Optimisation of a Radiofrequency Electron Photogun
Date
2024-01-03
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0002-0112-2144
Type
Thesis
Degree Level
Masters
Abstract
The thermionic electron source which injects electron bunches to the accelerating complex
of the Canadian Light Source (CLS) is ageing, does not produce electron bunches which
are frequency matched to a harmonic of the booster ring accelerating frequency, and is not
ideally suited to producing single bunches of electrons. To improve the single bunch injection
process and the overall injection efficiency, it has been proposed to install a high brightness
radiofrequency photogun as a secondary electron injector to the CLS linear accelerator. The
photogun which has been acquired by the CLS and is proposed to fulfil this need was not
constructed to resonate at 3000.24 MHz — the sixth harmonic of the CLS booster ring
accelerating field frequency — and as such the geometry of the photogun must be altered
such that the resonant frequency matches the sixth harmonic of the CLS booster ring. To
design changes to the photogun geometry 3D electromagnetic modelling software was used to
numerically simulate the electromagnetic field configuration within the photogun. Electrodynamic particle tracking software was used to predict the characteristics of electron bunches
produced by the photogun. Benchtop measurements using a vector network analyser were
performed to characterise the radiofrequency properties of the photogun. It was shown that
the photogun geometry can be altered such that the resonant frequency matches the desired
3000.24 MHz. The simulated electron bunches using the new field configuration were shown to
have kinetic energy of 3.2 MeV, bunch size less than 1 mm, normalised transverse emittance
less than 10 mm mrad, and an energy spread of 5 keV. These characteristics are appropriate for electron bunches which are to be injected into the CLS linear accelerator. The
work presented in this thesis indicates that the modified photogun is a suitable candidate
be installed as a branch line injector to the CLS linear accelerator. By including this re-optimised photogun as a secondary high brightness electron injector, the injection efficiency
can be improved by seamlessly transferring electron bunches from the electron source, to
the linear accelerator, to the booster ring by phase locking the harmonic frequencies of the
accelerating waves.
Description
Keywords
Electron source, photogun, radiofrequency, cavity resonator, accelerator
Citation
Degree
Master of Science (M.Sc.)
Department
Physics and Engineering Physics
Program
Physics