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Microprocessor-based control for independently-phased RF linac cavities

Description: A microprocessor based system has been built to control the RF amplifiers associated with independently phased linac cavities. The system has an 8080A at each amplifier station, together with associated ROM, RAM, I/O, etc. At a central NOVA 3 computer an additional 8080A system is incorporated in the interface to the NOVA I/O bus. The NOVA interface is connected by a bus of eighteen twisted pairs to each amplifier station, providing bilateral transmission between each station and the NOVA. The system architecture, bus protocol, and operating characteristics are described.
Date: January 1, 1979
Creator: Dawson, J.W.
Partner: UNT Libraries Government Documents Department

Plasma wake field accelerator

Description: A new scheme of electron acceleration, employing relativistic electron bunches in a cold plasma, is analyzed. The wake field of a leading bunch is derived in a single-particle model. We then extend the model to include finite bunch length effect. In particular, we discuss the relation between the charge distributions of the driving bunch and the energies transformable to the trailing electrons. It is shown that for symmetric charge distribution of the driving bunches, the maximum energy gain for a driven electron is 2..gamma../sub 0/mc/sup 2/. This limitation can be overcome by introducing asymmetric charge distributions. 13 refs., 5 figs.
Date: March 1, 1985
Creator: Chen, P. & Dawson, J.M.
Partner: UNT Libraries Government Documents Department

Development and performance of a calibration system for a large calorimeter array

Description: Experiment 609 at Fermilab is a study of the properties of high-p/sub t/ collisions using a large segmented hadron calorimeter. The calibration and monitoring of such a large calorimeter array is a difficult undertaking. This paper describes the systems developed by E609 for automatic monitoring of the phototube gains and performance of the associated electronics.
Date: January 1, 1982
Creator: Arenton, M.; Dawson, J. & Ditzler, W.R.
Partner: UNT Libraries Government Documents Department

Plasma wave accelerator. II

Description: It was shown that the insertion of a cross magnetic field prevents the particles from getting out of phase with the electric field of the plasma wave in the beat wave accelerator scheme. Thus, using a CO/sub 2/ laser, n/sub c//n/sub e/ = (..omega../sub 0//..omega../sub p/)/sup 2/ approx. 35, and a 300 kG magnetic field, electrons can be (in principle) accelerated to 100 GeV in 2 meters. For comparison without the magnetic field, the same energies may be obtained in a n/sub c//n/sub e/ approx. 10/sup 5/ plasma over a distance of 100 meters.
Date: January 1, 1982
Creator: Mori, W.; Joshi, C. & Dawson, J.M.
Partner: UNT Libraries Government Documents Department

Development of Radhard VLSI electronics for SSC calorimeters

Description: A new program of development of integrated electronics for liquid argon calorimeters in the SSC detector environment is being started at Argonne National Laboratory. Scientists from Brookhaven National Laboratory and Vanderbilt University together with an industrial participants are expected to collaborate in this work. Interaction rates, segmentation, and the radiation environment dictate that front-end electronics of SSC calorimeters must be implemented in the form of highly integrated, radhard, analog, low noise, VLSI custom monolithic devices. Important considerations are power dissipation, choice of functions integrated on the front-end chips, and cabling requirements. An extensive level of expertise in radhard electronics exists within the industrial community, and a primary objective of this work is to bring that expertise to bear on the problems of SSC detector design. Radiation hardness measurements and requirements as well as calorimeter design will be primarily the responsibility of Argonne scientists and our Brookhaven and Vanderbilt colleagues. Radhard VLSI design and fabrication will be primarily the industrial participant's responsibility. The rapid-cycling synchrotron at Argonne will be used for radiation damage studies involving response to neutrons and charged particles, while damage from gammas will be investigated at Brookhaven. 10 refs., 6 figs., 2 tabs.
Date: January 1, 1989
Creator: Dawson, J.W. & Nodulman, L.J.
Partner: UNT Libraries Government Documents Department

Calculation of the potentials and 3D electric fields in a proton decay detector

Description: An electrostatic detector for measuring the lifetime of the proton has been modeled in three dimensions. Linear hexahedral finite elements were used and the potential obtained at all nodes. The three components of the electric field were calculated and used to determine field lines, calculate drift fields and drift times. Effective aperture calculations agreed with the measurements.
Date: January 1, 1987
Creator: Lari, R.J.; Dawson, J.W. & Turner, L.R.
Partner: UNT Libraries Government Documents Department

