Radiative polarization at ultra-high energies

Possibilities of obtaining polarized electron and positron beams at arbitrarily high energies are studied in cases when spin-diffusion processes in inhomogeneous fields due to quantum fluctuations of radiation become essential. The requirements for precision of the magnetic systems are determined for providing a high degree of radiative polarization. Specially considered is the situation, characteristic of storage rings with a large number of elements, when perturbations of separate elements are statistically independent. The depolarizing effects are investigated at extremely high energies, when the spread of spin-precession frequencies exceeds the revolution frequency of particles in a storage ring. It is shown that the depolarizing influence of the colliding beam in the storage ring decreases as the maximum energy grows. In a special section, the main formulae are given and the energy dependence of the criteria for existence of the radiative polarization in the conventional-type storage rings is discussed. In conclusion, additional measures are considered that may be useful for obtaining radiative polarization of high-energy electrons and positrons. (author)