate potential wells within the otherwise linear drift potential. During the integration mode signal electrons are being accumulated within these wells. The removal of the barriers in an externally controlled way restores a uniform drift field that sweeps the electrons towards the readout anodes. The height of the confining barrier depends on the drift field and on the amplitude of the potential perturbation at the surface. An experimental study of the charge handling capability has been carried out as a function of the amplitude of the surface perturbation (up to 2.1 V) and as a function of the drift field (250-400 V/cm). The study provides a sensitive measurement of the actual potential barrier of the integration well in different operating conditions. A detailed analysis and characterisation of the mechanisms to confine the signal electrons in the 3D well is presented. For a drift field of 300 V/cm, storage of more than 105 electrons in 180 x 180 [micro][m.sup.2] pixels has been achieved with 1.67 V surface perturbation.

Gated X-ray images of laser-driven implosions can provide movies of typically 16 frames with ~80 ps time resolution and 10 [[micro]meter] spatial resolution. Cylindrical implosions allow study of convergent hydrodynamics but with excellent diagnostic access down the axis of the cylinder. This example from a recent cylindrical implosion campaign on the OMEGA laser provides quantitative data on the growth of ablative Rayleigh-Taylor instabilities in convergent geometry. Index Terms - Hydrodynamics, imaging/mapping, inertial confinement, X-ray measurements.

The consequences of a limited amount of charge multiplication on the electroluminescence yield and the energy resolution R of a xenon-neon gas proportional scintillation counter were studied using both Monte Carlo simulation and experimental measurements. By extrapolating the experimental results for R to infinite light yield, the intrinsic energy resolution for 5.9 keV x rays was obtained in all mixtures. From the results, Fw values can be obtained, where F is the relative variance in the number of primary electron.