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Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the horizontal emittance. At the zero-intensity limit, the vertical normalized emittance was less than 2.8 x 10(-8) rad m at beam energy 1.3 GeV. At high intensity, strong effects of intrabeam scattering were observed, which had been expected in view of the extremely high particle density due to the small transverse emittance.

If we try to measure the backward optical diffraction radiation (BODR) of high energy electrons from a conductive slit or a semi infinitive plate, the electron beam will pass thru the bending or steering magnets or magnet lenses before striking the target.The synchrotron radiation (SR) from these magnets can obscure the BODR measurements. An analysis of the properties of SR from these magnets is in this paper presented. A model based on the modified Lenar Wikherd potentials was created, and the SR angular distribution from relativistic electrons in bending and steering magnets for different conditions of radiation in the optical region was calculated. The analysis shows, that for the conditions of the KEK ATF extraction line, the intensity of SR exceeds that of the backward optical transition radiation (BOTR) from the conducting targets, and it is much lager than the intensity of the BODR. The SR intensity from the steering magnets depends on its tuning and may be comparable to BOTR. Thus, these results it is seen, that the problem of separation of the BODR and SR in the BODR measurements is important. Two methods resolving of this problem is in this article suggested.