## 2 Synthetic Diagnostics and Simulation Data  
The data used for generation of the synthetic diagnostic signals was taken from Ref. [6] and obtained by SolEdge3X-HDG simulation. The model is based on the Braginskii conservative equations for density, parallel momentum, total energy for singly charged ions, and electrons for the entire plasma volume. Neutral dynamics by simple diffusion model as well as Ohmic heating are also considered in the code. The latter one is calculated based on the current profile, obtained from the experimental data. Here, we will briefly describe only the simulation parameters. For a more detailed description of the code, the reader can refer to [5; 6]. The WEST discharge #54487 was chosen for simulation of the diagnostics in this paper and the results are taken from [6]. There are 403 different time steps with an interval of \(dt\) = 0.02 s. Perpendicular diffusion coefficients \(D,\ \mu,\ \chi_{i},\ \chi_{e}\) (for particle, momentum and ion and electron energy transport, respectively, across the magnetic field) are constant and equal to 0.5 m\({}^{2}\)s\({}^{-1}\). Parallel diffusion coefficients for ion and electron energy transport along the magnetic field lines are equal to \(k_{\parallel,i}\) = 60 [Wm\({}^{-1}\)V\({}^{-7/2}\)], \(k_{\parallel,e}\) = 2000 [Wm\({}^{-1}\)V\({}^{-7/2}\)]. The neutrals diffusion coefficient \(D_{n_{n}}\) is set to 2000 m\({}^{2}\)s\({}^{-1}\). The values of the transport coefficients were adjusted in a way to achieve the best possible match between line-integrated density in simulation with the interferometer data. Neutral sources are defined by pumping rates and recycling. The former was obtained from the WEST experimental database. The Eirene code was not used in this simulation in contrast to [1]. The recycling coefficient \(R\) is equal to 0.998. The mesh used in the SolEdge3X-HDG as well as in Cherab is shown in Figure 1.  
In addition, tungsten erosion was calculated with the Monte Carlo code ERO2.0 [20; 21] with a SolEdge3X-HDG output as a plasma background. The latter one provides spatial distribution of \(n_{e}\) (equal to the ion density), \(T_{e}\), the main ion temperature \(T_{i}\), the main ion parallel velocity \(v_{\parallel}\) and the magnetic field \(\mathbf{B}\). ERO2.0 is a 3D code; however, the discussed simulation was 2D, and therefore the wall geometry was just an axial extrusion of 2D poloidal section used in SolEdge3X-HDG. Such an assumption leads to the antenna-limiter being axysimmetric rather than a set of toroidally distributed antennae, as in the experiment. As was discussed in [22; 23], this implies a slight shift of the antenna off the plasma. Therefore, the erosion of tungsten is less compared with using the real 3D geometry of these PFCs [23]. This might be one of the reasons of bolometer signal  
Figure 1: SolEdge3X-HDG simulation mesh and lines of sight (LOSs) of bolometer system of the WEST tokamak, which is located in the horizontal diagnostics port. descrepancy, as will be discussed in Section 3.3. Oxygen is used as a proxy for light impurities in the ERO2.0 simulation, which are the main source for the tungsten sputtering. Its concentration was set to be constant at 3% over the plasma domain with fractional abundances, corresponding to [24] at the targets (\(n_{O^{+}}:n_{O^{2+}}:n_{O^{3+}}:n_{O^{4+}}:n_{O^{3+}}:n_{O^{6+}}:n_{O^{9+}}:n_{O ^{9+}}:n_{O^{9+}}:n_{O^{8+}}=0.40.15\):0.15\(:\)0.07\(:\)0.1\(:\)0.015\(:\)0.015\(:\)0.015\()\). The more precise ERO2.0 model description can be found in [22; 23]. The output of the code provide us with a map of tungsten densities \(n_{W^{2+}}\), where Z corresponds to the charge of the ion (or 0 in case of the atom). Obtained from SolEdge3X-HDG maps of the \(n_{e}\), \(n_{D^{+}}\), \(n_{D^{0}}\), \(T_{e}\), \(T_{i}\) (equal for all of the neutrals and ions), and \(n_{W^{2+}}\) from ERO2.0, are used to reproduce plasma radiation by using Cherab and Raysect. A constant concentration of oxygen of 3% as in ERO2.0 simulation is used as a light impurity proxy.