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Observation of cosmological time dilation using type Ia supernovae as clocks

Description: This work is based on the first results from a systematic search for high redshift Type Ia supernovae. Using filters in the R-band we discovered seven such SNe, with redshift z = 0.3-0.5, before or at maximum light. Type Ia SNe are known to be a homogeneous group of SNe, to first order, with very similar light curves, spectra and peak luminosities. In this talk we report that the light curves we observe are all broadened (time dilated) as expected from the expanding universe hypothesis. Small variations from the expected 1 + z broadening of the light curve widths can be attributed to a width-brightness correlation that has been observed for nearby SNe (z < 0.1). We show in this talk the first clear observation of the cosmological time dilation for macroscopic objects.
Date: September 1, 1998
Creator: Goldhaber, G., FNAL
Partner: UNT Libraries Government Documents Department

Time-resolved measurement of a self-amplified free-electron laser.

Description: We report on a time-resolved measurement of self-amplified spontaneous emission (SASE) free-electron laser (FEL) pulses. We observed that the spikes in the output of such free-electron laser pulses have an intrinsic positive chirp and the energy chirp in the electron bunch mapped directly into the FEL output. The measurement also provides rich information on the statistics of the FEL output.
Date: October 2, 2002
Creator: Li, Y.; Lewellen, J.; Huang, Z.; Sajaev, V. & Milton, S. V.
Partner: UNT Libraries Government Documents Department

Tomographic Imaging of Upper Mantle P- and S-wave Velocity Heterogeneity Beneath the Arabian Peninsula

Description: We report the estimates of three-dimensional P- and S-wave velocity structure beneath the Arabian Peninsula estimated from travel time delay tomography. We have completed travel time measurements and inversion of a partial data set provided by King Abdulaziz City for Science and Technology (KACST). This study builds on previous work by Benoit et al. (2003) following the methods of VanDecar and Crosson (1990) and VanDecar (1991). Data were collected from the Saudi Arabian National Digital Seismic Network (SANDSN) operated by KACST. The network consists of 38 stations (27 broadband and 11 short-period). We augmented the KACST data with delay times measured from permanent Incorporated Research Institutions for Seismology (IRIS) stations in the region (RAYN, EIL and MRNI) and the 1996 Saudi Arabian PASSCAL Experiment. This study shows the inverted P- and S-wave models computed with the combined data with all three different seismic networks (KASCST, IRIS, and the 1996 Saudi Arabian PASSCAL experiment) with best coverage beneath the Arabian Shield. Tomographic images reveal low velocity features in the upper mantle along a north-south line from the southern Asir region to the northeastern portion of the Arabian Shield.
Date: August 30, 2005
Creator: Park, Y; Nyblade, A; Rodgers, A & Al-Amri, A
Partner: UNT Libraries Government Documents Department

A method for calculating longitudinal phase space distribution when given the time profile of the bunch

Description: We will show in this paper a method for calculating the longitudinal phase space distribution when the time profile of the bunch as measured by a wall current monitor is given. The key to this method is the assumption that the bunch is matched to the bucket. With this assumption, we will show that the method boils down to solving a simple upper triangular matrix equation. We will also illustrate the method with two examples and show the method's shortcomings.
Date: July 30, 2001
Creator: Tan, Cheng-Yang
Partner: UNT Libraries Government Documents Department

Implementation of detonation electric effects. [Quarterly report], January--March 1971

Description: Detonation electric effect measurement was applied to a stack of PMMA discs on the output of an explosive PWL to resolve some anomalies previously observed in the arrival times of a shock wave as it passes through the various interfaces. A brief description of the experiments and some comments on the results are included.
Date: December 31, 1971
Creator: Boettner, J.K.
Partner: UNT Libraries Government Documents Department

Time Synchronization in Hierarchical TESLA Wireless Sensor Networks

Description: Time synchronization and event time correlation are important in wireless sensor networks. In particular, time is used to create a sequence events or time line to answer questions of cause and effect. Time is also used as a basis for determining the freshness of received packets and the validity of cryptographic certificates. This paper presents secure method of time synchronization and event time correlation for TESLA-based hierarchical wireless sensor networks. The method demonstrates that events in a TESLA network can be accurately timestamped by adding only a few pieces of data to the existing protocol.
Date: August 1, 2009
Creator: Wright, Jason L. & Manic, Milos
Partner: UNT Libraries Government Documents Department

