Range (English spelling)

Japanese: 飛程 - ひてい（英語表記）range

The distance a charged particle travels after entering a material before stopping. In general, the greater the particle's energy and the lighter the material, the longer the range. Charged particles other than electrons and positrons travel in an almost straight line, and their range is almost the same if the type of particle, energy, and material they pass through are the same. For electrons, the trajectory curves and there is a possibility of bremsstrahlung, so the range in the above sense cannot be determined. The practical range is the thickness of the absorption layer at which the number of electrons becomes zero when an absorption curve showing how the number of incident electrons decreases with the thickness of the material layer is measured and the steepest point of the slope is extrapolated with a straight line. The practical range is also defined in the same way for particles with a continuous energy spectrum, such as beta-ray electrons.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

荷電粒子が物質に入射して止るまでに走る距離。一般に粒子のエネルギーが大きいほど，また軽い物質中ほど飛程は長い。電子，陽電子以外の荷電粒子はほぼ直進し，粒子の種類，エネルギー，通過する物質の種類が同じなら飛程はほぼ同じである。電子では飛跡は曲り，また制動放射の起る可能性もあるので，前述の意味での飛程は定まらない。入射した電子数が物質層の厚さに伴って減少する様子を示す吸収曲線を測定し，その傾斜の最も急なところを直線で外挿して求めた電子数がゼロになる吸収層の厚さを実用飛程と呼ぶ。実用飛程は，β線の電子のようにエネルギーの連続スペクトルをもつ場合にも同様に定義される。

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