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Dose monitor chamber
30
Varian
Transmission ionization chamber that monitors and controls
delivered dose (MU), dose rate, beam symmetry and flatness.
The dosimetry system must contain
two independent channels.
Sealed or open compensated chambers
⇒
no dosimetric influence from
Utrecht 2016
ambient air pressure or temperature.
The E-field (bias voltage) should be
high (
∼
500 V/mm) in order to
minimize recombination/dose rate
dependence.
Commonly layered through thin and
strong foils with condensed Au or Cu.
Total thickness
∼
0.2 mm.
Elekta