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A 2D smart pixel detector for time-resolved protein crystallography

Description: A smart pixel detector is being developed for Time Resolved Crystallography for biological and material science applications. Using the Pixel detector presented here, the Laue method will enable the study of the evolution of structural changes that occur within the protein as a function of time. The x-ray pixellated detector is assembled to the integrated circuit through a bump bonding process. Within a pixel size of 150 x 150 {mu}m{sup 2}, a low noise preamplifier-shaper, a discriminator, a 3 bit counter and the readout logic are integrated. The readout, based on the Column Architecture principle, will accept hit rates above 5x10{sup 8}/cm{sup 2}/s with a maximum hit rate per pixel of 1 MHz. This detector will allow time resolved Laue crystallography to be performed in a frameless operation mode, without dead time. Target specifications, architecture, and preliminary results on the 8 x 8 front-end prototype and column readout are presented.
Date: October 1, 1995
Creator: Beuville, E.; Cork, C. & Earnest, T.
Partner: UNT Libraries Government Documents Department

The macromolecular crystallography facility at the Advanced Light Source

Description: Synchrotron radiation offers several advantages over the use of rotating anode sources for biological crystallography, which allow for the collection of higher-resolution data, substantially more rapid data collection, phasing by multiwavelength anomalous diffraction (MAD) techniques, and time-resolved experiments using polychromatic radiation (Laue diffraction). The use of synchrotron radiation is often necessary to record useful data from crystals which diffract weakly or have very large unit cells. The high brightness and stability characteristics of the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory, along with the low emittance and long straight sections to accommodate insertion devices present in third generation synchrotrons like the ALS, lead to several advantages in the field of macromolecular crystallography. We are presently constructing macromolecular Crystallography Facility at the ALS which is optimized for user-friendliness and high-throughput data collection, with advanced capabilities for MAD and Laue experiments. The x rays will be directed to three branchlines. A well-equipped support lab will be available for biochemistry, crystal mounting, and sample storage, as well as computer hardware and software available, along with staff support, allowing for the complete processing of data on site.
Date: October 1, 1995
Creator: Earnest, T.; Padmore, H. & Cork, C.
Partner: UNT Libraries Government Documents Department

Framework for control system development

Description: Control systems being developed for the present generation of accelerators will need to adapt to changing machine and operating state conditions. Such systems must also be capable of evolving over the life of the accelerator operation. In this paper we present a framework for the development of adaptive control systems.
Date: November 1, 1991
Creator: Cork, C. & Nishimura, Hiroshi.
Partner: UNT Libraries Government Documents Department

Si(Li) x-ray detectors with amorphous silicon passivation

Description: Lithium-drifted silicon (Si(Li)) detectors with thin lithium n/sup +/ contacts and amorphous silicon (..cap alpha..-Si) junction passivation are described. These detectors (7 mm thick, 9 cm/sup 2/ area) are intended for use in a six element detector array which is designed to measure trace amounts of plutonium in soil samples. Results are given showing a spectral resolution of approx. 400 eV (FWHM) for the 17.8 keV N/sub p/ L x-rays entering through either these detectors. Measurements on the effects of the fractional H/sub 2/ concentration on the electrical behavior of the ..cap alpha..-Si/Si interface are reported. The increase with time in the lithium window thickness when the detectors are stored at room temperature is discussed.
Date: October 1, 1983
Creator: Walton, J.T.; Pehl, R.H.; Wong, Y.K. & Cork, C.P.
Partner: UNT Libraries Government Documents Department

Transistor reset preamplifier for high-rate high-resolution spectroscopy

Description: Pulsed transistor reset of high resolution charge sensitive preamplifiers used in cooled semiconductor spectrometers can sometimes have an advantage over pulsed light reset systems. Several versions of transistor reset spectrometers using both silicon and germanium detectors have been built. This paper discusses the advantages of the transistor reset system and illustrates several configurations of the packages used for the FET and reset transistor. It also describes the preamplifer circuit and shows the performance of the spectrometer at high rates.
Date: October 1, 1981
Creator: Landis, D.A.; Cork, C.P.; Madden, N.W. & Goulding, F.S.
Partner: UNT Libraries Government Documents Department

