Experience on Fibre Optics Current Sensor operation in the JET harsh environment for the synthetic diagnostic validation

Fibre Optics Current Sensor (FOCS) will be installed in ITER to perform current measurements during steady state burning plasma operation. The ITER environment is extremely harsh and potentially can compromise the FOCS performance. The experience of using FOCS at such conditions is practically non-existing. In order to close this gap the Fibre Optics Current Sensor synthetic diagnostics (FOCS SD) is being developed. FOCS SD is a software that uses as the input a simulated ITER environment and information on the FOCS diagnostic system structure to mimic the output of the real diagnostic hardware. Operation of the FOCS SD needs to be validated. This task is performed by using experimental data obtained at the biggest European tokamak, the Joint European Torus (JET). JET offers a unique possibility to have an environment, which can be compared to ITER. In addition, the FOCS system already installed on JET allows to compare simulated and real measurements. The results of the comparison can be considered as a validation of the FOCS SD.