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Monitor feedback/Beam energy servo
33
Outer
hump
An increase in beam energy causes a rise
in the dose rate in the center of the field,
and vice versa.
The X-ray gun servo system of an Elekta
linac uses this property to detect energy
changes by using the two hump plates.
The difference between the two hump
plates is used to produce an error signal,
which gives a correction to the nominal
Lower
energy
Higher
energy
Utrecht 2016
Elekta Dosimetry
System
Inner
hump
level of gun current set by the operator.