Status of Proton Beam Commissioning at the Medaustron Ion Beam Therapy Centre

The MedAustron accelerator (Wiener Neustadt, Austria) will deliver clinical beams of protons (60 250 MeV) and carbon ions (120 400 MeV/n) to three ion beam therapy irradiation rooms (IR). Clinical beams and proton beams up to 800 MeV will be provided in a fourth IR, dedicated to non-clinical research. A slow-extracted proton beam of maximum clinical energy reached for the first time the IR3 in October 2014, thus providing the technical proof-of-principle of the entire accelerator chain. The main characteristics of the MedAustron accelerator system are presented, along with the results obtained along the ongoing commissioning. INTRODUCTION MedAustron is a synchrotron-based ion beam therapy centre. The accelerator supports beam rigidities up to 6.4 Tm. The accelerator layout is shown in Fig. 1. Its design [1] originates from those of PIMMS [2] and CNAO [3]. The injector produces beams of H3 or C, which are chopped with a fast electrostatic deflector, then bunched and pre-accelerated to 7 MeV/n with a Radiofrequency Quadrupole (RFQ) and an IH-DTL linac. In the Medium Energy Beam Transfer line (MEBT), the beam is stripped to H or C before injection into the synchrotron. The synchrotron has a superperiod of 2 with non-dispersive regions for injection and the Radiofrequency (RF) cavity. After acceleration, the beam is extracted via the thirdinteger resonance in the High Energy Beam Transfer Line (HEBT). Since last year [4-5], the installation of accelerator components for proton treatments in the two horizontal beam lines of IR2 and IR3 has been completed and a first beam of protons at 62.5 MeV reached IR3 in October 2014. Beam commissioning is currently resuming and passing the torch to medical commissioning. INJECTOR AND MEBT The commissioning of the beam from the source to the end of the MEBT has been completed at the end of 2014 with very positive results, in terms of intensity, transmission and stability. The main contributors to this progress have been: the extensive work on the IH stability (cooling and setpoint adjustment), optimization of the IH quadrupole strengths, steering at the source exit and in the matching section between RFQ and linac and finally, the increase of the RFQ output energy. The appropriate choice of the operation point of the linac was critical in stabilizing the energy of the beam injected into the ring. A summary is shown in Table 1. Table 1: Results of Commissioning up to the MEBT Parameter Performance