259 Matching Results

Search Results

Advanced search parameters have been applied.
in subjects: "Time Resolution"  
Results: 1 - 24 next

Isochronous Beamlines for Free Electron Lasers

Description: The transport systems required to feed a beam of highly relativistic electrons into a free electron laser have to satisfy very stringent requirements with respect to isochronicity and achromaticity. In addition, the line has to be tunable to match different operating modes of the free electron laser. Various beamlines emphasizing different aspects, such as quality of isochronicity and achromaticity, simplicity of the design, and space configurations are shown and compared. Solutions are presented having time resolution in the range of 2 to less than 0.5 picoseconds for one percent of energy spread.
Date: July 1, 1990
Creator: Berz, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

The Early Optical Brightening in the GRB 071010B

Description: We report the detection of early (60-230 s) optical emission of the gamma-ray burst afterglow of GRB071010B. No significant correlation with the prompt {gamma}-ray emission was found. Our high time-resolution data combining with other measurements within 2 days after the burst indicate that GRB071010B is composed of a weak early brightening ({alpha} {approx} 0.6), probably caused by the peak frequency passing through the optical wavelengths, followed by a decay ({alpha} {approx} -0.51), attributed to continuous energy injection by patchy jets.
Date: April 8, 2008
Creator: Wang, J H; Schwamb, M E; Huang, K Y; Wen, C Y; Zhang, Z W; Wang, S Y et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Seventh international conference on time-resolved vibrational spectroscopy

Description: The International Conference on Time-Resolved Vibrational Spectroscopy (TRVS) is widely recognized as the major international forum for the discussion of advances in this rapidly growing field. The 1995 conference was the seventh in a series that began at Lake Placid, New York, 1982. Santa Fe, New Mexico, was the site of the Seventh International Conference on Time-Resolved Vibrational Spectroscopy, held from June 11 to 16, 1995. TRVS-7 was attended by 157 participants from 16 countries and 85 institutions, and research ranging across the full breadth of the field of time-resolved vibrational spectroscopy was presented. Advances in both experimental capabilities for time-resolved vibrational measurements and in theoretical descriptions of time-resolved vibrational methods continue to occur, and several sessions of the conference were devoted to discussion of these advances and the associated new directions in TRVS. Continuing the interdisciplinary tradition of the TRVS meetings, applications of time-resolved vibrational methods to problems in physics, biology, materials science, and chemistry comprised a large portion of the papers presented at the conference.
Date: April 1, 1997
Creator: Dyer, R.B.; Martinez, M.A.D.; Shreve, A. & Woodruff, W.H.
Item Type: Refine your search to only Article
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.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

THE NEAR-INTEGER WORKING POINT FOR POLARIZED PROTONS IN THE RELATIVISTIC HEAVY ION COLLIDER

Description: To achieve the RHIC polarized proton enhanced luminosity goal of 150.10{sup 30} cm{sup -2}sec{sup -} on average in stores at 250 GeV, the luminosity needs to be increased by a factor of 3 compared to what was achieved in 2006. Since the number of bunches is already at its maximum of 1 1 1, limited by the injection kickers and the experiments' time resolution, the luminosity can only be increased by either increasing the bunch intensity and/or reducing the beam emittance. This leads to a larger beam-beam tuneshift parameter. Operations during 2006 has shown that the beam-beam interaction is already dominating the luminosity lifetime. To overcome this limitation, a near-integer working point is under study. We will present recent results of these studies.
Date: June 25, 2007
Creator: MONTAG,C.; BAI, M.; BEEBE-WANG, J.; CALAGA, R.; BLASKIEWICZ, M. & AL., ET
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Narrow Field of View Zenith Radiometer (NFOV) Handbook

Description: The two-channel narrow field-of-view radiometer (NFOV2) is a ground-based radiometer that looks straight up and measures radiance directly above the instrument at wavelengths of 673 and 870 nm. The field-of-view of the instrument is 1.2 degrees, and the sampling time resolution is one second. Measurements of the NFOV2 have been used to retrieve optical properties for overhead clouds that range from patchy to overcast. With a one-second sampling rate of the NFOV2, faster than almost any other ARM Climate Research Facility (ACRF) instrument, we are able, for the first time, to capture changes in cloud optical properties at the natural time scale of cloud evolution.
Date: November 1, 2008
Creator: Chiu, C; Marshak, A; Hodges, G; Barnard, JC & Schmelzer, J
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Distributed Coincidence Circuit

Description: A coincidence circuit using the traveling wave principle as applied to distributed amplification is described. The resolving time is about 10{sup -8} sec. when the device is used in connection with scintillation detectors.
Date: June 28, 1950
Creator: Weigand, Clyde
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Particle velocity measurements of the reaction zone in nitromethane

