Advanced

Impedance and Instabilities in the MAX IV 3 GeV Ring

Skripka, Galina LU (2015)
Abstract (Swedish)
Popular Abstract in Swedish

Laddade partiklar är kända för att sända ut ljus när de rör sig i en krökt bana. Detta ljus kallas synkrotronljus och upptäcktes i mitten av 1900-talet. Sedan dess har det använts i forskning inom kemi, biologi, medicin och materialvetenskap. Utveckling av speciella maskiner för att producera synkrotronljus blev nödvändig för att fortsätta att tillgodose behoven inom dessa forskningsområden. Kvaliteten på synkrotronljuset beror till stor del på en parameter för strålen som kallas emittans.

MAX IV 3 GeV ring kallas en lagringsringsbaserad synkrotronljuskälla. Ringen kommer att bli den första i sitt slag som kan lagra en hög ström av elektroner med extremt liten horizontal emittans på... (More)
Popular Abstract in Swedish

Laddade partiklar är kända för att sända ut ljus när de rör sig i en krökt bana. Detta ljus kallas synkrotronljus och upptäcktes i mitten av 1900-talet. Sedan dess har det använts i forskning inom kemi, biologi, medicin och materialvetenskap. Utveckling av speciella maskiner för att producera synkrotronljus blev nödvändig för att fortsätta att tillgodose behoven inom dessa forskningsområden. Kvaliteten på synkrotronljuset beror till stor del på en parameter för strålen som kallas emittans.

MAX IV 3 GeV ring kallas en lagringsringsbaserad synkrotronljuskälla. Ringen kommer att bli den första i sitt slag som kan lagra en hög ström av elektroner med extremt liten horizontal emittans på strålen. Den är byggd av en serie magneter som styr strålen i en sluten bana och använder speciella enheter, byggda av rader med magneter med växlande polaritet, som får elektronstrålen att svänga flera gånger och på så sätt sända ut intensivt ljus.

När laddade partiklar passerar vissa delar och komponenter i vakuumsystemet i lagringsringen, skapar de elektromagnetiska fält som kan verka tillbaka på de partiklar som kommer senare. Genom att använda ett fenomen kallat impedans, som både beror på tvärsnittet av vakuumsystemet (geometriskt) och den elektriska ledningsförmågan av materialet vakuumsystemet är byggt av (resistans), kan man beskriva växelverkan mellan partikelstrålen och dess egna fält och utvärdera om det har negativa konsekvenser.

Detta arbete diskuterar studier av fenomen som påverkar stabiliteten hos partikelstrålen i 3 GeV ringen på MAX IV vid olika intensitet på partikelstrålen. Maskinens impedans har tagits fram genom en speciell metod att bearbeta data numeriskt till en form mer lämplig för studier av strålstabilitet. Det numeriska verktyget utvecklades för att simulera hur partiklarnas rörelse påverkas av maskinens impedans och en speciell komponent i MAX IV 3 GeV ringen kallad passiv harmonisk kavitet. Harmoniska kaviteter används för att göra elektronpulserna längre, vilket resulterar i en minskning av partikelkollisioner och hjälper till att dämpa instabiliteter. Resultaten av simuleringarna diskuteras och det visas att de harmoniska kaviteterna är nödvändiga för att nå de uppsatta designmålen för MAX IV 3 GeV ringen.



Popular Abstract in English

Charged particles are known to emit radiation when travelling on a curved path. This radiation, called synchrotron radiation, was discovered in the middle of the 20th century and since then found research application in chemistry, biology, medicine and material science. To follow the progress of these fields, the development of high performance machines dedicated to the production of light became necessary. The quality of the synchrotron light depends on a beam parameter called emittance.

The MAX IV 3 GeV machine is called a storage-ring-based synchrotron light source. It will be the first one of its kind to store a high current electron beam with an extremely small horizontal beam emittance. It is built of a sequence of magnets that keep the beam on a closed orbit and uses special devices, built of arrays of magnets with alternating polarity, where the electron beam is bent multiple times resulting in production of high intensity radiation.

When charged particles travel in a certain environment created by the vacuum chamber and other elements of the storage ring, they create and leave behind electromagnetic fields which can act back on them and the following charges. Using the quantity called impedance, which depends both on the cross-section of the vacuum components (geometric) and the electric conductivity of materials they are made of (resistive wall), one can describe this interaction of the beam with its own wakefield and evaluate if it is destructive.

