This should help, would be better if in your own words.
MOS transistor Ionizing radiation sensor - Google Search
If this College stuff, forgive me, If you are wanting to be an Engineer or Scientist or whatever, It would not help you to give you the answer, I barely made it through High School. I am a Fire/Burglar/Electrical Contractor/Automator/Integrator, also a Pilot and other things, I didn't Cheat(I'm not saying your cheating). I took all Training Serious as Many Lives as well as my own are at risk.
I do hope the above link will help. Good Luck