The ambient dose equivalent from the secondary radiation produced during irradiation of a cylindrical water phantom with 200 MeV/u (12)C-ions was investigated at the biophysics cave at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Pencil-like ion beams were delivered by the heavy-ion synchrotron SIS18 using the slow extraction mode. Since the secondary radiation field outside the phantom is complex in its particle composition and particle energy distribution, microdosimetric methods developed for the dosimetry of the cosmic radiation field at flight altitudes, which is similar in terms of complexity, were applied. Lineal energy distributions and the ambient dose equivalent were measured with a tissue-equivalent proportional counter at different particle emission angles. An additional veto counter allowed the identification of the different contributions of charged and neutral particles. A significant increase in the mean quality factor was observed at large emission angles which could be attributed to the decreasing contributions of charged particles compared to the (relative) contributions from neutrons.
The directional distribution of the ambient neutron dose equivalent from 145-MeV (19)F projectiles bombarding a thick aluminium target is measured and analysed. The measurements are carried out with a commercially available dose equivalent meter at 0°, 30°, 60° and 90° with respect to the beam direction. The experimental results are compared with calculated doses from EMPIRE nuclear reaction code and different empirical formulations proposed by others. The results are also compared with the measured data obtained from an earlier experiment at a lower projectile energy of 110 MeV for the same target-projectile combination.
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