Helium sensitivity in oxygen deficiency measurement equipment

Most accelerators in operation today use liquid helium based superconducting technology in some capacity. Many of these facilities also use fixed and portable oxygen monitors to detect an oxygen deficient atmosphere were the helium to be accidentally released. When released, helium can expand 800 times its liquid volume. Recent helium spill tests at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) uncovered a fundamental flaw in certain types of oxygen deficiency monitoring equipment. The ensuing investigation found that the problem is endemic to a class of electrochemical oxygen sensors used throughout both the research and industrial communities. This paper describes the results of the Jefferson Lab investigation and steps taken to date to both solve the problem and inform the safety community at large.