Thermal Decomposition of New and Aged LX-04 and PBX 9501

Description: One-Dimensional-Time-To-Explosion (ODTX) experiments were conducted to study the thermal decomposition of new and aged LX-04, PBX 9501, HMX class 1 and class 2, Estane and EstaneBDNPA-F (PBX 950 1 plasticized-binder) materials. New and aged LX-04 showed comparable decomposition kinetics. The data for aged PBX 9501 showed slightly longer explosion times at equivalent temperatures. Analysis of the error in time measurement is complicated by several experimental factors but the small time change appears to be experimentally significant. The results suggest that aged PBX 9501 is slightly more thermally stable. The thermal decomposition of these materials were modeled using a coupled thermal and heat transport code (chemical TOPAZ) using separate kinetics for HMX and binder decomposition. The current kinetic models describe the longer explosion times by the loss of plasticizer-binder constituent, which was more thermally reactive.
Date: April 9, 2002
Creator: Tran, T. D.; Tarver, Craig M.; Idar, D. J. & Rodin, W. A.
Partner: UNT Libraries Government Documents Department

Real-Time Measurement of Rates of Outdoor Airflow into HVACSystems: A Field Study of Three Technologies

Description: Technologies for real-time continuous measurement of the flow rates of outdoor air (OA) into HVAC systems are now available commercially. Our prior papers reported on laboratory-based evaluations of these measurement technologies and this document describes the methods and results of a field study of the accuracy of three of these technologies. From the field study data, we determined that neither wind speed nor wind direction have an important adverse impact on measurement accuracy. The field study confirmed that these three measurement technologies can provide reasonably accurate measurements of outdoor air intake rates in field settings, if the pressure signals are measured with high accuracy. Some of the pressure transducers marketed for use with commercial HVAC systems were determined to be sufficiently accurate for this application. Given the significant impact of OA flow rates on both energy use and occupant health, more widespread use of technologies that provide for real time measurements of OA flow rates seems warranted.
Date: September 1, 2005
Creator: Fisk, William J.; Sullivan, Douglas P. & Faulkner, David
Partner: UNT Libraries Government Documents Department

A low-power wave union TDC implemented in FPGA

Description: A low-power time-to-digital convertor (TDC) for an application inside a vacuum has been implemented based on the Wave Union TDC scheme in a low-cost field programmable gate array (FPGA) device. Bench top tests have shown that a time measurement resolution better than 30 ps (standard deviation of time differences between two channels) is achieved. Special firmware design practices are taken to reduce power consumption. The measurements indicate that with 32 channels fitting in the FPGA device, the power consumption on the FPGA core voltage is approximately 9.3 mW/channel and the total power consumption including both core and I/O banks is less than 27 mW/channel.
Date: October 1, 2011
Creator: Wu, Jinyuan; /Fermilab; Shi, Yanchen; Zhu, Douglas & Acad., /Illinois Math. Sci.
Partner: UNT Libraries Government Documents Department

Recent Advances in Millimicrosecond Counting Techniques

Description: The author describes some of the changes that are now occurring or are likely to occur quite soon in the fast counting techniques. The author draws heavily on the information and advice of Dr. Clyde Wiegand and Mr. Quentin Kerns of the University of California Radiation Laboratory. The techniques the author mentions should be quite useful in several different types of experiments. The fast conicidence techniques are principally used for reducing background from accidental coincidences, for measuring times of flight of particles from one counter to another, and for measuring the life times of unstable particles.
Date: April 17, 1956
Creator: Chamberlain, Owen
Partner: UNT Libraries Government Documents Department


