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First results from a 10 µm MURA coded aperture optic for a full-field X-ray fluorescence microscope are presented., The design and construction of an instrument for full-field imaging of the X-ray fluorescence emitted by a fully illuminated sample are presented. The aim is to produce an X-ray microscope with a few micrometers spatial resolution, which does not need to scan the sample. Since the fluorescence from a spatially inhomogeneous sample may contain many fluorescence lines, the optic which will provide the magnification of the emissions must be achromatic, i.e. its optical properties must be energy-independent. The only optics which fulfill this requirement in the X-ray regime are mirrors and pinholes. The throughput of a simple pinhole is very low, so the concept of coded apertures is an attractive extension which improves the throughput by having many pinholes, and retains the achromatic property. Modified uniformly redundant arrays (MURAs) with 10 µm openings and 50% open area have been fabricated using gold in a lithographic technique, fabricated on a 1 µm-thick silicon nitride membrane. The gold is 25 µm thick, offering good contrast up to 20 keV. The silicon nitride is transparent down into the soft X-ray region. MURAs with various orders, from 19 up to 73, as well as their respective negative (a mask where open and closed positions are inversed compared with the original mask), have been made. Having both signs of mask will reduce near-field artifacts and make it possible to correct for any lack of contrast.

Arrays of silicon sensors can be used in those spectroscopic applications where a high event throughput is needed, for example, in synchrotron-based experiments. However, in such arrays, several noise contributions, beyond the well-known leakage, thermal, and flicker noises, can be present, which are absent in single-channel detectors. Additional noise is generated ultimately by the condition at the silicon/silicon-oxide interface, which in turn depends on the parameters of the silicon oxide over the not-implanted gaps. We discuss how to control this region to obtain the best spectroscopic performances.

A Maia detector array has been adapted and installed on the CSIRO-MARC Nuclear Microprobe. Maia uses an annular array of 384 silicon detectors to provide a solid-angle of 1.3 sr to improve the collection of X-rays induced by Particle Induced X-ray Emission (PIXE) using a micron focussed MeV proton beam. It features event-by-event data acquisition with dead-time correction and pileup rejection and a total count-rate capacity above 10 M/s, versatile stage and beam scanning modes (coupled to the DAQ-36 system described previously) to cater for a variety of sample configuration and experimental needs, precise measurement of transit time and integration of beam fluence per pixel, and spectral deconvolution of event data in real-time using the Dynamic Analysis method to provide element images during data collection. Here we demonstrate the system on thin sections made from geological samples extracted from active seafloor hydrothermal vents in the PACMANUS hydrothermal field in Papua New Guinea.

Germanium has been the material of choice in detectors of high-energy X-rays and gamma rays for many years, largely because it is relatively easy to obtain high-quality material in large quantities...

An on-chip implementable algorithm for allocation of an X-ray photon imprint, called a hit, to a single pixel in the presence of charge sharing in a highly segmented pixel detector is described. Its proof-of-principle implementation is also given supported by the results of tests using a highly collimated X-ray photon beam from a synchrotron source. The algorithm handles asynchronous arrivals of X-ray photons. Activation of groups of pixels, comparisons of peak amplitudes of pulses within an active neighborhood and finally latching of the results of these comparisons constitute the three procedural steps of the algorithm. A grouping of pixels to one virtual pixel , that recovers composite signals and event driven strobes, to control comparisons of fractional signals between neighboring pixels are the actuators of the algorithm. The circuitry necessary to implement the algorithm requires an extensive inter-pixel connection grid of analog and digital signals, that are exchanged between pixels. A test-circuit implementation of the algorithm was achieved with a small array of $32\times 32$ pixels and the device was exposed to an 8 keV highly collimated to a diameter of 3- $\mu \text{m}$ X-ray beam. The results of these tests are given in this paper assessing physical implementation of the algorithm.

This work was motivated by the possibility of simplifying the process steps on silicon device fabrication. This simplification could benefit other silicon detector fabrications and have the possibility of terminating the junction edges in other detector designs. This is our attempt of exploring the RIE trench technique onto silicon device process. This technique originated from the high-purified germanium (HPGe) detector fabrication. The results have shown good pixel isolations. It has also shown that the multiple guards to lower the potential from the active area are more effective for trenched guard rings than the planar-processed guard rings. Furthermore, it has shown that the inter-pixel capacitance decreases as the trench depth increases.

