First non-interceptive beam current measurement at the proton therapy facility PROSCAN
At PSI’s proton therapy facility PROSCAN, researchers including OMA Fellow Sudharsan Srinivasan have successfully demonstrated for the first time non-interceptive beam current measurement in the range 0.1-10 nA over the energy range 238-70 MeV, using a dielectric-filled reentrant cavity resonator.
This newly developed cavity operates with a so-called TM010 mode, also referred to as monopole mode, and is a realization from the lumped element model shown below. Beamline measurements were performed and compared to a reference ionization chamber.
A good agreement between the measured resonator sensitivity with the expected trend of sensitivity as a function of energy was found as indicated in the plot below.
Measured resonator sensitivity Vs expected trend of resonator sensitivity as a function of beam energy. (Images credit: PSI)
Sudharsan commented: “Our measurements have underlined the excellent potential of this cavity resonator to replace ionization chambers for beam current measurements at proton therapy facilities.“
The PSI cavity resonator will now be tested as a tool for beam control optimization; it’s comparably long signal integration time make it a promising complementary measurements that provides deeper insight into the characteristics of the beam.
Further information:
S Srinivasan, P-A Duperrex, J M Schippers, “Beamline characterization of a dielectric-filled reentrant cavity resonator as beam current monitor for a medical cyclotron facility”, European Journal for Medical Physics (2020), https://doi.org/10.1016/j.ejmp.2020.09.006