Description: The detonation reaction-zone length in neat, deuterated, and chemically sensitized nitromethane (NM) has been measured by using several different laser-based velocity interferometry systems. The experiments involved measuring the particle velocity history at a NM/PMMA (polymethylmethacrylate) window interface during the time a detonation in the NM interacted with the interface. Initially, Fabry-Perot interferometry was used, but, because of low time resolution (>5 ns), several different configurations of VISAR interferometry were subsequently used. Early work was done with VISARs with a time resolution of about 3 ns. By making changes to the recording system, we were able to improve this to {approx}1 ns. Profiles measured at the NM/PMMA interface agree with the ZND theory, in that a spike ({approx}2.45 mm/{micro}s) is measured that is consistent with an extrapolated reactant NM Hugoniot matched to the PMMA window. The spike is rather sharp, followed by a rapid drop in particle velocity over a time of 5 to 10 ns; this is evidence of early fast reactions. Over about 50 ns, a much slower particle velocity decrease occurs to the assumed CJ condition - indicating a total reaction zone length of {approx}300 {micro}m. When the NM is chemically changed, such as replacing the hydrogen atoms with deuterium or chemically sensitizing with a base, some changes are observed in the early part of the reaction zone.
Date: January 1, 2002
Creator: Sheffield, S. A. (Stephen A.); Engelke, R. P. (Raymond P.); Alcon, R. R. (Robert R.); Gustavsen, R. L. (Richard L.); Robbins, D. L. (David L.); Stahl, D. B. (David B.) et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Trends in on-road vehicle emissions of ammonia

Description: Motor vehicle emissions of ammonia have been measured at a California highway tunnel in the San Francisco Bay area. Between 1999 and 2006, light-duty vehicle ammonia emissions decreased by 38 {+-} 6%, from 640 {+-} 40 to 400 {+-} 20 mg kg{sup -1}. High time resolution measurements of ammonia made in summer 2001 at the same location indicate a minimum in ammonia emissions correlated with slower-speed driving conditions. Variations in ammonia emission rates track changes in carbon monoxide more closely than changes in nitrogen oxides, especially during later evening hours when traffic speeds are highest. Analysis of remote sensing data of Burgard et al. (Environ Sci. Technol. 2006, 40, 7018-7022) indicates relationships between ammonia and vehicle model year, nitrogen oxides, and carbon monoxide. Ammonia emission rates from diesel trucks were difficult to measure in the tunnel setting due to the large contribution to ammonia concentrations in a mixed-traffic bore that were assigned to light-duty vehicle emissions. Nevertheless, it is clear that heavy-duty diesel trucks are a minor source of ammonia emissions compared to light-duty gasoline vehicles.
Date: July 15, 2008
Creator: Kean, A.J.; Littlejohn, D.; Ban-Weiss, G.A.; Harley, R.A.; Kirchstetter, T.W. & Lunden, M. M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Study of timing properties of multi-pixel-photon-counter's illuminated by 630 nm and 405 nm PiLas laser light

Description: Timing measurements of Multy-Pixel-Photon Counters (MPPC's) at the picosecond level were performed at Fermilab. The core timing resolution of the amplifiers, discriminators and TAC/ADC combination to perform these measurements is approximately 2 picoseconds. The single photoelectron time resolution (SPTR) was measured for the signals coming from the MPPC's. An SPTR of about one hundred picoseconds was obtained for MPPC's illuminated by picosecond laser pulses. The SPTR depends on applied bias voltage and on the wavelength of the light. A simple model is proposed to explain the difference in the SPTR for blue and red light. Finally, requirements for the MPPC's temperature and bias voltage stability to maintain the time resolution are discussed.
Date: April 1, 2009
Creator: Ronzhin, Anatoly; Demarteau, Marcel; Los, Sergey; Ramberg, Erik & /Fermilab
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

TIME RESOLVED X-RAY SPOT DIAGNOSTIC

Description: A diagnostic was developed for the determination of temporal history of an X-ray spot. A pair of thin (0.5 mm) slits image the x-ray spot to a fast scintillator which is coupled to a fast detector, thus sampling a slice of the X-Ray spot. Two other scintillator/detectors are used to determine the position of the spot and total forward dose. The slit signal is normalized to the dose and the resulting signal is analyzed to get the spot size. The position information is used to compensate for small changes due to spot motion and misalignment. The time resolution of the diagnostic is about 1 ns and measures spots from 0.5 mm to over 3 mm. The theory and equations used to calculate spot size and position are presented, as well as data. The calculations assume a symmetric, Gaussian spot. The spot data is generated by the ETA II accelerator, a 2kA, 5.5 MeV, 60 ns electron beam focused on a Tantalum target. The spot generated is typically about 1 mm FWHM. Comparisons are made to an X-ray pinhole camera which images the X-Ray spot (in 2D) at four time slices.
Date: April 26, 2005
Creator: Richardson, R; Guethlein, G; Falabella, S; Chambers, F; Raymond, B & Weir, J
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Prospects for Electron Imaging with Ultrafast Time Resolution

