ESTRO PT 2018

Energy loss of charged particles

Bethe formula: The average energy loss increases quadratically with the inverse velocity (1/v 2 ) and the charge of the particle (Z 2 )!

R=16cm H2O

Protons Carbon

Energy (MeV/u)

150

300

Velocity (v/c)

0,26

0,43

Charge (Z)

1

6

Energy loss (Mev/cm)

5,5

128,1

Hans Bethe 1930

The energy loss of a carbon ion is much higher than for protons. Where does this energy go? Very many low energy electrons are produced!

Oliver Jäkel

Medical Physics

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