Physics and Engineering of Radiation Detection

666 Chapter 11. Dosimetry and Radiation Protection

follows.

HV L =

ln(2)

μ

=

ln(2)

1. 15

=0. 6 cm

TVL =

ln(10)

μ

=

ln(10)

1. 15

=1. 0 cm

A point to note here is that when very high energy photons pass through a ma-
terial, such as lead, they produce high energy electrons. These electrons quickly
loose their energy and as a result give rise to Bremsstrahlung radiation. This radia-
tion is also highly penetrating and therefore should be considered while estimating
the thickness of shielding material. Such computations are fairly complex and are
generally done by standard computer codes that simulate the passage of radiation
through matter. For safety reasons it is always a good practice to use shields much
thicker than required by simple calculations of exponential attenuation.