Data preprocessor and compactor for the Soudan 2 nucleon decay experiment

Description: This paper describes a prototype preprocessor data-compaction system for the Soudan 2 proton decay search experiment. The Soudan 2 experiment will have more than three million potential data words per event to examine, while less than one percent of these data words will have valid data for typical events. In an effort to reduce the amount of data to be stored and analyzed, a data preprocessor was developed which scans the data words. If a data word is valid (ADC count above a preset threshold), that data word is passed to the host computer for experiment monitoring and storage on magnetic tape. To obtain fast data compression, a hardware comparator is used. The hardware comparator places valid data into a FIFO (first in first out stack) where the host computer can acquire the data through CAMAC. The comparator and FIFO are controlled by a microprocessor (8086 CPU), and the microprocessor is programmed for decision-making and communication between the compactor, CAMAC, the host computer and a local terminal.
Date: January 1, 1984
Creator: Dawson, J.W.; May, E.N. & Solomey, N.
Partner: UNT Libraries Government Documents Department

Prospects of the surfatron laser plasma accelerator

Description: The surfatron concept is proposed as a possible solution to the problem of staging in the laser-plasma beat wave accelerator scheme. Prospects of a 100 GeV particle accelerator based on the surfatron concept are explored. Finite angle optical mixing appears to be a promising solution for drastically reducing the width of the plane wave, thereby, making the required laser power and the device size realizable for a proof-of-principle experiment. Our conclusions are based mainly on analytical theory and one-dimensional particle simulations.
Date: January 1, 1983
Creator: Katsouleas, T.; Joshi, C.; Mori, W. & Dawson, J.M.
Partner: UNT Libraries Government Documents Department

Fiber Laser Replacement for Short Pulse Ti:Sapphire Oscillators -- Scalable Mode Locking to Record Pulse Energies

Description: We have investigated fiber-based lasers that mode-lock via three nonlinear mechanisms: pulse evolution, bend loss, and tunneling. Experiments with nonlinear pulse evolution proved especially promising; we report here a fiber laser that produces 25 nJ, sub-200 fs pulses, an energy that is 60% higher than previous reports. Experiments with nonlinear bend loss were inconclusive; though bend-loss data show that the effect exits, we were not able to use the phenomenon to lock a laser. New models suggest that nonlinear tunneling could provide an alternate path.
Date: February 14, 2006
Creator: Dawson, J W; Messerly, M J & An, J
Partner: UNT Libraries Government Documents Department

Comparison of amplified spontaneous emission pulse cleaners for use in chirped pulse amplification front end lasers

Description: We compare various schemes for removing amplified spontaneous emission from seed laser pulses. We focus on compact schemes that are compatible with fiber laser front end systems with pulse energies in the 10nJ-1{micro}J range and pulse widths in the 100fs-10ps range. Pre-pulse contrast ratios greater than 10{sup 9} have been measured.
Date: July 2, 2007
Creator: Dawson, J.; Siders, C.; Phan, H.; Kanz, V. & Barty, C.
Partner: UNT Libraries Government Documents Department


Description: The development of microsatellites requires the development of engines to modify their orbit. It is natural to use solar energy to drive such engines. For an unlimited energy source the optimal thruster must use a minimal amount of expendable material to minimize launch costs. This requires the ejected material to have the maximal velocity and, hence, the ejected atoms must be as light as possible and be ejected by as high an energy density source as possible. Such a propulsion can be induced by pulses from an ultra-short laser. The ultra-short laser provides the high-energy concentration and high-ejected velocity. We suggest a microthruster system comprised of an inflatable solar concentrator, a solar panel, and a diode-pumped fiber laser. We will describe the system design and give weight estimates.
Date: February 5, 2010
Creator: Rubenchik, A M; Beach, R; Dawson, J & Siders, C W
Partner: UNT Libraries Government Documents Department