Journal of synchrotron radiation 23(6), 1550 - 1560(2016). doi:10.1107/S1600577516015289, The high brilliance of third-generation synchrotron sources increases thedemand for faster detectors to utilize the available flux. The Maia detector is anadvanced imaging scheme for energy-dispersive detection realising dwell timesper image-pixel as low as 50 ms and count rates higher than 10 106 s1. In thisarticle the integration of such a Maia detector in the Microprobe setup ofbeamline P06 at the storage ring PETRA III at the Deutsches Elektronen-Synchrotron (DESY) in Hamburg, Germany, is described. The analyticalperformance of the complete system in terms of rate-dependent energyresolution, scanning-speed-dependent spatial resolution and lower limits ofdetection is characterized. The potential of the Maia-based setup is demonstratedby key applications from materials science and chemistry, as well asenvironmental science with geological applications and biological questions thathave been investigated at the P06 beamline., Published by IUCr, Chester

We have developed a series of monolithic multi-element germanium detectors, based on sensor arrays produced by the Forschungzentrum Julich, and on Application-specific integrated circuits (ASICs) developed at Brookhaven. Devices have been made with element counts ranging from 64 to 384. These detectors are being used at NSLS-II and APS for a range of diffraction experiments, both monochromatic and energy-dispersive. Compact and powerful readout systems have been developed, based on the new generation of FPGA system-on-chip devices, which provide closely coupled multi-core processors embedded in large gate arrays. We will discuss the technical details of the systems, and present some of the results from them., 10 pages, 14 figures, Accepted J. Instrumentation

The vertically integrated photon imaging chip (VIPIC1) pixel detector is a stack consisting of a 500- $\mu \text{m}$ -thick silicon sensor, a two-tier 34- $\mu \text{m}$ -thick integrated circuit, and a host printed circuit board (PCB). The integrated circuit tiers were bonded using the direct bonding technology with copper, and each tier features 1- $\mu \text{m}$ -diameter through-silicon vias that were used for connections to the sensor on one side, and to the host PCB on the other side. The 80- $\mu \text{m}$ -pixel-pitch sensor was the direct bonding technology with nickel bonded to the integrated circuit. The stack was mounted on the board using Sn-Pb balls placed on a 320- $\mu \text{m}$ pitch, yielding an entirely wire-bond-less structure. The analog front-end features a pulse response peaking at below 250 ns, and the power consumption per pixel is 25 $\mu \text{W}$ . A successful completion of the 3-D integration is reported. In addition, all pixels in the matrix of $64\times 64$ pixels were responding on well-bonded devices. Correct operation of the sparsified readout, allowing a single 153-ns bunch timing resolution, was confirmed in the tests on a synchrotron beam of 10-keV X-rays. An equivalent noise charge of 36.2 $\text{e}^{-}$ rms and a conversion gain of 69.5 $\mu \text{V}/\text{e}^{-}$ with 2.6 $\text{e}^{-}$ rms and 2.7 $\mu \text{V}/\text{e}^{-}$ rms pixel-to-pixel variations, respectively, were measured.

Synchrotron radiation news 31(6), 21 - 27 (2018). doi:10.1080/08940886.2018.1528430, Published by Taylor & Francis, Philadelphia, Pa.

The VIPIC1 readout integrated circuit was designed for X-ray Photon Correlation Spectroscopy experiments that are typically performed using mono-energetic (8 keV) X-rays at a synchrotron radiation facility. The device is a pixel detector with sparsification and parallel readout from the groups, yielding high timing resolution. Recent improvements in bonding alignment of wafers resulted in deliveries of 3D bonded wafers. The stacks, bonded with both the Cu-Cu thermo-compression method and the Cu DBI bonding method, yielded operational devices that have been tested. Chips (with a pixel pitch of $80~\mu\hbox{m}$ ) were also bonded to silicon pixelated sensors (with a pixel pitch of $100~\mu\hbox{m}$ ) and the assemblies were exposed to X-ray sources for the first time. The paper focuses on the test results, including the calibrated noise (ENC) and the conversion gain. The noise measured corresponded to $39~\hbox{e}^ {- }$ and $70~\hbox{e}^ {- }$ , respectively for the readout channels that were not connected and connected to the sensor diodes. The conversion gain varied from 43 to $52~\mu\hbox{V/e}^ {- }$ as a function of the bias current in the front-end block. Essentially all the pixels on a small prototype were operational.

