Status of optical diffraction radiation experiment at KEK-ATF extraction line

At KEK-ATF extraction line detailed investigation of backward optical diffraction radiation (ODR) and its implementation to transversal beam parameter diagnostics is planned. We designed and constructed a target chamber with a precise target movement mechanism, a precise laser alignment system and an optical system. The first step to achieve success in the experiment is the tuning of the optical system using backward optical transition radiation (OTR). We believe that, if we are able to measure OTR spectral-angular characteristics with a proper accuracy, we may obtain good results for ODR measurements as the OTR effect is well experimentally and theoretically studied. Therefore, the first stage of our experiment assumes the measurements of backward OTR to analyze all possible types of radiation coming from the target, which could be obstacles for the ODR measurements. In the first series of experiments we have found that the angular distribution of the detected optical radiation is strongly asymmetric. One of the possible reasons for the asymmetry is the synchrotron radiation contribution from bending or steering magnets.