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Language:enStatus: Standard
Term: ambient dose equivalent
Symbol: H*(d)
Definition: dose equivalent at a point in a radiation field, produced by the corresponding aligned and expanded field, in the ICRU sphere at a depth d, on the radius opposing the direction of the aligned field

Note 1 to entry: In defining these quantities, it is useful to stipulate certain radiation fields that are derived from the actual radiation field. The terms "expanded" and "aligned" are used to characterise these derived radiation fields. In the expanded field, the fluence and its angular and energy distribution have the same values throughout the volume of interest as in the actual field at the point of reference. In the aligned and expanded field, the fluence and its energy distribution are the same as in the expanded field but the fluence is unidirectional.

Note 2 to entry: The ICRU sphere is a 30 cm diameter, tissue-equivalent sphere with a volumic mass of 1 g/cm3 and a mass composition of tissue equivalent material (see 393-14-78).

Note 3 to entry: The recommended depth d, for environmental monitoring in terms of H*(d) is 10 mm, and H*(d) may then be written as H*(10).

Note 4 to entry: An instrument that has an isotropic response and is calibrated in terms of H*(d) will measure H*(d) in any radiation fields that are uniform over the dimensions of the instrument.

Note 5 to entry: The definition of H*(d) requires the design of the instrument to take account of backscatter.

Note 6 to entry: This entry was numbered 393-14-95 in IEC 60050-393:2003.

Publication date:2014-03
Source: ICRU Report 39
Internal notes:
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