Two-dimensional pixel array image sensor for protein crystallography

Description: A 2D pixel array image sensor module has been designed for time resolved Protein Crystallography. This smart pixels detector significantly enhances time resolved Laue Protein crystallography by two to three orders of magnitude compared to existing sensors like films or phosphor screens coupled to CCDs. The resolution in time and dynamic range of this type of detector will allow one to study the evolution of structural changes that occur within the protein as a function of time. This detector will also considerably accelerate data collection in static Laue or monochromatic crystallography and make better use of the intense beam delivered by synchrotron light sources. The event driven pixel array detectors, based on the column Architecture, can provide multiparameter information (energy discrimination, time), with sparse and frameless readout without significant dead time. The prototype module consists of a 16x16 pixel diode array bump-bonded to the integrated circuit. The detection area is 150x150 square microns.
Date: July 1, 1996
Creator: Beuville, E.; Beche, J.-F. & Cork, C.
Partner: UNT Libraries Government Documents Department

Advanced Light Source control system

Description: The Advanced Light Source (ALS) is a third generation 1--2 GeV synchrotron radiation source designed to provide ports for 60 beamlines. It uses a 50 MeV electron linac and 1.5 GeV, 1 Hz, booster synchrotron for injection into a 1--2 GeV storage ring. Interesting control problems are created because of the need for dynamic closed beam orbit control to eliminate interaction between the ring tuning requirements and to minimize orbit shifts due to ground vibrations. The extremely signal sensitive nature of the experiments requires special attention to the sources of electrical noise. These requirements have led to a control system design which emphasizes connectivity at the accelerator equipment end and a large I/O bandwidth for closed loop system response. Not overlooked are user friendliness, operator response time, modeling, and expert system provisions. Portable consoles are used for local operation of machine equipment. Our solution is a massively parallel system with >120 Mbits/sec I/O bandwidth and >1500 Mips computing power. At the equipment level connections are made using over 600 powerful Intelligent Local Controllers (ILC-s) mounted in 3U size Eurocard slots using fiber-optic cables between rack locations. In the control room, personal computers control and display all machine variables at a 10 Hz rate including the scope signals which are collected though the control system. Commercially available software and industry standards are used extensively. Particular attention is paid to reliability, maintainability and upgradeability. 10 refs., 11 figs.
Date: March 1, 1989
Creator: Magyary, S.; Chin, M.; Cork, C.; Fahmie, M.; Lancaster, H.; Molinari, P. et al.
Partner: UNT Libraries Government Documents Department

Amorphous Ge bipolar blocking contacts on Ge detectors

Description: Semiconductor nuclear radiation detectors are usually operated in a full depletion mode and blocking contacts are required to maintain low leakage currents and high electric fields for charge collection. Blocking contacts on Ge detectors typically consist of n-type contacts formed by lithium diffusion and p-type contacts formed by boron ion implantation. Electrical contacts formed using sputtered amorphous Ge (a-Ge) films on high-purity Ge crystals were found to exhibit good blocking behavior in both polarities with low leakage currents. The a-Ge contacts have thin dead layers associated with them and can be used in place of lithium-diffused, ion-implanted or Schottky barrier contacts on Ge radiation detectors. Multi-electrode detectors can be fabricated with very simple processing steps using these contacts. 12 refs.
Date: October 1, 1991
Creator: Luke, P.N.; Cork, C.P.; Madden, N.W.; Rossington, C.S. & Wesela, M.F.
Partner: UNT Libraries Government Documents Department

A multi-channel monolithic Ge detector system for fluorescence x-ray absorption spectroscopy

