Online Total Ionisation Dosimeter (TID) monitoring using semiconductor based radiation sensors in the isis proton synchrotron

During routine operation, the radiation levels in the ISIS proton synchrotron become high enough to permanently affect systems and electronics. This can potentially cause critical components to fail unexpectedly or denature over time, causing disruption for users of the ISIS facility or a loss of accuracy on a number of systems. To study the long term effects of ionising radiation on ISIS systems and electronics, the total dose received by such components must be recorded. A semiconductor based online Total Ionisation Dosimeter (TID) was developed to do this, using pin diodes and Radiation sensing Field Effect Transistors (RadFETs) to measure the total ionisation dose. Measurements are made by feeding the TIDs with a constant current, with the threshold voltage on each device increasing in relation to the amount of radiation that it has received. This paper will look at preliminary offline results using off the shelf Field Effect Transistors (FETs) and diodes, before discussing the development of the RadFET online monitor and the results it has gathered thus far. Finally the paper will look at future applications and studies that this type of monitor will enable.