Plasma behaviour with molecular beam injection in the HL-1M tokamak
Plasma behaviour with molecular beam injection in the HL-1M tokamak
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DOI：
10.1088/0029-5515/38/4/312
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发表时间：
1998-04
期刊：
影响因子：
3.3
通讯作者：
L. Yao;Nianyi Tang;Z. Cui;Deming Xu;Z. Deng;X. Ding;Junlin Luo;J. Dong;G. Guo;Shi-han Yang
中科院分区：
文献类型：
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作者：
L. Yao;Nianyi Tang;Z. Cui;Deming Xu;Z. Deng;X. Ding;Junlin Luo;J. Dong;G. Guo;Shi-han Yang
在HL-1M托卡马克中引入了一种新的气体加注方法。该方法包括由拉瓦尔型喷嘴形成的脉冲高速分子束。准直氢束的速度约为500米/秒。每次脉冲中大约有6 × 1019个分子通过喷嘴进入真空室。向HL-1M低密度（e = 4 × 1018 m-3）氢等离子体注入一系列氦脉冲。当穿透深度达到12 cm时，电子密度de/dt在稳态下的上升速率高达3.1 × 1020 m-3s-1，等离子体密度达到e = 5.6 × 1019 m-3。氦分子束注入（MBI）后约100 ms的电子密度剖面峰因子Qn = ne(0)/ne达到最大值，大于1.51。抗磁法测得的能量约束时间τE为26 ms，比相同操作条件下气体膨化（GP）的约束时间τE长30%以上。MBI对τE的改善和Qn的增加与HL-1M中的小颗粒注射（PI）以及ASDEX中的慢颗粒注射（Kaufmann， M., et al., Nucl）相当。融合28(1988)827)。在HL-1M中，GP等离子体的密度峰因子Qn通常小于1.4，因此，除了氦粒子的同位素效应外，深度粒子注入诱导的密度峰分布也是约束改善的重要因素。与注入前相比，注入MBI后颗粒约束时间增加了6倍。
A new method of gas fuelling has been introduced in the HL-1M tokamak. The method consists of a pulsed high speed molecular beam formed by a Laval type nozzle. The velocity of the well collimated hydrogen beam is about 500 m/s. About 6 × 1019 molecules pass through the nozzle and into the vacuum chamber in each pulse. A series of helium pulses was injected into the HL-1M low density (e = 4 × 1018 m-3) hydrogen plasma. With penetration depth up to 12 cm, the ramp-up rate of the electron density, de/dt, was as high as 3.1 × 1020 m-3s-1 at steady state, and the resulting plasma density reached e = 5.6 × 1019 m-3. The profile peaking factor of the electron density, Qn = ne(0)/ne of about 100 ms after helium molecular beam injection (MBI) reached a maximum value of more than 1.51. The energy confinement time τE measured by diamagnetism is 26 ms, which is over 30% longer than that of the gas puffing (GP) results under the same operational conditions. The improvement of τE and increase of Qn for MBI were comparable to those of small pellet injection (PI) in HL-1M, as well as those of slow PI in ASDEX (Kaufmann, M., et al., Nucl. Fusion 28 (1988) 827). It is argued that the peaked density profile induced by the deepened particle injection is a factor essential for the confinement improvement apart from the isotope effect of helium particles, because the density peaking factor Qn is normally less than 1.4 for GP plasma in HL-1M. The particle confinement time with MBI increased sixfold in comparison with that before injection.