Beam position monitoring system and COD correction at the cooler synchrotron TARN II

At the cooler-synchrotron TARN II, light- and heavy-ion beams are stored, electron-cooled and accelerated for the research of atomic physics and accelerator studies. In these experiments, the closed orbit distortion (GOD) correction system plays an important role for improving the beam currents and lifetimes. In order to measure the position of a circulating faint beam in the ring, we developed beam diagnostic devices of high sensitivity and low noise. The beam positions can be measured with an accuracy of 0.3 mm at a circulating beam current of 1 mu A. It is the purpose of the present paper to describe details concerning the beam position monitor (BPM) system, an investigation of the sensitivities of the BPM from the point of view the S/N ratio, the experimental results of a COD correction and measurements of the accelerator parameters, such as the chromaticity and dispersion using this system.