Radiation shielding design evaluation for ITER VUV edge imaging spectrometer

Abstract The local radiation shielding design for the detector of ITER VUV edge imaging spectrometer is evaluated based on the MCNP calculation using a local port cell model of ITER upper port #18. A back-illuminated CCD (Charge-Coupled Device), the envisaged VUV (Vacuum Ultraviolet) detector for ITER VUV edge imaging spectrometer will be installed at ITER upper port #18 port cell region, in which a harsh radiation environment is expected with neutron flux higher than 10 5  neutrons cm −2  s −1 mainly thermalized from d-t neutrons in plasma as well as high gamma ray dose of several tens kGy mainly from 16 N isotopes in water coolant. For the evaluation of the radiation exposure to the detector, the local port cell model is developed to reduce both the calculation time and statistical error. The boundary neutron source based on MCNP result using C-lite model as well as gamma source based on ITER radiation map has been utilized for the analysis of local port cell model. Since the radiation exposure to the back-illuminated CCD should be mitigated as much as possible to minimize the radiation damage to the detector as well as single event upset, local shielding design options for the VUV detector with various shapes, thicknesses, and material compositions are evaluated. The result shows that the neutron flux and gamma dose at the location of VUV detector can be mitigated below 100 n cm −2  s −1 and 10 Gy, respectively, which are the alert thresholds for non-critical electronics in ITER.