Simulation of transition radiation based beam imaging from tilted targets

Abstract

Transverse beam profile diagnostics in linear electron accelerators is usually based on direct imaging of a beam spot via visible transition radiation. In this case the fundamental resolution limit is determined by radiation diffraction in the optical system. A method to measure beam sizes beyond the diffraction limit is to perform imaging dominated by a single-particle function (SPF), i.e. when the recorded image is dominated not by the transverse beam profile but by the image function of a point source (single electron). Knowledge of the SPF for an experimental setup allows one to extract the transverse beam size from an SPF dominated image. This paper presents an approach that allows one to calculate two-dimensional SPF dominated beam images, taking into account the target inclination angle and the depth-of-field effect. In conclusion, a simple fit function for beam size determination in the case under consideration is proposed and its applicability is tested under various conditions.

Spatial resolution improvement for an optical transition radiation monitor by asymmetric light collection

“… q the PSF influence is so small that fitting the convoluted data with a Gaussian function results in a rms beam size which practically coincides with the input size for the beam [13].…”

“…with 01 , qq being free fit parameters [13]. While q 0 is a simple amplitude factor, the parameter q 1 characterizes the PSF and can be used to give a resolution estimate as will be shown below.…”

“…The result of the convolution of a Gaussian beam profile with rms size σ and the PSF according to Eq. (9) can be expressed by the following analytical function [13]: The calculated function was fitted with the fit function Eq. (9), resulting in 1 2.0um q  .…”

“…As can be seen, for beam sizes  < 1 q the profiles exhibit a two-lobe structure. For this case (so called PSF dominated regime) the problem of reconstructing the initial beam profile is rather complicated, see [12,13]. Only in the case 1…”

Diffracted x-ray transition radiation by a “half-bare” electron

“…For instance, in [25,26] it was proposed to use such emission for diagnostics of high-energy charged particle beams. This is expected to bring new possibilities for diagnostics of beams of micrometer-scale (and smaller) transverse size together with the analogous techniques based on PXR [27,28] and optical transition radiation (see, e.g., [29,30]).…”