Far-Infrared Spectroscopy and Determination of Three-Dimensional Bunch Shape of Electrons by Coherent Transition Radiation

We have investigated fundamental properties of coherent transition radiation that the spectrum intensity has been enhanced by six order of magnitude compared with the ordinary transition radiation and that the intensity is proportional to the square of the beam current of the linear accelerator。We also confirmed the importance of the role of the formation zone in the process of the radiation.We have constructed a system of far-infrared spectroscopy using the light source of the transition radiation from the electron beam of a linac of the Laboratory of Nuclear Physics，Tohoku University(Tohoku Linac)。We have observed the transmission spectra of As_2S_3and As_2Se_3glass specimens in the wavelength region from1to5 mm with the accuracy of 3%.We have also constructed a similar system of spectroscopy at the Research Reactor Institute，Kyoto University。We were able to observe the transmission spectra of NaCl crystals doped with hydroxylions in the millimeter wave region from1to5 mm.We have determined the distribution function of electrons in the bunch for the electron beam of Tohoku Linac as a nearly Gaussian curve with the half width of 0.28 mm。The distribution function of KURRI linac was determined as a quadratic function with the half width of 9 mm。The longitudinal distribution function of the linac of Osaka University had a triangular shape with the half width of 8.4 mm and the emittance of the beam was determined as(4.0&lt；plus-minus&gt；2.0)x10^2 mm·mrad。Compared with the conventional method of beam diagnosis，our method has advantages that it can determine the functional form of the distribution and that it has an extremely high resolution.

We have investigated fundamental properties of coherent transition radiation that the spectrum intensity has been enhanced by six order of magnitude compared with the ordinary transition radiation and that the intensity is proportional to the square of the beam current of the linear accelerator. We also confirmed the importance of the role of the formation zone in the process of the radiation.We have constructed a system of far-infrared spectroscopy using the light source of the transition radiation from the electron beam of a linac of the Laboratory of Nuclear Physics, Tohoku University (Tohoku Linac) . We have observed the transmission spectra of As_2S_3 and As_2Se_3 glass specimens in the wavelength region from 1 to 5 mm with the accuracy of 3 %. We have also constructed a similar system of spectroscopy at the Research Reactor Institute, Kyoto University. We were able to observe the transmission spectra of NaCl crystals doped with hydroxylions in the millimeter wave region from 1 to 5 mm.We have determined the distribution function of electrons in the bunch for the electron beam of Tohoku Linac as a nearly Gaussian curve with the half width of 0.28mm. The distribution function of KURRI linac was determined as a quadratic function with the half width of 9 mm. The longitudinal distribution function of the linac of Osaka University had a triangular shape with the half width of 8.4 mm and the emittance of the beam was determined as (4.0 <plus-minus>2.0) x10^2mm・mrad. Compared with the conventional method of beam diagnosis, our method has advantages that it can determine the functional form of the distribution and that it has an extremely high resolution.