Mosfit dosimeters in mixed gamma-neutron and mega voltage x-ray fields : the role of device encapsulation

Radiation sensitive metal oxide semiconductor field effect transistors (MOSFET) can be used as absorbed dose dosimeters for space craft and for use in accident gamma and proton dosimetry, in mixed gamma-neutron fields for separate gamma dose measurements as well as in radiation oncology. Most of the clinical applications have dealt with in vivo dose measurement in electron equilibrium conditions for megavoltage X-ray or Co-60 fields. Our purposes here are: (1) to investigate the application of the MOSFET for dosimetry of the gamma component in mixed gamma-neutron fields of reactor beams with large thermal and epithermal neutron components (109 n/cm2), as is typical during boron-neutron capture therapy (BNCT). (2) to investigate the absorbed dose enhancement (ADE) in the application of the MOSFET to skin dose measurements and buildup measurement in regions of strong electron dis-equilibrium behind the surface of solid water phantoms irradiated by 6MeV X-ray from a medical linear accelerator. Poster 196. (author)