## 1 Introduction
One of the widest family of the tokamak diagnostics are the ones dealing with plasma radiation. The Cherab [8] Python library, which is based on the Raysect [9] ray-tracing framework, was designed specifically to describe plasma radiation diagnostic systems. Ray-sect is a 3D spectral geometric ray tracer, which does not cover dispersion and dissipative effects. It has a collection of observers and, so-called primitives ranging from simple geometric shapes to detailed meshes for sophisticated computer-aided design (CAD) models. The user can specify surface and volume properties of the primitives such as bidirectional reflectance distribution function (BRDF) or anisotropic volumetric radiation. With the help of the Cherab library, various plasma parameters, such as magnetic configuration or particle distributions can be associated with the primitives. The more detailed description of the libraries with the underlying equations can be found in [8]. All in all, the Cherab-Raysect framework allows us to comprehensively describe both plasma radiation and optical properties of PFCs in the common fashion for different diagnostics. Here are only a few of its applications: bolometry on JET [10], charge exchange recombination spectroscopy (CXRS) diagnostics on COMPASS upgrade [11], and design of H\({}_{\alpha}\) emission diagnostics on ITER [12]. Moreover, SolEdge3X-HDG has the potential to cover the 3D plasma domain as well as the details of the tokamak PFCs. Even though toroidal symmetry is usually supposed, localised tokamak elements will cause the simulated plasma parameters to vary not only in poloidal cross-section, but also with toroidal angle, as in the real devices. Moreover,visible diagnostics are influenced by reflections on the vessel elements. Hence, employing a 3D ray-tracing tool will lead to a more realistic description for the synthetic diagnostics. The development of synthetic diagnostics using Cherab-Raysect framework is now ongoing for the WEST tokamak and is improving both the measurement quality and its interpretation. For example, bolometer cameras are used for radiated power measurement. On the one hand, this diagnostic can be used to evaluate the power radiated by heavy impurities in the core, which is not favorable for fusion reaction. On the other hand, it can be used to control the particle heat flux on the divertor plates by following the light impurity injection. Although the bolometry system is well-designed and operational on the WEST tokamak [13], the synthetic diagnostic code SYNDI [13] currently used to predict bolometry signals is not able to handle non-axysimmetric geometries of PFCs and the tokamak vessel. Moreover, because bidirectional BRDF is still under investigation for the WEST PFCs [14], one can use the Cherab library to adjust optical properties in the model by using a similar approach to that used in [8] and investigating the influence of different materials on the signals. Another form of diagnostics which are still not widely used on the WEST tokamak are visible cameras, which are now operated for observation purposes. This instrument could be a powerful tool for numerous tasks such as plasma boundary or last-closed flux surface (LCFS) detection [15; 16], attention-needed area detection and localization (which also can employ neural networks) [17; 18], or even for tomographic inversion of detected radiation [19] and calculation of the sources of particles from these. However, visible cameras are struggling with the poor description of the reflection properties of the PFCs [8], which can lead to misinterpreting of the experimental images. Cherab and Raysect allow us to deal with this issue, introducing flexible ways to describe optical properties of the surfaces and to implement visible cameras' technical characteristics. Together with simulation in SolEdge3X-HDG, this can lead us to the design of novel, more comprehensive ways to exploit such diagnostics on the WEST tokamak.