A new SDD-Maia detector is being currently developed, consisting of an array of 384 silicon drift detectors (SDDs), each having a surface area of 1 mm2. The shape of each individual pixel is square in order to coincide with the footprint of the diode-based Maia detector. Each SDD pixel is made of a few concentric “rings” that supply a voltage gradient to form the drift field within the silicon. The detector has a double metal scheme that supplies biases to the single SDD rings. All 384 anodes of SDDs are connected to individual electronic channels. This effort was motivated by the need of improving the energy resolution and the throughput of existing diode-based Maia detectors.

We have constructed a pixelated germanium detector using a technique which has been shown to provide good isolation between adjacent pixels. In this work we present initial tests of the application of a low-noise CMOS ASIC to read out this detector. The detector has 64 pixels, each 0.5mm × 5mm, arranged as a series of strips. It is connected by wire-bonds to two 32-channel ASICs (Application-Specific Integrated Circuit) which provide a complete photon-counting chain for every channel. Since the size of the pixel array is no longer restricted by the difficulties of instrumenting large channel-count conventional electronics, this development will open up the possibility of even larger arrays, similar to those offered by silicon detectors.

The eLine10k is a fast-frame, 64-channel readout ASIC for SLAC Linac Coherent Light Source (LCLS) detectors. The circuit has been designed to integrate the charge from high-capacitance 2D sensors with rolling shutter and ID strip sensors. It is suitable for applications requiring large input signal range, on the order of 104 photons/pixel/pulse at 8keV (22Me-), and a resolution of half a photon FWHM (500e- r.m.s). 2D sensors with a rolling shutter like the X-ray Active Matrix Pixel Sensor (XAMPS), for which the ASIC has been optimized, present several pixels which are bussed on the same readout line. Large input capacitance to each channel is expected leading to stringent noise optimization requirements. The large required number of pixels per channel, and the fixed LCLS beam period impose limitations on the time available for the readout of each single pixel. Giving the periodic nature of the LCLS beam, the ASIC developed for this application is a time-variant system, providing low-noise charge integration, filtering and correlated double-sampling, and a processing speed up to 500k pixel/s on each channel. To cope with the large input dynamic range, a charge pump scheme has been implemented using a synchronous zero-balance measurement method. It provides on-chip 4-bit coarse digital conversion of the integrated charge. The residual charge is sampled using correlated double sampling into an analog memory, multiplexed and measured with the required resolution using an external ADC. In this paper, the ASIC architecture and performance of the final release are presented.

The Vertically Integrated Photon Imaging Chip (VIPIC) project explores opportunities of the three-dimensional integration for imaging of X-rays. The design details of the VIPIC1 chip are presented and are followed by results of testing of the chip. The VIPIC1 chip was designed in a 130 nm process, in which through silicon vias are embedded right after the front-end-of-line processing. The integration of tiers is achieved by the Cu-Cu thermo-compression or Cu-based oxide-oxide bonding. The VIPIC1 readout integrated circuit was designed for high timing resolution, pixel based, X-ray Photon Correlation Spectroscopy experiments typically using 8 keV X-rays at a synchrotron radiation facility. The design was done for bonding a Silicon pixel detector, however other materials can be serviced as long as the positive polarity of charge currents is respected.

A new Maia detector is being currently developed, consisting of an array of 384 silicon drift detectors (SDDs), each having an area of 1 mm2. The detector features a new double metal scheme that supplies biases to the pixel SDD rings. All 384 anodes of SDDs are meant to be connected to individual electronic channels. This effort was motivated by the need of improving the energy resolution and the throughput of the existing Maia detectors whose pixels are based on p-in-n diodes. In order to use the existing circuit boards and back-end electronics that have already developed for the original Maia, the SDD-Maia detector was designed with an identical footprint, after replacing the p-in-n diodes with SDDs. The design, fabrication and performance of a first prototype detector will be presented.

