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A high-speed, one-dimensional detector array for electrons and UV/X-ray photons has been developed. The detector is capable of handling the high countrates encountered in at third generation synchrotron radiation sources and is free from nonlinearity problems present in charge coupled device (CCD) detectors. Electrons are counted by a configuration of microchannel plates, an array of charge collection electrodes, and custom-designed integrated circuits (IC) assembled on a ceramic hybrid. The charges are collected on 768 strips with a 48 /spl mu/m pitch that are wire-bonded to 6 pairs of signal processing ICs. Each front-end IC has 128 channels of amplifiers (peaking time 25 ns) and discriminators. The pulse-pair resolution is 50 ns leading to a maximum linear countrate/channel of 2 MHz. The second, custom-designed IC features 24-b buffered counters and a serial link for the transfer of commands and data. A possible deadtime-less readout of all channels in 150 /spl mu/s opens the door to time resolved experiments. The complete detector system includes the high-voltage power supply, a field programmable gate array (FPGA)-based data acquisition system, and supporting software. Special care has been taken to insure reliable operation in an ultra-high vacuum environment. The detector architecture and design is described and measured performance characteristics such as spatial resolution and count-rate linearity are presented.

We report on the design and construction of a next-generation, ultrahigh-speed, one-dimensional detector for electron and other spectroscopies, and discuss some first experimental results obtained with it. This detector is capable of recording spectra over 768 channels with ∼1.5 channels (∼75 μm) resolution and with good linearity up to countrates of >1 MHz per channel or >1 GHz overall. In first experiments with it, photoelectron spectra spanning several hundred channels of resolution have been obtained in as little as 50 ms; with future system improvements, this time should be reduced to 150 μs. The data obtained include rapid X-ray photoelectron diffraction scans and time-resolved core-level observations of a surface reaction process. This detector should open up several types of new experiment, including more rapid real-time observations of surface reaction kinetics by means of inner-shell spectroscopies.

FNAL E871 (HyperCP) collected over 38 terabytes of data during the 1997 fixed-target run at Fermilab. The data-acquisition (DAQ) system wrote data to tape with a typical rate of 13 MB/s. A second data collection period in 1999 allowed for the collection of a further 82 terabytes of data. However, changes in the spill structure and an increase in primary beam intensity necessitated an upgrade of the 1997 DAQ system. The 1999 run of HyperCP featured a DAQ system which recorded data on 20,421 8 mm tapes at a sustainable rate of 27 MB/s. The rationale and methods for this upgrade are detailed within.

We constructed two small-area pixelated detectors, which can record signals produced by 800-MeV proton beam micropulses with a repetition rate of 358 ns. The first detector was built around a two-dimensional (2-D) photodiode array. The array was illuminated by light emitted by a monolithic 1.7-mm-thick lutetium oxy-orthosilicate (LSO) scintillator and imaged by a simple optical system. The other detector was a hydrogen ion chamber operated at 1 to 2.5 atm. The anode was divided into an array of 8/spl times/8 1 mm/sup 2/ pixels. The fast positive-ion drift velocity in hydrogen helps to minimize the space charge build up. However, for beam pulses spaced in time closer than 1 /spl mu/s, there appears to be a substantial accumulation of space charge. The electronic readout chain, for each of the 64 channels, consisted of an externally clocked fast-gated integrator and an amplifier coupled to an on-board analog-to-digital converter (ADC) and a first-in-first-out storage (FIFO). The detectors were tested with beam pulses up to 4/spl times/10/sup 6/ protons per mm/sup 2/ delivered in 30 to 120 ns wide microbursts.

The Fermilab HyperCP experiment has accumulated the world's largest sample of Ξ− and Ξ + hyperon decays within two running periods in 1997 and 1999. The primary goal of the experiment is to search for direct CP violation in the decay sequences Ξ− → Λ π− → p π− π− and Ξ + → Λ π+ → p π+ π+. A violation of CP would manifest itself as a difference between the angular distribution of the proton and the antiproton in the Λ and Λ helicity frame. The amount of data is enough to reach a statistical sensitivity of 1.4 × 10−4 in the CP violating asymmetry A ΞΛ = (αΞ αΛ − α Ξ α Λ )/(αΞ αΛ + α Ξ α Λ ). We present an analysis method used to take into account the slight differences in the production of the Ξ− and Ξ + samples. A preliminary results on A ΞΛ at the level of a few 10−3 and based on a few percent of the 1997 data will be presented.

