Controlled beam loss experiment at SIS18

The FAIR beam loss monitoring (BLM) system is based on different types of particle detectors. Its main purpose is the minimisation of beam losses around the SIS100 synchrotron and protection of machine components from unnecessary activation. As a part of a BLM feasibility study an experiment with controlled losses on a scraper was performed at SIS18 section. The aim of this study is the production of beam losses at a well defined position and the measurement of the shower intensity with BLM detectors. In the present setup two plastic scintillators of the existing BLM system were used. They are installed downstream of a scraper at a distance of 2 and 5 meters, respectively. The scraper was positioned close to the beam orbit. Uranium beams of different energies and intensities in the range of 100-900 MeV/u and 10-10 particles were utilized. The beam was injected into the SIS18 synchrotron, accelerated and then stored for several seconds. During that time the beam was excited and was slowly impinging on the scraper. The resulting count rates in the scintillators were monitored through the ABLASS data acquisition system[1] and further analysed with a ROOT code[2]. Figure 1 shows one BLM signal (blue curve) and the DC current transformer signal DCT (black curve) in arbitrary units. In the flattop region no significant BLM signal is detected. After 2 seconds the exciter was turned on and produced the shown BLM signal. It was carefully checked that no significant losses were produced at other locations around the sychrotron.