The motion of atoms on interatomic potential energy surfaces is fundamental to the dynamics of liquids and solids. An accelerator-based source of femtosecond x-ray pulses allowed us to follow directly atomic displacements on an optically modified energy landscape, leading eventually to the transition from crystalline solid to disordered liquid. We show that, to first order in time, the dynamics are inertial, and we place constraints on the shape and curvature of the transition-state potential energy surface. Our measurements point toward analogies between this nonequilibrium phase transition and the short-time dynamics intrinsic to equilibrium liquids.

The objective of this paper is to describe a Switcher ASIC with 64 high voltage output channels. Each channel provides two high voltage control pulses with maximum amplitudes of 32 V. The high voltage level shifter was designed with a current mirror switching circuit that has a readily adjustable switching speed, unlike conventional switching circuits. The logic control circuit uses a forward and reverse chain of Flip-Flops along with other combinational logic gates to generate bidirection sequential control pulses with adjustable pulsewidth and polarity. The layout was carefully designed to achieve a 14 μ m width for the last stage transistors' drain path based on the 50 μm output channel pitch set up. At least a 200 mA current driving capability was obtained for each channel. The design was fabricated using TSMC's 180 nm CMOS HV technology. The paper further discusses the critical design steps including chip architecture, layout, simulation and bench test. The final experimental results demonstrate that the Switcher ASIC meets requirements and the rising time could reach 480 ns with a 1 nF capacitive load at 15 V pulse amplitude. With this load, the total power consumption of the chip was measured to be approximately 4 mW when the input clock period was 42.2 μs. In addition to use in a charge-pump detector, the ASIC can be used to control the charge accumulation and readout in other detectors, such as X-ray pump probe detectors (XPP).

The fundamental parameter method for quantitative SXRF and PIXE analysis and imaging using the dynamic analysis method is extended to model the changing X-ray yields and detector sensitivity with angle across large detector arrays. The method is implemented in the GeoPIXE software and applied to cope with the large solid-angle of the new Maia 384 detector array and its 96 detector prototype developed by CSIRO and BNL for SXRF imaging applications at the Australian and NSLS synchrotrons. Peak-to-background is controlled by mitigating charge-sharing between detectors through careful optimization of a patterned molybdenum absorber mask. A geological application demonstrates the capability of the method to produce high definition elemental images up to ∼100 M pixels in size.

Application of nuclear microprobe event-by-event data acquisition approaches to synchrotron elemental imaging is at the heart of the design of a large energy-dispersive detector array called Maia, under development by CSIRO and BNL for SXRF elemental imaging on the X-ray microprobe. A new project is aimed at harnessing this development to provide high throughput PIXE imaging on the CSIRO Nuclear Microprobe. Maia combines a 1.2 sr solid-angle 384 detector array, integrated scanning and real-time processing including spectral deconvolution of full-spectral data. Results using a Maia prototype demonstrate the potential using SXRF application data with elemental images of up 100 M pixels.

Micro-fabricated bi-prisms have been used to create an interference pattern from an incident hard X-ray beam, and the intensity of the pattern probed with fluorescence from a 30 nm-thick metal film. Maximum fringe visibility exceeded 0.9 owing to the nano-sized probe and the choice of single-crystal prism material. A full near-field analysis is necessary to describe the fringe field intensities, and the transverse coherence lengths were extracted at APS beamline 8-ID-I. It is also shown that the maximum number of fringes is dependent only on the complex refractive index of the prism material.

Synchrotron X-ray fluorescence (SXRF) and X-ray absorption spectroscopy (XAS) have become standard tools to measure element concentration, distribution at micrometer- to nanometer-scale, and speciation (e.g., nature of host phase; oxidation state) in inhomogeneous geomaterials. The new Maia X-ray detector system provides a quantum leap for the method in terms of data acquisition rate. It is now possible to rapidly collect fully quantitative maps of the distribution of major and trace elements at micrometer spatial resolution over areas as large as 1 × 5 cm2. Fast data acquisition rates also open the way to X-ray absorption near-edge structure (XANES) imaging, in which spectroscopic information is available at each pixel in the map. These capabilities are critical for studying inhomogeneous Earth materials. Using a 96-element prototype Maia detector, we imaged thin sections of an oxidized pisolitic regolith (2 × 4.5 mm2 at 2.5 × 2.5 μm2 pixel size) and a metamorphosed, sedimentary exhalative Mn-Fe ore (3.3 × 4 mm2 at 1.25 × 5 μm2). In both cases, As K -edge XANES imaging reveals localized occurrence of reduced As in parts of these oxidized samples, which would have been difficult to recognize using traditional approaches.

