Analyses and structural integrity estimation of the ITER divertor Thomson scattering system

This article reports the results of the assessment performed on the ITER Divertor Thomson Scattering (DTS). It is designed to provide an instrument capable of measuring the electron temperature and the related density profiles in the outer divertor plasma, relying on Thomson scattering method. The DTS main components are front rack, back rack, neutron shielding and diagnostic mirrors. Current DTS design has been modified compared to the one described in the previous article dedicated to this object. The most significant changes are: Upper neutron shielding has been removed. It is now not connected directly with the DTS system. It helped to reduce total weight of the construction; Dielectric insertions were added in order to reduce influence of the ponderomotive forces on construction strength; DTS supports were redesigned. Connections of the DTS with radial rails on which the construction is mounted on the sides were explored. Corresponding contact problem was solved and the structure integrity in this area was assessed. Mirrors made of SiC material are the DTS diagnostic elements. They are installed into front and back diagnostic racks. Other elements of the DTS are made of 316L(N)-IG steel. The contact pads on the radial rails are made of 660 steel. The whole Divertor Thomson Scattering system has to withstand all the loads (thermal, mechanical, electromagnetic and seismic) acting on the in-vessel region in which it is located without compromising its integrity. Its design layout is being modified and optimized according to the outcome of the structural assessment. Every step of the design update brings the construction closer to satisfying all of the criterions of structural integrity. This paper describes some important steps that really help moving forward to the DTS implementation.