John Weizeorick

A fast, direct x-ray detection charge-coupled device

A charge-coupled device (CCD) capable of 200 Mpixels/s readout has been designed and fabricated on thick, high-resistivity silicon. The CCDs, up to 600 microm thick, are fully depleted, ensuring good infrared to x-ray detection efficiency, together with a small point spread function. High readout speed, with good analog performance, is obtained by the use of a large number of parallel output ports. A set of companion 16-channel custom readout integrated circuits, capable of 15 bits of dynamic range, is used to read out the CCD. A gate array-controlled back end data acquisition system frames and transfers images, as well as provides the CCD clocks.

Development of a compact fast CCD camera and resonant soft x-ray scattering endstation for time-resolved pump-probe experiments

The designs of a compact, fast CCD (cFCCD) camera, together with a resonant soft x-ray scattering endstation, are presented. The cFCCD camera consists of a highly parallel, custom, thick, high-resistivity CCD, readout by a custom 16-channel application specific integrated circuit to reach the maximum readout rate of 200 frames per second. The camera is mounted on a virtual-axis flip stage inside the RSXS chamber. When this flip stage is coupled to a differentially pumped rotary seal, the detector assembly can rotate about 100°/360° in the vertical/horizontal scattering planes. With a six-degrees-of-freedom cryogenic sample goniometer, this endstation has the capability to detect the superlattice reflections from the electronic orderings showing up in the lower hemisphere. The complete system has been tested at the Advanced Light Source, Lawrence Berkeley National Laboratory, and has been used in multiple experiments at the Linac Coherent Light Source, SLAC National Accelerator Laboratory.

High speed, direct detection 1k Frame-Store CCD sensor for synchrotron radiation

This work presents the development of a high speed, direct detection, 1k Frame Store CCD camera for synchrotron radiation. We review the research and development of this detector from small scale prototypes to a megapixel sensor, highlighting design challenges and solutions, and reporting on the achieved imaging performance. Further, we report on performance improvements obtained by implementing a second-generation fast readout integrated circuit manufactured in 0.25µm CMOS technology, as well as a voltage buffer chip manufactured in high voltage 0.35µm CMOS technology. The camera presented in this paper is high vacuum-compatible to allow for soft X-ray detection.

Firmware lower-level discrimination and compression applied to streaming x-ray photon correlation spectroscopy area-detector data

We present a data acquisition system to perform on-the-fly background subtraction and lower-level discrimination compression of streaming x-ray photon correlation spectroscopy data from a fast charge-coupled device (CCD) area detector. The system is built using a commercial frame grabber with an on-board field-programmable gate array. The system is capable of continuously processing at least 60 CCD frames per second each consisting of 1024 × 1024 16-bit pixels with ≲ 15,000 photon hits per frame at a maximum compression factor of ≈95%.

A new detector for time-resolved small angle X-ray scattering studies

A new detector for time-resolved small-angle X-ray scattering has been designed and built for experiments at the Advanced Photon Source of Argonne National Laboratory. This detector is made from a 500 mum thick by 150 mm diameter ultra-high purity silicon wafer, which directly converts X-rays into electron-hole pairs. The electrodes are concentric rings that integrate the scattered X-rays over the azimuthal angle. The widths of the rings are optimized for the size of the X-ray beam and its energy spread. Only 128 rings, or channels, are needed to measure a scattering profile. The read-out electronics consist of preamplifiers with pulse-shaping, which are mounted on the detector, and 12-bit, 20 MHz digitizers. The resolving time of the electronics is 300 ns, which is sufficient to isolate a single pulse of scattered X-rays when the synchrotron is operated with a hybrid or asymmetric fill pattern. The data acquisition hardware can average a programmable number of digital samples, up to 64, every 3.68 mus (the period of the synchrotron) to provides a single 12-bit average of the voltage from the analog amplifier chain. The temporal range of the detector is 3.68 seconds or longer and may be controlled by the experimenter. An alpha source is used to calibrate the detector and electronics, and document their performance. Preliminary results obtained during the commissioning of the detector are presented

A 1MPixel fast CCD sensor for X-ray imaging

This paper describes the performance of a 1MPixel Frame Store CCD sensor for soft X-ray applications at synchrotron light sources. This camera can be operated in frame store mode with a 1Mpixel imaging area running at 200fps, or in full frame mode with a 2M pixels imaging area running at 100fps. The CCD has 192 outputs that are serviced by custom-designed integrated circuits that perform correlated double-sampling signal processing and digitization. The digitized data is acquired by a custom made image acquisition and camera controller board based on the Advanced Telecommunication Computing Architecture system. Results obtained during a test run at the Advanced Light Source are presented demonstrating the X-ray camera performance.

