Diffracted Transitive Radiation as a Means for Indicating the Divergence of an Ultrarelativistic Electron Beam
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DIFFRACTED TRANSITIVE RADIATION AS A MEANS FOR INDICATING THE DIVERGENCE OF AN ULTRARELATIVISTIC ELECTRON BEAM S. V. Blazhevich,1 M. V. Bronnikova,1 and A. V. Noskov2
UDC 537.8
Diffracted transition radiation (DTR) emitted by a beam of relativistic electrons traversing a thin single-crystal plate in the Laue scattering geometry is considered. An expression has been obtained describing the angular DTR density when the electron path length in a target is far less than the extinction length of x-rays in the crystal. It is shown that in this case, the DTR process has a clearly pronounced kinematic character. Numerical calculations of the DTR photon yield in the direction of Bragg’s scattering performed for different solid angles of recording show that it is significantly affected by the electron beam divergence. We have concluded that the DTR photon yield measured for a given solid angle can be used for indicating the electron beam divergence. Results of model calculations of the electron beam divergence parameters for a given yield of DTR photons traversing the slit collimator have shown that the formula proposed in this work can be successfully used as a basis for the development of methods for measuring the divergence of ultrahigh-energy relativistic electron beams based on the angular DTR distribution. Keywords: relativistic electrons, diffracted transition radiation, indicating the electron beam divergence.
INTRODUCTION When carrying out fundamental and applied experimental investigations of high-energy electron beams, the researchers face the problem of insufficient information on the parameters of the employed beams. The transverse sizes and the divergence are the key parameters of the beams. The main problem for physicists dealing with the electron beams having energies in the range 100–1000 MeV is measuring the transverse beam sizes, because the beam divergence of modern accelerators (of the order of 0.001 mrad) is insignificant for the beams with transverse sizes of the order of or greater than 10 m. Nowadays two new electron-positron colliders are being developed [1, 2]. In these colliders, electrons and positrons will be accelerated to energy of 250 GeV in beams with very small transverse sizes (~5–100 nm), and the main problem here will be the measurement of the beam divergence. A solution of this problem will allow experimental data of both fundamental and applied research to be interpreted more precisely. In [3, 4] the feasibility of application of relativistic electrons of parametric x-ray radiation (PXR) for diagnostics of the transverse relativistic beam sizes was experimentally investigated. The influence of the electron beam divergence on PXR in a crystal was experimentally investigated in Tomsk and Tokyo [5] for electrons with energies of 600 and 800 MeV, respectively. The researchers showed that the orientational dependence of PXR generated by relativistic electrons in a crystal was sensitive to the beam divergence and proposed to use PXR as a simple means for determining the angular divergenc
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