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Transition radiation (TR) is a form of electromagnetic radiation emitted when a charged particle passes through inhomogeneous media, such as a boundary between two different media. This is in contrast to Cherenkov radiation, which occurs when a charged particle passes through a homogeneous dielectric medium at a speed greater than the phase velocity of electromagnetic waves in that medium. ==History== Transition radiation was demonstrated theoretically by Ginzburg and Frank in 1945. They showed the existence of Transition radiation when a charged particle perpendicularly passed through a boundary between two different homogeneous media. The frequency of radiation emitted in the backwards direction relative to the particle was mainly in the range of visible light. The intensity of radiation was logarithmically proportional to the Lorentz factor of the particle. This provided a new way of measuring the Lorentz factor of the relativistic particles. But the energy of radiation was very small, which made it difficult to measure.〔Boris Dolgoshein ("Transition radiation detectors" ), Nuclear Instruments and Methods in Physics Research A326 (1993) 434-469〕 In 1959 Garibian showed theoretically that energy losses of an ultrarelativistic particle, when emitting TR while passing the boundary between media and vacuum, were directly proportional to the Lorentz factor of the particle. Additional research pointed out that the reason for that dependency was that the radiation emitted in the direction of movement of particle included also X-ray frequencies. Theoretical discovery of X-Ray transition radiation, which was directly proportional to the Lorentz factor, made possible further use of TR in high-energy physics. Thus, from 1959 intensive theoretical and experimental research of TR, and X-ray TR in particular began.〔(),"Health Physics Division annual progress report",Oak Ridge National Laboratory, p.137,1959〕 〔("Some New Developments on Transition Radiation Detectors" )L. C. Yuan,Brookhaven National Laboratory,p.2,Upton, New York, USA and CERN, Geneva, Switzerland〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「transition radiation」の詳細全文を読む スポンサード リンク
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