STATUS OF THE HZB# CYCLOTRON: EYE TUMOUR THERAPY IN BERLIN

The mission of the ion beam laboratory (Ionenstrahllabor) ISL was the provision of fast ions for solid state physics, materials analysis and medical applications in basic as well as applied research. Eye tumours are treated since 1998 with 68 MeV protons in collaboration with the University Hospital Benjamin Franklin, now Charite Campus Benjamin Franklin. In autumn 2004 the board of directors of the HMI decided to close down ISL at the end of 2006. In December 2006, a cooperation contract between the Charite and the HMI was signed to assure the continuity of the eye tumour therapy, at this moment being the only facility in Germany. We have now experienced the first three years under the new boundary conditions; treating more than 600 patients in that time. The main challenge is to supply protons for the therapy with less man-power but keeping the same high reliability as before. The conversion process is not yet finished. The installation and commissioning of a new, facile injector for protons will be discussed. In addition to the routine treatment, proton therapy of ocular tumours for very young children under general anaesthesia was performed. ACCELERATOR OPERATION Since 2007, the cyclotron was operated for the most part for medical purpose. Hence, the scheduled beam time hours decreased tremendously (fig. 1). The new financial boundary conditions lead to a reduction of the man-power for accelerator operation to a third of the original crew. Hence, the accelerator operation was changed from a three-shift to a two-shift mode. Over night the machine idles, monitored by new control programmes. Nevertheless, operation continued smoothly. The reliability of the machine was kept at a high level: Beam time losses due to break-downs were between 2% and 5%. Due to the small number of scheduled beam time hours, single major breakdowns have huge impacts on the beam statistics. An example is an internal water leak in the RF system of the cyclotron, leading, for the first time since 1998, to an interruption of the therapy week. In 2008, one fifth of the unscheduled down time was caused by failures in the electric power supply of the laboratory. Some of these failures lasted for almost 1 sec. Beam tests were performed for the change from the three-shift to two-shift mode in order to test the monitoring control programs. Further tests were made for the commissioning of the tandetron (see below). Figure 1: Operation statistics of ISL (1995-2006) and the HZB cyclotron (since 2007)