Radiation-hard non-contact fluid sensor for radionuclide production applications

It is often necessary to be able to detect the presence or absence of fluids in tubing located in high γ-ray or neutron flux areas. Non-contact methods are essential when direct electrode contact with the fluid has the potential for generating impurities. Optical sensing utilizing a light source and a photodetector is probably the most prevalent method used for non-contact fluid measurement. However, this method is not always suitable for use in high radiation flux area because the phototransistor or photodiode used for light detection can be susceptible to radiation damage. The sensor described here detects changes in capacitance between two electrodes located on the outside of a length of non-conductive tubing. This sensor can be used for remote indication of target filling operations, as well as for fluid sensing in automated radiopharmaceutical synthesis systems.