• S. Yaramyshev, W. Barth, M. Maier, A. Orzhekhovskaya, B. Schlitt, H. Vormann
  GSI, Darmstadt
• R. Cee, A. Peters
  HIT, Heidelberg

The Therapy Linac in Heidelberg (HIT) was successfully commissioned in 2006. Required beam parameters were reached except of the beam intensity. The achieved particle transmission for C⁴⁺ (design ion) is significantly lower than design. Particle losses are mainly observed in the RFQ. One critical point is the matching section of the RFQ electrodes - Input Radial Matcher (IRM). The original design requires too rigid and narrow beam Twiss-parameters at the RFQ entrance. Also the measured emittance is about twice higher compared to the design. Numerically and experimentally it was proven that the solenoid, used for the beam matching to the RFQ, is not able to provide for the necessary beam size and convergence. As it was shown by beam dynamics simulations using the code DYNAMION, a minor modification of the IRM allows for an improvement of the beam transmission (up to 50%). The proposed measure was realized for an advanced HIT-RFQ-layout, which is recently under test stage. The same modification is already proposed for the linac frontend at Italian Hadrontherapy Center (CNAO, Pavia).

Slides

• O. Kester
  MSU/NSCL, East Lansing
• W. Barth, G. Clemente, L. Dahl, P. Gerhard, F. Herfurth, M. Kaiser, H.-J. Kluge, S. Koszudowski, C. Kozhuharov, G. Maero, W. Quint, A. Sokolov, Th. Stöhlker, W. Vinzenz, G. Vorobjev, D. F. A. Winters
  GSI, Darmstadt
• J. Pfister, U. Ratzinger, A.C. Sauer, A. Schempp
  Goethe Universität Frankfurt/IAP, Frankfurt

Funding: Work supported by the BMBF.

The GSI accelerator facility provides highly charged ion beams up to U⁹²⁺ at the energy of 400 MeV/u. These are cooled and decelerated down to 4 MeV/u in the Experimental Storage Ring. Within the Heavy Ion Trap facility HITRAP the ions are decelerated further down. The linear decelerator comprises a 108/216 MHz doubledrift- buncher, a 108 MHz-IH-structure, a spiral-type rebuncher, and an RFQ-decelerator with an integrated debuncher providing energy spread reduction. Finally the beam is injected with the energy of 6 keV/u into a Penning trap for final cooling. The decelerator is installed completely and first sections have been successfully commissioned. For commissioning of the individual sections different ion species, e.g. ⁶⁴Ni²⁸⁺, ²⁰Ne¹⁰⁺, ¹⁹⁷Au⁷⁹⁺ were used. Each section was studied with comprehensive beam diagnostics to measure energy, emittance, intensity, transverse profiles, and bunch structure of the beam. The report gives an overview of the beam dynamics, the decelerator structures, and some results of the different commissioning runs.

Slides