A sensitive search for direct CP violation in Ξ− (Ξ+) and Λ (Λ) decays is underway at FNAL. Experiment E871 (HyperCP) intends to perform a precision measurement of the angular distribution of protons (anti-protons) with respect to the helicity axis in the rest frame of the Λ (Λ). The slopes of these distributions give the decay parameters αΞαΛ and αΞαΛ. An asymmetry parameter A in terms of these decay parameters has been defined for which a non-zero value would be unambiguous evidence for direct CP violation. Theoretical predictions for A range from no asymmetry up to ∼ 10−3. HyperCP expects to measure A with an uncertainty of ∼ 2 × 10−4.

A 2D pixel array detector prototype is being designed for static and time resolved protein crystallography. This pixel detector will significantly enhance time resolved laue protein crystallography by two or three orders of magnitude compared to existing sensors such as films or phosphor screens coupled to CCDs. The resolution in time and dynamic range of this type of detector will allow to study structural changes that occur within the protein as a function of time (concurrent readout and acquisition). The prototype consists of an array of 16 × 16 pixels of 150 × 150 μ m 2 size. The individual pixel processor consists of a low-noise amplifier shaper followed by a differential threshold comparator which provides the counting of individual photons with energies above a programmable threshold. To accommodate the very high rates, above 5 × 10 8 /cm 2 /s, each pixel processor has a 3 bit pre-scaler which divides the event rate by 8. Overflow from the divider which defines a pseudo fourth bit will generate a readout sequence providing the pixel address. Addresses, generated locally as quantified analog signals, will be used to increment a location in an histogramming memory from which the computerized image of the Laue diagram will be generated.

An 8 × 8 pixel array X-ray detector prototype ( 1 100 maximum is less than 1 pixel width (150 μm), which is less than ( 1 2 ) that of a CCD and ( 1 7 ) that of an imaging plate detector [1].

The video wave-form of CCD photocharge, clocked out at very high pixel rates, is a sequence of narrow voltage pulses. Pulse height is proportional to the recovered charge. A method and circuits are described for digitizing such waveforms in a 10-bit range at rates exceeding 75 MHz. Signal processing includes a wide-band clamping amplifier, a self-clocked peak detector, a very fast track/hold amplifier and a 75 MSPS, 10-bit flash converter. Digital data can be stored either in a local high speed RAM or transferred by a fast fiber-optic link to the remote digital storage. Test results (such as linearity, dynamic range and signal/noise ratio) are also given. >

A high-resolution linear TV camera is described for readout of phosphors illuminated by gated microchannel plate image intensifiers. The 2592-element array clocking scheme allows for simultaneous readout of even and odd pixels combined into a single photoelement. An improved signal-to-noise ratio results, exceeding 1000:1 for a single video line readout. The camera can be reset at any time and unwanted photocharge dumped. Integration time is adjustable to match phosphor decay time and clock rates exceeding 20 MHz allow for a fast readout. Measurements including the resolution, responsivity, and dynamic range of the camera, are presented. >

Simulation results of the Beam Rate of Neutrals (BRAN) luminosity detector for the CERN Large Hadron Collider are presented. The detectors are intended to measure the bunch-by-bunch relative luminosity at the ATLAS and CMS experiments. Building up from experimental results from test runs at the SPS, RHIC and ALS we extend the simulated setup to the TAN neutral absorbers located at 140 m at both sides the IP1 and IP5 interaction points. The expected signal amplitudes are calculated for pp-collisions energies between 450 GeV and 7 TeV using the Monte Carlo package FLUKA and its graphical user interface FLAIR.

The time at which an input signal crosses the reference level of a voltage comparator can be used in the analog-to-digital conversion of fast single waveform transients. In such a converter, an array of identical comparators, properly biased, provides stop inputs to a picosecond-resolution multistop time digitizer. Each stop represents a point in the voltage-time reconstruction of the measured waveform. A number of state-of-the-art comparators, bipolar and GaAs, have been evaluated for this application to determine the differences in their time propagation as a function of the input signal overdrive and risetime. Normalized data are presented to assist in the correction of a digitizer's measurement errors. A picosecond time resolution measurement system used in the tests is described. >

For the Compton Polarimeter experiment at the Stanford Linear Accelerator the crossin point of a laser beam across the path ob an electron beam must be kept accurate and stable. An electronic system is described for automatic tracking and correction of the beam crossing. A remote CCD camera, relatively insensitive to electromagnetic disturbance, records small displacements of the pulsed laser beam. Video signals are anal zed at a remote station, the amount of drift from the selectedreference point determined and the appropriate correction command sent to the motorizedmirror deflectingthe laser beam. A description of the system, its performance and the test results are presented.

