A. Kuczewski

The Maia Spectroscopy Detector System: Engineering for Integrated Pulse Capture, Low-Latency Scanning and Real-Time Processing

The Maia detector system is engineered for energy dispersive x‐ray fluorescence spectroscopy and elemental imaging at photon rates exceeding 107/s, integrated scanning of samples for pixel transit times as small as 50μs and high definition images of 108 pixels and real‐time processing of detected events for spectral deconvolution and online display of pure elemental images. The system developed by CSIRO and BNL combines a planar silicon 384 detector array, application‐specific integrated circuits for pulse shaping and peak detection and sampling and optical data transmission to an FPGA‐based pipelined, parallel processor. This paper describes the system and the underpinning engineering solutions.

The New Maia Detector System: Methods For High Definition Trace Element Imaging Of Natural Material

Motivated by the need for megapixel high definition trace element imaging to capture intricate detail in natural material, together with faster acquisition and improved counting statistics in elemental imaging, a large energy‐dispersive detector array called Maia has been developed by CSIRO and BNL for SXRF imaging on the XFM beamline at the Australian Synchrotron. A 96 detector prototype demonstrated the capacity of the system for real‐time deconvolution of complex spectral data using an embedded implementation of the Dynamic Analysis method and acquiring highly detailed images up to 77 M pixels spanning large areas of complex mineral sample sections.

Maia X-ray fluorescence imaging: Capturing detail in complex natural samples

Motivated by the challenge of capturing complex hierarchical chemical detail in natural material from a wide range of applications, the Maia detector array and integrated realtime processor have been developed to acquire X-ray fluorescence images using X-ray Fluorescence Microscopy (XFM). Maia has been deployed initially at the XFM beamline at the Australian Synchrotron and more recently, demonstrating improvements in energy resolution, at the P06 beamline at Petra III in Germany. Maia captures fine detail in element images beyond 100 M pixels. It combines a large solid-angle annular energy-dispersive 384 detector array, stage encoder and flux counter inputs and dedicated FPGA-based real-time event processor with embedded spectral deconvolution. This enables high definition imaging and enhanced trace element sensitivity to capture complex trace element textures and place them in a detailed spatial context. Maia hardware and software methods provide per pixel correction for dwell, beam flux variation, dead-time and pileup, as well as off-line parallel processing for enhanced throughput. Methods have been developed for real-time display of deconvoluted SXRF element images, depth mapping of rare particles and the acquisition of 3D datasets for fluorescence tomography and XANES imaging using a spectral deconvolution method that tracks beam energy variation.

Development of a high-rate high-resolution detector for EXAFS experiments

A new detector for EXAFS experiments is being developed. It is based on a multi-element Si sensor and dedicated readout application specific integrated circuit (ASIC). The sensor is composed of 384 pixels, each having 1 mm/sup 2/ area, arranged in four quadrants of 12/spl times/8 elements and it is wire-bonded to 32-channel ASICs. Each channel implements low-noise preamplification with self-adaptive continuous reset, high-order shaper, bandgap referenced baseline stabilizer, one threshold comparator, and two digital-analog converter (DAC) adjustable window comparators, each followed by a 24-bit counter. Fabricated in 0.35 /spl mu/m CMOS, the ASIC dissipates about 8 mW per channel. First measurements show at room temperature a resolution of 14e/sup -/ rms without the detector and 40 e/sup -/ rms (340 eV) with the detector connected and biased. Cooling to -35 C a full width at half maximum (FWHM) of 205 eV (167 eV from electronics) was measured at the Mn-K/spl alpha/ line. A resolution of about 300eV was measured for rates approaching 100 kc/s per channel, corresponding to an overall rate in excess of 10 Mc/s/cm/sup 2/. Channel-to channel threshold dispersion after DAC adjustment 2.5 was e/sup -/ root mean square.

Acoustic Injectors for Drop-On-Demand Serial Femtosecond Crystallography

X-ray free-electron lasers (XFELs) provide very intense X-ray pulses suitable for macromolecular crystallography. Each X-ray pulse typically lasts for tens of femtoseconds and the interval between pulses is many orders of magnitude longer. Here we describe two novel acoustic injection systems that use focused sound waves to eject picoliter to nanoliter crystal-containing droplets out of microplates and into the X-ray pulse from which diffraction data are collected. The on-demand droplet delivery is synchronized to the XFEL pulse scheme, resulting in X-ray pulses intersecting up to 88% of the droplets. We tested several types of samples in a range of crystallization conditions, wherein the overall crystal hit ratio (e.g., fraction of images with observable diffraction patterns) is a function of the microcrystal slurry concentration. We report crystal structures from lysozyme, thermolysin, and stachydrine demethylase (Stc2). Additional samples were screened to demonstrate that these methods can be applied to rare samples.

Revealing hidden paint layers in oil paintings by means of scanning macro-XRF: a mock-up study based on Rembrandt's “An old man in military costume”

Over the past several decades the oeuvre of Rembrandt has been the subject of extensive art historical and scientific investigations. One of the most striking features to emerge is his frequent re-use of canvases and panels. The painting An Old Man in Military Costume (78.PB.246), in the collection of the J. Paul Getty Museum, is an example of such a re-used panel. Conventional imaging techniques revealed the presence of a second portrait under the surface portrait, but the details of this hidden portrait have not yet been revealed. Vermilion (HgS) has been identified to have been used nearly exclusively in the flesh tones of the lower painting, suggesting that element-specific XRF imaging might successfully image the hidden portrait. To test this hypothesis, a full-scale mock-up of the painting was created, including a “free impression” of the hidden portrait, reproducing as closely as possible the pigments and paint stratigraphy of the original painting. XRF imaging of the mock-up painting was conducted using three different XRF imaging systems: a mobile X-ray tube based system and two synchrotron-based setups (one equipped with multiple SDDs and one equipped with a Maia detector). The sensitivity, limits of detection and imaging capabilities of each system under the chosen experimental conditions are evaluated and compared. The results indicate that an investigation of the original painting by this method would have an excellent chance of success.

High-throughput X-ray fluorescence imaging using a massively parallel detector array, integrated scanning and real-time spectral deconvolution

A step improvement in X-ray fluorescence imaging performance is demonstrated through close integration of a large detector array, dedicated data acquisition, stage control and real-time parallel data processing, to achieve efficient elemental imaging with <1 ms per pixel, image sizes in excess of 4 megapixels, full-spectral data collection and spectral deconvolution, at detected photon rates up to 6 M/s, in prototype tests at the NSLS using a 96 detector array.

Maia X-ray Microprobe Detector Array System

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.

A High-speed Detector System for X-ray Fluorescence Microprobes

We have developed a high-speed system for collecting X-ray fluorescence microprobe data, based on ASICs developed at BNL and high-speed processors developed by CSIRO. The system can collect fluorescence data in a continuous raster scan mode, and present elemental images in real time using Ryans Dynamic Analysis algorithm. We will present results from a 32-element prototype array illustrating the concept. The final instrument will have 384 elements arranged in a square array around a central hole.

A monolithic segmented germanium detector with highly integrated readout

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.