Thesis (Ph. D.)--University of Wisconsin-Madison, 1989. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves: 108-122).

Thesis (Ph.D.)--Ohio University, March, 2006. / Title from PDF t.p. Includes bibliographical references (p. 240-246)

The FONT beam-based, intra-train feedback system has been designed to provide beam position stabilisation in single-pass accelerators. A FONT feedback system utilising position information from three high-resolution cavity beam position monitors (BPMs) has been commissioned at the interaction point (IP) of the Accelerator Test Facility 2 (ATF2) at KEK, Japan. The ultimate goal of the feedback in the IP region is to stabilise the low-emittance electron beam to the nanometre level. The operation, optimisation and resolution performance of this IP system forms the subject of this thesis. The IP feedback system makes use of beam position measurements from the BPMs to drive an upstream kicker and provide a local correction. The BPMs have a fast decay time of ~25 ns to allow bunches within the beam train to be resolved. The operation of the IP BPMs, the noise floor, and position sensitivity to phase are discussed in detail. Attempts are made to diagnose an unwanted ~60 MHz oscillation in the cavity signals, which is bunch charge-dependent and thus likely beam generated. The BPM resolution estimate was notably improved from 50 nm to 20 nm using waveform integration in analysis of the BPM signals. A multi-parameter fit was used to address inaccurate calibrations and charge-dependencies to achieve more consistent resolution performance and produce a best-ever resolution estimate for the BPMs of 17.5 ± 0.4 nm. A novel mode of IP beam position stabilisation using two BPMs as input to the feedback has been successfully demonstrated. The beam position was stabilised to 57 ± 4 nm, as measured at an independent BPM. Feedback performance was improved to this level by sampling the waveform to optimise bunch-to-bunch correlation. Analysis suggests correction capability could be enhanced by firmware waveform integration to achieve a measurable beam stabilisation of ~40 nm in the future.

The FONT beam-based, intra-train feedback system has been designed to provide beam stability at single-pass accelerators, such as at the interaction point (IP) of the International Linear Collider. Two FONT feedback systems have been commissioned at the Accelerator Test Facility (ATF) at KEK, Japan, and the operation, optimisation and performance of these systems is the subject of this thesis. For each system, the accelerator is operated with two-bunch trains with a bunch separation of around 200 ns, allowing the first bunch to be measured and the second bunch to be subsequently corrected. The first system consists of a coupled-loop system in which two stripline beam position monitors (BPMs) are used to characterise the incoming beam position and angle, and two kickers are used to stabilise the beam. A BPM resolution of about 300 nm has been measured. On operating the feedback system, a factor ~ 3 reduction in position jitter has been demonstrated at the feedback BPMs and the successful propagation of this correction to a witness BPM located 30 m downstream has been confirmed. The second system makes use of a beam position measurement at the ATF IP that is used to drive a kicker to provide a local correction. The measurement is performed using a high-resolution cavity BPM with a fast decay time of around 20 ns designed to allow multiple bunches to be resolved. The linearity of the cavity BPM system and the noise floor of the electronics are discussed in detail. The performance of the BPM system under standard ATF operation and with the beam waist at the BPM is described. A BPM resolution of about 50 nm has been measured. This IP feedback system has been used to stabilise the beam position to the 75 nm level.

