FTh4E.6.pdf
Frontiers in Optics/Laser Science 2015 © OSA 2015
Fiber optic radiation sensor systems for particle accelerators Jochen Kuhnhenn Fraunhofer INT, Appelsgarten 2, 53879 Euskirchen, Germany
[email protected]
Abstract: Sensing radiation with optical fibers has become a valuable tool especially at accelerators over the last decade. This presentation will present principles, constraints and options to detect radiation via different effects induced in optical fibers. OCIS codes: (060.2370); (060.2270)
1. Overview At high-energy physics accelerators the advantages of optical fiber sensors enable the measurement of a variety of parameters otherwise impossible due to multitude of specific constraints. For instance, at many locations around or inside of accelerators very well defined magnetic fields shall not be disturbed by active electrical sensors. Also areas of interest might not be accessible by conventional sensors due to space constraints of very narrow slits or extremely compact geometries. All these challenges can be met with fiber optic sensors due to their electromagnetic immunity and small dimension. Also typically accelerators are usually extended installations of up to 27 km in length in the case of the Large-Hadron-Collider (LHC) at CERN. Here distributed sensing is essential to cover the whole length of interest. Among the many parameters to be monitored at nuclear installations the level of radiation is of highest interest to protect equipment and personnel against harmful doses, to detect and correct malfunctions resulting in particle losses or for routine surveillance and optimization of operation. To detect ionizing radiation with optical fibers several effects can be utilized. The most common and obvious change induced in optical fibers by ionizing radiation is an increase of attenuation. This radiation-induced attenuation (RIA) depends on many parameters, such as the radiation properties, the fiber type and operation conditions. But radiation does not only reduce the transmission of light in optical fibers, it can also induce light in the fiber material by luminescence effects. Finally changes of the material properties resulting in a variation of the refractive index can be observed after irradiation.
