Linac Commissioning for the Heavy Ion Cancer Therapy Facility HIT

The accelerator part of the clinical facility for cancer therapy HIT using energetic proton and ion beams (C, He and O) has been installed during 2006 at the Radiologische Universitätsklinik in Heidelberg, Germany [1]. The commissioning of the injector linac was performed in three steps for the LEBT, the RFQ and the IH-DTL and has successfully ended in December 2006. Some major results are briefly reported in this contribution. Introduction The commissioning of the linac shown schematically in Figure 1 was done in three consecutive steps as listed in Table 1 starting in April 2006 [2][3]. For each commissioning step a dedicated beam diagnostics test bench was designed to allow for beam current-, profile-, energyand emittance measurements. Different ion species were used: H2, H3, He, He, C and O. In this contribution selected results for C are reported. Profile grid L2DG1 Profile grids N1DG1/2 Profile grid I1DG3 Figure 1: Overview of the injector linac (solenoids SOL, quadrupole triplets QT, doublets QD, singlets QS). Table 1: Assembly and commissioning milestones. LEBT Figure 2 shows a typical ion source spectrum obtained for carbon operation. The specified intensity of the separated C beam from the ion source is 200 eμA. The beam profiles along the LEBT are shown in Figure 3 (for the grid positions compare to Figure 1). For this setting a beam current of 184 eμA corresponding to a transmission of 92 % in the LEBT was achieved. Figure 2: Ion source spectrum for carbon operation. Figure 3: Beam profiles along the LEBT for C. RFQ Before installation of the RFQ in Heidelberg, the RFQ had been investigated and tested with proton beams at a dedicated test bench at GSI [4]. As an example of measurements performed in Heidelberg, Figure 4 shows the energy of the C beam behind of the RFQ versus the tank voltage. The working point of the RFQ is marked, as well as the energy range required for injection into the adjacent IH-DTL. Figure 4: Beam energy measurements versus tank voltage to determine the RFQ working point for C. November 05 − March 06 LEBT, ECRIS installation & functional tests of components April / May 06 ECRIS May – July 06 LEBT successful beam commissioning July / August 06 RFQ installation of RFQ & testbench, RF commissioning September 06 RFQ beam acceleration to 400 keV/u October 06 IH-DTL completing of linac with IH-DTL & stripper-section November 06 IH-DTL RF commissioning December 06 IH-DTL first 7 MeV/u C beams (35 eμA) N1DG1 N1DG2 L2DG1 EXTERNAL-HIT-02