Optimization of CFETR baseline performance by controlling rotation shear and pedestal collisionality through integrated modeling

Abstract

The optimization of a CFETR baseline scenario (Chan et al 2015 Nucl. Fusion 55 023017) with an electron cyclotron (EC) wave and neutral beam (NB) is performed using a multi-dimensional code suite. TGLF and NEO are used to calculate turbulent and neoclassical transport. The evaluation of sources and sinks, as well as the current evolution, are performed using ONETWO, and the equilibrium is updated using EFIT. The pedestal is consistent with the EPED model.Rotation shear is controlled using NB. It has been found that both fusion gain Q and NB power deposited in the edge increase with decreasing NB energy, with NB providing current drive, torque, energy and particle source simultaneously. By using an optimized combination of two NBs, Q can be kept at a high level while the NB edge power is reduced. Pedestal collisionality is controlled to find an optimization path for Q by trading off between the pedestal density and temperature with the pedestal pressure fixed. It has been found that Q increases with pedestal collisionality, while the density peaking factor (DPF) remains almost unchanged. The invariance of DPF can be explained by the change of the dominant type of turbulence from the core to the edge (i.e. trapped electron mode in the core and ion temperature gradient mode at the edge), and collisionality has the opposite effect on particle transport for these two modes. A weaker dependence of DPF on collisionality makes a higher density operation more favorable for fusion gain.

MHD analysis on the physical designs of CFETR and HFRC

“…To achieve the mission goal of fusion power production of 1GW , the self-consistent steady-state scenarios for CFETR with fully sustained non-inductive current drive and as well hybrid mode scenarios are developed using a multi-dimensional code suite with physics-based models as shown in [15,16]. The equilibrium profiles for the steady-state and hybrid scenarios presented in Figs.…”

Discrete Alfvén eigenmodes excited by energetic particles in China Fusion Engineering Test Reactor

“…其运行将分为两 个阶段: 第一阶段实现200 MW的聚变功率和氚自持 的稳态运行(装置的大半径R = 5.7 m, 小半径a=1.6 m, 中心磁场B T =5.0 T); 第二阶段实现1000 MW的聚变功 率并示范聚变电能输出 [25][26][27] . 为了在CFETR上演示氚 自持的稳态运行以及聚变电能输出, 提出了两种稳态 运行模式, 分别为基准(Baseline)和先进(Advanced)稳 态运行模式 [28][29][30] , 后者将获得比前者更高的聚变功率, 有望达到CFETR最终的科学目标. 此外, CFETR装置 的相关不稳定性的预研是其投入建设的重要基础, 为 了通过先进运行模式实现其最终的目标, 首先基于装 置的基准运行模式预研阿尔芬本征模的相关不稳定 性, 并且在该装置上已有TAE, RSAE及BAE的相关理 论研究工作 [31,32] .…”

Low-$n$ global ideal MHD instabilities in CFETR baseline scenario

“…The equilibrium of CFETR baseline scenario considered in our calculation was generated through the integrated modeling in OMFIT framework [7]. The plasma size is slightly smaller than ITER, with a major radius of 5.7 m and a minor radius of 1.6 m. The toroidal magnetic field (5T) and the plasma current (10 MA) at magnetic axis are listed in Table 1 of reference [7], among others. Since the baseline case is not designed for demonstrating high fusion gain, the normalized β N is set to 1.88.…”

“…In the baseline scenario, the current drive sources are deposited far off-axis, and as a result there is a reversed magnetic shear with the minimum of safety factor q min > 2 located at an outer radius [6]. Fully non-inductive operation requires at least 36% of bootstrap current fraction (see Table-1 of [7]), which leads to high pedestal pressure gradient and peaked edge current. Such a configuration is expected to be unstable to both ballooning and external kink modes [8].…”