This work discusses the studies of different phenomena affecting the intensity-dependent beam stability in the MAX IV 3 GeV ring. The machine impedance was obtained using a special approach in processing the data obtained numerically into the practical form for beam stability studies. The numerical tool was developed to simulate how the motion of the particles is affected by the machine impedance and a special component of the MAX IV 3 GeV ring called a passive harmonic cavity. This component is introduced to make the electron bunches longer which results in a reduction of the particle scattering processes and helps to damp instabilities. The simulation results are discussed and it is shown that the harmonic cavities are necessary to reach the design performance of the MAX IV 3 GeV machine. (Less)
Abstract
To ensure the beam with an ultralow emittance and high current the possible effects deteriorating the beam stability must be investigated. When ultrarelativistic particles travel in the vacuum chamber they induce electromagnetic fields which can act back on them and the following particles. The interaction of the beam with the surrounding environment can be described by wakefields in time domain and impedance in frequency domain.

In this work the geometric and resistive wall impedance effects on the beam stability in the MAX IV 3 GeV ring are studied. The geometric impedance of different recurrent elements of the storage ring was numerically calculated using an electromagnetic field solver, and a possibility to use a... (More)
To ensure the beam with an ultralow emittance and high current the possible effects deteriorating the beam stability must be investigated. When ultrarelativistic particles travel in the vacuum chamber they induce electromagnetic fields which can act back on them and the following particles. The interaction of the beam with the surrounding environment can be described by wakefields in time domain and impedance in frequency domain.

In this work the geometric and resistive wall impedance effects on the beam stability in the MAX IV 3 GeV ring are studied. The geometric impedance of different recurrent elements of the storage ring was numerically calculated using an electromagnetic field solver, and a possibility to use a semi-analytical method was investigated as well. To quantitatively evaluate the effect of geometric impedance on the beam stability the total machine impedance budget of the MAX IV 3 GeV ring was built and introduced into the beam dynamics simulation.

The particle tracking code was developed to account for different possible effects impacting the beam, namely, geometric and resistive wall impedance and passive harmonic cavities that lengthen bunches and increase the synchrotron tune spread. The former helps to make the beam less influenced by the intrabeam scattering processes and the machine impedance, and the latter introduces the Landau damping of instabilities. The results of the particle tracking are discussed in this work. The presence of harmonic cavities in the MAX IV storage ring turned out to significantly improve the beam stability and to be the key in achieving the design parameters. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Dr. Kuske, Peter, Helmholtz-Zentrum Berlin
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Collective effects, geometric impedance, resistive wall impedance, wakefields, particle tracking, harmonic cavity
pages
130 pages
publisher
MAX IV Laboratory, Lund University
defense location
Lundmarksalen
defense date
2015-12-03 13:15
ISBN
978-91-7623-428-0 (print)
978-91-7623-429-7 (pdf)
language
English
LU publication?
yes
id
e942a23d-8962-47c5-9d0d-901a1fdf7ddd (old id 8147511)
date added to LUP
2015-11-24 17:41:07
date last changed
2016-09-19 08:45:08
@phdthesis{e942a23d-8962-47c5-9d0d-901a1fdf7ddd,
  abstract     = {To ensure the beam with an ultralow emittance and high current the possible effects deteriorating the beam stability must be investigated. When ultrarelativistic particles travel in the vacuum chamber they induce electromagnetic fields which can act back on them and the following particles. The interaction of the beam with the surrounding environment can be described by wakefields in time domain and impedance in frequency domain.<br/><br>
In this work the geometric and resistive wall impedance effects on the beam stability in the MAX IV 3 GeV ring are studied. The geometric impedance of different recurrent elements of the storage ring was numerically calculated using an electromagnetic field solver, and a possibility to use a semi-analytical method was investigated as well. To quantitatively evaluate the effect of geometric impedance on the beam stability the total machine impedance budget of the MAX IV 3 GeV ring was built and introduced into the beam dynamics simulation.<br/><br>
The particle tracking code was developed to account for different possible effects impacting the beam, namely, geometric and resistive wall impedance and passive harmonic cavities that lengthen bunches and increase the synchrotron tune spread. The former helps to make the beam less influenced by the intrabeam scattering processes and the machine impedance, and the latter introduces the Landau damping of instabilities. The results of the particle tracking are discussed in this work. The presence of harmonic cavities in the MAX IV storage ring turned out to significantly improve the beam stability and to be the key in achieving the design parameters.},
  author       = {Skripka, Galina},
  isbn         = {978-91-7623-428-0 (print)},
  keyword      = {Collective effects,geometric impedance,resistive wall impedance,wakefields,particle tracking,harmonic cavity},
  language     = {eng},
  pages        = {130},
  publisher    = {MAX IV Laboratory, Lund University},
  school       = {Lund University},
  title        = {Impedance and Instabilities in the MAX IV 3 GeV Ring},
  year         = {2015},
}