Statistical studies of density operating space for ohmic discharges on HL-2A tokamak

doi:10.16568/j.0254-6086.202504009

Abstract

Abstract: Based on the ohmic discharge experimental database of the HL-2A tokamak since 2017, the density operating space of ohmic discharge is statistically analyzed and experimentally studied. The results show that the Greenwald density fractio f_GW≡n₀/n_G of the operating space is between 0.11 and 1.40. The siliconization wall conditioning is beneficial to improve the maximum density before the density limit. The highest density(~6.9×10¹⁹ m⁻³, ~1.40nG) of the operating space is achieved by gas puff fueling. The degree of density peaking under different fueling methods is analyzed. It is found that there is no significant difference in the density peaking factor under the four fueling conditions (no fueling, gas puffing, supersonic molecular beam injection, gas puffing + supersonic molecular beam injection), all of which are about 2.0. The relationship between the plasma confinement time and the density under different currents is studied. The phenomenon of transition from linear ohmic confinement (LOC) to saturated ohmic confinement (SOC) and the increase of density peaking during the transition are observed.

Key words: Tokamak, Density limit, Density peaking, LOC-SOC transition

摘要： 基于 HL-2A 装置从 2017 年以来的欧姆放电实验数据库，对欧姆放电的密度运行区间进行了统计分析和实验研究。统计结果显示，欧姆放电密度运行区间的 Greenwald 密度分数 f_GW≡n ₀/n _G 介于 0.11 和 1.40 之间。硅化壁处理有利于密度极限的提高。密度运行区间的最高密度(~6.9×10¹⁹ m⁻³，~1.40nG)是在普通送气加料下实现的。分析了不同加料方式下的密度峰化程度，发现 4 种加料情形(无加料、普通送气、超声分子束注入、普通送气+超声分子束注入)下的密度峰化因子无显著差异，均在 2.0 左右。研究了不同电流下的等离子体约束性能随密度的变化关系，观察到了由线性欧姆约束到饱和欧姆约束的转换现象、以及在转换过程中的密度峰化程度提升。

关键词: 托卡马克, 密度极限, 密度峰化, LOC-SOC 转换

CLC Number:

TL61+2.11

LIU Yan-min, LONG Ting, TIAN Wen-jing, ZHAO Ju, LI Yong-gao, LI Bo, WANG Zhan-hui, CHEN Wei, XU Min. Statistical studies of density operating space for ohmic discharges on HL-2A tokamak[J]. Nuclear Fusion and Plasma Physics, 2025, 45(4): 430-436.

刘延民, 龙婷, 田文静, 赵菊, 李永高, 李波, 王占辉, 陈伟, 许敏. HL-2A 托卡马克欧姆放电下的密度运行区间统计与研究[J]. 核聚变与等离子体物理, 2025, 45(4): 430-436.

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