Several sets of hexagonal Silicon Drift Detector (SDD) arrays were produced by Brookhaven National Laboratory (BNL) and by the commercial vendor, KETEK. These detector arrays were tested at BNL. Each array consists of 14 independent SDD detectors (pixels) and two additional test pixels located at two corners of the array. The side of the detector upon which the X-ray radiation is incident (window side) has a thin junction covering the entire active area. The opposite side (device side) contains a drift-field electrode structure in the form of a hexagonal spiral and an electron collecting anode. There are four guard rings surrounding the 14-pixel array area on each side of the detector. Within each array, seven pixels have aluminum field plates - interrupted spirals that stabilize the electric potential under the Si- SiO2 interface, while the other seven do not. Three bias voltages are applied to control the drift field in the silicon volume; one is applied to a rectifying contact surrounding the central anode (one for each pixel), one is applied to the detector entrance window (common to the full array), and a third bias is applied to a contact on the outer portion of the spiral, common to all pixels in the array. Some arrays were recently tested in NSLS beam line U3C at BNL. For this work, we installed the complete assemblies in the vacuum and cooled them to -27degC. During this beam run, we collected spectra for energies ranging between 350 and 900 eV in several pixels, some with field plates and others without. The detailed testing results of several arrays are reported here.

A detector concept is described that integrates a large solid-angle detector array developed at Brookhaven National Laboratory and a high speed pipelined parallel processing engine developed at CSIRO for machine vision, with an embedded implementation of the Dynamic Analysis method for fluorescence spectra deconvolution and image projection, to yield a detection system capable of energy-dispersive detection, spectral deconvolution and real-time elemental imaging at ∼108 events per second for PIXE elemental imaging using the nuclear microprobe and SXRF elemental imaging using the synchrotron X-ray microprobe.

Measurement of X-rays produced in nonlinear Thomson scattering of high power laser and electron beams is a good test of electrodynamics in the high field region. We performed an experiment of head-on collision between sub-terawatt CO 2 laser and 60-MeV electron beams at Brookhaven National Laboratory, Accelerator Test Facility. Angular distributions of X-rays produced in Thomson scattering were measured and contribution of the second order nonlinear interaction was observed by comparing the distributions with Monte Carlo simulations based on the semi-classical theory of photon-electron interactions.

Thomson scattering of high-power laser and electron beams is a good test of electrodynamics in the high-field region. We demonstrated production of high-intensity X-rays in the head-on collision of a CO2 laser and 60-MeV electron beams at Brookhaven National Laboratory, Accelerator Test Facility. The energy of an X-ray photon was limited at 6.5 keV in the linear (lowest order) Thomson scattering, but the nonlinear (higher order) process produces higher energy X-rays. We measured the angular distribution of the high-energy X-rays and confirmed that it agrees with theoretical predictions.

