Mikio Kobayakawa

Proton Channeling in Fluorite-Type Single Crystals

In order to study the proton channeling process in the single crystals of CaF 2 and BaF 2 the half-angles and minimum yields for axes and planes were measured by means of Rutherford backscattering in the energy range 0.60-1.20 MeV and of gamma rays from the 873 keV resonance in the 19 F(p,αγ) 16 O reaction. The parameter dependence of the half-angles observed for the axes ( , , and ) is dependent on the target crystals, and that for the planes ({110} and {112}) depends on the Miller index of planes. if the effects of thermal vibration and planar spacing are taken into account on the basis of Barretts calculations, the parameter dependence and magnitudes of the measured half-angles show reasonable agreement with the calculations. The minimum yields for the mixed and monatomic rows along the axes agree reasonably with the predicted values; however, the minimum yields for the planes are considerably larger than those predicted.

Evaluation of minimum yields for planar channeling in CaF2 and BaF2

Abstract Minimum yields for planar channeling in CaF 2 and BaF 2 have been calculated using an average potential model. The use of the Lentz-Jensen ionic potential gives results consistent with the experimental data. The validity of the model and the dependence of the minimum yields on the potential are discussed.

Planar Channeling of 0.9 MeV Protons in Fluorite-Type Crystals

By means of 873 keV protons and of the 873 keV gamma resonance in the 19 F(p, αγ) 16 O reaction, channeling parameters of half-angles and minimum yields have been measured for the mixed [{100}, {112}, and {113}] and separate [{100} and {111}] planar directions of CaF 2 and BaF 2 . The experimental results for the half-angle agree with the estimation from the Gemmell model for the polyatomic case, except for the {111} anion plane of BaF 2 . The experimental minimum yields are considerably larger than the predicted values. The angular dependence of gamma rays for the {111} direction of BaF 2 has double yield peaks around the aligned direction; this is fairly different from he gamma-ray angular dependences for the other directions.