Thesis (Ph. D.)--University of Wisconsin--Madison, 1976. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 201-207).

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The Advanced Wakefield Experiment, or AWAKE, is an experiment based at CERN (European Organization for Nuclear Research) whose purpose is to demon- strate the acceleration of electrons using plasma wakefields driven by a charged par- ticle bunch. As a proof-of-principle experiment, AWAKE will be propagating a high- energy proton bunch through 10 meters of plasma to drive the wakefields for electron acceleration. To accelerate the electrons, we want to inject them into regions of both focusing and acceleration within these wakefields behind the proton bunch. In order for the electrons to stay within this optimal accelerating/focusing region, we need to maintain uniform plasma density within 0.2%, and we need to inject when the wakefield phase-velocity is constant. To preserve uniform plasma density, we use a liquid heat-exchanging pipe which can maintain stable temperatures, and therefore uniform rubidium vapor/plasma densities, to within 0.2%. We show that this is pos- sible using Galden HT270 as a heat-exchanging liquid. We also show that additional components required for this system will need external heating to prevent heat-loss, and therefore temperature non-uniformity. Furthermore, using the PIC simulation OSIRIS, we study how changing size parameters of the initial proton bunch by ±5% a ects the phase-velocity of the wakefield. It is seen that these parameter variations will not significantly affect the optimal region size and energy gain of injected elec- trons; so long as the electrons are injected at regions of ξ near σzb of the proton bunch and after 4 m of bunch propagation length in the plasma. / Graduate

The non-linear beam dynamics of a circular accelerator, such as the Large Hadron Collider, can have a significant impact on its operation. In order to avoid limitations on the performance reach of the accelerator, and ensure machine protection, it is vital that the beam dynamics are well understood and controlled. This thesis presents the results of studies of non-linear beam dynamics undertaken on the Large Hadron Collider at CERN, during the 2010 to 2013 period. It sets out to quantify the understanding of the non-linear beam dynamics through the comparison of beam-based measurements to simulation, and where able and appropriate seeks to explain deviations of measurement from the model, and define corrections for relevant aspects of the dynamics. The analyses presented in this thesis represent considerable advances in the understanding of the LHC beam dynamics which should allow for an improved operation of the machine in the coming years.

Charged particle accelerators often have strict requirements on the beam energy, and timing to calibrate, or control background processes. Longitudinal Phase Space Tomography is a technique developed in 1987 to visualize the time, and energy coordinates of a beam. With non-invasive detectors, the beam can be visualized at any point during operation of a synchrotron. With the progress of computing power over the last 27 years, it is now possible to compute tomographic reconstructions in real time accelerator operations for many bunches around the accelerator ring. This thesis describes a real-time, multi-bunch tomography system developed and implemented in Fermilab's Main Injector and Recycler Rings, and a study of bunch growth when crossing transition. Implications of these studies for high intensity operation of the Fermilab accelerators are presented. / text

An Interaction Point Collision Feedback System is necessary to achieve design luminosity at the future International Linear Collider (ILC). This is proposed to include a stripline beam position monitor (BPM) positioned 3 m from the Interaction Point (IP). The BPM is required to be able to measure the position of the outgoing electron or positron beam with a resolution of 1 m. Prototype feedback systems have been built and tested at the Next Linear Collider Test Accelerator (NLCTA) at the Stanford Linear Accelerator Center in the USA (SLAC) and also at the Accelerator Test Facility (ATF) at the High Energy Research Laboratory in Japan (KEK). The successful correction of position osets is demonstrated with the lowest latency achieved 24 ns, the best position resolution 4 m and the best correction ratio 23:1. To make the feedback system a more powerful tool, a digital processor is added. It raises the total latency of the feedback system to 140 ns. Its ability to perform algorithms is demonstrated with charge normalisation. Preliminary results indicate a resolution of 8 m and correction ratio 7:1. Backgrounds at the ILC comprise mainly electron-positron pairs from the beam-beam interaction. For the high luminosity 1TeV accelerator parameters, 105 pairs are produced per bunch crossing. This is the worst case for ILC pair backgrounds. These pairs produce 5 105 particle hits on a stripline of the IP feedback BPM. In two experiments at End Station A (ESA) at SLAC, a stripline BPM was exposed to secondary particle backgrounds to determine if the particle hits degraded the ability of the stripline BPM to resolve micron-level position osets. The experiments agree that the worst ILC pair backgrounds degrade the resolution by less than 8.5 nm (95% confidence level). It is concluded that micron-level resolution will not be aected by the ILC pair backgrounds. Studies of stripline signals caused by backgrounds led to the development of a GEANT3- based tool that could predict the signals. The prediction tool was tested against one of the experiments at ESA and used to predict the signals on the ILC feedback BPM striplines. The results confirm that the ILC pair backgrounds do not produce micron-level errors in position measurement, indicating that the degradation in resolution by the worst pair backgrounds expected was under 13 nm.

