Physics Bucharest 2017

photon-electron junctions

SSD= 100 cm electrons: applicator-skin= 5 cm 6 MV 10 MeV

SSD= 110 cm electrons: applicator-skin= 15 cm 6 MV 10 MeV

photons 1 photons 2 photons 3 electrons 1 electrons 2 electrons 3

photons 1 photons 2 photons 3 electrons 1 electrons 2 electrons 3

100

100

80 SSD=110 cm for electrons makes the problem of matching electron and photon beams depth independent 80

60

60

40

40

20

20

0

0

-30 -20 -10 0 10 20 30 40 50

-30 -20 -10 0 10 20 30 40 50

- reduced dependence electron beam penumbra on depth - electron beam penumbra more shallow

- strong dependence electron beam penumbra on depth