A High-Speed One-Dimensional Detector for Time-Resolved Small-Angle X-Ray Scattering: Design and Characterization

A high-speed one-dimensional detector for time-resolved small-angle x-ray scattering has been designed and built for experiments at the Advanced Photon Source of Argonne National Laboratory. This detector is made from a 500-μm thick by 150-mm diameter ultra-high-purity n-type silicon wafer. The electrodes, which are a series of concentric rings that are deposited in the wafer, integrate the scattered x-rays over the azimuthal angle and, thereby, produce a one-dimensional detector. This design yields 128 rings, which allows parallel processing of the signal from each ring. The readout electronics consist of transimpedance front-end amplifiers, one for each ring, followed by active pulse-shaping filters. The amplifier signals are digitized using 12-bit analog-to-digital converters, one per ring, which operate at 20 MHz. The frame rate of the system is 271 kHz. Up to 220 - 1 scattering profiles may be stored on a random access memory chip and transferred to a data file at a rate of 16 × 103 profiles/sec. For X-ray energies between 3.5 and 13.2 keV the efficiency exceeds 80%. The resolving time of the electronics is 300 ns, which is sufficient to isolate electronically a single pulse of scattered x-rays when the synchrotron is operated in a hybrid or asymmetric fill pattern. Therefore, laser-pump/x-ray-probe experiments can be performed without a mechanical shutter. Examples of time-resolved speckle and the kinetics of the formation of sodium chloride particles are presented. This detector is capable of acquiring small-angle x-ray scattering profiles over multiple time scales, which are needed to characterize many chemical, physical, and biological processes. In addition, this detector may be tested and calibrated before experimental runs, without access to an intense beam of x-rays, with alpha particles from a radioactive source such as 241Am.

2-D scintillation position-sensitive neutron detector

A new 2-dimensional scintillation position-sensitive neutron detector (PSND) with an active area of 155times155 mm2 was developed for use on the single crystal diffractometer at the intense pulsed neutron source at Argonne National Laboratory. The detector is based on the well-proven Anger camera technique and uses a 6Li glass scintillator as the neutron converter. This PSND incorporates a 6times6 PMT array with 29.6 mm pitch and optimized optics to achieve an average spatial resolution of 1.75 mm full width at half maximum. The detector read-out has separate electronics for each PMT and the neutron position is calculated by a microprocessor during acquisition. A newly developed position extraction algorithm makes use of an analytical calculation to determine the event position. This new method improves the linearity of the calculated position, provides a slight improvement in resolution, and in principle allows for the correct determination of position to the edge of the scintillator. The design of the detector enclosure allows multiple detectors to be tiled with minimal dead space between them. In addition, the design incorporates a means of attaching external shielding plates that minimizes the shielding surface area required

Real-time MPI-based software for processing of XPCS data

We describe a software library, called MPIFCCD, based on the Message Passing Interface (MPI) for real-time parallel computing on data continuously streamed from the Frame Store Fast Charge-Coupled Device (FSFCCD) Detector located at the Advanced Photon Source (APS) at Argonne National Laboratory. The FSFCCD is used to collect data for X-ray Photon Correlation Spectroscopy (XPCS) experiments at Sector 8-ID at APS. MPIFCCD is integrated into another software package called CINController, developed at APS and Lawrence Berkeley National Laboratory to serve as a QT-based user interface for control and data collection from the FSFCCD. Real-time calculations performed by MPIFCCD include dark image integration and subtraction, noise image integration, image descrambling, and lower-level discrimination. MPIFCCD allows for continuous real-time data collection of FSFCCD data at image rates of 100 frames- per-second (fps) for 1 mega-pixel images and 1000fps for 10 kilo-pixel images. In the future, more complex computations will be implemented in real time with MPIFCCD.

Development of an ATCA based data acquisition system for high speed, direct detection X-ray pixel sensors

Large format X-ray pixel sensors operating at frame rates higher than 100 frames per second have driven the need to develop data acquisition systems capable of handling large volumes of acquired data using ultra-fast communication links operating at 10 Gigabit/s rates. The new generation 1 Megapixel X-Ray cameras currently being developed at LBNL, operating at readout speeds of up to 200 frames per second, are capable of producing greater than 400 Megabytes of image data per second. Because these sensors are used in continuous source applications with long acquisition periods (e.g., at synchrotron radiation light sources), the acquired data must be reliably processed and stored in real-time to minimize exposure dead time or data loss that could compromise the integrity of the data and thus limit the scientific reach of the experiment. This work describes the development and performance of an Advanced Telecommunications Computing Architecture (ATCA) based data acquisition system used for high speed, direct detection X-ray pixel sensors, focusing on the technical challenges and solutions of moving large data volumes through digital signal processing algorithms and to storage arrays in real-time.