Neutron production at the GSI fragment separator

The fragment separator at the future GSI facility has to be regarded as a strong source of neutron radiation. The shielding design of the instrument requires knowledge of the produced neutron fields. In this paper the neutron fields of the present fragment separator were characterized by the use of thermoluminescence dosimetry applied during an irradiation period of uranium-beams impinging on a thin Be-target with a mean energy of 0.8 GeV/u. In addition time of flight measurements of neutrons were performed in Cave B of GSI. Neutron spectra produced by carbon and uranium beams at 1 GeV/u (thick iron target, 10 x 10 x 20 cm"3) for the angular range from 0 to 90 relative to the incident ion beam were measured with a BaF_2 scintillator detection system. Conclusions for the shielding design of the planned superconducting fragment separator are drawn on the basis of the measured dose distributions at the present fragment separator. (orig.)Available from TIB Hannover: RO 801(2002-32) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Experimental carbon ion range verification in inhomogeneous phantoms using prompt gammas

International audiencePurpose:The purpose of this study was to experimentally assess the possibility to monitor carbon ion range variations—due to tumor shift and/or elongation or shrinking—using prompt-gamma (PG) emission with inhomogeneous phantoms. Such a study is related to the development of PG monitoring techniques to be used in a carbon ion therapy context.Methods:A 95 MeV/u carbon ion beam was used to irradiate phantoms with a variable density along the ion path to mimic the presence of bone and lung in homogeneous humanlike tissue. PG profiles were obtained after a longitudinal scan of the phantoms. A setup comprising a narrow single-slit collimator and two detectors placed at 90° with respect to the beam axis was used. The time of flight technique was applied to allow the selection between PG and background events.Results:Using the positions at 50% entrance and 50% falloff of the PG profiles, a quantity called prompt-gamma profile length (PGPL) is defined. It is possible to observe shifts in the PGPL when there are absolute ion range shifts as small as 1–2 mm. Quantitatively, for an ion range shift of −1.33 ± 0.46 mm (insertion of a Teflon slab), a PGPL difference of −1.93 ± 0.58 mm and −1.84 ± 1.27 mm is obtained using a BaF2 and a NaI(Tl) detector, respectively. In turn, when an ion range shift of 4.59 ± 0.42 mm (insertion of a lung-equivalent material slab) is considered, the difference is of 4.10 ± 0.54 and 4.39 ± 0.80 mm for the same detectors.Conclusions:Herein, experimental evidence of the usefulness of employing PG to monitor carbon ion range using inhomogeneous phantoms is presented. Considering the homogeneous phantom as reference, the results show that the information provided by the PG emission allows for detecting ion range shifts as small as 1–2 mm. When considering the expected PG emission from an energy slice in a carbon ion therapy scenario, the experimental setup would allow to retrieve the same PGPL as the high statistics of the full experimental dataset in 58% of the times. However, this success rate increases to 93% when using a better optimized setup by means of Monte Carlo simulations

Nuclear physics and particle therapy

The use of charged particles and nuclei in cancer therapy is one of the most successful cases of application of nuclear physics to medicine. The physical advantages in terms of precision and selectivity, combined with the biological properties of densely ionizing radiation, make charged particle approach an elective choice in a number of cases. Hadron therapy is in continuous development and nuclear physicists can give important contributions to this discipline. In this work some of the relevant aspects in nuclear physics will be reviewed, summarizing the most important directions of research and development