Soudan 2 data acquisition and trigger electronics

Description: The 1.1 kton Soudan 2 detector is read out by 16K anode wires and 3 2K cathode strips. Preamps from each wire or strip are bussed together in groups of 8 to reduce the number of ADC channels. The resulting 6144 channels of ionization signal are flash-digitized every 150 ns and stored in RAM. The raw data hit patterns are continually compared with programmable trigger multiplicity and adjacency conditions. The data acquisition process is managed in a system of 24 parallel crates each containing an Intel 8086 microprocessors, which supervises a pipe-lined data compactors, and allows transfer of the compacted data via CAMAC to the host computer. The 8086's also manage the local trigger conditions and can perform some parallel processing of the data. Due to the scale of the system and multiplicity of identical channels, semi-custom gate array chips are used for much of the logic, utilizing 2.5 micron CMOS technology.
Date: January 1, 1985
Creator: Dawson, J.; Laird, R.; May, E.; Mondal, N.; Schlereth, J.; Solomey, N. et al.
Partner: UNT Libraries Government Documents Department

a-c losses of 19-strand subcables for the ANL 3. 3-MJ coil

Description: From the time constant and the hysteresis loss measurements of the subcables, it is estimated that approximately 60% of the ac losses of the ANL 3.3 MJ coil at 6 T/s of the central field are due to the losses within the 19-strand subcable itself. The remaining 40% of the losses seem to come mainly from the coupling among the weakly insulated 19-strand subcables in the final cable. The outer sheath copper wires of the subcable improve the stability of the subcable, especially when it is soldered. It is shown, however, that the ac losses are not increased significantly due to the copper stabilizer.
Date: January 1, 1983
Creator: Kim, S.H.; Dawson, J.W.; McGhee, D.G. & Shen, S.S.
Partner: UNT Libraries Government Documents Department

Legume hays for milk production.

Description: Argues the case for using legume hays on the farm. Describes the advantages of legume hays for profitability and increased nutrients per acre.
Date: October 1928
Creator: Dawson, J. R. (James Robert), b. 1894
Partner: UNT Libraries Government Documents Department

Moving from self-regulation to external regulation of Department of Energy facilities

Description: This paper discusses the initiative to transfer the regulation of Department of Energy (DOE) nuclear facilities to the US Nuclear Regulatory Commission (NRC). The paper gives an overview of some of the major technical, policy and legal issues that accompany this initiative. The paper focuses on specific issues and how they may be affected by external regulation of occupational radiation protection at DOE facilities. Differences between the NRC and the DOE approach to regulating nuclear safety are compared and contrasted. Some projected impacts from this transition are examined. Finally, recommendations are provided that may enhance the transition, increasing the likelihood of successful external NRC regulation.
Date: March 1, 1999
Creator: Wishau, R.J.; Dawson, J. & Lee, D.W.
Partner: UNT Libraries Government Documents Department

A prototype ROI builder for the second level trigger of ATLAS implemented in FPGA's.

Description: In an effort to reduce data transfer and rate requirements, the Higher Level Trigger of the ATLAS Detector uses Region of Interest (ROI) information forwarded from Level 1 Partitions on a Level 1 Accept. The ROI Builder receives these ROI fragments, which may be considerably skewed in time and may be interspersed with fragments from other events, organizes and formats from these fragments a record for each event accepted by Level 1, selects a processor to manage the event, and transfers via S-link the assembled ROI record to the target processor. The ROI Builder must fulfill these requirements at the Level 1 Trigger rate of 100 kHz while accommodating S-link flow control. A design for the ROI Builder was developed emphasizing parallelism, implemented in FPGA's, and has been run in testbeds at Saclay and CERN.
Date: December 7, 1999
Creator: Blair, R. E.; Dawson, J. W.; Haberichter, W. N. & Schlereth, J. L.
Partner: UNT Libraries Government Documents Department

Trigger processor for the APEX experiment at Argonne

Description: An electron-positron spectrometer is being constructed at Argonne to search for correlated pairs emitted after heavy ion collisions. The trigger for this experiment requires the detection of a positron in either arm of the spectrometer. We describe the trigger for the experiment which selects events with positron annihilation radiation detected in an array of NaI crystals. 1 ref., 3 figs.
Date: January 1, 1990
Creator: Dawson, J.W.; Freedman, S.J. & Haberichter, W.N.
Partner: UNT Libraries Government Documents Department

Concentration of radionuclides in fresh water fish downstream of Rancho Seco Nuclear Generating Plant

