## 3 Results
### Confrontation between Simulated and Experimental Bolometer Signals  
To compare with the experiment, four stages of the discharge were chosen, first corresponding to the limiter phase and the other three to the divertor phase: ramp-up, flat-top, and ramp-down. These correspond to times of \(t=0.26\), \(1\), \(4.48\), and \(7.52\) s. The experimental channel #9 was affected by some calibration issues, so it is omitted from the plots. We demonstrate individual contributions from deuterium and tungsten, as well as from proxy oxygen to assess the sensitivity of the Cherab framework to the different sources of radiation. The comparison of the simulated and experimental results is demonstrated in Figure 6.  
We can see a good agreement of deuterium and tungsten contributions with experimental signals for the limiter phase of the discharge. During this stage, sputtering occurs  
Figure 5: Influence of the different optical description of the WEST PFCs on the bolometer signals for absorbing, lambertian, rough tungsten, and specular tungsten surface models for limiter (**a**) and divertor (**b**) phases. Figure 6: Comparison between bolometer experimental and simulated signals for \(t=0.26\) (**a**) (limiter phase), \(1\) (**b**), \(4.48\) (**c**), and \(7.52\) s (**d**) (divertor phase). Contributions from deuterium (orange), tungsten (magenta), and oxygen (blue) are shown on the simulated signal. from the HFS limiters, which can be seen in Figure 3. However, there is a signal spike for the channels from 12 to 14 (Figure 6a), which is caused by a tungsten radiation contribution. According to Figure 3m, tungsten is accumulated near the separatrix at the upper part of the plasma. This is a rather numerical artifact, which probably originates from the fact that SolEdge3X-HDG is not field-aligned. Therefore, when passing output data to the ERO2.0 input format, calculated parallel temperature gradients might be too high. This leads to higher thermal forces tending to extra tungsten accumulation. Despite the fact that this effect is a theoretically predicted effect [28], it should be less pronounced. This numerical error will be eliminated improving the compatibility of SolEdge3X-HDG and ERO2.0 codes. The total synthetic signals, including oxygen contribution, is of the same order as the experimental signal for \(t=1\) s. However, we obtain a huge overestimation of oxygen radiation at the later phases of the discharge. This is due to the fact that our simplified model of constant oxygen concentration is not good enough to describe experiment. Moreover, oxygen concentration might be changing in time during the discharge. To have a good comparison with the experiment for each time moment a scan over different oxygen concentrations both for ERO2.0, as well as for Cherab, should be made. However, it was not the goal of this paper. At the \(t=1\) and 4.48 s, there might also be a tungsten erosion underestimation; at these stages, LFS limiters are supposed to be under high particle flux, but, as was mentioned before, in current ERO2.0 simulation these PFCs were moved slightly away from the plasma. In addition, according to the experimental data at \(t=4.48\) s, the LFS limiter was close to the separatrix, which is not taken into account. This may cause an increase of radiation in the experiment, which is not covered by simulations. There is one more possible reason of discrepancy, the diffusion coefficients are taken constant, which is a simplification. The resulting electron and ion profiles from SolEdge3X-HDG simulation also affect ERO2.0 calculations. It is well known that due to neoclassical effects, impurities tend to peak in the core region [29]. These processes, as well as turbulence transport, should be taken into account in further versions of the SolEdge3X-HDG for more accurate simulations. Nonetheless, from such a comparison we can clearly see the sensitivity of Cherab simulations to the presence of different raditation sources.