Royal Holloway, University of London
Simulation of Coherent Diffraction Radiation Process
ESR: Konstantin Lekomtsev (k.v.lekomtsev@rhul.ac.uk)
Superivsor: Pavel Karataev (pavel.karataev@rhul.ac.uk)
Any method for diagnostics of a charged particle beam is based on interaction of the particles or fields generated by the particles with surrounding media losing a small fraction of their energy. A part of the lost energy is transformed into electromagnetic (EM) radiation whose characteristics depend on different particle beam parameters. By measuring the EM radiation characteristics, or, to be more precise, their distortion, one can measure such particle beam parameters as transverse size and divergence, position, bunch length and chromaticity. In most cases the ideal EM radiation characteristics must be predictable either for diagnostics itself or for optimization of the device performance before manufacturing it.
One method for longitudinal particle beam profile diagnostics is the analysis of Coherent Diffraction Radiation (CDR) generated when a charged particle (electron) moves in the vicinity of a conducting screen.
The beauty of the phenomenon is that the particle beam does not directly interact with the screen hence excluding changes in the beam parameters introduced by the screen itself. In order to derive the longitudinal profile of the bunch from a measured spectrum one must know the spectrum generated by a single electron. Therefore the screen configuration is usually chosen to be as simple as possible to predict the spectrum using some approximation theory. However, such a simple target is often not an ideal approach.
Within this project, the characteristics of CDR for different target geometries are being investigated in detail through simulations. Therefore, a dedicated computer code for the simulation of the CDR process has been developed and the results benchmarked against measurements at CTF3 (CERN).
Development of Beam Position and Tilt Monitors for ITB, CTF3 and CLIC
ESR: Nirav Joshi (j.nirav@rhul.ac.uk)
Supervisor: Stewart Boogert (sboogert@pp.rhul.ac.uk)
Beam position monitors are essential diagnostics devices for monitoring the beam relative to magnetic devices and extracting important properties of magnetic lattices.
In addition, position and angle feedback signals from BPMs can be used as a signal for closed loop feedback applications, where the response of the BPM is used directly after some processing to modify the beam control, such as kickers, steering magnets and quadrupoles.
The main aim of this project is the development of a new type of beam position monitor for electron accelerator facilities such as ILC or CTF3/CLIC. The main aim of the project is to develop a beam position monitor for CLIC-like probe beams. Particular emphasis is placed on the electromagnetic design, ease of fabrication and analogue signal processing.
In collaboration with CERN experts and collaborators in KEK and SLAC the next generation of beam position monitors is being developed. An integral part of the project is to understand with industry the most cost effective, yet high performance design.
Development of a beam profile monitor for CLIC using laser-wire systems
ESR: Thomas Aumeyr (t.aumeyr@rhul.ac.uk)
Supervisior: Grahame Blair (g.blair@rhul.ac.uk)
Laser-wire systems use a finely focused beam of laser-light to scan across the particle beam in order to measure the transverse beam profiles; measurement of the transverse beam profile is an essential input into determining the transverse beam emittance. Laser-wires can be employed at electron machines using the Compton Effect, where the laser photons are scattered by the electrons and can be detected downstream as gamma rays in a calorimeter; alternatively the scattered electrons can be detected because they are over-focused by downstream magnets. Within this project a laser-wire monitor at PETRAIII is being developed for application at future accelerators.
The electron machine under study is the newly-completed PETRAIII accelerator at DESY, Hamburg. PETRAIII is a new synchrotron light source and is the world’s most brilliant source of synchrotron light in the wavelengths it offers. Understanding the emittance of PETRAIII is very important to achieving its ultimate performance; the electron beam size is typically of order ten microns. The laser-wire experiment at PETRAIII was installed in early 2009, using green laser-light, and within a week was producing first data; this was a remarkable achievement, building on experience at the previous PETRAII system. Using a vertical optical table, laser light can be directed so as to scan in either the vertical or horizontal directions.
The trainee, Thomas Aumeyr, was heavily involved in testing the system at RHUL before it was shipped to DESY and he has also been heavily involved in its commissioning. The current emphasis is on automation and on integrating the laser-wire data acquisition into the PETRA system so that the laser-wire will become a central diagnostic tool for the machine operators. Once this is complete, the emphasis will shift to data taking and analysis in the context of PETRAIII optimisation. This work, with associated simulations, will provide important input into the CLIC Conceptual Design Report.