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Adjustment of the PTB nanodosemeter for examining the track structure of therapeutic carbon ions at the Heidelberg Ion-Beam Therapy Center (HIT)

23.12.2020

The examinations of the track structure carried out so far with the PTB nanodosemeter in nanometric volumes were realized by means of protons and helium ions with energies between 0.1 MeV and 20 MeV provided by PTB's accelerators. Further examinations were performed with carbon ions between 45 MeV and 150 MeV at the accelerators of the HIL in Warsaw and the LNL‑INFN in Legnaro. The ion beams used were monoenergetic and free from secondary particles – like those generated by fragmentation or collision processes, for example.

To be able to examine track structures in the therapeutic radiation fields of the Heidelberg Ion‑Beam Therapy Center (HIT), the PTB nanodosemeter was adjusted to the beam line which is available at the HIT for research purposes.

Besides the track structure of the incident monoenergetic primary carbon ions, especially track structures of radiation fields at different tissue depths are relevant. This is because these radiation fields – besides the primary ions with a broadened energy and directional distribution – additionally contain the secondary particles which are generated by fragmentation or collision processes of primary ions.

The different tissue depths are simulated by PMMA absorbers of different layer thicknesses. In beam direction, the beams are shaped behind the PMMA absorbers in a collimator which also consists of PMMA.

To mount and adjust the absorber and the collimator, a suitable support and adjustment device was built. In addition, the PTB nanodosemeter was equipped with a second position‑sensitive strip detector which was mounted in front of the interaction volume. In beam direction, the interaction volume is thus located between two position‑sensitive strip detectors. In this way, the two position‑sensitive detectors allow the trajectory of an ionizing particle to be reconstructed due to the interaction volume.

Your contact at PTB:

Opens local program for sending emailG. Hilgers, Department 6.3, Working Group 6.36