John Joseph

Frequency multiplexed superconducting quantum interference device readout of large bolometer arrays for cosmic microwave background measurements

A technological milestone for experiments employing transition edge sensor bolometers operating at sub-Kelvin temperature is the deployment of detector arrays with 100s-1000s of bolometers. One key technology for such arrays is readout multiplexing: the ability to read out many sensors simultaneously on the same set of wires. This paper describes a frequency-domain multiplexed readout system which has been developed for and deployed on the APEX-SZ and South Pole Telescope millimeter wavelength receivers. In this system, the detector array is divided into modules of seven detectors, and each bolometer within the module is biased with a unique ∼MHz sinusoidal carrier such that the individual bolometer signals are well separated in frequency space. The currents from all bolometers in a module are summed together and pre-amplified with superconducting quantum interference devices operating at 4 K. Room temperature electronics demodulate the carriers to recover the bolometer signals, which are digitized separately and stored to disk. This readout system contributes little noise relative to the detectors themselves, is remarkably insensitive to unwanted microphonic excitations, and provides a technology pathway to multiplexing larger numbers of sensors.

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.

Integrating Substrateless Electrospinning with Textile Technology for Creating Biodegradable Three-Dimensional Structures

The present study describes a unique way of integrating substrateless electrospinning process with textile technology. We developed a new collector design that provided a pressure-driven, localized cotton-wool structure in free space from which continuous high strength yarns were drawn. An advantage of this integration was that the textile could be drug/dye loaded and be developed into a core-sheath architecture with greater functionality. This method could produce potential nanotextiles for various biomedical applications.

Femtosecond X-ray magnetic circular dichroism absorption spectroscopy at an X-ray free electron laser

X-ray magnetic circular dichroism spectroscopy using an X-ray free electron laser is demonstrated with spectra over the Fe L(3,2)-edges. The high brightness of the X-ray free electron laser combined with high accuracy detection of incident and transmitted X-rays enables ultrafast X-ray magnetic circular dichroism studies of unprecedented sensitivity. This new capability is applied to a study of all-optical magnetic switching dynamics of Fe and Gd magnetic sublattices in a GdFeCo thin film above its magnetization compensation temperature.

Electrospun Polymeric Core–sheath Yarns as Drug Eluting Surgical Sutures

Drug-coated sutures are widely used as delivery depots for antibiotics and anti-inflammatory drugs at surgical wound sites. Although drug-laden coating provides good localized drug concentration, variable loading efficiency and release kinetics limits its use. Alternatively, drug incorporation within suture matrices is hampered by the harsh fabrication conditions required for suture-strength enhancement. To circumvent these limitations, we fabricated mechanically robust electrospun core-sheath yarns as sutures, with a central poly-l-lactic acid core, and a drug-eluting poly-lactic-co-glycolic acid sheath. The electrospun sheath was incorporated with aceclofenac or insulin to demonstrate versatility of the suture in loading both chemical and biological class of drugs. Aceclofenac and insulin incorporated sutures exhibited 15% and 4% loading, and release for 10 and 7 days, respectively. Aceclofenac sutures demonstrated reduced epidermal hyperplasia and cellularity in skin-inflammation animal model, while insulin loaded sutures showed enhanced cellular migration in wound healing assay. In conclusion, we demonstrate an innovative strategy of producing mechanically strong, prolonged drug-release sutures loaded with different classes of drugs.

Data Acquisition and Trigger System of the Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA)

The Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA), capable of determining the energy and position (within 2 mm) of each gamma-ray interaction point and tracking multiple gamma-ray interactions, has been designed. GRETINA will be composed of seven detector modules, each with four highly pure germanium crystals. Each crystal has 36 segments and one central contact instrumented by charge sensitive amplifiers. Two custom designed modules, the Digitizer/Digital Signal Processing (DSP) and the Trigger Timing and Control, compose the electronics of this system. The digitizer/DSP converts the analog information with 14-bit analog to digital converters operating at 100 MS/s, and digitally processes the data to determine the energy and timing information of the gamma interactions with the crystal. Each Digitizer/DSP is controlled by and sends trigger information to the Trigger Timing & Control system through a bidirectional Gbit link. Presently four different trigger algorithms are planned for the trigger system and can be selected for trigger decision. In this paper the details of the electronics and algorithms of the GRETINA data acquisition and trigger system are presented and the performance is reviewed.

