DORIS - a status report

The status of the DORIS double storage ring with the energy ranged between 1.5 and 2.7 GeV per beam with the peak value of luminosity 3.5x1030 cm-2s-1 is presented. Between experimental runs 1600 hours per year are available for studies of beam properties. 400 mA beam current has been reached in both rings at 2.6 GeV. The behaviour of weak positron bunches colliding with strong electron bunches was studied. The lifetime of positrons was found to be drastically reduced while crossing satellite resonance frequencies. 25-vertical resonances were observed. Iron shims were mounted in order to enlarge the effect for compensation of the vertical chromaticity. A new 3-antenna system was developed using ferrite absorbers for damping of cavity modes. The use of DORIS as an intermediate storage ring for positron injection into PETRA is planned