Radiation transport analyses for design optimisation of the ITER core lidar diagnostic

Systematic analysis of the radiation fields throughout the ITER core LIDAR diagnostic system were performed to support the design optimisation and assessment process, aiming at achieving the required performance in terms of reliability, occupational safety and interface with neighboring systems. Neutron, photon, nuclear heat and material activation responses were estimated for a variety of configurations, and improved using a combination of analytical "rules of thumb" and numerical computations with the ATTILA™ and FISPACT codes. The neutron flux at the backplate of the port plug was significantly reduced (to ∼2×10⁷ n/cm²-s) by fine-tuning the reference geometry of the laser labyrinth, and guidelines were provided for quick estimation of the effect of future design changes. The current design has adequate lifetime of essential optical components, in particular absorption in collection windows below ∼1%, and reduced dose to workers during maintenance according to the ALARA principle.