Abstract
The applicability of optical transition radiation (OTR) for measurements of micron sized transverse electron beam profiles is limited not only by the optical system resolution which has a fundamental limit imposed by the uncertainty principle. In the case of OTR generation, a single electron crossing the boundary between vacuum and screen cannot be considered as a single emitting point with isotropic angular distribution. On the contrary, the radiation is emitted from an area with a transverse range that is defined by the radial extension of the electron's Lorentz contracted Coulomb field and is typically estimated as γλ (with γ the Lorentz factor and λ the wavelength of observation). The OTR angular distribution has a characteristic "funnel" shape. As a result the one-dimensional image of a single electron measured with an ideal thin lens has a double lobe shape, and the resolution of any OTR based imaging system is determined by this double lobe function which is also known as OTR Point Spread Function (PSF). As a consequence, the reconstruction of micron sized electron beam profiles is hampered not only due to the fundamental diffraction limit, but also due to the PSF lobe shape. In this paper we present two approaches to improve the spatial resolution of an OTR monitor based on asymmetric light collection using a traditional optical system which allows blocking of one of the lobes. With such a scheme, an OTR PSF can be achieved that is comparable to the one of an ideal point source (Airy distribution).
Highlights
Transverse beam profile diagnostics based on optical transition radiation (OTR) is a routine technique at most modern electron linear accelerators [1,2,3]
The spatial resolution of a transverse beam size monitor based on OTR is determined by the so-called Point Spread Function (PSF) or, in other words, by the response of the monitor optical system to a point charge crossing the target
Drawback of asymmetric OTR observation geometries is a decrease in the overall intensity
Summary
Transverse beam profile diagnostics based on optical transition radiation (OTR) is a routine technique at most modern electron linear accelerators (linacs) [1,2,3]. The spatial resolution of a transverse beam size monitor based on OTR is determined by the so-called Point Spread Function (PSF) or, in other words, by the response of the monitor optical system to a point charge crossing the target. In the first approximation for E > 100 MeV the PSF can be obtained based on approximations of classical optics In this approach the field of a relativistic point charge is considered as a set of the electromagnetic waves (the pseudo photon approximation) see, for example [6,7,8,9]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
