[1] 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.
His theory predicted some remarkable features for transition radiation in the x-ray region.
[3] 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.
[4] 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.
[6][7] Transition radiation in the x-ray region (TR) is produced by relativistic charged particles when they cross the interface of two media of different dielectric constants.
The emitted radiation is the homogeneous difference between the two inhomogeneous solutions of Maxwell's equations of the electric and magnetic fields of the moving particle in each medium separately.
The total energy loss of a charged particle on the transition depends on its Lorentz factor γ = E/mc2 and is mostly directed forward, peaking at an angle of the order of 1/γ relative to the particle's path.
More elaborate analysis of the emitted visual radiation may allow for the determination of γ and emittance.
The characteristics of this electromagnetic radiation makes it suitable for particle discrimination, particularly of electrons and hadrons in the momentum range between 1 GeV/c and 100 GeV/c.
This allows a much higher number of photons to be obtained in a smaller angular "volume".
Applications of this x-ray source are limited by the fact that the radiation is emitted in a cone, with a minimum intensity at the center.
X-ray focusing devices (crystals/mirrors) are not easy to build for such radiation patterns.
It is emitted provided that a charged particle crosses a medium with randomly inhomogeneous dielectric permittivity^{9,10,11}.
^S.R.Atayan and Zh.S.Gevorkian, Pseudophoton diffusion and radiation of a charged particle in a randomly inhomogeneous medium, Sov.Phys.JETP,v.71(5),862,(1990).\\ 10.
^Zh.S.Gevorkian, Radiation of a relativistic charged particle in a system with one-dimensional randomness, Phys.Rev.E,v.57,2338,(1998).\\ 11.
^ Zh.S.Gevorkian, C.P.Chen and Chin-Kun Hu, New Mechanism of X-ray radiation from a relativistic charged particle in a dielectric random medium, Phys.Rev.Lett.