Description: Fish were collected for radionuclide analysis over a 5-month period in 1984 from creeks downstream of the Rancho Seco Nuclear Generating Plant, which has been discharging quantities of some fission and activation products to the waterway since 1981. Among the fish, the bluegill was selected for intensive study because it is very territorial and the radionuclide concentrations detected should be representative of the levels in the local environment at the downstream locations sampled. Among the gamma-emitting radionuclides routinely released, only /sup 134/Cs and /sup 137/Cs were detected in the edible flesh of fish. Concentrations in the flesh of fish decreased with distance from the plant. The relationship between concentration and distance was determined to be exponential. Exponential equations were generated to estimate concentrations in fish at downstream locations where no site-specific information was available. Mean concentrations of /sup 137/Cs in bluegill collected during April, May, July and August from specific downstream stations were not significantly different in spite of the release of 131 mCi to the creeks between April and August. The concentrations in fish are not responding to changes in water concentrations brought about by plant discharges. Diet appears to be a more significant factor than size or weight or water concentration in regulating body burdens of /sup 137/Cs in these fish.
Date: December 27, 1984
Creator: Noshkin, V.E.; Eagle, R.J.; Dawson, J.M.; Brunk, J.L. & Wong, X.M.
Partner: UNT Libraries Government Documents Department

Vapor locking and heat transfer under transient and steady state conditions

Description: The study was undertaken to determine the vapor locking in the cooling channels of a cryostable superconducting magnet, to investigate the heat transfer characteristics under steady state and transient conditions, and to study the effects of vapor accumulation of the multiple coil layers. Based on the experimental results obtained the following conclusions can be made: (1) the critical steady state heat flux for the transition from nucleate boiling to film boiling is about 0.4 w/cm/sup 2/; (2) the critical transient energy density for the boiling transition is about 100 mJ/cm/sup 3/; (3) the front channel is easier to reach the film boiling regime than rear channel, due to that the wetted area of front side is more than the wetted area of rear side; and (4) no temperature rise greater than 1/sup 0/K is possible if the heat flux does not exceed the critical heat flux under steady state condition or the energy density does not exceed the critical energy density under transient condition.
Date: January 1, 1979
Creator: Chen, C J; Wang, S T & Dawson, J W
Partner: UNT Libraries Government Documents Department

Rad-hard electronics study for SSC detectors

Description: The radiation environment in a SSC detector operating at a luminosity of 10{sup 33} cm{sup {minus}2}s{sup {minus}1} will put stringent requirements on radiation hardness of the electronics. Over the expected 10 year life-time of a large detector, ionizing radiation doses of up to 20 MRad and neutron fluences of 10{sup 16} neutrons/cm{sup 2} are projected. At a luminosity of 10{sup 34} cm{sup {minus}2}s{sup {minus}1} even higher total doses are expected. the effect of this environment have been simulated by exposing CMOS/bulk and CMOS/SOS devices from monolithic processes to neutrons and ionizing radiation. leakage currents, noise variations, and DC characteristics have been measured before and after exposure in order to evaluate the effects of the irradiations. As expected the device characteristics remained virtually unchanged by neutron irradiation, while ionizing radiation caused moderate degradation of performance. 5 refs., 6 figs.
Date: January 1, 1991
Creator: Ekenberg, T.; Dawson, J.; Stevens, A. & Haberichter, W.
Partner: UNT Libraries Government Documents Department

Two-dimensional beat wave acceleration simulation

Description: Finite laser beam particle simulations of beat wave acceleration show that a coherent plasma wave excited by two-colinear laser beams at a difference frequency equal to the plasma frequency can produce maximum electron energies as predicted by simple one-dimensional theory. The time to saturation and the saturation amplitude of the plasma wave electric field agrees with the Rosenbluth-Liu theory. Stimulated Raman scattering does not appear to degrade the electron acceleration process. Eventually self-focussing and filamentation limit the lifetime of the coherent plasma wave to tens of picoseconds for an intense CO/sub 2/ laser beam.
Date: January 1, 1984
Creator: Kindel, J.M.; Forslund, D.W.; Mori, W.B.; Joshi, C. & Dawson, J.M.
Partner: UNT Libraries Government Documents Department

A grating-less, fiber-based oscillator that generates 25 nJ pulses

Description: We report a passively mode-locked fiber-based oscillator that has no internal dispersion-compensating gratings. This design, the first of its kind, produces 25 nJ pulses at 80 MHz with the pulses compressible to 150 fs. The pulses appear to be self-similar and initial data imply that their energy is further scalable.
Date: December 28, 2006
Creator: An, J; Kim, D; Dawson, J W; Messerly, M J & Barty, C J
Partner: UNT Libraries Government Documents Department