Super-X Divertor Simulation for HCSB-DEMO Conception Design

Abstract

HCSB-DEMO concept design is carried out at SWIP. In order to handle power from a core plasma region, a super-X divertor is preliminarily designed and investigated for HCSB-DEMO. It increases the target surface area by expanding the magnetic flux surface with another X-point generated near the targets and increases the parallel connection length by moving the outer divertor target to larger 𝑅 and 𝑍. The heat load at the targets is investigated by B2.5-Eirene. With heating power flowing into SOL/divertor regions being 𝑃 = 600 MW, when the density at the separatrix is 𝑛𝑒 = 3.5 × 10 19 m −3 , the peak heat load at the inner and outer divertor is 9.2 MW/m 2 and 3.7 MW/m 2 , respectively, which is much less than those of the standard divertor without impurity seeding, and also below the design targets (10 MW/m 2 ). Thus the super-X divertor may work well for HCSB-DEMO to solve the high heat load problem at the divertor target without impurity seeding from this preliminary concept design and simulation.

A review of radiative detachment studies in tokamak advanced magnetic divertor configurations

“…Same conclusions were reached in a similar computational assessment of another concept-a National High-Power Tokamak Experiment [147]. A study of the 500 MW input power Chinese DEMO reactor using the B2.5-EIRENE code concluded that adequate outer divertor heat loads (under 10 MW m −2 ) and low divertor T 5 eV e  could be obtained in the Super-X divertor configuration by raising density and without impurity seeding [10]. The inner divertor, however, had a potential for impurity sputtering because of high T 150 eV e …”

“…However, in high-power tokamak devices beyond ITER such as the proposed fusion nuclear science facilities or the DEMO reactor, divertor radiation may be insufficient for mitigating power loads. Compared in table 1 are three metrics, the P R heat , the steady-state peak divertor heat flux q peak , and steady-state upstream (before divertor entrance) parallel heat flux q P in present-day devices, ITER, and some DEMO concepts [9][10][11]. The comparison demonstrates significant gaps between the present state of physics and technology and DEMO-class device requirements, which typically must rely on highly radiative divertor solutions, with radiated power fractions up to 80%-90% of total input power.…”

“…A comparison of power and divertor conditions in present day tokamaks, ITER and DEMO devices[9][10][11].…”