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Cavity Field Control for Linear Particle Accelerators

Troeng, Olof LU (2019) In PhD Thesis TFRT-1127
Abstract
High-energy linear particle accelerators enable exploration of the microscopic structure of pharmaceuticals, solar cells, fuel cells, high-temperature superconductors, and the universe itself. These accelerators accelerate charged particles using oscillating magnetic fields that are confined in metal cavities. The amplitudes and phases of the electromagnetic fields need to be accurately controlled by fast feedback loops for proper accelerator operation.

This thesis is based on the author's work on performance analysis and control design for the field control loops of the linear accelerator at the European Spallation Source (ESS), a neutron microscope that is under construction in Lund, Sweden. The main contribution of the thesis... (More)
High-energy linear particle accelerators enable exploration of the microscopic structure of pharmaceuticals, solar cells, fuel cells, high-temperature superconductors, and the universe itself. These accelerators accelerate charged particles using oscillating magnetic fields that are confined in metal cavities. The amplitudes and phases of the electromagnetic fields need to be accurately controlled by fast feedback loops for proper accelerator operation.

This thesis is based on the author's work on performance analysis and control design for the field control loops of the linear accelerator at the European Spallation Source (ESS), a neutron microscope that is under construction in Lund, Sweden. The main contribution of the thesis is a comprehensive treatment of the field control problem during flat-top, which gives more insight into the control aspects than previous work. The thesis demonstrates that a key to understand the dynamics of the field control loop is to represent it as a single-input single-output system with complex coefficients. This representation is not new itself but has seen limited use for field control analysis.

The thesis starts by developing practical and theoretical tools for analysis and control design for complex-coefficients systems. This is followed by two main parts on cavity field control. The first part introduces parametrizations that enable a better understanding of the cavity dynamics and discusses the most essential aspects of cavity field control. The second part builds on the first one and treats a selection of more advanced topics that all benefit from the complex-coefficient representation: analysis of a polar controller structure, field control design in the presence of parasitic cavity resonances, digital downconversion for low-latency feedback, energy-optimal excitation of accelerating cavities, and an intuitive design method for narrowband disturbance rejection. The results of the investigations in this thesis provide a better understanding of the field control problem and have influenced the design of the field controllers at ESS.
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Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Dr Höfle, Wolfgang, CERN, Genève, Schweiz
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Particle accelerators, Cavity field control, LLRF, Complex-coefficient systems, Q design, Disturbance-rejecting peak filters
in
PhD Thesis TFRT-1127
pages
226 pages
publisher
LTH, Lund University
defense location
Lecture hall B, building E, Ole Römers väg 3, Lund University, Faculty of Engineering LTH, Lund
defense date
2019-11-29 10:15:00
ISSN
0280-5316
ISBN
978-91-7895-277-9
978-91-7895-276-2
project
Cavity Field Control for Linear Particle Accelerators
language
English
LU publication?
yes
id
f5b28bb1-35a4-4a5d-bc6b-d464cc37cc05
date added to LUP
2019-11-05 14:44:47
date last changed
2020-12-03 10:59:12
@phdthesis{f5b28bb1-35a4-4a5d-bc6b-d464cc37cc05,
  abstract     = {{High-energy linear particle accelerators enable exploration of the microscopic structure of pharmaceuticals, solar cells, fuel cells, high-temperature superconductors, and the universe itself. These accelerators accelerate charged particles using oscillating magnetic fields that are confined in metal cavities. The amplitudes and phases of the electromagnetic fields need to be accurately controlled by fast feedback loops for proper accelerator operation.<br/><br/>This thesis is based on the author's work on performance analysis and control design for the field control loops of the linear accelerator at the European Spallation Source (ESS), a neutron microscope that is under construction in Lund, Sweden. The main contribution of the thesis is a comprehensive treatment of the field control problem during flat-top, which gives more insight into the control aspects than previous work. The thesis demonstrates that a key to understand the dynamics of the field control loop is to represent it as a single-input single-output system with complex coefficients. This representation is not new itself but has seen limited use for field control analysis.<br/><br/>The thesis starts by developing practical and theoretical tools for analysis and control design for complex-coefficients systems. This is followed by two main parts on cavity field control. The first part introduces parametrizations that enable a better understanding of the cavity dynamics and discusses the most essential aspects of cavity field control. The second part builds on the first one and treats a selection of more advanced topics that all benefit from the complex-coefficient representation: analysis of a polar controller structure, field control design in the presence of parasitic cavity resonances, digital downconversion for low-latency feedback, energy-optimal excitation of accelerating cavities, and an intuitive design method for narrowband disturbance rejection. The results of the investigations in this thesis provide a better understanding of the field control problem and have influenced the design of the field controllers at ESS.<br/>}},
  author       = {{Troeng, Olof}},
  isbn         = {{978-91-7895-277-9}},
  issn         = {{0280-5316}},
  keywords     = {{Particle accelerators; Cavity field control; LLRF; Complex-coefficient systems; Q design; Disturbance-rejecting peak filters}},
  language     = {{eng}},
  month        = {{11}},
  publisher    = {{LTH, Lund University}},
  school       = {{Lund University}},
  series       = {{PhD Thesis TFRT-1127}},
  title        = {{Cavity Field Control for Linear Particle Accelerators}},
  url          = {{https://lup.lub.lu.se/search/files/71528958/thesis_troeng.pdf}},
  year         = {{2019}},
}