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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Design of a non-scaling fixed field alternating gradient accelerator for charged particle therapy

Sheehy, Suzanne Lyn January 2010 (has links)
This thesis describes the design a novel type of particle accelerator for charged particle therapy. The accelerator is called a non-scaling, Fixed Field Alternating Gradient (ns-FFAG) accelerator, and will accelerate both protons and carbon ions to energies required for clinical use. The work is undertaken as part of the PAMELA project. An existing design for a ns-FFAG is taken as a starting point and analysed in terms of its ability to suit the charged particle therapy application. It is found that this design is particularly sensitive to alignment errors and would be unable to accelerate protons and carbon ions at the proposed acceleration rate due to betatron resonance crossing phenomena. To overcome this issue, a new type of non-linear ns-FFAG is developed which avoids resonance crossing and meets the requirements provided by clinical considerations. Two accelerating rings are required, one for protons up to 250 MeV and fully stripped carbon ions to 68 MeV/u, the other to accelerate the carbon ions up to 400-430 MeV/u. Detailed studies are undertaken to show that this new type of accelerator is suitable for the application. An alignment accuracy of 50 micrometers will not have a detrimental effect on the beam and the dynamic aperture for most lattice configurations is found to be greater than 50 pi.mm.mrad normalised in both the horizontal and vertical plane. Verification of the simulation code used in the PAMELA lattice design is carried out using experimental results from EMMA, the world's first ns-FFAG for 10-20 MeV electrons built at Daresbury Laboratory, UK. Finally, it is shown that the described lattice can translate into realistic designs for the individual components of the accelerator. The integration of these components into the PAMELA facility is discussed.
52

Short pulse x-ray generation in synchrotron radiation sources

Martin, Ian Peter Stephen January 2011 (has links)
This thesis describes an investigation into the performance of different schemes for generating short x-rays pulses via synchrotron radiation emission. A review is given of the methods that have been previously proposed for this task. From this review, three leading schemes are selected for in-depth investigations, each of which explores the boundary of what is presently achievable in accelerator-based light sources. The first scheme generates short x-ray pulses by operating an electron storage ring in a quasi-isochronous state using a ‘low-alpha’ lattice. High and low emittance lattices are developed, studied through simulation and then implemented on the Diamond storage ring. Beam dynamics and bunch length measurements are presented for a variety of machine conditions, and an assessment is made of the minimum practically achievable bunch length for stable user operation. Radiation pulses of 1 ps r.m.s. are demonstrated using this scheme. The second and third schemes investigate performance limits for a linac-based light source through numerical simulations. The first of these generates ultra-short pulses by passing a highly compressed electron bunch through a long undulator to radiate in the ‘single-spike’ regime. A comparison is made with theoretical predictions for the required electron bunch length to operate in this way, which highlights the need for accurate start-to-end simulations. The final scheme generates ultra-short x-ray pulses through laser manipulation of the electron bunches. The modulated electrons pass through a long undulator with tapered gap, such that only the centre of the modulated portion experiences high free-electron laser (FEL) gain. A method to enhance the FEL output from this scheme using a wavelength filter and grating-compressor is investigated. The sensitivity of the two schemes to jitter sources is determined, and it is demonstrated both schemes are capable of generating GW-level, fully coherent sub-fs soft x-ray pulses. Such pulses would open up the development of time-resolved science to new regimes.
53

Accelerator Mass Spectrometry Studies of Highly Charged Molecular Ions

Kim, Yong-Dal 12 1900 (has links)
The existence of singly, doubly, and triply charged diatomic molecular ions was observed by using an Accelerator Mass Spectrometry (AMS) technique. The mean lifetimes of 3 MeV boron diatomic molecular ions were measured. No isotopic effects on the mean lifetimes of boron diatomic molecules were observed for charge state 3+. Also, the mean lifetime of SiF^3+ was measured.
54

Numerical methods for design of the transfer line of the ESSnuSB project : Independent Project in Engineering Physics

Boholm Kylesten, Karl-Fredrik January 2019 (has links)
ESS neutrino Super Beam (ESSnuSB) is a project that aim to create ahigh energy beam of neutrinos and anti-neutrinos to study thephenomenon neutrino oscillation and learn more about symmetryviolations in quantum mechanics. To create the neutrino beam, negativeHydrogen ions must be transported from the ESS linear accelerator at2.5 GeV, to a proton accumulation ring. This is done through a transferline, that shall direct the ion beam while preserve the beam as much aspossible. In thisproject, there was an attempt at finding a design for this transferline. Preferably, the line consists of a long main line of FODO cellsand two matching sections at each end. A simulation of the beam wasdone that gives the progression beta and dispersion functions,statistical measurements of the particle distribution, through a partof the transfer line. A design for the main line was found. For tuningthe quadrupole magnets, an iterative method using the system's responsematrix was used. However, it could not match more than four parametersat the time, while six was required for complete matching. Because ofthis, it is not able to match thedispersion.
55