High-energy transmission x-ray diffraction techniques have been applied to investigate the crystal quality of CdZnTe (CZT). CdZnTe has shown excellent performance in hard x-ray and gamma detection; unfortunately, bulk nonuniformities still limit spectroscopic properties of CZT detectors. Collimated high-energy x-rays, produced by a superconducting wiggler at the National Synchrotron Light Source’s X17B1 beamline, allow for a nondestructive characterization of thick CZT samples (2–3 mm). In order to have complete information about the defect distribution and strains in the crystals, two series of experiments have been performed. First, a monochromatic 67 keV x-ray beam with the size of 300×300 µm2 was used to measure the rocking curves of CZT crystals supplied by different material growers. A raster scan of a few square centimeter area allowed us to measure the full-width at half-maximum (FWHM) and shift in the peak position across the crystal. The rocking curve peak position and its FWHM can be correlated with local stoichiometry variations and other local defects. Typically, the FWHM values ranging from 8.3 arcsec to 14.7 arcsec were measured with the best crystal used in these measurements. Second, transmission white beam x-ray topography (WBXT) was performed by using a 22 mm×200 µm beam in the energy range of 50 keV to 200 keV. These types of measurements allowed for large area, high-resolution (50 µm) scans of the samples. Usually, this technique is used to visualize growth and process-induced defects, such as dislocations, twins, domains, inclusions, etc. the difference in contrast shows different parts of the crystal that could not be shown otherwise. In topography, good contrast is indicative of a high quality of the sample, while blurred gray shows the presence of defects. Correlation with other techniques (e.g., infrared (IR) mapping and gamma mapping) was also attempted. Our characterization techniques, which use highly penetrating x-rays, are valid for in-situ measurements, even after electrical contacts have been formed on the crystal in a working device. Thus, these studies may lead to understanding the effects of the defects on the device performance and ultimately to improving the quality of CZT material required for device fabrication. It is important to study crystals from different ingot positions (bottom, center, and top); consequently, more systematic studies involving scans from center to border are planned.

Maia Mapper is a laboratory μXRF mapping system for efficient elemental imaging of drill core sections serving minerals research and industrial applications. It targets intermediate spatial scales, with imaging of up to ~80 M pixels over a 500×150 mm2 sample area. It brings together (i) the Maia detector and imaging system, with its large solid-angle, event-mode operation, millisecond pixel transit times in fly-scan mode and real-time spectral deconvolution and imaging, (ii) the high brightness MetalJet D2 liquid metal micro-focus X-ray source from Excillum, and (iii) an efficient XOS polycapillary lens with a flux gain ~15,900 at 21 keV into a ~32 μm focus, and (iv) a sample scanning stage engineered for standard drill-core sections. Count-rates up to ~3 M/s are observed on drill core samples with low dead-time up to ~1.5%. Automated scans are executed in sequence with display of deconvoluted element component images accumulated in real-time in the Maia detector. Application images on drill core and polished rock slabs illustrate Maia Mapper capabilities as part of the analytical workflow of the Advanced Resource Characterisation Facility, which spans spatial dimensions from ore deposit to atomic scales.

The use of bent asymmetric Laue crystals to sagittally focus high-energy synchrotron X-rays calls for an understanding of the mechanisms affecting X-ray diffraction by such crystals. The rocking-curve width, a measurable quantity directly related to the distortion of the lattice planes, is the necessary first step towards such an understanding. A model is formulated for assessing the rocking-curve widths of sagittally bent Laue crystals, considering the elastic anisotropy. A method for depth-resolved measurement of the rocking curves was also developed to verify the model. The model successfully explains the wide range of rocking-curve widths of a large number of reflections from silicon crystals with two different orientations.

An on-chip algorithm for the allocation of a hit to a single pixel in the presence of charge sharing in a highly segmented pixel detector is presented. It has been developed to advance pixel detector technology for experiments with X-ray beams at a synchrotron facility. Its key elements are: activation of groups of pixels (neighborhood_active), comparisons of peak amplitudes within the active neighborhood, virtual pixels that recover composite signals, ability to create event driven strobes to control comparisons of fractional signals between neighboring pixels and finally latching of the results of these comparisons. The miniVIPIC prototype was designed in a 130 nm process, as a proof of feasibility. The chip contains an array of 32×32 100×100 µm2 pixels. Analog and digital signals are exchanged between pixels, forming an extensive inter-pixel connection grid, whose routing to minimize parasistics, represented the major challenge. The design details of the chip are provided.

A comprehensive study of microgravity and ground-grown chicken egg-white lysozyme crystals is presented using synchrotron X-ray reciprocal-space mapping, topography techniques and diffraction resolution. Microgravity crystals displayed reduced intrinsic mosaicities on average, but no differences in terms of strain over their ground-grown counterparts. Topographic analysis revealed that in the microgravity case the majority of the crystal was contributing to the peak of the reflection at the appropriate Bragg angle. In the ground-control case only a small volume of the crystal contributed to the intensity at the diffraction peak. The techniques prove to be highly complementary, with the reciprocal-space mapping providing a quantitative measure of the crystal mosaicity and strain (or variation in lattice spacing) and the topography providing a qualitative overall assessment of the crystal in terms of its X-ray diffraction properties. Structural data collection was also carried out at the synchrotron.