Description: The Peak Detector/Derandomizer ASIC (PDD) provides threshold discrimination, peak detection, time-to-amplitude conversion, analog memory, sparsification, and multiplexing for 32 channels of analog pulse data. In this work the spectroscopic capabilities of the chip (high resolution and high rate) are demonstrated along with correlated measurements of pulse risetime. Imaging and coincidence detection using the PDD chip will also be illustrated.
Date: October 16, 2004
Partner: UNT Libraries Government Documents Department

Method and apparatus for detecting timing errors in a system oscillator

Description: This invention is comprised of a method of detecting timing errors in a system oscillator for an electronic device, such as a power supply, includes the step of comparing a system oscillator signal with a delayed generated signal and generating a signal representative of the timing error when the system oscillator signal is not identical to the delayed signal. An LED indicates to an operator that a timing error has occurred. A hardware circuit implements the above-identified method.
Date: December 31, 1991
Creator: Gliebe, R.J. & Kramer, W.R.
Partner: UNT Libraries Government Documents Department

A Cray T3D performance study

Description: We carry out a performance study using the Cray T3D parallel supercomputer to illustrate some important features of this machine. Timing experiments show the speed of various basic operations while more complicated operations give some measure of its parallel performance.
Date: May 1, 1996
Creator: Nallana, A. & Kincaid, D.R.
Partner: UNT Libraries Government Documents Department

SAO HMC photodetector/event timer engineering model test report

Description: The test unit is a custom photodetector/event timer, PET, built for the Smithsonian Astrophysical Observatory, SAO, by Los Alamos which records elapsed time in 10 ps steps. The 1 Kg, 12 cm diameter PET unit uses 10 watts of electrical power and was tested to SAO`s specified flight conditions. The event timer has two inputs -- a reference clock oscillator input and a stop signal. Like a stop watch with split timing capability, the event timer records the instant a stop signal arrives. At that sample instant, the number of elapsed clock cycles are stored and the sample instant position between two reference clock edges is interpolated and stored. Then that stored data can be shifted serially to an external computer. The photodetector part of the PET responds to an optical input and provides the electrical output signal to the event timer specifying the sample instant. This test report discusses the event timer test results. Test equipment is shown for most of the operational tests. The relay rack contains test pursers and clocks. The environmental chamber controls temperature. The computer reads and records the serial data from the PET. Reported testing topics include: Pulse shapes to be used as test inputs, test results obtained using the electrical source`s input, optical test results which are the best simulation of specified operational conditions, heat sink operation in vacuum. Vibration tests performed to SAO`s specification.
Date: October 5, 1994
Partner: UNT Libraries Government Documents Department

Early-time measurements of laser-plasma conditions in omega-upgrade ICF targets. Semi-annual report, October 1, 1997--March 31, 1998

Description: Since arrival of FY-98 funding under this grant in December, we have been preparing for our first series of experiments under this grant at the University of Rochester Laboratory for Laser Energetics (LLE) on the Omega laser facility, now scheduled the week beginning May 4, 1998. We will again be fielding our flat-field, grazing-incidence extreme-ultraviolet (euv) spectrograph with a four-channel gated-stripline microchannel plate (MCP) detector, which is mounted on the outside of the vacuum chamber approximately 60 inches from the center. In addition, we will be using for the first time our newly constructed flat field spectrograph covering the spectral range of 30-250 {angstrom} (hv = 50-400 eV), designed to fit into a Ten Inch Manipulator (TIM). As such, it can be located closer to the central target position, with an expected enhancement in sensitivity of at least a factor-of-ten. It is the preparation of this instrument that mainly has occupied our attention so far in this grant period and discussed in this report.
Date: April 4, 1998
Creator: Griem, H.R. & Elton, R.C.
Partner: UNT Libraries Government Documents Department

Early-time measurements of laser-plasma conditions in OMEGA-Upgrade ICF Targets. Final report, April 1, 1997--March 31, 1998

