Sub-micron scale transverse electron beam size diagnostics methodology based on the analysis of optical transition radiation source distribution

Optical Transition Radiation (OTR) appearing when a charged particle crosses a boundary between two media with different dielectric properties has widely been used as a tool for transverse profile measurements of charged particle beams in numerous facilities worldwide. The resolution of the conventional monitors is defined by the dimensions of the Point Spread Function (PSF) distribution, i.e. the source distribution generated by a single electron and projected by an optical system onto a detector. The PSF form significantly depends on various parameters of the optical system like diffraction of the OTR tails, spherical and chromatic aberrations. The beam image is a convolution of the PSF with a transverse electron distribution in a beam. In our experiment we designed and built a system that can measure the transverse electron beam size through the analysis of the PSF distribution shape. In this paper we present the hardware, data analysis, calibration technique, a discussion on the main source of uncertainties and initial measurements of a micron-scale electron beam size with sub-micrometre resolution.