An experimental demonstration showing that a one-dimensional focus can be produced by using the principle of inclined diffraction from a perfect crystal is presented. By machining a groove with a controlled cross-sectional profile it is shown that it is possible to vary the out-of-plane deviations in a controlled manner and hence generate a focus. Also demonstrated is the use of four reflections in (−,+,+,−) dispersive geometry resulting in the cancellation of all beam-spreading in the orthogonal direction. The experiment used an energy of 15 keV with a source-to-crystal distance of 13.5 m and crystal-to-focus distance of 4.5 m. A focus of width 0.29 mm was produced from an incident beam of width 2.7 mm. It is clear from the measurements that a better surface finish would result in a smaller focal spot.

Fast centroid-finding electronics are being developed for a range of position-sensitive gas proportional detectors. Each cathode strip feeds a preamplifier, shaper and a free-running ADC. Increased total count rate is achieved by dividing the detector into several segments with parallel processing that introduces no common dead time. Each segment has central-channel finding logic and event listing realized in a FPGA, followed by a DSP that performs the centroid calculation and histogramming. Measured count-rate per segment exceeds 10/sup 6/ per second, with virtually no dead time.

Polarization phenomena are present in every radiative transition, whether it is of atomic or nuclear origin. Nuclear resonant scattering of synchrotron radiation is an ideal technique for their study because (a) the probing radiation is in a well characterized polarization state, in most cases linear, (b) the scattered radiation can be efficiently analyzed with polarization filters, and (c) synchrotron pulses are very short compared to the lifetime of a nuclear resonance, resulting in a clean signal. In the following article we describe experimental and theoretical studies of the 14.4 keV Mossbauer resonance of 57Fe and its transitions with linear and circular polarization. After introducing the required instrumentation a formalism to calculate time dependent polarization phenomena is derived. With the help of different scattering geometries we illustrate various aspects, such as polarization mixing and selective excitation of subsets of the resonance. Perhaps the most fascinating example is the Faraday geometry where the E-vector rotates several 360ο turns during the lifetime of the resonant scattering. A comparison of this phenomenon with the optical Faraday effect is given. New powerful synchrotron radiation sources will enable researchers to exploit polarization phenomena in nuclear resonant scattering to detect subtle changes in physically and chemically relevant systems.

We describe here the data acquisition subsystem of the Quick EXAFS (QEXAFS) experiment at the National Synchrotron Light Source of Brookhaven National Laboratory. For ease of future growth and flexibility, almost all software components are open source with very active maintainers. Among them, Linux running on x86 desktop computer, RTAI for real-time response, COMEDI driver for the data acquisition hardware, Qt and PyQt for graphical user interface, PyQwt for plotting, and Python for scripting. The signal (A/D) and energy-reading (IK220 encoder) devices in the PCI computer are also EPICS enabled. The control system scans the monochromator energy through a networked EPICS motor. With the real-time kernel, the system is capable of deterministic data-sampling period of tens of micro-seconds with typical timing-jitter of several micro-seconds. At the same time, Linux is running in other non-real-time processes handling the user-interface. A modern Qt-based controls-front end enhances productivity. The fast plotting and zooming of data in time or energy coordinates let the experimenters verify the quality of the data before detailed analysis. Python scripting is built-in for automation. The typical data-rate for continuous runs are around ten mega-bytes per minute.

The use of a thin metal edge, or blade, to generate controlled electron multiplication in a gas has been studied. Measurements with X-rays have been made on assemblies of an anode blade and two adjacent cathodes to determine optimum operating parameters in gas proportional mode, with the goal of producing position sensitive detectors with good position resolution and high counting rate. Under specific conditions, energy resolution comparable to that from a wire proportional chamber can be achieved. The devices 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. The design of detectors suitable for use with synchrotron radiation, is discussed.

The high aspect ratio, deep x-ray lithography and electrodeposition process [Becker et al. (1986)] can be expensive unless throughput is high enough. The use of a very high energy synchrotron has allowed the cost of exposure to be significantly reduced through simultaneous exposure of stacked photoresist [Guckel et al (1994)]. Synchrotron radiation at high photon energies has resulted the use of a large area x-ray mask. Both stacked exposures and a large area x-ray masks have significantly increased the throughput of the deep x-ray lithography and electrodeposition process.

