7 Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya
th1Studies of power load with localised neon injection in HL-2M111113345

D.M.Fan ,W.L.Zhong , H.L.Du, G.L.Xiao , J.M.Gao , X.L.Zou , J.Harrison , D.Moulton , H.Freirichs , and Y.H.Feng
1Southwestern Institute of Physics, Chengdu, China
2
Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), CEA/Cadarache, France
3Culham Science Centre, Abingdon, United Kingdom
4
University of Wisconsin, Madison, USA5Max-Planck-Institut für Plasmaphysik, Greifswald, Germany
e-mail (speaker): fandongmei@swip.ac.cn
The controllability of the power exhaust in thedivertor could be one of the critical problems to besolved in order to ensure the success for a steady state
tokamak[1]. Impurity seeding is an important tool tomitigate the peak power loads and temperatures at thedivertor targets in tokamak devices[2]. Experiments withimpurity(neon, nitrogen, argon, etc) seeding have been
carried out on machines worldwide, especially forlarge-size devices such as JET and JT-60U, impurity gas
seeding has been ascertained to be a good solution forcontrolling the heat loads on divertor targets. However,in most cases, the impurity will be injected through one
or a set of toroidally distributted localized gas valvessituated below the divertor cassettes, in which case thespatial localization of the impurity source may result intoroidal asymmetries in the raidated power and the heat
flux to the divertor, even more worse if the extrinsic gas
is only partially recyling[3,4]. To improve the physics
understanding and provide predictive capabilities for theimpact of impurity seeding on the plasma and mitigate
the heat loads, different impurity seeding methods haveto be investigated and compared to each other.
In this paper, we report the first 3D EMC3-EIRENE
simulations of neon seeded H-mode plasmas in HL-2M.
EMC3-EIRENE is a 3D edge plasma fluid and neutral
particle transport code. As a primary and fairly important
step, the implementation of EMC3-EIRENE to HL-2M
and the validation against the 2D simulations withSOLPS has been carried out, showing a quantitively
good agreement. The neon impurity seeded at different
poloidal positions has been investigated to understandthe properties of impurity concentration and heat load
distributions for a single toroidally localised injection
and multi-toroidally distributed injections. The
investigated gas puffing cases include the divertor,midplane and top gas puffing. The majority of thestudied neon injections gives rise to a toroidally
asymmetric profile of heat load deposition on the inneror outer divertor targets. It has been found that the levelof toroidal asymmetry in divertor conditions resulting
from single toroidally localized divetor impurity seedingshow a much more stronger toroidal peaking in heatloads and divertor electron temperatures and pressurescompared to the other poloidal injections. However, theheat loads cannot be reduced below the acceptable level
along the whole torus for a single toroidally localised

injection. The influences of gas puff rate and particle
transport parameters on the SOL density are investigated.
The parameter scans indicated that the high neon
injection flux results in the highest neon particles densityand energy loss in the edge plasma, which leads to aneffective mitigation of heat load(as shown in Figure1). In
addition, the neon injection on the outer midplane wasfound to give rise to an undesirable level of Zeff at thepedestal region, which in contrast the neon impurity wasscreened to an acceptable level for the divertor neon
injection case.
In order to achieve the heat load mitigation along
the entire torus, modelling of single and simultaneous
multi-toroidal neon injections near the outer strike points
has been simulated, which indicates that thesimultaneous multi-toroidal neon injections show a better
heat flux mitigation on both outer divertor targets. Inaddition, it is found that the increased number of neon
toroidal injection locations can cause a relatively
uniform reduction of heat loads along the entire torus(asshown by Figure 2).
From our studies, it can be inferred that using
divertor gas valves closer to the strike point is theoptimized way in terms of minimizing heat power
loading on the targets. Further studies will be focus on
the scenarios of combined gas puffing frommulti-toroidal positions and give more qunatitative
predictions of heat load mitigation and impuritycontamination. This work is supported by the national
key R&D program of China under grant No.
2022YFE03030002 and the national natural science
foundation of China under grant No. 12275072.
References[1] R. Behrisch and V. Prozesky, Nucl. Fusion 30 2166(1990).
[2] A Kallenbach et al., Plasma Phys. Control. Fusion 55 124041(2013).
[3] J. Rapp et al., Nucl. Fusion 44 312 (2004).
[4] J.D. Lore et al., Phys. Plasmas 22 056106 (2015).

Figure 2. Heat flux distribution on the outer target for the neon
injection at the divertor under (a)single (b)three (c)six toroidal
positions. The toroidal positions for gas valve are denoted by the arrow.

Figure 1. Left: Poloidal cross-section of HL-2M shows the gas routepuffed from different gas valves. Right: The toroidal distributions ofheat flux deposition on the outer targets with various gas puff rates.