infinite source thickness

https://doi.org/10.1351/goldbook.I03030
For a specified
radiation
, the minimum thickness of a flat preparation of a
radioactive
material where the
intensity
of the specified radiation at the surface does not increase when the thickness is increased by adding more of similar
radioactive
material.
Source:
PAC, 1982, 54, 1533. (Glossary of terms used in nuclear analytical chemistry (Provisional)) on page 1544 [Terms] [Paper]