We present new characterization results for a large format, 15 um pixel pitch, 2kx4k format, p-channel CCD fabricated on high resistivity silicon at Lawrence Berkeley National Laboratory. The fully-depleted device is 300 um thick and backside illuminated utilizing 4-side buttable packaging. We report on measurements of standard operating characteristics including charge transfer efficiency, readout noise, cosmetics performance, dark current, and well depth. We have also made preliminary measurements of the device's X-Ray energy resolution and tests of device linearity.

The status of CCD development efforts at Lawrence Berkeley National Laboratory is reviewed. Fabrication technologies for the production of back-illuminated, fully depleted CCD’s on 150 mm diameter wafers are described. In addition, preliminary performance results for high-voltage compatible CCD’s, including a 3512 × 3512, 10.5 µm pixel CCD for the proposed SuperNova Acceleration Probe project, are presented.

An ultra high‐speed, one‐dimensional multi‐channel detector for electrons and soft x‐ray photons has been developed to permit full utilization of fluxes from third‐ and fourth‐generation synchrotron radiation sources. The detector has 768 channels of buffered counters with a maximum linear countrate per channel exceeding 2 MHz. With an overall countrate of ∼2 GHz, this detector is approximately 100 times faster than any other presently available. The 48 μm spacing from channel to channel also provides excellent spatial resolution, and thus also excellent energy resolution with dispersive spectrometers. This detector represents several improvements in reliability and ruggedness over an earlier prototype. The detector is capable of operating in a typical UHV environment and is presently installed in a Scienta electron analyzer at the ALS for testing and first data taking. A total countrate exceeding 1 GHz and a position resolution of about two channels have been experimentally demonstrated. It should be pos...

An overview of CCD development efforts at Lawrence Berkeley National Laboratory is presented. Operation of fully-depleted, back-illuminated CCD's fabricated on high resistivity silicon is described, along with results on the use of such CCD's at ground-based observatories. Radiation damage and point-spread function measurements are described, as well as discussion of CCD fabrication technologies.

A system of 110 high-performance ADCs (analog-to-digital converters), required for the Gammasphere Project at the Lawrence Berkeley Laboratory, is described. The ADCs are compact and linear (+or-0.006% integral, +or-0.5% differential), with a conversion deadtime of 6.5 mu s and a channel profile flatness of 50%. The converter is based on a new low-power (0.25 W), low-cost, monolithic high-speed sampling ADC, exhibiting a very high stability and no missing codes over the entire 16-bit range. Differential linearity was achieved by applying the Gatti method, covering a 6-b range. Measured data and methods of testing the ADC are also presented. >

Up to 9216 fast discriminators are required for processing signals of the Fermilab silicon strip detector preamplifiers in experiment E789. Signals exceeding a preset discriminator threshold voltage are first stored in a clocked latch and then delayed by three 19-ns clock cycles with a shift resister. Discriminators are organized in 75 identical 128-channel subsystems. Each has four 32-channel PC boards housed in a signal routing motherboard. Eight 16-channel line driver boards transfer events from the motherboard through cables to the remote processing electronics. Three subsystems fit into the frame of a standard CAMAC crate. The authors describe the design considerations of the system and its performance, based on several months of testing the completed system. >

A high-resolution linear TV camera is described for readout of phosphors illuminated by gated microchannel plate image intensifiers. The 2592-element array clocking scheme allows for simultaneous readout of even and odd pixels combined into a single photoelement. Improved signal-to-noise ratio results, exceeding 1000:1 for a single video time readout. The camera can be reset at any time and unwanted photocharge dumped. Integration time is adjustable to match phosphor decay time and clock rates exceeding 20 MHz allow for a fast readout. Measurements including resolution, responsitivity, and dynamic range of the camera alone and intensified are presented. >

A new type of p-channel CCD constructed on high-resistivity n-type silicon was exposed to 12 MeV protons at doses up to 1x1011 protons/cm2. The charge transfer efficiency was measured as a function of radiation dose and temperature. We previously reported that these CCDs are significantly more tolerant to radiation damage than conventional n-channel devices. In the work reported here, we used pocket pumping techniques and charge transfer efficiency measurements to determine the identity and concentrations of radiation induced traps present in the damaged devices.

