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photon-electron junctions
- strong dependence electron
beam penumbra on depth
0
20
40
60
80
100
-30 -20 -10 0 10 20 30 40 50
photons 1
photons 2
photons 3
electrons 1
electrons 2
electrons 3
SSD=
100
cm
electrons: applicator-skin=
5
cm
6 MV 10 MeV
0
20
40
60
80
100
-30 -20 -10 0 10 20 30 40 50
photons 1
photons 2
photons 3
electrons 1
electrons 2
electrons 3
SSD=
110
cm
electrons: applicator-skin=
15
cm
6 MV 10 MeV
- reduced dependence electron
beam penumbra on depth
- electron beam penumbra
more shallow
SSD=110 cm for electrons makes the problem of matching
electron and photon beams depth independent