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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

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

Analog and digital-multistage time-averaging filters

Description: In time measurements involved in the detection of elementary particles using large counters, the time uncertainty introduced by the finite propagation velocity of the produced signal may be significant compared to the desired time resolution. A novel method, the essential ingredients of which are the time properties of delay lines and AND and OR logic gates, is introduced to reduce this effect drastically. The basic circuit is described, and then the synthesis of time averaging filters, a four-stage filter (implementation and testing), experimental results, and future applications are discussed. The problem of precise timing with a counter of large dimensions can also be solved by means of an analog method; the principle involved, implementation, testing, and time resolution and deadtime are considered. (RWR) 7 figures
Date: January 1, 1980
Creator: Theodosiou, G.E. & Dawson, J.W.
Partner: UNT Libraries Government Documents Department

Vapor locking and heat transfer of multiple layers

Description: The cryogenic stability of a superconducting magnet depends on the heat transfer characteristics of the liquid helium cooling channels. One of the factors which affects the heat transfer to the channel is the amount of vapor accumulated in the channel. It is especially important to design a large magnet with cooling channels large enough to ensure the recovery of a normal zone produced in the magnet following the mechanical disturbances. A study of the vapor formation and heat transfer of multiple layers under both steady state and transient conditions is presented. The change in capacitance between the two sides of the heated channel is measured to determine the volume fraction of the vapor in the cooling channel. It is found that the heat transfer characteristics depend on the vapor accumulation and the velocity of vapor flow. The vapor locking heat flux is decreased when the vapor accumulation is increased. The samples were made to simulate the real cryostable superconductor and the cooling channels to be used in the large MHD superconducting magnet, designated as CFFF-SCMS, currently under construction at Argonne National Laboratory (ANL). (WHK)
Date: January 1, 1980
Creator: Chen, C.J.; Wang, S.T. & Dawson, J.W.
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

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

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

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

Prototype VME data acquisition card for the ZEUS calorimeter

Description: This paper discusses the design of a prototype data acquisition (DAQ) card for the ZEUS calorimeter. The card accepts two multiplexes analog data streams at a 1 MHz rate, and digitizes and stores the data for subsequent transfer through VME to a host computer. The data is buffered by a high-speed asynchronous FIFO following the A/D converters, and written into Data Memory on the card, either directly or after processing by an on-board digital signal processor (DSP). Each card has a 16-bit control-status register (CSR), the bits of which configure the hardware and define the hardware options. The 1/4 Mbyte of high speed CMOS static RAM appears either as a FIFO, or mapped memory depending upon a bit in the CSR. The card is designed to make use of the 32-bit data and address buses supported by VME, and accordingly can be most efficiently utilized in conjunction with a processor in the VME environment such as the 68020, which supports longword transfers in a 32-bit address space. The card is constructed on a ten layer printed circuit, with almost all components being surface-mount devices. All logic is implemented in PLD's. 5 refs., 4 figs., 3 tabs.
Date: January 1, 1988
Creator: Dawson, J.W.; Berg, J.S.; Schlereth, J.L. & Stanek, R.
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

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

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

High energy mode locked fiber oscillators for high contrast, high energy petawatt laser seed sources

Description: In a high-energy petawatt laser beam line the ASE pulse contrast is directly related to the total laser gain. Thus a more energetic input pulse will result in increased pulse contrast at the target. We have developed a mode-locked fiber laser with high quality pulses and energies exceeding 25nJ. We believe this 25nJ result is scalable to higher energies. This oscillator has no intra-cavity dispersion compensation, which yields an extremely simple, and elegant laser configuration. We will discuss the design of this laser, our most recent results and characterization of all the key parameters relevant to it use as a seed laser. Our oscillator is a ring cavity mode-locked fiber laser [1]. These lasers operate in a self-similar pulse propagation regime characterized by a spectrum that is almost square. This mode was found theoretically [2] to occur only in the positive dispersion regime. Further increasing positive dispersion should lead to increasing pulse energy [2]. We established that the positive dispersion required for high-energy operation was approximately that of 2m of fiber. To this end, we constructed a laser cavity similar to [1], but with no gratings and only 2m of fiber, which we cladding pumped in order to ensure sufficient pump power was available to achieve mode-locked operation. A schematic of the laser is shown in figure 1 below. This laser produced low noise 25nJ pulses with a broad self similar spectrum (figure 2) and pulses that could be de-chirped to <100fs (figure 3). Pulse contrast is important in peta-watt laser systems. A major contributor to pulse contrast is amplified spontaneous emission (ASE), which is proportional to the gain in the laser chain. As the oscillator strength is increased, the required gain to reach 1PW pulses is decreased, reducing ASE and improving pulse contrast. We believe these lasers can be ...
Date: June 15, 2006
Creator: Dawson, J W; Messerly, M J; An, J; Kim, D & Barty, C J
Partner: UNT Libraries Government Documents Department

