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Surface Characterization and Field Emission Measurements of Copper Samples inside a Scanning Electron Microscope
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
2016 (English)Conference paper, Published paper (Other academic)
Abstract [en]

Vacuum breakdown in normal-conducting accelerating structures is a limiting factor for high gradient acceleration.Many aspects of the physics governing the breakdown process and its onset are yet to be fully understood. At Uppsala University we address these questions with an in-situ experi-mental setup mounted in an environmental scanning electron microscope. It consists of a piezo motor driven tungsten needle and a sample surface mounted on a piezo stage, allowing for nano-meter 3D-position control. One of the piezomotors controls the needle-sample gap while the two otherscan across the surface. A DC-voltage up to 1 kV is  applied across the gap and field emission currents from a coppersurface are measured with an electrometer. Here we presentthe setup and some initial results.

Place, publisher, year, edition, pages
2016. 2083-2085 p.
National Category
Accelerator Physics and Instrumentation Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-298811OAI: oai:DiVA.org:uu-298811DiVA: diva2:947498
Conference
the 7th International Particle Accelerator Conference IPAC16 in Busan, South Korea, May 2016
Available from: 2016-07-08 Created: 2016-07-08 Last updated: 2017-10-19Bibliographically approved
In thesis
1. Beam Diagnostics and Dynamics in Nonlinear Fields
Open this publication in new window or tab >>Beam Diagnostics and Dynamics in Nonlinear Fields
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 87 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1583
Keyword
Beam diagnostics, Nonlinear beam dynamics, Accelerator physics
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-330975 (URN)978-91-513-0121-1 (ISBN)
Public defence
2017-12-08, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2017-11-15 Created: 2017-10-19 Last updated: 2017-11-15

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