Description: Under this FY-97 NLUF grant, we primarily carried out spectral line and continuum diagnostics at early times and in the coronal region of the plasma using our flat-field grazing-incidence spectrograph, improved to incorporate time resolution at wavelengths extending below the carbon K-absorption edge using a gated microchannel plate detector. These experiments were carried out on the OMEGA facility. Fifty-nine beams were focused onto the target, providing nominally 18 kJ of energy in a 1 ns pulse for an irradiance of {approximately}2{times}10{sup 14}/cm{sup 2}. Some beam smoothing, provided by spectral dispersion, was used, but may not have been particularly effective alone, i.e., without the presence of distributed phase plates in the beams. The plastic microballoon targets were nominally 900 {mu}m in diameter with 10- and 20-{mu}m thick walls, and were filled with neon to a pressure of 10 atm. Overcoatings of Mg and Al in thicknesses ranging from 0.2 to 4 {mu}m were applied. A 1-{mu}m thick layer of CH was added in some early shots to reduce the rate of expansion of the metallic coatings. In the extreme ultraviolet (euv) spectral region, we observed n=3 to n=2 emissions from Li-, He- and H-like ions from the Mg and Al coatings. We also obtained evidence confirming our previously-published laser-field-induced satellites lines at 53.1 {Angstrom} and 62.8 {Angstrom}, apparently at the peak of the Gaussian drive pulse. Both the Mg-line and the continuum euv emissions are high during the radial collapse. The metallic coating materials appear to be in place to some degree during the compression phase, i.e., are not all blown away as coronal plasma at earlier times as modeled. This also is apparent in the Al Lyman-{alpha} x-ray measurements before and after compression. Here, however, higher line opacity made it difficult to track the resonance lines through the compression phase. ...
Date: April 4, 1998
Creator: Griem, H.R. & Elton, R.C.
Partner: UNT Libraries Government Documents Department

Early-time measurements of soft x-ray emission in an omega-upgrade laser-produced plasma. Semi-annual report, October 1, 1996--March 31, 1997

Description: Beginning in January 1997 (following arrival of the FY-97 funding) we have been preparing for our first series of experiments under this grant at the University of Rochester Laboratory for Laser Energetics (LLE) on the Omega Upgrade laser facility, now scheduled to commence June 2, 1997. For these experiments we have purchased (just arrived) a four-channel gated-stripline microchannel plate (MCP) detector to be coupled to our soft x-ray flat-field grazing incidence spectrograph used previously at LLE. This will permit time-resolved `snapshots` of the complete spectra with a resolution to times as short as 180 ps per strip. An advantage of this technique over the streak camera used previously is the lack of any carbon absorbers such as in the thin plastic cathode required for the streak camera. This eliminates absorption in the 30-44 {angstrom} spectral region in which we are interested for intermediate-Z target materials such as Mg, Al and Si. An auxiliary turbomolecular-drag pump has also been installed in order to obtain the necessary vacuum for optimum MCP operation.
Date: March 31, 1997
Creator: Griem, H.R.; Elton, R.C. & Welch, B.L.
Partner: UNT Libraries Government Documents Department

Graphical Analysis of PET Data Applied to Reversible and Irreversible Tracers

Description: Graphical analysis refers to the transformation of multiple time measurements of plasma and tissue uptake data into a linear plot, the slope of which is related to the number of available tracer binding sites. This type of analysis allows easy comparisons among experiments. No particular model structure is assumed, however it is assumed that the tracer is given by bolus injection and that both tissue uptake and the plasma concentration of unchanged tracer are monitored following tracer injection. The requirement of plasma measurements can be eliminated in some cases when a reference region is available. There are two categories of graphical methods which apply to two general types of ligands--those which bind reversibly during the scanning procedure and those which are irreversible or trapped during the time of the scanning procedure.
Date: November 18, 1999
Creator: Logan, Jean
Partner: UNT Libraries Government Documents Department