Description: Many pivotal aspects of material science, biomechanics, and chemistry would benefit from nanometer imaging with ultrafast time resolution. Here we demonstrate the feasibility of short-pulse electron imaging with t10 nanometer/10 picosecond spatio-temporal resolution, sufficient to characterize phenomena that propagate at the speed of sound in materials (1-10 kilometer/second) without smearing. We outline resolution-degrading effects that occur at high current density followed by strategies to mitigate these effects. Finally, we present a model electron imaging system that achieves 10 nanometer/10 picosecond spatio-temporal resolution.
Date: January 26, 2007
Creator: Armstrong, M R; Reed, B W; Torralva, B R & Browning, N D
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Analysis of digital timing methods with BaF(sub 2) scintillators

Description: Various digital methods were examined for determining the relative arrival times of pulses from to 5.08 x 2.54 cm BaF{sub 2} scintillators. In this study, pulses from the photomultiplier tubes were digitized by a 1 Gs/s analog to digital converter and post processed with multiple techniques. These techniques include: (1) leading edge discrimination, (2) moment-analysis, (3) constant fraction discrimination, (4) digital constant traction discrimination, (5) triangular pulse shaping with a leading edge linear regression, and (6) pulse-shape fitting. Average timing resolutions of 456 {+-} 8 ps were obtained with constant fraction discrimination, which is slightly higher than the analog average resolution of 419 {+-} 7 ps. This study explores the application of these digital techniques for pulse-timing applications and their potential advantages and limitations.
Date: January 1, 2002
Creator: Nelson, M. A. (Mark A.); Rooney, B. D. (Brian D.); Dinwiddie, D. R. (Derek R.) & Brunson, G. S. (Glenn S.)
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

'Giant' multishell CdSe nanocrystal quantum dots with supporessed blinking: novel fluorescent probes for real-time detection of single-molecule events

Description: We reported for the first time that key nanocrystal quantum dot (NQD) optical properties-quantum yield, photobleaching and blinking-can be rendered independent ofNQD surface chemistry and environment by growth of a very thick, defect-free inorganic shell. Here, we show the precise shell-thickness dependence of these effects. We demonstrate that 'giant-shell' NQDs can be largely non-blinking for observation times as long as 54 minutes and lhat on-time fractions are independent of experimental time-resolution from 1-200 ms. These effects are primarily demonstrated on (CdSe)CdS (core)shell NQDs, but we also show that alloyed shells comprising Cd.Znl.'S and terminated with a non-cytotoxic ZnS layer exhibit similar properties. The mechanism for suppressed blinking and dramatically enhanced stability is attributed to both effective isolation of the NQD core excitonic wavefunction from the NQD surface, as well as a quasi-Type II electronic structure. The unusual electronic structure provides for effective spatial separation of the electron and hole into the shell and core, respectively, and, thereby, for reduced efficiencies in non-radiative Auger recombination.
Date: January 1, 2009
Creator: Hollingsworth, Jennifer A; Vela, Javier; Htoon, Han; Klimov, Victor I; Casson, Amy R & Chen, Yongfen
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Transistor Counting Systems for Scintillation Detectors

Description: The requirements for multiple-coincidence counting systems with 10{sup -8}- to 10{sup -9}-sec time resolution can be met economically with presently available high-frequency transistors. The design of solid-state coincidence circuits, amplitude discriminators, and decade scalers is considered and their operation discussed. Several systems have been designed utilizing up to 180 channels from scintillation detectors.
Date: February 17, 1960
Creator: Baker, Stanley C.; Jackson, Horace G. & Mack, Dick A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Time-Dependent Phase-Space Mapping of Space-Charge-Dominated Beams

Description: In this paper we report on a proof of principle experiment for demonstrating the possibility of reconstructing the time resolved-phase-space distribution of a space-charge dominated beam by a tomographic technique which provides us with far more information than a time-sliced emittance. We emphasize that this work describes and demonstrates a new methodology which can be applicable to any beam pulse using imaging methods with the appropriate time resolution for the pulse duration. The combination of a high precision tomographic diagnostic with fast imaging screens and a gated camera are used to produce phase space maps of two beams: one with a parabolic current profile and another with a short perturbation atop a rectangular pulse. The correlations between longitudinal and transverse phase spaces are apparent and their impact on the dynamics is discussed.
Date: May 2009
Creator: Stratakis, D.; Fiorito, R. B.; Haber, I.; Kishek, R. A.; O'Shea, P. G.; Reiser, M. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