Description: Construction and performance of a monolithic quad-pixel Ge detector for fluorescence x-ray absorption spectroscopy (XAS) at synchrotron radiation sources are described. The detector semiconductor element has an active surface area of 4.0 cm{sup 2} which is electrically separated into four 1.0 cm{sup 2} pixels, with little interfacial dead volume. Spatial response of the array shows that cross-talk between adjacent pixels is < 10% for 5.9 keV photons that fall within 0.5 mm of the pixel boundaries. The detector electronics system uses pre-amplifiers built at LBNL with commercial Tennelec Model TC 244 amplifiers. Using an {sup 55}Fe test source (MnK{sub {alpha}}, 5.9 keV), energy resolution of better than 200 eV is achieved with a 4 {mu}sec peaking time. At 0.5 {mu}sec peaking time, pulse pileup results in a 75% throughput efficiency for an incoming count rate of 100 kHz. Initial XAS fluoresncece measurements at the beamline 4 wiggler end stations at SSRL show that the detector system has several advantages over commercial x-ray spectrometers for low-concentration counting.
Date: March 1, 1995
Creator: Bucher, J.J.; Allen, P.G.; Edelstein, N.M.; Shuh, D.K.; Madden, N.W.; Cork, C. et al.
Partner: UNT Libraries Government Documents Department

A variable temperature cryostat that produces in situ clean-up germanium detector surfaces

Description: Variable temperature cryostats that can maintain germanium detectors at temperatures from 82 K to about 400 K while the thermal shield surrounding the detectors remains much colder when the detectors are warmed have been developed. Cryostats such as these offer the possibility of cryopumping material from the surface of detectors to the colder thermal shield. The diode characteristics of several detectors have shown very significant improvement following thermal cycles up to about 150 K in these cryostats. Important applications for cryostats having this attribute are many. 4 figs.
Date: November 1, 1988
Creator: Pehl, R.H.; Madden, N.W.; Malone, D.F.; Cork, C.P.; Landis, D.A.; Xing, J.S. et al.
Partner: UNT Libraries Government Documents Department

Second generation dichotomous sampler for large-scale monitoring of airborne particulate matter

Description: The differences which exist between fine (< 2.5 ..mu..m) and coarse (> 2.5 ..mu..m) airborne particles with respect to their origin, chemical properties, and environmental impact, call for their separate collection and analysis. An automated dichotomous sampler (ADS), equipped with a high efficiency single-stage virtual impactor and a microprocessor-based controller to self-correct fault conditions including filter overload, has been developed as a model for commercial production.
Date: January 1, 1979
Creator: Loo, B.W.; Adachi, R.S.; Cork, C.P.; Goulding, F.S.; Jaklevic, J.M.; Landis, D.A. et al.
Partner: UNT Libraries Government Documents Department

Imaging Performance of the Si/Ge Hybrid Compton Imager

Description: The point spread function (PSF) of a fully-instrumented silicon/germanium Compton telescope has been measured as a function of energy and angle. Overall, the resolution ranged from 3{sup o} to 4{sup o} FWHM over most of the energy range and field of view. The various contributions to the resolution have been quantified. These contributions include the energy uncertainty and position uncertainty of the detector; source energy; Doppler broadening; and the 1/r broadening characteristic of Compton back-projection. Furthermore, a distortion of the PSF is observed for sources imaged off-axis from the detector. These contributions are discussed and compared to theory and simulations.
Date: November 10, 2005
Creator: Burks, M; Chivers, D; Cork, C; Cunningham, M; Fabris, L; Gunter, D et al.
Partner: UNT Libraries Government Documents Department

First-Generation Hybrid Compact Compton Imager

Description: At Lawrence Livermore National Laboratory, we are pursuing the development of a gamma-ray imaging system using the Compton effect. We have built our first generation hybrid Compton imaging system, and we have conducted initial calibration and image measurements using this system. In this paper, we present the details of the hybrid Compton imaging system and initial calibration and image measurements.
Date: November 7, 2005
Creator: Cunningham, M; Burks, M; Chivers, D; Cork, C; Fabris, L; Gunter, D et al.
Partner: UNT Libraries Government Documents Department

