Stopping Power

Discuss the difference between Stopping Power and Restricted Stopping Power.

Podgorsak pg 25.

The stopping power focuses on the energy loss by an electron moving
through a medium. When attention is focused on the absorbing medium,
one is interested in the linear rate of energy absorption by the absorbing
medium as the electron traverses the medium. The rate of energy
absorption, called the linear energy transfer (LET), is defined as the
average energy locally imparted to the absorbing medium by an electron
of specified energy in traversing a given distance in the medium.
● In radiation dosimetry the concept of restricted stopping power (SD/r) is
introduced, which accounts for that fraction of the collisional stopping
power (S/r)col that includes all the soft collisions plus those hard collisions
that result in delta rays with energies less than a cut-off value D. In
radiation dosimetry this cut-off energy is usually taken as 10 keV, an
energy that allows an electron just to traverse an ionization chamber gap
of 1 mm in air. Delta rays are defined as electrons that acquire sufficiently
high kinetic energies through hard collisions so as to enable them to carry
this energy a significant distance away from the track of the primary
particle and produce their own ionizations of absorber atoms.