Data bandwidth, timing resolution and resource utilization in readouts of radiation detectors are a constant challenge. Event driven solutions are pushing against well -trenched framed solutions. The idea for an asynchronous readout architecture called EDWARD (Event -Driven With Access and Reset Decoder) was presented at the TWEPP 2021 conference. Here we show the progress of our work which resulted in two chip prototypes. The first one, named 3FI65P1, is a full device with the analog pixel circuitry suited for full -field fluorescence imaging. It is already manufactured, and preliminary results are presented. The second chip, named EDWARD65P1, contains digital pulse generators with Poisson -exponential distribution in each pixel for extraction of the performance matrix of the EDWARD architecture alone.

There is a strong need for a spectroscopy detector for high-energy X-ray application where silicon, the material of choice for direct detection becomes X-ray transparent. Spectroscopic performance needs excellent noise performance and the Equivalent Noise Charge (ENC) in a simple model is directly proportional to the total capacitance at the preamplifier input. Efforts to minimize the pixel capacitance led to the invention of the Silicon Drift Detector (SDD) by Pavel Rehak and Emilio Gatti, at Brookhaven National Laboratory. SDDs are successfully implemented in spectroscopy beamlines at synchrotrons, electron microscopes, handheld devices, etc. However, implementing the drift topology in other semiconductors has been challenging. This has created a major hurdle for high-energy fluorescence experiments where there are clear advantages of using K - shell fluorescence lines. To address these, we propose to fabricate a planar germanium (Ge) drift detector (GDD) which has been attempted but never fabricated successfully. The detector would be fabricated with trenches separating the drift rings and the anode. Details of the sensor, and the spectroscopic performance of the GDD will be presented.

Development of a robust, thin, hole-blocking (n+) contact on high purity germanium (HPGe) has been the main challenge in the development of Ge-based radiation sensors. Yttrium has been reported to be a viable hole-blocking contact on HPGe, and detectors with low leakage have been fabricated. Niobium has also been considered as a potential hole-blocking contact due to its low work function. Here, we investigate interface chemistry and the Schottky barrier height of Y and Nb, as well as electron-blocking contacts Au and Pt, on Ge(100) surfaces using hard x-ray photoelectron spectroscopy. We find a barrier height of 1.05 ± 0.10 eV for Y/HPGe, confirming the formation of a hole-blocking barrier. For Nb/HPGe, the barrier height of 0.13 ± 0.10 eV demonstrates that the interface is not hole-blocking. The Schottky barrier of Au and Pt was found to be 0.45 ± 0.10 and 0.51 ± 0.10 eV, respectively.

A full field X-ray fluorescence imaging system requires two major subsystems: an optical system which provides suitable magnification of the emissions to provide the required spatial resolution while remaining achromatic, and a detector capable of spectral resolution in each pixel. In this work, we will present two examples of full-field imaging optics that satisfy this requirement. The first is a tapered polycapillary optic, the second is a Modified Uniform Redundant Array (MURA) coded aperture. Polycapillary optics have the advantage of giving direct imaging of a sample but are not strictly achromatic. We will show fluorescence slice tomography data from samples using a tapered polycapillary optic with a 5:1 taper. MURAs use the concept of coded aperture arrays which have the attraction of having higher efficiency with 50% open area. Our arrays have 7 µm openings and are truly achromatic in our energy regime (2-14 keV) but require computation to form an image. Using our silicon laboratory at Brookhaven National Laboratory we have produced various orders of MURAs made from gold on a 1 µm thick silicon nitride membrane. A custom detector is being designed for this project. That design is being presented separately at this conference. It will offer 128 x 128 pixels, each 100 µm square, and will provide spectra with around 200eV resolution at 5.9keV. Readout will be sparsified to minimize the required readout bandwidth.

Recent progress in the field of micron-scale spatial resolution direct conversion X-ray detectors for high-energy synchrotron light sources serve applications ranging from nondestructive and noninvasive microscopy techniques which provide insight into the structure and morphology of crystals, to medical diagnostic measurement devices. Amorphous selenium ( a -Se) as a wide-bandgap thermally evaporated photoconductor exhibits ultra-low thermal generation rates for dark carriers and has been extensively used in X-ray medical imaging. Being an amorphous material, it can further be deposited over large areas at room temperatures and at substantially lower costs as compared to crystalline semiconductors. To address the demands for a high-energy and high spatial resolution X-ray detector for synchrotron light source applications, we have thermally evaporated a -Se on a Mixed-Mode Pixel Array Detector (MM-PAD) Application Specific Integrated Circuit (ASIC). The ASIC format consists of 128 × 128 square pixels each 150 μm on a side. A 200 μm a -Se layer was directly deposited on the ASIC followed by a metal top electrode. The completed detector assembly was tested with 45 kV Ag and 23 kV Cu X-ray tube sources. The detector fabrication, performances, Modulation Transfer Function (MTF) measurements, and simulations are reported.

An array of small-area Silicon Drift Detectors (SDD), named Hera, has been developed at Brookhaven National Laboratory (BNL) in the past few years. Its primary application is high-rate spectroscopy at synchrotrons. Each SDD pixel is a 1 mm × 1 mm square to match the footprint of the original diode-based pixel detector called Maia, which was developed for the same application. The replacement of the diode with an SDD allows for better energy resolution at short shaping times and an increased stability of the detector. 32, 96, and 384-channel arrays were designed and fabricated and achieved a Full Width Half Maximum (FWHM) as low as 176 eV at 5.9 keV with peaking time of 1 μs at -13°C. The sensor design, simulation, fabrication, its readout system, and its spectroscopic performance are reported.

