View source for Fluence

{{SI}}


==Overview==
In [[physics]], '''fluence''' is defined as the number of particles that intersect a unit area . Its units are m<sup>-2</sup>. In particular, it is used to describe the strength of a radiation field.  It is considered one of the fundamental units in [[dosimetry]].  

It has two equivalent definitions:

1) Imagine that an infinitesimal sphere of cross sectional area d''a'' is impinged upon by d''N'' particles of a certain type.  Then, the fluence is:

<math>\Phi =  \frac{{\rm d} N}{{\rm d} a}</math>.

2) Using the same image of a small sphere as above:

<math>\Phi =  \frac{\sum {\rm d \ell} }{{\rm d} V}</math>,

where <math>{\rm d} V </math> is the infintesimal volume and <math>\sum {\rm d \ell}</math> is the sum of all the path lengths of the particles that transverse the volume.


==References==
ICRU 33: Radiation Quantities and Units, April, 1980. (www.icru.org)

[[Category:Radiobiology]]
[[Category:Radiation oncology]]
[[Category:Nuclear physics]]
{{WH}}
{{WikiDoc Sources}}