The primary purpose of the HyperCP experiment at Fermilab is to test CP in hyperon decays by comparing the decay distributions for Ⅺ− (“cascade”) decays in the decay sequence: Ⅺ− → π− + Λ0, Λ0 → π− + p, with those for the antiparticle Ⅺ+. In addition, we can test CP in charged kaon decays by comparing the slopes of the Dalitz plot for Κ+ and Κ− decays. We are also looking at rare decay modes of charged kaons and hyperons, particularly those involving muons. In two runs in 1997 and 1999, we collected approx. 500 millon charged kaon decays, 2.5 billion Ⅺ− and Ⅺ+ decays, and 19 million Ω− and Ω+ decays. This is the largest sample of fully reconstructed particle decays ever collected.

The Los Alamos National Laboratory in support of Department of Energy and Department of Defense projects is developing a continuous recording, intensified, CCD camera system having a high-frame rate and fast shutter capability. The camera frame rates can range from 1 to approximately 3500 frames per second with sub-nanosecond shuttering capability. Camera shuttering (or gating) is provided by a microchannel plate image intensifier employing a Los Alamos designed stripline geometry that incorporates impedance matching to reduce pulse reflections and dispersion. The CCD pixel array size is 512 X 512, which provides good-resolution over a relatively wide field of view. Video data readout from the CCD is through 16 parallel ports with a pixel rate of up to 75 Mpixels/s per port. Camera outputs include 16 ports of both analog video and digital video provided by 10-bit onboard digitizers. A computer controlled frame grabber is being fabricated which will record data from the digital outputs and store the data in a local memory for transfer into a non-volatile storage medium such as a removable disk drive. Salient characteristics and performance data of a prototype camera are presented and range gated imaging applications are discussed.

A high frame rate optically shuttered CCD camera for radiometric imaging of transient optical phenomena has been designed and several prototypes fabricated, which are now in evaluation phase. the camera design incorporates stripline geometry image intensifiers for ultra fast image shutters capable of 200ps exposures. The intensifiers are fiber optically coupled to a multiport CCD capable of 75 MHz pixel clocking to achieve 4KHz frame rate for 512 X 512 pixels from simultaneous readout of 16 individual segments of the CCD array. The intensifier, Philips XX1412MH/E03 is generically a Generation II proximity-focused micro channel plate intensifier (MCPII) redesigned for high speed gating by Los Alamos National Laboratory and manufactured by Philips Components. The CCD is a Reticon HSO512 split storage with bi-direcitonal vertical readout architecture. The camera main frame is designed utilizing a multilayer motherboard for transporting CCD video signals and clocks via imbedded stripline buses designed for 100MHz operation. The MCPII gate duration and gain variables are controlled and measured in real time and up-dated for data logging each frame, with 10-bit resolution, selectable either locally or by computer. The camera provides both analog and 10-bit digital video. The camera's architecture, salient design characteristics, and current test data depicting resolution, dynamic range, shutter sequences, and image reconstruction will be presented and discussed.

Fermilab experiment 871, HyperCP, is a search for direct CP violation in Ⅺ and Λ hyperon decays. A non-zero value in the asymmetry parameter A, defined in terms of the decay parameter products αⅪαΛ and αⅪαΛ, would be unambiguous evidence for direct CP violation. The first data-taking run finished at the end of 1997 and accumulated over one billion Ⅺ− and Ⅺ+ decays. A sensitivity in A of ≈10−4 is expected. A review of CP violation in hyperon decays is given, the HyperCP detector is described, and the status of the data analysis is discussed.

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.