Thesis (Masters Diploma (Technology) Cape Technikon, 1988 / Radioactivity and radioactive radiation are two scientific phenomena which man has always approached with great caution, if not fear. Radioactive radiation cannot be sensed by any of the human senses and experience has proved just how hazardous it can be to the human body. This caution is therefore by no means unfounded and through the years a set of standards has been derived as to what can be regarded as a safe dose to the human body. At the National Accelerator Centre radioisotopes are being produced by a chemical recovery process from targets which have been irradiated by a high energy proton beam. Targets are prepared by compressing salts, containing the elements to become radioisotopes, into tablets. The high energy protons collide with particles in the targets which give off radioactive radiation. The targets in their turn become radioactive and the isotopes that are produced from these targets are radioactive. The level of radioactive radiation is extremely hazardous and it is therefore impossible for any human being to come into close contact with any of the targets or isotopes. It is for these reasons that an electrical rail transport system was installed at the National Accelerator Centre to transport highly radioactive sources. The transport system links the two irradiation vaults to the two rows of hot cells, where the chemical recovery takes place, and to a well shielded storage area for storage of isotopes and radioactive waste. A transport system, performing tasks of this nature, must be, above all, extremely reliable. Secondly, commands entered by an operator to control the system, must be simple and straight forward. This thesis describes the control of the transport system at the National Accelerator Centre, including alI of its features, advantages and disadvantages.

Includes bibliographical references and index. / The design and implementation of a method to software interface high level applications programs used for the control and monitoring of a Particle Accelerator is described. Effective methods of interfacing the instrumentation bus system with a Real time multitasking computer operating system were examined and optimized for efficient utilization of the operating system software and available hardware. Various methods of accessing the instrumentation bus are implemented as well as demand response servicing of the instruments on the bus.

In view of the advantages of its type, the decision to construct a neutron source of the particle accelerator type was made. The purpose of this thesis is to survey the problems encountered in the construction of the source.

Experiments were performed at the Nuclear Engineering Teaching Laboratory (NETL) in 2005 and 2006 in which a 20 MeV linear electron accelerator operating as a photoneutron source was coupled to the TRIGA (Training, Research, Isotope production, General Atomics) Mark II research reactor at the University of Texas at Austin (UT) to simulate the operation and characteristics of a full-scale accelerator driven subcritical system (ADSS). The experimental program provided a relatively low-cost substitute for the higher power and complexity of internationally proposed systems utilizing proton accelerators and spallation neutron sources for an advanced ADSS that may be used for the burning of high-level radioactive waste. Various instrumentation methods that permitted ADSS neutron flux monitoring in high gamma radiation fields were successfully explored and the data was used to evaluate the Stochastic Pulsed Feynman method for reactivity monitoring. / text

Thesis (MScEng (Electrical and Electronic Engineering))--Stellenbosch University, 2007. / Particle accelerators today have numerous magnets that require controlling. These include magnets for analysing, beam-path selection, focusing, etc. Also, design specifications are becoming tighter. A typical modern magnet power supply is expected to have a resolution of 16-bit and a stability of 10 ppm. This thesis addresses two research areas. First, various aspects of high-performance accelerator magnet power supplies are investigated. An isolated dual-stage 3.5 kW converter is designed. The concept is verified through practical measurements. The control system and high-resolution pulse-width modulation are implemented within a field-programmable gate array. Second, a nuclear-magnetic resonance probe is designed and simulated. It is intended to provide a measurement of field-strength for feed-back purposes. Some adjustments are made with existing technology in order to decrease the time between successive measurements to the order of 10 μs. Also, the support systems (central processing unit, hardware drivers, etc.) are designed, implemented in the field-programmable gate array and tested successfully.

The developments of nuclear medicine lead to an increasing demand for the production of radioisotopes with suitable nuclear and chemical properties. Furthermore, from the literature it is evident that the production of radioisotopes using charged-particle accelerators instead of nuclear reactors is gaining increasing popularity. The main advantages of producing medical isotopes with accelerators are carrier free radionuclides of short lived isotopes, improved handling, reduction of the radioactive waste, and lower cost of isotope fabrication. Proton-rich isotopes are the result of nuclear interactions between enriched stable isotopes and energetic protons. An interesting observation is that during the production of proton-rich isotopes, fast and intermediately fast neutrons from nuclear reactions such as (p,xn) are also produced as a by-product in the nuclear reactions. This observation suggests that it is perhaps possible to use these neutrons to activate secondary targets for the production of neutron-rich isotopes. The study of secondary radioisotope production with fast neutrons from (p,xn) reactions using a particle accelerator is the main goal of the research in this thesis.