Measuring spectroscopy and magnetism of extracted and intracellular magnetosomes using soft X-ray ptychography

Significance Magnetotactic bacteria are one of the simplest systems that perform biomineralization: organisms that create inorganic materials using biochemistry under genetic control. They synthesize magnetosomes, which are intracellular, membrane-bound nanoscale single crystals of magnetite, a magnetic iron oxide. We studied the magnetism of individual magnetosomes inside individual cells with spectro-ptychography, a new technique of high-resolution X-ray microscopy. Our results help us to understand how the cells biomineralize magnetosomes and their function in the cell ecophysiology. In addition to demonstrating a large improvement in spatial resolution relative to earlier nonptychography studies, the results presented provide insights into magnetosome biomineralization. Characterizing the chemistry and magnetism of magnetotactic bacteria (MTB) is an important aspect of understanding the biomineralization mechanism and function of the chains of magnetosomes (Fe3O4 nanoparticles) found in such species. Images and X-ray absorption spectra (XAS) of magnetosomes extracted from, and magnetosomes in, whole Magnetovibrio blakemorei strain MV-1 cells have been recorded using soft X-ray ptychography at the Fe 2p edge. A spatial resolution of 7 nm is demonstrated. Precursor-like and immature magnetosome phases in a whole MV-1 cell were visualized, and their Fe 2p spectra were measured. Based on these results, a model for the pathway of magnetosome biomineralization for MV-1 is proposed. Fe 2p X-ray magnetic circular dichroism (XMCD) spectra have been derived from ptychography image sequences recorded using left and right circular polarization. The shape of the XAS and XMCD signals in the ptychographic absorption spectra of both sample types is identical to the shape and signals measured with conventional bright-field scanning transmission X-ray microscope. A weaker and inverted XMCD signal was observed in the ptychographic phase spectra of the extracted magnetosomes. The XMCD ptychographic phase spectrum of the intracellular magnetosomes differed from the ptychographic phase spectrum of the extracted magnetosomes. These results demonstrate that spectro-ptychography offers a superior means of characterizing the chemical and magnetic properties of MTB at the individual magnetosome level.

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.

A model driven engineering approach based on aspects for high speed scientific X-rays cameras

High-speed scientific cameras have been demanding more from their control systems as the number of pixels, and number of frame increases and therefore the required total bandwidth. One way to cope with this demand is to perform realtime image processing. The challenge on that is the fact that each experiment requires a different processing algorithms and one needs to reconfigure it frequently. An example of this system is the LBNL high-speed cameras based on FPGAs used on X-rays and electron microscopy experiments. These camera systems can benefit from modern design methodologies that explore higher abstraction level modeling, which includes both functional and non-functional requirements specification and that take advantage of techniques such as object-oriented and aspect-oriented methodologies. This paper introduces HIPAO, a Hardware Image Processing system based on model driven engineering and Aspect-Oriented modeling. Some examples are shown for each step of the methodology that goes from requirements modeling to automatic code generation.

Implementation and performance of the electronics and computing system of the Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA)

The Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA), a germanium detector system capable of measuring energy and position (within better than 2 mm rms) of gamma-ray interaction points and tracking multiple gamma-ray interactions, has been built. GRETINA is composed of seven detector modules, each with four high purity germanium crystals. Four custom designed electronics support the operation of the detectors: Digitizer/Digital Signal Processing (DSP), Trigger/Timing, Breakout Chassis and the Detector Interface Box. The Digitizer/DSP converts the analog information with 14-bit analog to digital converters operating at 100 MS/s, and digitally processes the data to determine the energy and timing information of the gamma interactions within a crystal. The computing system is composed of VME readout CPUs running VxWorks, which communicate with 62 dual-processor farm (each processor with four cores) through a 10 Gb/s Ethernet switch. The CPUs read out the digitizer/DSPs and send the data to the farm. The processors compute the position and track of the interactions of the gamma-ray inside the crystals. The processor farm is capable of processing in real-time the position of 20 000 gamma-ray/s. In this paper we will present the details of the implementation and performance of the electronics and computing system of GRETINA.