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Program Information

Fragmentation Experiments with Helium Ions

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K Zink

F Horst1,2 , C. Schuy2 , U Weber2 , K-T Brinkmann3 , K Zink1,4*, (1) Institute of Medical Physics and Radiation Protection, THM University of Applied Sciences, Giessen, Germany (2) Biophysics Department, GSI Helmholtz Centre for Heavy Ion Research, Darmstadt, Germany (3) II. Physics Institute, JLU University, Giessen, Germany (4) Department of Radiotherapy and Radiooncology, University Hospital Giessen-Marburg, Marburg, Germany


SU-I-GPD-T-115 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: ⁴He ions are considered as a possible alternative to protons and ¹²C ions. Due to nuclear fragmentation of the projectiles during their penetration through tissue the Bragg curve gets altered and has a tail. This means that treatment planning codes must have realistic nuclear reaction models implemented. There is a lack of measurement data in the therapeutic energy range, therefore experiments were performed to measure nuclear cross sections at 4 energies from 90 to 220 MeV/u on thin graphite targets at the Heidelberg ion beam therapy center (HIT).

Methods: For measuring the cross sections, a common attenuation method was applied at low intensities of about 500 ions/s: The ⁴He ions remaining after and the ³He fragments generated within the targets (3 thicknesses from 5 to 10 mm plus a no-target measurement for each energy) were identified by a ∆E-E-telescope consisting of a thin plastic scintillator and a thick BaF₂ scintillator triggered by a start scintillator. For improving the particle identification capability, the BaF₂ pulse shape was analyzed by means of fast waveform sampling. The mass- and charge-changing cross sections could then be calculated from the number of remaining ⁴He ions and generated ³He fragments as a function of target thickness.

Results: The results of the cross section measurements will be presented and compared to the nuclear reaction model implemented in the GSI treatment planning code TRiP98.

Conclusion: The measured data can also be compared to the nuclear reaction models implemented in various Monte Carlo codes and be used for their optimization and will therefore have the potential to improve the dose calculation in helium ion radiotherapy.

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