Explain the main differences between plane parallel chambers and thimble ionization chambers.
Give an example of when you would use each.
DRR
The parallel plate chamber is one in which voltage is applied to two thin, closely separated parallel plates that collect ions. The measurement positon is defined as just inside of the front electrode. (ref Berman). We call this the "pancake chamber" in our clinic and it is typically used for monthly output. The chamber is recommended for measurement of electron beams with E<10 MeV. (So we should research why do we use this for higher energies on the Varian?)
The thimble ionization chamber is a coaxial chamber with one electrode that forms a thimble shaped shell around the collecting volume and the oterh electrode is a narrow central rod. In our clinic we commonly call this the "Farmer" chamber. It can be used to measure higher energy radiation beams. (Research again the reasoning why we use such a chamber for our annual)
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