Development of a custom monolithic device for data acquisition from a scintillating calorimeter at the superconducting super collider

Description: A clock-driven continuous sequential write/random read data acquisition architecture for a scintillating calorimeter at the SSC is presented. Simplicity of design and operation as well as potentially dead time-less operation are the motivations of this effort. The architecture minimizes the number of fast control signals, thereby reducing pickup from digital control lines by sensitive analog circuits in the front-end device. This architecture also reduces the logic necessary on the front-end device improving reliability and easing design and operation. Operation and design of the front-end device are discussed. 3 refs., 7 figs.
Date: January 1, 1991
Creator: Ekenberg, T.; Dawson, J.W.; Talaga, R.L.; Stevens, A.E. & Haberichter, W.N.
Partner: UNT Libraries Government Documents Department

A gigabit ethernet link source card.

Description: A Link Source Card (LSC) has been developed which employs Gigabit Ethernet as the physical medium. The LSC is implemented as a mezzanine card compliant with the S-Link specifications, and is intended for use in development of the Region of Interest Building (ROIB) in the Level 2 Trigger of ATLAS. The LSC will be used to bring Region of Internet Fragments from Level 1 Trigger elements to the ROIB, and to transfer compiled Region of Interest Records to Supervisor Processors. The card uses the LSI 8101/8104 Media Access Controller (MAC) [1] and the Agilent HDMP-1636 Transceiver. An Altera 10K50A FPGA [2] is configured to provide several state machines which perform all the tasks on the card, such as formulating the Ethernet header, read/write registers in the MAC, etc. An on-card static RAM provides storage for 512K S-Link words, and a FIFO provides 4K buffering of input S-Link words. The LSC has been tested in a setup where it transfers data to a NIC in the PCI bus of a PC.
Date: September 18, 2002
Creator: Blair, R. E.; Dawson, J. W.; Drake, G.; Haberichter, W. N. & Schlereth, J. L.
Partner: UNT Libraries Government Documents Department

Environmental radiological studies downstream from Rancho Seco Nuclear Power Generating Station

Description: This report summarizes the information compiled in 1984 while assessing the environmental impact of radionuclides in aquatic releases from the Rancho Seco Nuclear Power Generating Station. Gamma-emitting radionuclides discharged since 1981 are found in many of the dietary components derived from the creeks receiving the effluent wastewater. Some soils and crops are found to contain radionuclides that originate from the contaminated water that was transferred to land during the irrigation season. /sup 134/Cs and /sup 137/Cs are the primary gamma-emitting radionuclides detected in the edible flesh of fish from the creeks. Concentrations in the flesh of fish decreased exponentially with distance from the plant. No significant differences in the /sup 137/Cs activity were found between male and female fish of equal size, but concentrations may vary in fish of different size, with the season and diet. 21% of the total /sup 137/Cs and /sup 134/Cs discharged between 1981 and 1984 is associated with the creek sediments to a distance of 27 km from the plant. Fractions of the missing inventory have been transferred to land during the irrigation season or to downstream regions more distant than 27 km from the plant. The radiocesium content of the sediments in 1984 decreased significantly in a downstream direction, much in the same manner as concentrations decreased in fish. Radioactivity originating from the plant was not above detection limits in any terrestrial food item sampled beyond 6.5 km from the plant. Based on the usage factors provided by individuals interviewed in a 1984 survey, the fish and aquatic-organism ingestion pathway contributed the largest radiological dose to humans utilizing products contaminated with the radionuclides in the liquid wastes discharged from the Rancho Seco Nuclear Power Generating Station in 1984.
Date: March 22, 1985
Creator: Noshkin, V.E.; Wong, K.M.; Eagle, R.J.; Dawson, J.W.; Brunk, J.L. & Jokela, T.A.
Partner: UNT Libraries Government Documents Department

Fiber laser front end for high energy petawatt laser systems

Description: We are developing a fiber laser front end suitable for high energy petawatt laser systems on large glass lasers such as NIF. The front end includes generation of the pulses in a fiber mode-locked oscillator, amplification and pulse cleaning, stretching of the pulses to >3ns, dispersion trimming, timing, fiber transport of the pulses to the main laser bay and amplification of the pulses to an injection energy of 150 {micro}J. We will discuss current status of our work including data from packaged components. Design detail such as how the system addresses pulse contrast, dispersion trimming and pulse width adjustment and impact of B-integral on the pulse amplification will be discussed. A schematic of the fiber laser system we are constructing is shown in figure 1 below. A 40MHz packaged mode-locked fiber oscillator produces {approx}1nJ pulses which are phase locked to a 10MHz reference clock. These pulses are down selected to 100kHz and then amplified while still compressed. The amplified compressed pulses are sent through a non-linear polarization rotation based pulse cleaner to remove background amplified spontaneous emission (ASE). The pulses are then stretched by a chirped fiber Bragg grating (CFBG) and then sent through a splitter. The splitter splits the signal into two beams. (From this point we follow only one beam as the other follows an identical path.) The pulses are sent through a pulse tweaker that trims dispersion imbalances between the final large optics compressor and the CFBG. The pulse tweaker also permits the dispersion of the system to be adjusted for the purpose of controlling the final pulse width. Fine scale timing between the two beam lines can also be adjusted in the tweaker. A large mode area photonic crystal single polarization fiber is used to transport the pulses from the master oscillator room to the main ...
Date: June 15, 2006
Creator: Dawson, J W; Messerly, M J; Phan, H; Mitchell, S; Drobshoff, A; Beach, R J et al.
Partner: UNT Libraries Government Documents Department