Rates exceeding 1000 frames/s can be achieved with multiport CCD state-of-art video sensors. In order to provide sufficient spatial resolution, sensor configurations of 512 X 512 pixels are typical. Image area is divided into segments with individual video ports. Each port includes a photocharge sensitive amplifier, typically comprising sample/hold and charge reset circuits. Some amplifiers are even provided with a double correlated sample circuit for improving the signal/noise ratio. Frame rates are proportional to the number of ports, since the individual sensor segments are run in parallel. Unfortunately, the amount of external circuitry required for signal processing increases accordingly, 16-port sensors are a quite common configuration. Cameras with even higher number of ports are prohibitively expensive. Therefore, in order to achieve very high frame readout rates with a moderate number of ports, the sensor's charge transport clock frequencies must be increased to the limit. Horizontal charge transfer frequencies exceeding 30 MHz have been achieved. The quality of the video signal deteriorates with frequency due to bandwidth limitation of the photocharge detecting amplifier. Its sample/hold and double correlated sample circuits are useless at such rates. Methods and circuits for the processing of video signals under such conditions are described. The circuits include wide bandwidth video buffer amplifiers/level translator/line drivers, fast peak stretchers, 10-bit resolution (or more) A/D converters and fiber optic data links to a remote mass digital data storage and processors. Also, the circuits must satisfy a number of practical conditions (size, power dissipation, cost) in order to make such camera useful in applications where space is limited and multiple head high frame rate cameras are required.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Video baseline drift in CCD cameras with variable frame formats is often difficult to correct. Conventionalbaseline restorers generally do not work well at very high frame rates, since frequently a only a short, few nanosecondwide point in each video line is available for reference. A.C. coupled video level drifts as the signal average changes

Test results obtained from two recently developed multiport Charge-Coupled Devices (CCDs) operated at pixel rates in the 10-to-100 MHz range will be presented. The CCDs were evaluated in Los Alamos National Laboratory's High Speed Solid State Imager Test Station (HSTS) which features PC-based programmable clock waveform generation (Tektronix DAS 9200) and synchronously clocked Digital Sampling Oscilloscopes (LeCroy 9424/9314 series) for CCD pixel data acquisition, analysis, and storage. The HSTS also provided special designed optical pinhole array test patterns in the 5-to-50 micron diameter range for use with Xenon Strobe and pulsed laser light sources to simultaneously provide multiple single-pixel illumination patterns to study CCD point-spread-function (PSF) and pixel smear characteristics. The two CCDs tested, EEV model CCD-13 and EG&G Reticon model HSO512J are both 512 X 512 pixel arrays with eight and sixteen video output ports respectively. Both devices are generically Frame Transfer CCDs designed for parallel bi- directional vertical readout to augment their multiport design for increased pixel rates over common single port serial readout architecture. Although both CCDs were tested similarly, differences in their designs precluded normalization or any direct comparisons of test results. Rate dependent parameters investigated include S/N, PSF, and MTF. The performance observed for the two imagers at various pixel rates from selected typical output ports is discussed.

High frame rate CCD video cameras require high clock frequencies for running photocharge transport registers, especially when the sensor has only a single video port. It was found that some sensors of the interline transfer architecture allow for horizontal charge transport clock rates in excess of 75 MHz while still producing images of acceptable quality. We describe a relatively inexpensive method for analog-to-digital processing of video images at rates of 75 MSPS and 10-bit range. Images are stored in a fast, 512 X 512 X 12 kbit random access memory (RAM). Upon the data transfer into a processor, the public domain `NIH IMAGE' software is used for image analysis.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A versatile new camera, the Los Alamos National Laboratory (LANL) model GY6, is described. It operates at a wide variety of frame rates, from RS-170 to 700 frames per second. The camera operates as an NTSC compatible black and white camera when operating at RS- 170 rates. When used for variable high-frame rates, a simple substitution is made of the RS- 170 sync/clock generator circuit card with a high speed emitter-coupled logic (ECL) circuit card.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The imaging performance of an 8-port Full Frame Transfer Charge Coupled Device (FFT CCD) as a function of several parameters including pixel clock rate is presented. The device, model CCD-13, manufactured by English Electric Valve (EEV), is a 512 X 512 pixel array designed with four individual programmable bidirectional serial registers and eight output amplifiers permitting simultaneous readout of eight segments (128 horizontal X 256 vertical pixels) of the array. The imager was evaluated in Los Alamos National Laboratory's High-Speed Solid-State Imager Test Station at true pixel rates as high as 50 MHz for effective imager pixel rates approaching 400 MHz from multiporting. Key response characteristics measured include absolute responsivity, Charge-Transfer-Efficiency (CTE), dynamic range, resolution, signal-to-noise ratio, and electronic and optical crosstalk among the eight video channels. Preliminary test results and data obtained from the CCD-13 are presented and the versatility/capabilities of the test station are reviewed.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A PC-based programmable solid-state imager test station has been designed and is in final development phases. It is designed to provide a flexible universal high-speed platform for evaluation of different imager designs and formats including various multiport configurations. The system provides drive and acquisition circuitry and components to allow electro-optic characterization of imagers as a function of pixel readout rate. The data are scan-converted to RS-170 format for analysis. The system's functional capabilities and performance are presented. Examples of program code to generate three phase clocks for an 8-port Frame Transfer EEV CCD are included. A sampling of preliminary results obtained from variable rate clocking of this imager are discussed.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The use of a high-speed (up to 100 MHz.) programmable pattern generator and special clock driver/translator circuits for clocking solid-state multiple output imagers is discussed. A specific example of clocking a developmental 256 x 512 two-port CCD is illustrated. Reference to a prior report of clocking an eight-port CCD is included. Future use in clocking a CID imager is discussed.

