Divertor simulator

This complicated situation is fundamentally different from small linear plasma devices, in which the MAR chain has been seen to lead to enhanced plasma recombination In a tokamak divertor, distinct from these divertor-simulation experiments, the molecular pressure is not an externally controlled parameter but must be established by the recycling plasma itself. Detailed and consistent modeling, verified by dedicated spectroscopy, shows that processes that lead to a reduction of the molecular density (such as MAR and MAD), therefore, can have entirely different effects on plasma dynamics in real divertors and in divertor simulators. 

Fig. 1.9. ERO code simulation of carbon and beryllium erosion and transport inside the divertor of JET showing the multi-step transport of C in contrast to the one step erosion-deposition of Be...

Fig. 5.4. Spectral profiles of Da line [12]. (a) 8cm and (b) 0.5 cm away from the outer divertor plates. The viewing chords are shown in the upper figure. The thick and thin lines indicate the observed and simulated profiles, respectively. Compositions for the simulated 7r-component line are also shown. The kinetic energy of the D atoms corresponding to the wavelength shift is indicated above figure (a). The electron temperature and density were, respectively, 90 eV and 0.5 x 1019m 3 at the outer separatrix strike point. The toroidal magnetic field at the outer separatrix strike point was 4.15 T...

In the above simulation, only production of CD4 molecules at the divertor plates is considered, although higher hydrocarbon molecules such as C2D are also produced by chemical sputtering at the actual divertor plates, and they can also contribute to the CD band emission [17]. The reason for the discrepancy between the observed CD band intensity and the simulated one might be that only CD4 production is considered in the simulation. Reliable data for all relevant hydrocarbon molecules are required for more accurate simulations. 

CH4, cd4) + (°) Bands of radicals (CH, CH2,...) near carbon walls, limiters and divertors excitation rates for the visible exist and have been measured in plasma simulators and tokamaks... 

CH,CD + + Bands been measured in plasma simulators at limiters divertors further check of break-up chain advisable include new data origin molecule of CH ne-dependence ... 

Simulating erosion and re-deposition processes in fusion devices lead to a better understanding of the processes involved. The 3-dimensional Monte-Carlo code ERO-TEXTOR [35,36] has been developed to model the plasma-wall interaction and the transport of eroded particles in the vicinity of test limiters exposed to the edge plasma of TEXTOR. Important problems concerning the lifetime of various wall materials (high Z vs. low Z) under different plasma conditions and the transport of eroded impurities into the main plasma can be treated with the ERO-TEXTOR code. Recently, the divertor geometries have been implemented to carry out simulations for JET, ASDEX and ITER [37], In addition, first attempts have been made to simulate erosion and re-deposition processes in the linear plasma device PISCES to analyze the effect of beryllium. 

---