One dimensional time-to-explode (ODTX) in HMX spheres

Description: In a series of papers researchers at Lawrence Livermore National Laboratory (LLNL) have reported measurements of the time to explosion in spheres of various high explosives following a rapid, uniform increase in the surface temperature of the sphere. Due to the spherical symmetry, the time-dependent properties of the explosive (temperature, chemical composition, etc.) are functions of the radial spatial coordinate only; thus the name one-dimensional time-to-explosion (ODTX). The LLNL researchers also report an evolving series of computational modeling results for the ODTX experiments, culminating in those obtained using a sophisticated heat transfer code incorporating accurate descriptions of chemical reaction. Although the chemical reaction mechanism used to describe HMX decomposition is quite simple, the computational results agree very well with the experimental data. In addition to reproducing the magnitude and temperature dependence of the measured times to explosion, the computational results also agree with the results of post reaction visual inspection. The ODTX experiments offer a near-ideal example of a transport process (heat transfer in this case) tightly coupled with chemical reaction. The LLNL computational model clearly captures the important features of the ODTX experiments. An obvious question of interest is to what extent the model and/or its individual components (specifically the chemical reaction mechanism) are applicable to other experimental scenarios. Valid exploration of this question requires accurate understanding of (1) the experimental scenario addressed by the LLNL model and (2) details of the application of the model. The author reports here recent work addressing points (1) and (2).
Date: June 2, 1997
Creator: Breshears, D.
Partner: UNT Libraries Government Documents Department


Description: A271 COMPLETE SUPPRESSION OF THE M=2/N-1 NEOCLASSICAL TEARING MODE USING ELECTRON CYCLOTRON CURRENT DRIVE ON DIII-D. The first suppression of the important and deleterious m=2/n=1 neoclassical tearing mode (NTM) is reported using electron cyclotron current drive (ECCD) to replace the ''missing'' bootstrap current in the island O-point. Experiments on the DIII-D tokamak verify the maximum shrinkage of the m=2/n=1 island occurs when the ECCD location coincides with the q = 2 surface. The DIII-D plasma control system is put into search and suppress mode to make small changes in the toroidal field to find and lock onto the optimum position, based on real time measurements of dB{sub {theta}}/dt, for complete m=2/n=1 NTM suppression by ECCD. The requirements on the ECCD for complete island suppression are well modeled by the modified Rutherford equation for the DIII-D plasma conditions.
Date: March 1, 2003
Partner: UNT Libraries Government Documents Department


Description: We describe a new ASIC for accurate and efficient processing of high-rate pulse signals from highly segmented detectors. In contrast to conventional approaches, this circuit affords a dramatic reduction in data volume through the use of analog techniques (precision peak detectors and time-to-amplitude converters) together with fast arbitration and sequencing logic to concentrate the data before digitization. In operation the circuit functions like a data-driven analog first-in, first-out (FIFO) memory between the preamplifiers and the ADC. Peak amplitudes of pulses arriving at any one of the 32 inputs are sampled, stored, and queued for readout and digitization through a single output port. Hit timing, pulse risetime, and channel address are also available at the output. Prototype chips have been fabricated in 0.35 micron CMOS and tested. First results indicate proper functionality for pulses down to 30 ns peaking time and input rates up to 1.6 MHz/channel. Amplitude accuracy of the peak detect and hold circuit is 0.3% (absolute). TAC accuracy is within 0.3% of full scale. Power consumption is less than 2 mW/channel. Compared with conventional techniques such as track-and-hold and analog memory, this new ASIC will enable efficient pulse height measurement at 20 to 300 times higher rates.
Date: November 10, 2002
Partner: UNT Libraries Government Documents Department

Dynamic Time Expansion and Compression Using Nonlinear Waveguides

Description: Dynamic time expansion or compression of a small amplitude input signal generated with an initial scale is performed using a nonlinear waveguide. A nonlinear waveguide having a variable refractive index is connected to a bias voltage source having a bias signal amplitude that is large relative to the input signal to vary the reflective index and concomitant speed of propagation of the nonlinear waveguide and an electrical circuit for applying the small amplitude signal and the large amplitude bias signal simultaneously to the nonlinear waveguide. The large amplitude bias signal with the input signal alters the speed of propagation of the small-amplitude signal with time in the nonlinear waveguide to expand or contract the initial time scale of the small-amplitude input signal.
Date: June 22, 2004
Creator: Findikoglu, Alp T.; Hahn, Sangkoo F. & Jia, Quanxi
Partner: UNT Libraries Government Documents Department