Numerical analysis of thermoelectric instability in tokamak divertor

The thermoelectric instability in tokamak divertor has been studied numerically by using a five-point model. When the divertor plasma temperature T_div decreases below a critical temperature, this instability arises in a symmetric equilibrium of scrape-off layer (SOL) and divertor plasmas, and stable asymmetric equilibria are found. The SOL current causes spontaneously the divertor asymmetry at the onset of the thermoelectric instability. In an asymmetric equilibrium, the SOL current flows from the higher-T_div side to the lower-T_div side. The heat flux flowing into the divertor plate of the higher-T_div side becomes larger than that of the lower-T_div side. The heat flux asymmetry is larger for cases of high recycling and low heating power.