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IUPAC - half thickness (H02721)

half thickness

in radiochemistry
https://doi.org/10.1351/goldbook.H02721
The thickness of a specified substance which, when introduced into the path of a given beam of radiation, reduces the value of a specified radiation quantity by one half.
Source:
PAC, 1994, 66, 2513. (Nomenclature for radioanalytical chemistry (IUPAC Recommendations 1994)) on page 2520 [Terms] [Paper]