The atoms of a molecule are always restless and are constantly moving in one way or another.Apart from rotations and translations, they may vibrate in many different modes. They may moveradially toward or from each other, so called stretching. This can be done symmetrically or asymmetrically.The angels between a pair of atoms may change seen from a common atom, so calledbending. This may be done in a common plane like scissoring or rocking, or out of plane like waggingor twisting.Anyhow, it is of interest to study these movements — since they work as a fingerprint of themolecule. Two methods for studying these behavior are Raman- and IR-spectroscopy. Some vibrations,such as symmetric stretching, are mainly seen using Raman spectroscopy (Raman active); whilebending and asymmetric stretching are primarily detected by IR spectroscopy (IR active) However,all types of combinations exist, so there are no watertight compartments between them. Instead, themethods are complementary to each other.In this article, I build up a semi-classical model of the vibrations for the case of IR-spectroscopy,and implement it in Mathematica to test the model. It is based on classical physics such as vibratingspringmechanics and Maxwell’s electrodynamics, but the vibrations are computed using modernphysics quantum mechanics. Since there are several atoms involved (say N) and the vibrations betweenthese atoms are in 3 dimensions, this may be described by 3N coupled 1-dimensional harmonicoscillators. By suitable transformations these oscillators are uncoupled, but results in a wave functionwhich is the product of 3N eigenfunctions, one for each oscillator’s eigenfunction of a given mode.Adding a time varying electric field (the IR-illumination), we need the time dependent SchrödingerEquation, where the potential is time varying sinusoidally. Necessary perturbation theory for suchtime dependency is described in some details, and an expression for the dipole moment needed forthe estimation of the IR absorption by the molecule is given. However, the model also depend onthe electrons’ orbitals and the total bond energy within the molecule. These are given by a DFT(Density Functional Theory) computer code, which serve as input to my calculations.The standard approach to do IR-spectrum calculations is to use DFT also to move the atoms inthe directions of the vibrations and compute how the dipole moments for the molecules change. Mymethod is instead to use SE directly for the many vibrating particle problem based on the knownexact solutions to the one dimensional harmonic oscillator. This is followed by perturbation theoryfor the time dependency of the IR-field to get the dipole moments.The drawback with my approach is that the electron clouds around the atoms are not affectedat all by the vibrations, they just follow the nuclei. The DFT approach takes care of the changingelectron density functions. However, my approach solves the vibrational problem more directly withthe SE and takes care of the time dependent potential using perturbation theory.Computational results for seven molecules containing between 2 and 11 atoms are shown andcompared with spectroscopic parameters and measurements compiled by established references. Theconclusion is that my model and computational output are well in accordance with these references,and some shortcomings and possible enhancements are pointed out. The drawback with the electronclouds might affect the absorption levels of the vibrations rather than their energies and are possiblein future work to take into account. / <p>Till minne av Ulf Oreborn (1957-2018)</p>

abstract: The holy grail of computer hardware across all market segments has been to sustain performance improvement at the same pace as silicon technology scales. As the technology scales and the size of transistors shrinks, the power consumption and energy usage per transistor decrease. On the other hand, the transistor density increases significantly by technology scaling. Due to technology factors, the reduction in power consumption per transistor is not sufficient to offset the increase in power consumption per unit area. Therefore, to improve performance, increasing energy-efficiency must be addressed at all design levels from circuit level to application and algorithm levels. At architectural level, one promising approach is to populate the system with hardware accelerators each optimized for a specific task. One drawback of hardware accelerators is that they are not programmable. Therefore, their utilization can be low as they perform one specific function. Using software programmable accelerators is an alternative approach to achieve high energy-efficiency and programmability. Due to intrinsic characteristics of software accelerators, they can exploit both instruction level parallelism and data level parallelism. Coarse-Grained Reconfigurable Architecture (CGRA) is a software programmable accelerator consists of a number of word-level functional units. Motivated by promising characteristics of software programmable accelerators, the potentials of CGRAs in future computing platforms is studied and an end-to-end CGRA research framework is developed. This framework consists of three different aspects: CGRA architectural design, integration in a computing system, and CGRA compiler. First, the design and implementation of a CGRA and its instruction set is presented. This design is then modeled in a cycle accurate system simulator. The simulation platform enables us to investigate several problems associated with a CGRA when it is deployed as an accelerator in a computing system. Next, the problem of mapping a compute intensive region of a program to CGRAs is formulated. From this formulation, several efficient algorithms are developed which effectively utilize CGRA scarce resources very well to minimize the running time of input applications. Finally, these mapping algorithms are integrated in a compiler framework to construct a compiler for CGRA / Dissertation/Thesis / Doctoral Dissertation Computer Science 2015

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