On-chop processing for the wave union TDC implemented in FPGA

Description: The wave union TDC implemented in FPGA utilizes multiple measurement method to reach time resolution beyond the natural carry cell delay in FPGA. Lacking of analog compensation for bin width control available in ASIC, the wave union TDC takes the after-fact digital calibration approach. In addition to the temperature drift, non-uniformity of the carry chain structure in FPGA causes complicate differential nonlinearity pattern which imposes significant on-chip calibration challenge. In this paper, processing strategies for the wave union TDC are discussed. Actual implementations in low-cost FPGA with 20ps and 10ps RMS resolutions are also presented.
Date: May 1, 2009
Creator: Wu, Jinyan
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Soft x-ray microscopy - a powerful analytical tool to image magnetism down to fundamental length and times scales

Description: The magnetic properties of low dimensional solid state matter is of the utmost interest both scientifically as well as technologically. In addition to the charge of the electron which is the base for current electronics, by taking into account the spin degree of freedom in future spintronics applications open a new avenue. Progress towards a better physical understanding of the mechanism and principles involved as well as potential applications of nanomagnetic devices can only be achieved with advanced analytical tools. Soft X-ray microscopy providing a spatial resolution towards 10nm, a time resolution currently in the sub-ns regime and inherent elemental sensitivity is a very promising technique for that. This article reviews the recent achievements of magnetic soft X-ray microscopy by selected examples of spin torque phenomena, stochastical behavior on the nanoscale and spin dynamics in magnetic nanopatterns. The future potential with regard to addressing fundamental magnetic length and time scales, e.g. imaging fsec spin dynamics at upcoming X-ray sources is pointed out.
Date: August 1, 2008
Creator: Fischer, Peter
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Characterization of beam dynamics in the APS injector rings using time-resolved imaging techniques

Description: Images taken with streak cameras and gated intensified cameras with both time (longitudinal) and spatial (transverse) resolution reveal a wealth of information about circular accelerators. The authors illustrate a novel technique by a sequence of dual-sweep streak camera images taken at a high dispersion location in the booster synchrotron, where the horizontal coordinate is strongly correlated with the particle energy and the {open_quotes}top-view{close_quotes} of the beam gives a good approximation to the particle density distribution in the longitudinal phase space. A sequence of top-view images taken fight after injection clearly shows the beam dynamics in the phase space. We report another example from the positron accumulator ring for the characterization of its beam compression bunching with the 12th harmonic rf.
Date: June 1, 1997
Creator: Yang, B.X.; Lumpkin, A.H. & Borland, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Feasibility study into the use of mechanical choppers to alter the natural time structure of the APS

Description: In a very general way, one can divide time-resolved experiments into two broad classes: (1) those that take advantage of techniques that permit data to be collected in a more rapid fashion and (2) those that take advantage of the natural time-structure or modulation of the radiation produced by storage ring sources. It is with the latter group of experiments that this report is primarily concerned. Researchers planning to use the time structure are considering both experiments that can be cyclically pumped and probed. The natural time-structure of the storage ring may not, unfortunately, be optimal for all time-resolved experiments.
Date: April 11, 1988
Creator: Mills, D.M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Transient frequency-modulated spectroscopy: Application to the measurement of vector and scalar correlations in molecular photodissociation

Description: An intrinsically time-resolved version of frequency-modulation (FM) spectroscopy has been recently developed and applied to the study of gas-phase photodissociation dynamics. Transient FM spectroscopy allows low background detection of radical species with shot-noise limited sensitivities, time resolution sufficient for detection of collisionless photoproducts, and frequency resolution characteristic of single-mode cw lasers. Methods for the quantitative analysis of Doppler-broadened FM line shapes to give velocity and rotational polarization information have been established permitting the measurement of scalar and vector properties of molecular fragmentation in exquisite detail. Several recent examples of the application of transient FM spectroscopy will be presented and discussed, including correlated scalar distributions in the dissociation of ketene from CH{sub 2}(a{sup 1} A{sub 1}) Doppler profiles, and the full vector correlation analysis of CN (X {sup 2}{Sigma}{sup +}) fragments arising from ICN dissociation.
Date: April 1, 1998
Creator: North, S.W. & Hall, G.E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department