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Touschek- and Gas Scattering Lifetime Investigations in the MAX IV 3 GeV Storage Ring

Sundberg, Jens LU (2017) MAXM30 20171
Department of Physics
MAX IV Laboratory
Abstract
The MAX IV 3 GeV storage ring is a fourth-generation electron synchrotron. At the time of writing in May 2017, it is the lowest emittance light source in the world. To study its performance is of foremost importance for the MAX IV Laboratory, its users and for upcoming synchrotrons. In this thesis, the MAX IV 3 GeV beam lifetime has been divided into its different components by experiments using in-vacuum copper blade scrapers. Touschek- and gas scattering lifetimes have been measured. The overall lattice momentum acceptance has been estimated by comparing measured Touschek scattering lifetimes with simulations. Observed and calculated current decays have been compared, based on a model using diverse types of decays for different lifetimes.
Popular Abstract
Electrons are among the smallest constituents of matter we know. They are parts of atoms that build up anything and everything, like stones, humans and trees. At the MAX IV Laboratory, electrons are accelerated into very high energies, and reach velocities near the speed of light. The electrons are held circulating in large rings, called storage rings. These rings are made up by vacuum chamber pipes, surrounded by magnets. The electrons are steered and focused by the magnets, and form an electron beam.

An electron is a negatively charged particle - it repels other negatively charged particles and attracts positively charged particles. When a charged particle is steered by a magnetic field, it will emit light. It is this emitted light... (More)
Electrons are among the smallest constituents of matter we know. They are parts of atoms that build up anything and everything, like stones, humans and trees. At the MAX IV Laboratory, electrons are accelerated into very high energies, and reach velocities near the speed of light. The electrons are held circulating in large rings, called storage rings. These rings are made up by vacuum chamber pipes, surrounded by magnets. The electrons are steered and focused by the magnets, and form an electron beam.

An electron is a negatively charged particle - it repels other negatively charged particles and attracts positively charged particles. When a charged particle is steered by a magnetic field, it will emit light. It is this emitted light that is used for scientific purposes at a synchrotron light source. By aiming and focusing the highly intensive light towards various material samples, information about for instance atomic structure and surface properties of these materials can be obtained. For instance, hidden text in painted antique parchments can be revealed using synchrotron light.

In this work, the electron beam lifetime at the MAX IV 3 GeV storage ring is studied. The electron beam lifetime tells at which pace the electrons are lost from the beam. The lifetime is an important parameter in a storage ring - it determines how often new electrons need to be accelerated and reinjected into the ring. There are mainly two effects causing electrons to be lost from the electron beam in a synchrotron storage ring. The two causes are called gas- and Touschek scattering, and make up two different electron beam lifetimes. These two lifetimes have been characterized during this thesis, which yields a better understanding of the total electron beam lifetime.

The gas scattering lifetime is a measurement of how many electrons from the beam that are lost by encounters with residual gas molecules inside the vacuum chamber pipes. The electrons in the beam are travelling inside the vacuum chambers at speeds near the speed of light. If the electrons were not travelling inside vacuum chambers, they would constantly come across particles from the surrounding gas. Yet, there are always some residual gas molecules left inside the vacuum chambers. The electrons from the beam will occasionally encounter these molecules, and might scatter. If the electrons scatter to a degree where they eventually hit the wall of the vacuum chamber, they are lost from the electron beam.

The Touschek scattering lifetime is a measurement of how many electrons from the beam that are lost by encounters with other beam electrons. As the electrons in the electron beam circulate around the storage ring, they will not only encounter residual gas molecules inside the vacuum chambers, but will also occasionally encounter each other. The electrons may then scatter, and can be lost from the electron beam because of this.

The MAX IV Laboratory is a world-leading light source facility, located in Lund, Sweden. The facility was inaugurated in June 2016. The lifetime of the electron beam is an influential parameter of a storage ring’s performance. Studying it is of uttermost importance for the diagnostics of the storage ring. (Less)
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author
Sundberg, Jens LU
supervisor
organization
course
MAXM30 20171
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Lifetime, Scraper, Scattering, MAX IV, Touschek, Storage Ring, Synchrotron
language
English
id
8921156
date added to LUP
2017-08-03 00:10:46
date last changed
2017-08-03 00:10:46
@misc{8921156,
  abstract     = {The MAX IV 3 GeV storage ring is a fourth-generation electron synchrotron. At the time of writing in May 2017, it is the lowest emittance light source in the world. To study its performance is of foremost importance for the MAX IV Laboratory, its users and for upcoming synchrotrons. In this thesis, the MAX IV 3 GeV beam lifetime has been divided into its different components by experiments using in-vacuum copper blade scrapers. Touschek- and gas scattering lifetimes have been measured. The overall lattice momentum acceptance has been estimated by comparing measured Touschek scattering lifetimes with simulations. Observed and calculated current decays have been compared, based on a model using diverse types of decays for different lifetimes.},
  author       = {Sundberg, Jens},
  keyword      = {Lifetime,Scraper,Scattering,MAX IV,Touschek,Storage Ring,Synchrotron},
  language     = {eng},
  note         = {Student Paper},
  title        = {Touschek- and Gas Scattering Lifetime Investigations in the MAX IV 3 GeV Storage Ring},
  year         = {2017},
}