The authors present initial results for a position-sensitive photodiode/BGO (bismuth germanate) detector for high-resolution, multilayer positron emission tomography (PET). Position sensitivity is achieved by dividing the 3 mm*20 mm rectangular photosensitive area along the diagonal to form two triangular segments. Each segment is individually connected to a low-noise charge amplifier. The photodiodes and crystals are cooled to -100 degrees C to reduce dark current and increase the BGO signal. With an amplifier peaking time of 17 mu s, the sum of the signals (511-keV photopeak) was 3200 electrons with a full width at half maximum (FWHM) of 750 electrons. The ratio of one signal to the sum determined the depth of interaction with a resolution of 11 mm FWHM. >

A small, versatile CCD (charge coupled device) camera is described. Frame readout times from one second to milliseconds can be changed continuously or at random by a programmable clock. A very large range of light intensity is thus covered without the need for mechanical aperture control. The camera can be reset at any time and then restarted at a different frame rate after the pause of a selected duration. The ICX016AL sensor was found especially suitable for clock rates up to 50 MHz. Image smear, blooming an dnoise are substantially lower than in earlier interline-transfer CCD sensors. Critical circuits are described and measured data are presented. >

An ultrahigh-speed data transmission system using optical fibers and gallium arsenide digital integrated circuits has been investigated. The system is designed to meet the increased data rate requirements of modern information processing systems as well as those of future imaging devices and high-spatial-resolution detectors. A description of the system, which uses available components made for the transmission and reception of data at 780-Mb/s rates, is given. Methods for digitizing, multiplexing, demultiplexing, error checking, etc. are also described, and the reliability of components is discussed. >

An automated system for the evaluation of fast-risetime voltage discriminators is described. A high-performance time digitizer is used to determine the elapsed time between the generation of a test pulse and the response of the discriminator under test. The measurement is repeated for a series of discriminator threshold levels generated by a digital-to-analog converter, and the results are compared to a photograph of the leading edge of the pulse obtained with a sampling oscilloscope. To obtain high accuracy, an average of several thousand individual digitizations is used in each measurement to reduce the uncertainty to a maximum of +or-3 ps. The measurement system is used with a test fixture to evaluate the performance of a number of tunnel diodes and in preliminary measurements of a prototype discriminator of novel design. At present the prototype discriminator exhibits a time walk of about 15 ps per dB change of input pulse amplitude, and work is underway to evaluate and minimize this effect. >

The signal processing for an optical wideband transmission system using gallium arsenide (GaAs) digital integrated circuits and optical fibers has been investigated. Multiplexing, coding, synchronization, demultiplexing, and error checking at 780 Mb/s data rates are described. Data storage in memory for linking to a computer is also considered. The design uses available GaAs and silicon components. The reliability of GaAs components is discussed as well as the layout and thermal considerations required for a high-speed system. >

An automated system for the testing and performance evaluation of high-resolution, long-range time digitizers is described. The test system uses an IBM PC/XT or PC/AT personal computer together with appropriate hardware interfacing modules to control the digitizer under test. Precise timing intervals for testing are generated by a pulse-calibration module driven by a programmable low-phase-noise frequency synthesizer. The time intervals measured by the digitizer are compared under computer control with the actual intervals produced by the synthesizer for a sufficient number of cases to establish the digitizer performance. The hardware and software components used are discussed. >

