51 research outputs found
Radiation of a Charge Exiting Open-Ended Waveguide with Dielectric Filling
We consider a semi-infinite open-ended cylindrical waveguide with uniform
dielectric filling placed into collinear infinite vacuum waveguide with larger
radius. Electromagnetic field produced by a point charge or Gaussian bunch
moving along structure's axis from the dielectric waveguide into the vacuum one
is investigated. We utilize the modified residue-calculus technique and obtain
rigorous analytical solution of the problem by determining coefficients of mode
excitation in each subarea of the structure. Numerical simulations in CST
Particle Studio are also performed and an excellent agreement between
analytical and simulated results is shown. The main attention is paid to
analysis of Cherenkov radiation generated in the inner dielectric waveguide and
penetrated into vacuum regions of the outer waveguide. The discussed structure
can be used for generation of Terahertz radiation by modulated bunches (bunch
trains) by means of high-order Cherenkov modes. In this case, numerical
simulations becomes difficult while the developed analytical technique allows
for efficient calculation of the radiation characteristics.Comment: 13 pages, 11 figure
SUB-MICROMETER RESOLUTION TRANSVERSE ELECTRON BEAM SIZE MEASUREMENT SYSTEM BASED ON OPTICAL TRANSITION RADIATION
Optical Transition Radiation (OTR) appears 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 Point Spread Function (PSF) dimension - The source distribution generated by a single electron and projected by an optical system onto a screen. For small electron beam dimensions, the PSF form significantly depends on various parameters of the optical system like diffraction of the OTR tails, spherical and chromatic aberrations, etc. In our experiment we managed to create a system which can practically measure the PSF distribution and using a new self-calibration method we are able to calculate transverse electron beam size. Here we represent the development, data analysis and novel calibration technique of a sub-micrometer electron beam profile monitor based on the measurements of the PSF shape, which visibility is sensitive to sub-micrometer electron beam dimensions. Copyright Β© 2011 by IPAC'11/EPS-AG
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