Development of an array of cooled large area Si(Li) detectors

Description: A system containing six cooled, 34 mm diam by 7 mm thick, high-resolution Si(Li) detectors designed to maximize the sensitivity for counting x rays in the 10-30 keV range to measure trace radionuclides in soil samples has been successfully fabricated. The detectors were mounted in a paddle-shaped cryostat with a single large beryllium window on each side. This configuration provides for efficient anticoincidence background suppression and effectively doubles the sensitive detector area because x rays can impinge on the detectors from both sides. To maximize detection efficiency, the thickness of the cryostat was held to a bare minimum (25 mm); this caused severe difficulties during fabrication of the system. Cutting down the rim of the detectors reduced to an acceptable level the microphony caused by movement of the beryllium window that faces the lithium-diffused contact of the detectors. Since this system will be used for low level counting. careful testing was performed to select materials having the lowest radioactivity.
Date: October 1, 1985
Creator: Pehl, R.H.; Madden, N.W.; Walton, J.T.; Malone, D.F.; Landis, D.A.; Goulding, F.S. et al.
Partner: UNT Libraries Government Documents Department

LBL/UCSB /sup 76/Ge double beta decay experiment: first results

Description: A paper given at the IEEE Nuclear Science Symposium last year presented the scientific justification for this experiment and discussed the design of the detector system. At the present time two of the dual detector systems (i.e., four out of a final total of eight detectors) are operating in the complete active/passive shield in the low background laboratory at LBL. Early results (1620 h) of an experiment using two detectors yield a limit of 4 x 10/sup 22/ years (68% confidence) for the half life of the neutrinoless double beta decay (..beta beta../sub o nu/) of /sup 76/Ge. Although this experiment was carried out above ground, the result approaches those achieved by other groups in deep underground laboratories. Based on studies of the origins of background in our system, we hope to reach a limit of 3 x 10/sup 23/ years (or more) in a two month/four detector experiment to be carried out soon in an underground facility.
Date: October 1, 1984
Creator: Goulding, F.S.; Cork, C.P.; Landis, D.A.; Luke, P.N.; Madden, N.W.; Malone, D.F. et al.
Partner: UNT Libraries Government Documents Department

Magnetic measurements at Lawrence Berkeley Laboratory

Description: Recent magnetic measurement activities at LBL have been concentrated in two separate areas, electro-magnets and permanent magnets for the Advanced Light Source (ALS), and superconducting magnets for the Superconducting Super Collider Laboratory (SSCL). A survey of the many different measurement systems is presented. These include: AC magnetic measurements of an ALS booster dipole engineering model magnet, dipole moment measurements of permanent magnet blocks for ALS wigglers and undulators, permeability measurements of samples destined for wiggler and undulator poles, harmonic error analysis of SSC one meter model dipoles and quadrupoles and five meter long SSC prototype quadrupoles, harmonic error analysis of ALS dipoles, quadrupoles, and sextupoles, precision Hall probe mapping of ALS storage ring combined function magnets, and the design of the ALS insertion device magnets mapping system. We also describe a new UNIX based data acquisition system that is being developed for the SSC. Probes used for magnetic measurements include Helmholtz coils, integral coils, point coils, and bucking harmonic analysis coils, several different types of Hall probes, and nuclear magnetic resonance magnetometers. Both analog and digital integrators are used with the coils. Some problems that occurred and their rectification is described. The mechanisms used include rotating systems with optical encoders, X-Y mapping systems with optical encoders and a laser position measuring device. 10 refs., 3 figs., 1 tab.
Date: August 1, 1991
Creator: Green, M.I.; Barale, P.; Callapp, L.; Case-Fortier, M.; Lerner, D.; Nelson, D. et al.
Partner: UNT Libraries Government Documents Department