Maia is an advanced system designed specifically for scanning x-ray fluorescence microprobe applications. It consists of a large array of photodiode detectors and associated signal processing, closely coupled to an FPGA-based control and analysis system. In this paper we will describe the architecture and construction of the system.

Growth-induced defects in lysozyme crystals were observed by white-beam and monochromatic X-ray topography at the National Synchrotron Light Source (NSLS) at the Brookhaven National Laboratory (BNL). The topographic methods were non-destructive to the extent that traditional diffraction data collection could be performed to high resolution after topography. It was found that changes in growth parameters, defect concentration as detected by X-ray topography, and the diffraction quality obtainable from the crystals were all strongly correlated. In addition, crystals with fewer defects showed lower mosaicity and higher diffraction resolution as expected.

X-ray fluorescence images acquired using the Maia large solid-angle detector array and integrated real-time processor on the X-ray Fluorescence Microscopy (XFM) beamline at the Australian Synchrotron capture fine detail in complex natural samples with images beyond 100M pixels. Quantitative methods permit real-time display of deconvoluted element images and for the acquisition of large area XFM images and 3D datasets for fluorescence tomography and chemical state (XANES) imaging. This paper outlines the Maia system and analytical methods and describes the use of the large detector array, with a wide range of X-ray take-off angles, to provide sensitivity to the depth of features, which is used to provide an imaging depth contrast and to determine the depth of rare precious metal particles in complex geological samples.

Mossbauer spectroscopy using synchrotron radiation has previously been limited by the presence of a large non-resonant radiation background which dominates the detector performance and in turn limits the useable incident flux. In this paper we show that it is possible, by using the polarization properties of hyperfine-split Mossbauer resonances in conjunction with a perfect-crystal polarimeter, to completely remove this limitation for enriched samples. For samples with natural isotopic abundance, signal-to-noise ratios close to unity are demonstrated.

Phase I of the X21 beamline at the National Synchrotron Light Source was commissioned during 1993. The research program at the X21 beamline is focused on the study of electronic excitations in condensed matter with total energy resolution of 0.1–1.0 eV. The source is a 27‐pole hybrid wiggler. A water‐cooled horizontal focusing Si(220) monochromator and a spherically bent Si(444) analyzer were installed and commissioned. At 8 keV the energy resolution of the monochromator is about 0.7 eV, and the energy resolution of the analyzer is about 0.1 eV. Results from several selected experiments are also discussed.

"eLine", a class of multichannel time-variant integrating front-end Application Specific Integrated Circuits (ASICs), has been completed at SLAC National Accelerator Laboratory for applications at the Linac Coherent Light Source (LCLS). The class, designed for pixelated sensors with column-parallel readout, is composed of two front-end ASICs: one designed for high-dynamic range applications (eLine10k) and one designed for ultra-low noise applications (eLine100). The first allows large input full-scale signals, on the order of 104 8keV photons, with a resolution of half a photon FWHM; while the second provides low noise charge integration, up to a full-scale signal of 100 8keV photons, with an equivalent noise charge (ENC) of 55e- r.m.s. Three different prototype systems utilizing the ASICs are described. The first is a 32k-pixel X-ray Active Matrix Pixel Sensor (XAMPS) detector developed at Brookhaven National Laboratory (BNL) for the X-ray Pump Probe instrument (XPP) at LCLS. The XAMPS are monolithic detectors with fast-frame readout and large full-scale signal. In particular, they provide a full well capacity on the order of 104 8keV photons per pixel and a resolution of half a photon FWHM. The second prototype, developed around eLine10k, is a beam finder with high dynamic range. The third prototype is developed around eLine100 to be used as detector in a spectrometer. Applications, test results and performance are discussed.

The resonant forward scattering of X-rays from57Fe nuclei is strongly polarization dependent. The broad band excitation provided by synchrotron radiation (SR) results in an interesting time-dependent polarization mixing. This mixing can be used to substantially reduce the nonresonant (nonrotated) scattering from electrons. The presented technique will allow the full utilization of next-generation synchrotron facilities as a source for Mossbauer experiments.