Construction and operation of a drift-collection calorimeter

Description: Large areas planar drift chambers with long drift distance (up to 50 cm) have been developed for possible use in the new Soudan 2 nucleon decay detector. Design goals included fine sampling to determine the topology of complex events with several low-energy tracks. The large scale of the experiment (> 1000 metric tons) required large area inexpensive chambers, which also had good position resolution and multi-track separation. The chambers were to be installed between thin sheets of steel to form a finegrained detector. A second goal was the sampling of dE/dx with each position measurement, in order to determine the direction and particle identity of each track. In this paper we report on the construction and operation of a prototype dectector consisting of 50 chambers, separated by 3 mm-thick steel plates. Readout of drift time and pulse height from anode wires and an orthogonal grid of bussed cathode pads utilized 6-bit flash ADC's. This application of the drift-collection calorimeter technique to a nucleon decay detector follows the investigation by a number of groups of calorimeters for high energy detectors based on long drifting.
Date: January 1, 1984
Creator: Ambats, I.; Ayres, D.S.; Dawson, J.W.; Hoftiezer, J.H.; Mann, W.A.; May, E.N. et al.
Partner: UNT Libraries Government Documents Department

The ATLAS level 2 trigger supervisor.

Description: This paper presents an overview of the hardware and software proposed for the ATLAS level 2 Trigger ROI Builder/Supervisor. The essential requirements of this system are that it operate at the design Level 1 Trigger rate of 100kHz and that it support the technical requirements of the architectures suggested for the ATLAS Level 2 Trigger. Commercial equipment and software support are used to the maximum extent possible, with support from dedicated hardware. Timing requirements and latencies are discussed and simulation results are presented.
Date: April 3, 1997
Creator: Abolins, M.; Blair, R. E.; Dawson, J. W.; Owen, D.; Pope, B. G.; Schlereth, J. L. et al.
Partner: UNT Libraries Government Documents Department

Argonne program to assess superconducting stability

Description: To assess superconductor stability, a complete program is developed to obtain basic information on the effects of local mechanical perturbations on the cryostatic stability. An analytical model for computing the transient recovery following the mechanical perturbation is developed. A test program is undertaken to develop data needed to verify the conclusions reached through the analytical studies.
Date: January 1, 1978
Creator: Wang, S.T.; Turner, L.R.; Huang, Y.C.; Dawson, J.W.; Harrang, J.; Hilal, M.A. et al.
Partner: UNT Libraries Government Documents Department

10-kJ Status and 100-kJ Future for NIF PetaWatt Technology

Description: We discuss the status of the NIF ARC, an 8-beam 10-kJ class high-energy petawatt laser, and the future upgrade path of this and similar systems to 100-kJ-class with coherent phasing of multiple apertures.
Date: July 2, 2007
Creator: Siders, C W; Crane, J K; Rushford, M C; Haefner, L C; Hernandez, J E; Dawson, J W et al.
Partner: UNT Libraries Government Documents Department

Power scaling analysis of fiber lasers and amplifiers based on non-silica materials

Description: A developed formalism for analyzing the power scaling of diffraction limited fiber lasers and amplifiers is applied to a wider range of materials. Limits considered include thermal rupture, thermal lensing, melting of the core, stimulated Raman scattering, stimulated Brillouin scattering, optical damage, bend induced limits on core diameter and limits to coupling of pump diode light into the fiber. For conventional fiber lasers based upon silica, the single aperture, diffraction limited power limit was found to be 36.6kW. This is a hard upper limit that results from an interaction of the stimulated Raman scattering with thermal lensing. This result is dependent only upon physical constants of the material and is independent of the core diameter or fiber length. Other materials will have different results both in terms of ultimate power out and which of the many limits is the determining factor in the results. Materials considered include silica doped with Tm and Er, YAG and YAG based ceramics and Yb doped phosphate glass. Pros and cons of the various materials and their current state of development will be assessed. In particular the impact of excess background loss on laser efficiency is discussed.
Date: March 30, 2010
Creator: Dawson, J W; Messerly, M J; Heebner, J E; Pax, P H; Sridharan, A K; Bullington, A L et al.
Partner: UNT Libraries Government Documents Department