Optimizations of CFETR steady state H-mode scenario with localized reversed shear enhanced internal transport barrier

Abstract

Both a fully noninductive steady state operation scenario and a hybrid scenario with fusion power ∼ 1 GW and fusion gain >10 are being considered to fulfill the mission of a Chinese fusion engineering testing reactor. Compared to the hybrid scenario, plasma current is generally lower in steady state operation, so that better confinement and stabilization of MHD instability introduced by higher normalized beta (possibly beyond the ideal MHD limit without a wall) are required to achieve the same fusion performance. Integrated modeling is used to find candidate scenarios to match both these requirements at the same time. By creating a localized strong reversed magnetic shear using radio frequency wave driven current, a strong off-axis internal transport barrier is formed, so that the target fusion power and fusion gain are achieved for Chinese fusion engineering testing reactor steady state operation. Further optimizing the location of the reversed magnetic shear by modifying radio frequency wave launch parameters can keep the normalized beta below the ideal MHD no-wall limit while the fusion power remains beyond 1 GW. Based on this finding, several combinations of heating and current drives are proposed with fusion gain close to 12.5.

Numerical study of alpha particle loss with toroidal field ripple based on CFETR steady-state scenario

“…The parameters and profiles used in our alpha particle loss simulations are based on the CFETR steady-state scenario. [28] The first wall used in our simulations is from the equilibrium data of the CFETR steady-state scenario. Some parameters in the CFETR steady-state scenario are as follows.…”

“…The safety factors at the magnetic axis and 95% of the poloidal magnetic flux are q ss 0 = 3.9 and q ss 95 = 7.3, respectively. The profiles of density and temperature of electron and deuterium in the CFETR steady-state scenario, which were obtained by integrated modeling, [28] is shown in Fig. 3.…”

“…The GYCAVA code as well as the NBI code TGCO [25] have been used for studying effects of the resonant magnetic perturbations [26] and the toroidal field ripple [27] on NBI ion losses in the EAST tokamak. In our previous work, the GYCAVA code has been used to numerically study alpha particle losses with the toroidal field ripple in the CFETR steady-state [28] and hybrid [29] scenarios for different loss boundaries. [13] The numerical results show that the alpha particle loss fraction in the steady-state scenario is much larger than that in the hybrid scenario on CFETR for a large toroidal field ripple.…”

Discrete Alfvén eigenmodes in the CFETR steady-state scenario

“…Based on the ITER design, the reversed magnetic shear (RS) scenario of CFETR achieves better confinement by modifying radiofrequency wave launch parameters. [24] In the ITER scenario of Ref. [25], the αTAEs are trapped in the electron cyclotron (EC) power deposition region and other regions.…”

“…There are two typical scenarios of CFETR: the RS Hmode scenario with an enhanced internal transport barrier (ITB) [24] and the local negative shear at large minor radius (negative off-axis magnetic shear) scenario. [26] Both the fusion performance target (P fusion > 1000 MW, Q plasma > 10) and the avoidance of global ideal MHD instabilities can be reached simultaneously in the RS H-mode scenario with enhanced ITB for CFETR.…”