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The stopping power of water for carbon ions in the Bragg peak area

23.12.2020

Figure 1: Results of this work compared to other semi-empirical and theoretical values.

Because carbon ions can achieve high selectivity for dose distribution, their use in radiation therapy has been increasing. Within the scope of the BA5371‑3‑1 DFG project, the stopping powers of water have been determined experimentally for carbon ions with energies in the Bragg peak area. These data are important for determining the biologically effective range of 12C therapy beams at the distal end.

Figure 1 shows the results of the project compared to other semi‑empirical and theoretical data. The data above 6 MeV are values that were extrapolated using the semi‑empirical approach of Paul and Schinner [1]. For the energies above the maximum of the stopping power, the results obtained are in good agreement with the data newly recommended by ICRU [2] within the experimental uncertainties. Below the maximum, the values given in the Errata and Addenda of the ICRU Report No. 73 [3] agree with the results obtained in this work. It is striking that the values predicted by the SRIM 2013 code [4] are much higher than those of other codes and of this experiment for kinetic energies above 3 MeV.

Figure 1 shows that the results of this work, the data newly recommended by ICRU [2], and the values computed by means of the CASP code [5] converge at high energies. Since both the value calculated using the CASP code and the new ICRU data are based on an I value of 78 eV for water, the present measurement confirms this I value.

 

References

[01]    H. Paul and A. Schinner, Nucl. Instr. and Methods Phys. Res. B 195, 166 (2002).

[02]    ICRU Report 90, International Commission on Radiation Units and Measurements, J. ICRU 14, No. 1, (Oxford Univ. Press, 2014).

[03]    P. Sigmund, A. Schinner, and H. Paul, Errata and Addenda for ICRU Report 73 (2009).

[04]    J. F. Ziegler, M. D. Ziegler, and J. P.  Biersack, Nucl. Instrum. Methods Phys. Res. B 268, 1818 (2010).

[05]    G. Schiwietz and P. L. Grande, Phys. Rev. A 84, 052703 (2011).

 

Contact

Opens local program for sending emailW. Y. Baek, Department 6.3, Working Group 6.36