Properties of the Absorption Coefficient
*There is a sharp discontinuity in the dependence of the absorption coefficient on energy (wavelength) at the energy corresponding to the energy required to eject an inner-shell electron.
*The discontinuity is known as an absorption edge.
*Away from an absorption edge, each “branch” of the absorption curve is given by:
? /?=k ?3 Z3
k : a constant. Z :atomic number of absorber.
Filters
When the energy of a photon beam is just above the excitation potential or absorption edge of a material, that material strongly absorbs the given photon beam. If another substance can be found that has an absorption edge between the K? and K? lines of the incident photon beam, this other substance can be used to significantly reduce the intensity of the K? line relative to the K? line. The absorption edges of elements with Z Filter = ZTarget - 1 (or - 2) meet this requirement. The thickness of the filtering material is usually chosen to reduce the intensity of the K? line by a factor of 100 while reducing the intensity of the K? line by a factor of 10 or less .the propose from filter to absorb the K? component much more strongly than K? component ,because of the abrupt change in its absorption coefficient between two wavelengths .
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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