Detachment in helium(He)discharges has been achieved in the EAST superconducting tokamak equipped with an ITER-like tungsten divertor.This paper presents the experimental observations of divertor detachment achieved b...Detachment in helium(He)discharges has been achieved in the EAST superconducting tokamak equipped with an ITER-like tungsten divertor.This paper presents the experimental observations of divertor detachment achieved by increasing the plasma density in He discharges.During density ramp-up,the particle flux shows a clear rollover,while the electron temperature around the outer strike point is decreasing simultaneously.The divertor detachment also exhibits a significant difference from that observed in comparable deuterium(D)discharges.The density threshold of detachment in the He plasma is higher than that in the D plasma for the same heating power,and increases with the heating power.Moreover,detachment assisted with neon(Ne)seeding was also performed in L-and H-mode plasmas,pointing to the direction for reducing the density threshold of detachment in He operation.However,excessive Ne seeding causes confinement degradation during the divertor detachment phase.The precise feedback control of impurity seeding will be performed in EAST to improve the compatibility of core plasma performance with divertor detachment for future high heating power operations.展开更多
A new pellet injection system has been equipped on the experimental advanced superconducting tokamak（EAST） in the 2012 campaign,with a pellet size of Ф 2 mm×2 mm,a frequency of1 Hz–10 Hz and velocity of 150 m...A new pellet injection system has been equipped on the experimental advanced superconducting tokamak（EAST） in the 2012 campaign,with a pellet size of Ф 2 mm×2 mm,a frequency of1 Hz–10 Hz and velocity of 150 m s^-1–300 m s^-1.The deuterium pellet is well-known for plasma fuelling as well as for triggering the edge localized mode（ELM）.In the 2012 campaign,pellet injection experiments were successfully carried out on EAST.Temporary plasma detachment achieved by deuterium pellets has been observed in a double null（DN） divertor configuration,with multi-pellet injections at a repetition frequency of 2 Hz.The partial detachment of the outer divertors and complete detachment of the inner divertors was achieved after 35 ms of each pellet injection,which have a duration of 30–60 ms with the maximum degree of detachment（DOD） reaching 3.5 and 37,respectively.Meanwhile,the multifaceted asymmetric radiation from the edge（MARFE） phenomena was also observed at the high field side（HFS） near both the lower and upper X-points with radiation loss suddenly increased to about 15%–70%,which may be the main cause of divertor plasma detachment.The temporary detachment induced by pellet injection may act as a new way to study divertor detachment behaviors.展开更多
基金supported by the National Key Research and Development Program of China(Nos.2017YFA0301300,2017YFE0402500 and 2019YFE03030000)National Natural Science Foundation of China(Nos.11905255,12005004,12022511,U1867222 and U19A20113)+3 种基金the Institute of Energy,Hefei Comprehensive National Science Center(No.GXXT-2020-004)AHNSF(No.2008085QA38)the CASHIPS Director’s Fund(No.BJPY2019B01)the Key Research Program of Frontier Sciences of CAS(No.ZDBS-LY-SLH010)。
文摘Detachment in helium(He)discharges has been achieved in the EAST superconducting tokamak equipped with an ITER-like tungsten divertor.This paper presents the experimental observations of divertor detachment achieved by increasing the plasma density in He discharges.During density ramp-up,the particle flux shows a clear rollover,while the electron temperature around the outer strike point is decreasing simultaneously.The divertor detachment also exhibits a significant difference from that observed in comparable deuterium(D)discharges.The density threshold of detachment in the He plasma is higher than that in the D plasma for the same heating power,and increases with the heating power.Moreover,detachment assisted with neon(Ne)seeding was also performed in L-and H-mode plasmas,pointing to the direction for reducing the density threshold of detachment in He operation.However,excessive Ne seeding causes confinement degradation during the divertor detachment phase.The precise feedback control of impurity seeding will be performed in EAST to improve the compatibility of core plasma performance with divertor detachment for future high heating power operations.
基金supported by National Natural Science Foundation of China(Nos.11575236,11275231,11305206)the National Magnetic Confinement Fusion Science Program of China(Nos.2013GB107003,2014GB106005,2015GB101000)
文摘A new pellet injection system has been equipped on the experimental advanced superconducting tokamak（EAST） in the 2012 campaign,with a pellet size of Ф 2 mm×2 mm,a frequency of1 Hz–10 Hz and velocity of 150 m s^-1–300 m s^-1.The deuterium pellet is well-known for plasma fuelling as well as for triggering the edge localized mode（ELM）.In the 2012 campaign,pellet injection experiments were successfully carried out on EAST.Temporary plasma detachment achieved by deuterium pellets has been observed in a double null（DN） divertor configuration,with multi-pellet injections at a repetition frequency of 2 Hz.The partial detachment of the outer divertors and complete detachment of the inner divertors was achieved after 35 ms of each pellet injection,which have a duration of 30–60 ms with the maximum degree of detachment（DOD） reaching 3.5 and 37,respectively.Meanwhile,the multifaceted asymmetric radiation from the edge（MARFE） phenomena was also observed at the high field side（HFS） near both the lower and upper X-points with radiation loss suddenly increased to about 15%–70%,which may be the main cause of divertor plasma detachment.The temporary detachment induced by pellet injection may act as a new way to study divertor detachment behaviors.