A scheme for detecting low-intensity images with a CCD (charge coupled device) camera is described in which successive images are digitized at fast frame rates and averaged to enhance the signal-to-noise ratio. The results demonstrate that a dynamic range in excess of 10000:1 can be obtained using an uncooled device and averaging times of 100 s, a sensitivity comparable to that obtained with cooled devices. The technique is illustrated by imaging the weak fluorescence produced by an ethidium bromide stained DNA electrophoresis gel. >

A single‐photon timing system is described which is capable of extracting fluorescence lifetimes as short as 25 ps. The system is an improved version of an earlier apparatus. The new system uses a synchronously pumped, mode‐locked dye laser with 10‐ps pulses operating at 82‐MHz repetition rate. A fast photodetector and a leading‐edge discriminator were developed to use with this light source. Also, a special rate reduction circuit was built to eliminate large oscillations in fluorescence decay spectra due to the excessive stop rates that overload commercial time‐to‐amplitude converters.

The salient electro-optic properties of typical Fairchild model 222 interline transfer charge-coupled devices when exposed to single impulses of visible light (100 ps to 10 As) and with subsequent fast single-frame readout (4 ms) are presented. Identification and differentiation between CCD video components arising from the intended image area or photosites and those arising from the vertical registers are discussed, with emphasis on possible ambiguities resulting from improper or random combination of the two components. In addition, CCD/camera signal-to-noise ratio and resolution as functions of readout rate and spectral input are included. Fast readout philosophy, design criteria, and circuitry are discussed.

Los Alamos National Laboratory (LANL) has designed and prototyped high-frame rate intensified/shuttered Charge-Coupled-Device (CCD) cameras capable of operating at Kilohertz frame rates (non-interfaced mode) with optical shutters capable of acquiring nanosecond-to- microsecond exposures each frame. These cameras utilize an Interline Transfer CCD, Loral Fairchild CCD-222 with 244 (vertical) X 380 (horizontal) pixels operated at pixel rates approaching 100 Mhz. Initial prototype designs demonstrated single-port serial readout rates exceeding 2.97 Kilohertz with greater than 5 lp/mm spatial resolution at shutter speeds as short as 5 ns. Readout was achieved by using a truncated format of 128 X 128 pixels by partial masking of the CCD and then subclocking the array at approximately 65 Mhz pixel rate. Shuttering was accomplished with a proximity focused microchannel plate (MCP) image intensifier (MCPII) that incorporated a high strip current MCP (28 uA/sq.cm) and a LANL design modification for high-speed stripline gating geometry to provide both fast shuttering and high repetition rate capabilities. Later camera designs use a close-packed quadrupole head geometry fabricated using an array of four separate CCDs (pseudo 4-port device). This design provides four video outputs with optional parallel or time-phased sequential readout modes. Parallel readout exploits the full potential of both the CCD and MCPII with reduced performance whereas sequential readout permits 4X slower operation with improved performance by multiplexing, but requires individual shuttering of each CCD. The quad head format was designed with flexibility for coupling to various image intensifier configurations, including individual intensifiers for each CCD imager, a single intensifier with fiber optic or lens/prism coupled fanout of the input image to be shared by the four CCD imagers or a large diameter phosphor screen of a gateable framing type intensifier for time sequential relaying of a complete new input image to each CCD imager. Camera designs and their potential use in ongoing military and medical time-resolved imaging applications are discussed.

P-channel backside illuminated silicon charge-coupled devices (CCDs) were developed and fabricated on high-resistivity n-type silicon. The devices have been exposed up to 1 /spl times/ 10/sup 11/ protons/cm/sup 2/ at 12 MeV. The charge transfer efficiency and dark current were measured as a function of radiation dose. These CCDs were found to be significantly more radiation tolerant than conventional n-channel devices. This could prove to be a major benefit for space missions of long duration.

A new, 8/spl times/8-element pixel detector array for time resolved protein crystallography has been developed at the Lawrence Berkeley National Laboratory (LBNL). Each element has its own on-chip charge sensitive preamplifier and shaper with a peaking time of 100 ns. A total of 64 parallel analog to digital processing channels are required to support the detector. We describe a low-cost, low-power AD processing system, comprising a fast peak-sensing amplifier/stretcher, followed by a slower 12-bit ADC. Each channel also includes a histogramming memory for a fully stand-alone operation of the system. Circuit performance and test data are also presented.