1kW Class-E solid state power amplifier for cyclotron RF-source

Book, Stefan January 2018 (has links)
This thesis discusses the design, construction and testing of a highefficiency, 100 MHz, 1 kW, Class-E solid state power amplifier. The design was performed with the aid of computer simulations using electronic design software (ADS). The amplifier was constructed around Ampleon's BLF188XR LDMOS transistor in a single ended design. The results for 100 MHz operation show a power added efficiency of 82% at 1200 W pulsed power output. For operation at 102 MHz results show a power added efficiency of 86% at 1050 W pulsed power output. Measurements of the drain- and gate voltage waveforms provide validation of Class-E operation.
56

Beam Diagnostics and Dynamics in Nonlinear Fields

Ögren, Jim January 2017 (has links)
Particle accelerators are indispensable tools for probing matter at the smallest scales and the improvements of such tools depend on the progress and understanding of accelerator physics. The Compact Linear Collider (CLIC) is a proposed, linear electron–­positron collider on the TeV-scale, based at CERN. In such a large accelerator complex, diagnostics and alignment of the beam are crucial in order to maintain beam quality and luminosity. In this thesis we have utilized the nonlinear fields from the octupole component of the radio-frequency fields in the CLIC accelerating structures for beam-based diagnostics. We have investigated methods where the nonlinear position shifts of the beam are used to measure the strength of the octupole component and can also be used for alignment. Furthermore, from the changes in transverse beam profile, due to the nonlinear octupole field, we determine the full transverse beam matrix, which characterizes the transverse distribution of the beam. In circular accelerators, nonlinear fields result in nonlinear beam dynamics, which often becomes the limiting factor for long-term stability. In theoretical studies and simulations we investigate optimum configurations for octupole magnets that compensate amplitude-dependent tune-shifts but avoid driving fourth-order resonances and setups of sextupole magnets to control individual resonance driving terms in an optimal way.
57

Podnikatelské akcelerátory. Význam a přínosy. / Business Accelerators. Their Significance and Contributions

Nipoti, Vladimir January 2014 (has links)
The aim of this thesis is to analyse and compare the contributions of business or startup accelerators. The contributions are compared from the point of view of the managers of accelerators, startups and investors. Business accelerators help new firms accelerate their growth. The aid can be provided in a material form through financial capital and services or in an educational form through workshops and mentoring. The first chapter deals with the definition of the accelerator, its history and differences with incubators. The second chapter engages in the causes of the phenomenon of startups and accelerators, the model of lean startup, the impacts of accelerators on the economy and the current situation of accelerators in the world. The third chapters analyses the oldest and the most famous accelerator in the world Y Combinator. The last part evaluates the contributions of accelerators based on the inquiry among experts.
58

Transients and Coil Displacement in Accelerator Magnets

Wallin, Marcus January 2019 (has links)
For a long time voltage spikes has been seen in measurement data from accelerator magnets during current ramps. These has been believed to be caused by movements, but has never before been studied in depth. The purpose of this thesis is therefore to prove, or disprove, that these events are caused by movements and to analyse what kind of displacements that actually occur. Measurement data from coil voltage, magnetic pick-up coils and current during transients has been acquired and analysed for the Nb3Sn-dipole magnets FRESCA2 and 11T models—named MBHSP107 and MBHSP109. The measurement data is compared to movement simulations that was done with the ROXIE-program, which is used to calculate mutual inductance change for a number of different movement types. The study strongly suggests that the transients are caused by movements, and also indicates that the maximal length of a single slip-stick motion can be up to around 10 micrometers, mostly in the direction of the magnet’s internal forces. The study has proven that transients in measurement data occur due to coil movements, and that these can be quantified—a discovery that can possibly affect future construction and design of accelerator magnets.
59

Novel FFAG gantry and transport line designs for charged particle therapy

Fenning, Richard January 2012 (has links)
This thesis describes the design of novel magnetic lattices for the transport line and gantry of a charged particle therapy complex. The designs use non-scaling Fixed Field Alternating Gradient (ns-FFAG) magnets and were made as part of the PAMELA project. The main contributions in this thesis are the near-perfect FFAG dispersion suppression design process and the designs of the transport line and the gantry lattices. The primary challenge when designing an FFAG gantry is that particles with different momenta take up different lateral positions within the magnets. This is called dispersion and causes problems at three points: the entrance to the gantry, which must be rotated without distortion of the beam; at the end of the gantry where reduced dispersion is required for entry to the scanning system; and a third of the way through the gantry, where a switch in curvature of the magnets is required. Due to their non-linear fields, dispersion suppression in conventional FFAGs is never perfect. However, as this thesis shows, a solution can be found through manipulation of the field components, meaning near-perfect dispersion suppression can be achieved using ns-FFAG magnets (although at a cost of irregular optics). The design process for an FFAG dispersion suppressor shown in this thesis is a novel solution to a previously unsolved problem. Other challenges in the gantry lattice design, such as height and the control of the optics, are tackled and a final gantry design presented and discussed. The starting point for the transport line is a straight FFAG lattice design. This is optimised and matched to a 45o bend. Fixed field solutions to the problem of extracting to the treatment room are discussed, but a time variable field solution is decided on for practical and patient safety reasons. A matching scheme into the gantry room is then designed and presented.
60

Design and Testing of a Positive Ion Accelerator and Necessary Vacuum System

McKay, Vern A. 08 1900 (has links)
This thesis is a study of the design and testing of a positive ion accelerator and necessary vacuum system.

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