A precise energy control system has been constructed for the U.B.C. electrostatic accelerator. Over the past six months it has provided analyzed beams of protons as large as 4½ microamperes on a target with an energy homogeneity of 0.1%. In the system adopted, the accelerated positive ions are analyzed by a 90° deflection magnet provided with entrance and exit slits to define the beam path. The magnetic field is stabilized to a few parts in 100,000, and controlled by a nuclear magnetic resonance method. A fraction of the emergent beam falls on two insulated slits, "sniffers", connected to a differential amplifier, the output of which varies as the beam impinges more on one than the other. Thus an error signal is obtained according to the shift in energy and hence position of the beam, which is used to modulate a reverse beam of electrons sent up the differential pumping tube of the generator. This beam loads the generator so as to maintain its voltage, and hence the energy of the ions, constant. The main central part of the beam passes through the slits onto the target mounted beyond. One-dial control over a range of 20 KeV is achieved by simply tuning the oscillator controlling the frequency of the nuclear magnetic resonance fluxmeter head. The energy of the ions can be varied in steps as fine as 0.2 KeV in 1,000 KeV. The generator's voltage scale (the generating volt-meter) and energy scale (the magnetic field of the analyzing magnet) have been calibrated relative to the currently accepted standard value of Herb, Snowdon, and Sala of 0.8735 MeV for the strong F¹⁹(p, α ɤ )O¹⁶ resonance and checked with the 0.3404 MeV resonance occurring in the same reaction. Additional calibration points were obtained using mass 2 and 3 beams. The complete gamma ray excitation curve for the reactions from F¹⁹ bombarded with protons has been taken up to 2 MeV and new resonances found at 1.62 and 1.84 MeV. The 1.355, 1.381 MeV doublet was resolved with a peak to trough value of 9/1 which is excellent confirmation of the homogeneity of the proton beam. The resonances in the N¹⁵¹⁹(p, α ɤ )C¹² reaction have also been investigated and background yields from various target backing materials measured up to 2 MeV. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This thesis investigates the properties of coherent Smith-Purcell radiation (cSPr) at femtosecond-scale in the case of electrons bunches in the ultrarelativistic regimes. Of particular interest is the use of cSPR as a diagnostic tool to determine the longitudinal time profiles of such bunches, the study of azimuthal distribution of the radiated energy, and a contribution to the understanding of polarization properties. The study consists in a first theoretical part carried mostly in the context of the surface-current theory, supported with insights from particle-in-cell simulations. Then, as a step toward a better determination of time profile, the question of phase reconstruction is addressed through the design of a new algorithm proposed in this thesis and tested in known challenging cases. Experimental results are then presented, spanning shifts having taken place at the FACET facility at SLAC, Stanford, between 2013 and 2015.

No description available.

The acceleration of electrons in a laser produced plasma wave was studied experimentally. A plasma with a modulated density was produced by illuminating a grating with a ruby laser at an intensity of 10¹⁰ W/cm². The plasma expanding above the surface of the grating was diagnosed using interferometry, shadowgraphy and Raman-Nath scattering. The plasma density was found to be modulated with an amplitude of [formula omitted]/n=8% for grating spacings ranging from 6 to 35 µm. A CO₂ laser of intensity 7xlO¹¹ W/cm2 then irradiated this modulated plasma and generated plasma waves. The phase speeds of the plasma waves are v[formula omitted] = ±[formula omitted]k[formula omitted], where k[formula omitted] is the wavenumber of the grating and [formula omitted] is the frequency of the CO₂ laser. Electrons were injected at an energy of 25 keV in one of the plasma waves. In order for the phase speed of the wave to synchronize with the accelerating electrons, a grating with constantly increasing line spacing was used. No conclusive evidence of electron acceleration was obtained, even after the injection energy was increased to 92 keV. This lack of evidence was the result of a large electric field perpendicular to the surface of the grating, which deflected the electrons onto the grating. This detrimental electric field is produced when fast electrons are emitted by the plasma and leave it positively charged. At the low laser intensity used in this experiment, the origin of these electrons could not be identified. Some techniques to remedy this difficulty are proposed. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Programmers invest extensive development effort to optimize a GPU program to achieve peak performance. Achieving this requires an efficient usage of global memory, and avoiding memory bandwidth underutilization. The OpenACC programming model has been introduced to tackle the accelerators programming complexity. However, this model’s coarse-grained control on a program can make the memory bandwidth utilization even worse compared to the version written in a native GPU languages such as CUDA. We propose an extension to OpenACC in order to reduce the traffic on the memory interconnection network, using a compression method on floating point numbers. We examine our method on six case studies, and achieve up to 1.36X speedup. / Graduate / 0544 / 0984 / ebads67@uvic.ca

No description available.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 97-103). Available also in a digital version from Dissertation Abstracts.

Not available / text

The Main Injector Neutrino Oscillation Search (MINOS) is a two detector long-baseline neutrino experiment designed to study the disappearance of muon neutrinos. MINOS will test the v[subscript mu] → v[subscript tau] oscillation hypothesis and measure precisely [Delta]m[superscript 2 subscript 23] and sin² 2[theta subscript 23] oscillation parameters. The source of neutrinos for MINOS experiment is Fermilab's Neutrinos at the Main Injector (NuMI) beamline. The energy spectrum and the composition of the beam is measured at two locations, one close to the source and the other 735 km downstream in the Soudan Mine Underground Laboratory in northern Minnesota. The precision measurement of the oscillation parameters requires an accurate prediction of the neutrino flux at the Far Detector. This thesis discusses the calculation of the neutrino flux at the Far Detector and its uncertainties. A technique that uses the Near Detector data to constrain the uncertainties in the calculation of the flux is described. The data corresponding to an exposure of 2.5×1020 protons on the NuMI target is presented and an energy dependent disappearance pattern predicted by neutrino oscillation hypotheses is observed in the Far Detector data. The fit to MINOS data, for given exposure, yields the best fit values for [Delta]m[superscript 2 subscript 23] and sin² 2[theta subscript 23] to be (2.38[superscript +0.20, subscript -0.16] x 10⁻³eV²/c⁴ and 1.00[subscript -0.08], respectively. / text

In the experiment E683 at Fermi National Accelerator Lab (FNAL) in Batavia, Illinois, a modular, high-energy sampling calorimeter was the basis of the detector system. In order to monitor each of the 528 modules of the calorimeter, an embedded LED was flashed directly into each of the 528 PMT tubes (which normally pick up the light from the sampling modules of the calorimeter) and their responses were recorded. The purpose of this investigation was to observe, study, and possibly make corrections for any fluctuations in the PMT response to the LED signals. Also, as a check, the PMT data was analyzed to see if any LED fluctuations were correlated with any fluctuations in the calorimeter module data coming from particles produced when targets were exposed to accelerator beam particles. These studies were done using a VAXstation model 4000/60, and the database and graphics components (called 'N-tuples' and `PAW' respectively) of a High Energy Physics math package called 'CERNLIB'. By putting the analyzed data into n-tuple files, many different modelings of the same data could be checked more efficiently. The study found that the LED system was useful for detecting and correcting for signal degradation due to calamp failure and these corrections were put in the E683 analysis package. It was also found that long term LED response signal fluctuations were not completely explained, but that there was no correlation with beam induced calorimeter response signal fluctuations. / Department of Physics and Astronomy