| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 1999: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1998: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
Stopping powers of Ti, Fe, Ni, Cu and Zn were measured for median- and high-velocity protons. The uncertainty of the present results were ±0.4%. In high-velocity regime stopping powers were theoretically described by the Bethe-Bloch formula which could reproduce experimental values very well (within 1% accuracy). It is necessary to use rather thick foils in order to know their accurate thickness, which are essential to obtain accurate stopping power data. For a thick target incident protons may lose more than 50% of their initial energy within a target foil. Under such a condition the actual path length of protons becomes slightly longer than the target thickness. When we wish to measure very accurate stopping powers of elements, we can not neglect such an effect.
To estimate actual path length corrections we need the knowledge on the angular distributions due to multiple scattering. Therefore, we measured angular distributions due to multiple scattering for 26 kinds of target thickness
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and incident energy combinations. Comparing measured results with theoretical predictions, we found that an excellent agreement was obtained for both Moliere theory and the theory of Sigmund and Winterbon. With these theories we can obtain a reliable estimation of the correction.
The present stopping powers were compared with compilation values of ICRU Report 49 and of Andersen and Ziegler. In general, the present results were found to be slightly smaller than compilation values. In case of Fe, however, the present results were smaller by 〜10% than those ICRU Report 49 at around 0.2 MeV. Mean excitation energies of Ti, Fe, Ni, Cu and Zn were extracted from the present stopping powers. The I-values are 236.7 eV, 287.9 eV, 313.6 eV, 319.8 eV and 326.8 eV for Ti, Fe, Ni, Cu and Zn, respectively. These I-values are compared with those obtained by other authors.
The Bethe-Bloch formula is generally used for description of stopping powers for protons above 1.0 MeV. In the present study it is found that the formula can be used for protons above 〜0.7 MeV or possibly above 0.5 MeV. Less
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