An Etymological Dictionary of Astronomy and Astrophysics

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فرهنگ ریشه‌شناختی اخترشناسی-اخترفیزیک

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half-value layer (HVL)
  لایه‌ی ِ نیم-تنکش  
lâye-ye nim-tonokeš
Fr.: couche de demi-atténuation  

The thickness of material required to reduce the intensity of an → X-ray beam to one half of its initial value. The HVL is an indirect measure of the photon energies of a beam.

See also: → half; → value; → layer; → attenuation.