We have developed an ionization chamber with fully integrated electronics. It features an extremely low noise charge digitizer, an embedded EPICS IOC and an integrated HV generator capable of providing up to 2000V. It requires only a 5V supply and an Ethernet connection for operation. Its construction uses standard PCB technology to form a rigid chamber with fringe-field correction side plates. Its aperture is 40 mm horizontally by 5 mm vertically, and it is 230 mm (9 inches) long. Its collection plate is split by a zig-zag break to provide approximately 5 mm of position indication in one dimension. When used as a position sensor it gives a position accuracy of 0.8 um standard deviation when operated at 15nA ion current.

There is a strong need for spectroscopy detector for high-energy X-ray application where silicon, the material of choice for direct detection becomes X-ray transparent. Current effort for high-Z materials for high-energy X-ray application is limited to imaging applications. In this work we have fabricated a custom 7-channel germanium pixel detector and instrumented using a low-noise commercial charge sensitive pre-amplifier. The sensor is cooled at about 100K with a commercial closed cycle system, while the in vacuum readout board is thermally isolated from the cold finger. Details of the sensor characteristics and detector performances will be discussed.

Monolithic arrays of silicon p-n junctions are commonly used to deliver spatial information on impinging radiation, with the advantages of low-noise and fast signal generation. Additionally, array geometries also allow for a segmentation of a large area into individual channels that can be read out in parallel, so that a high-event rate can be managed. To optimize the noise performance, however, some key points must be addressed to control the silicon/silicon oxide interface. Replacing the p-n junctions with silicon drift sensors avoids noise related to the interface states, at the expense of a more complicated process and slower signals. In this paper, some of the aspects needing consideration when engineering a monolithic array of silicon sensors are reviewed.

A novel event driven readout architecture, EDWARD (Event Driven with Access and Reset Decoder) architecture, for highly granular pixel detectors is presented. It incorporates, inter alia, an asynchronous arbitration tree based on Seitz’ arbiters, removing the need for an imposed prioritization scheme. It also provides protection against glitches during readout. The system allows not only reading pixel activities, but also retrieving additional data, both analog and digital, from the pixels. A novel in-channel logic allows the entire readout process to be split into consecutive phases for additional flexibility. All operations are controlled by only one edge of the clock signal, seen as an acknowledge token, so there is no dead time between readouts.

In this paper, we summarize briefly some of the future trends in synchrotron science as seen at the National Synchrotron Light Source II, a new, low emittance source recently commissioned at Brookhaven National Laboratory. We touch upon imaging techniques, the study of dynamics, the increasing use of multimodal approaches, the vital importance of data science, and other enabling technologies. Each are presently undergoing a time of rapid change, driving the field of synchrotron science forward at an ever increasing pace. It is truly an exciting time and one in which Roger Cowley, to whom this journal issue is dedicated, would surely be both invigorated by, and at the heart of.

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.

We developed a new front-end application specific integrated circuit (ASIC) for the upgrade of the Maia x-ray microprobe. The ASIC instruments 32 configurable front-end channels that perform either positive or negative charge amplification, pulse shaping, peak amplitude and time extraction along with buffered analog storage. At a gain of 3.6 V/fC, 1 $\mu$s peaking time and a temperature of 248 K, an electronic resolution of 13- and 10 electrons rms was measured with and without a SDD sensor respectively. A spectral resolution of 170 eV FWHM at 5.9 keV was obtained with an $^{55}$Fe source. The channel linearity was better than $\pm$ 1 % with rate capabilities up to 40 kcps. The ASIC was fabricated in a commercial 250 nm process with a footprint of 6.3 mm x 3.9 mm and dissipates 167 mW of static power.

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.

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.

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...

A decade ago, prototypes of the Maia detector successfully demonstrated a fresh approach to X-ray fluorescence microscopy (XFM) imaging that combined a massively parallel detector architecture with dedicated pulse shaping and capture on each channel, asynchronous acquisition of X-rays as an event stream, and real-time processing of the event data [1, 2]. Today, a number of XFM beamlines that raster scan a sample through a focused X-ray beam to construct images of element concentration and chemical state use a 384-detector array version of Maia for high-throughput, high-definition XFM. The beamlines include those at the Australian Synchrotron (AS) in Melbourne [3], the PETRA III synchrotron at DESY, Hamburg [4], the CHESS synchrotron at Cornell University in Ithaca [5], and the NSLS-II at Brookhaven National Laboratory (BNL) in New York...

We have investigated the band alignment at the interface of amorphous aluminum oxide (am-Al2O3) grown by atomic layer deposition on p-Ge(100) and the effects of postgrowth annealing using hard x-ray photoelectron spectroscopy and density function theory (DFT). Accurate determination of the valence-band offsets was obtained by comparing the experimentally measured valence bands with DFT-calculated densities of states. The am-Al2O3 density of states calculated from a weighted ensemble of crystalline Al2O3 structures gives excellent agreement with experiment, sufficiently capturing the nonlinear shape of the valence-band edge. We report a valence-band offset of 2.60 +/- 0.1 eV for am-Al2O3/p-Ge, which is reduced by 0.20 eV upon annealing as interfacial GeOx is formed.

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