Raman distributed temperature sensing at CERN

A field trial has been performed at the CERN high-energy accelerator-mixed (CHARM) field facility, newly developed for testing devices within accelerator representative radiation environments, to validate the use of Raman-based optical fiber sensors for distributed temperature measurements in highly radiative environments. Experimental results demonstrate that Raman distributed temperature sensors, operating in loop configuration on radiation-tolerant optical fibers, are able to compensate for wavelength-dependent losses and are, therefore, robust to harsh environments, in which a mixed-field radiation, including protons, neutrons, photons, and other particles, is potentially altering the fiber material properties. The temperature profile measured on commercial radiation-tolerant optical fibers shows that a temperature resolution <;1 °C, 0.5-m spatial resolution, is highly reliable and sets the first step toward a distributed measurement system able to monitor the temperature at the CERN's large hadron collider for safety purposes. Such a system will also be helpful in correcting the radiation-induced attenuation temperature dependence in distributed radiation sensing systems based on radiation-sensitive optical fibers.