ESTRO PT 2018

Collisions with electrons

Stopping Power « S » = dE / dx

Mean Energy dE lost in electronic collisions while traversing a distance dx [ MeV / mm]

t

p+

F

e-

dx

2 e 4 (N

A Z ) { ln (2mv 2 / I (1- b 2 )) - b 2 - S (Ci/Z) } A m e v 2

(dE/dx)= 4 p z

eff

Small Energy  High Stopping Power