Impact of an alternative divertor configuration on plasma detachment: pure deuterium simulations using the SOLEDGE2D-EIRENE edge transport code for HL-2M scenarios

Abstract

The SOLEDGE-EIRENE edge plasma code provides solutions for particle & energy transport in the plasma edge within complex and realistic 2D geometries [1]. In this work, divertor detachment is simulated on the HL-2M alternative magnetic configurations in pure Deuterium plasma. Starting from typical HL-2M low single-null (SN) configuration, the snowflake plus (SF+) and snowflake minus (SF-) configurations have been investigated. Detachment of the outer target is studied in these configurations during plasma density ramps controlled by a fueling source, at constant input power and constant radial transport coefficients. Some typical characteristics of detachment, like threshold, depth and upstream window of detachment are investigated. In the three geometries, detachment onset and evolution with upstream plasma density is characterized by the gradual displacement of a radiation front from the outer target to the main X-point, as observed in experiments. It is found that, whatever the detachment in terms of particle, momentum or power dissipation, the detachment threshold is dominated primarily by the geometrical structure of divertor plate and it does not exhibit dependence on the magnetic configuration of the diverted plasma volume. In particular, the parallel connection length in the divertor is not found to affect the detachment threshold, in contrast with simple expectations from the 2-point model, but in agreement with experimental findings.

Experimental study on plasma generated by a tapered coaxial accelerator and its damage effects on a tungsten target at different angles

“…The damage effect of plasma on the target is mainly due to the increase in surface temperature caused by the energy accumulation on the surface. The sudden cooling and heating of the target surface makes the tungsten material brittle [1,10,14], and the large surface temperature gradient produces uneven expansion deformation. The surface cracks are formed in the process of the damage effect.…”

“…In the current tokamak operating state, the angle between the plasma transport direction and the vertical direction of the divertor target is variable. The damage effect of the varying angles on the target is different [14]. NSC-KIPT have used a variety of measuring instruments to observe the bombardment process at different angles and different pulses by QSPA/QSPA-M [10,15].…”

Novel SOLPS-ITER simulations of X-point target and snowflake divertors

“…Despite the potential of Snowflake and XPT divertors, neither geometry has been widely simulated in codes with kinetic neutrals, particularly in the simulation code SOLPS-ITER [13,14]. In fact, though snowflakes have been simulated in codes such as EMC3-EIRENE [15][16][17], they have only been simulated once before in SOLPS-ITER [18], and XPTs have never been simulated previously using the code due to the rigidity of the physics modules and grid generators [14]. The benefits of using SOLPS-ITER include the complex kinetic treatment of neutrals through its coupling to the EIRENE Monte-Carlo solver, the ability to activate drifts and currents, and the extensive history and benchmarking of the code [14].…”

Modeling of the effects of impurity seeding on plasma detachment and impurity screening of snowflake divertor on HL-2M tokamak by SOLPS-ITER

“…The advanced divertor magnetic configurations such as snowflake divertor (SFD) [11] and X-divertor (XD) [12], have been proposed as a promising solution aiming to solve the issue of heat exhaust [13], which has been investigated experimentally in TCV [14][15][16], DIII-D [17,18], NSTX [19], EAST [20], and numerically in TCV [21], NSTX [22], ASDEX Upgrade [23,24], EAST [25,26], CFETR [27][28][29], DTT [30] and HL-2M [31][32][33]. These studies demonstrated that SFD/XD can notably reduce the deposited heat flux on the divertor via increasing the plasma-wetted area due to the intense poloidal flux expansion, and can diminish the parallel heat and particle fluxes via volumetric losses due to the longer connection length and larger radiative volume.…”