The effect of tearing modes on the confinement of runaway electrons is studied in Experimental Advanced Superconducting Tokamak(EAST).The general tendency of the radial diffusion coefficient of runaway electrons(REs)D...The effect of tearing modes on the confinement of runaway electrons is studied in Experimental Advanced Superconducting Tokamak(EAST).The general tendency of the radial diffusion coefficient of runaway electrons(REs)Dr is derived based on the time response relation between the tearing modes and runaway electrons.The results indicate that,the magnetic fluctuations of tearing modes will enhance the radial diffusion of runaway electrons when the magnetic island is small.Following the increasing of the magnetic fluctuations of the tearing modes,the formed large magnetic island may weaken the radial diffusion of runaway electrons.The results can be important to understand the confinement of runaway electrons when large magnetic islands exist in the plasma.展开更多
Neutron emission in EAST was investigated by a time-resolved monitor system which consists of four 3He proportional counters and a 235U fission chamber. The D-D neutron flux increased approximately an order of magnitu...Neutron emission in EAST was investigated by a time-resolved monitor system which consists of four 3He proportional counters and a 235U fission chamber. The D-D neutron flux increased approximately an order of magnitude during the 27 MHz ion-cyclotron radio frequency （ICRF） heating, demonstrating that the ICRF wave heated the plasma effectively. In addition in lower hybrid wave （LHW） experiment with higher plasma parameters D-D neutrons were also detected. However, masses of photoneutrons were generated in Ohmic discharges with low plasma density. Effect of plasma density on the production of photoneutrons was studied, and it is found that LHW can suppress the generation of the runaway electrons and reduce the share of the photoneutrons effectively.展开更多
A detailed analysis of the synchrotron radiation intensity and energy of runaway electrons is presented for the Experimental Advanced Superconducting Tokamak（EAST）. In order to make the energy of the calculated runa...A detailed analysis of the synchrotron radiation intensity and energy of runaway electrons is presented for the Experimental Advanced Superconducting Tokamak（EAST）. In order to make the energy of the calculated runaway electrons more accurate, we take the Shafranov shift into account. The results of the analysis show that the synchrotron radiation intensity and energy of runaway electrons did not reach the maximum at the same time. The energy of the runaway electrons reached the maximum first, and then the synchrotron radiation intensity of the runaway electrons reached the maximum.We also analyze the runaway electrons density, and find that the density of runaway electrons continuously increased. For this reason, although the energy of the runaway electrons dropped but the synchrotron radiation intensity of the runaway electrons would continue rising for a while.展开更多
In this paper,the singular value decomposition（SVD） method as a filter is applied before the tomographic inversion of soft-X-ray emission.Series of ＇filtered＇ signals including specific chronos and topos are obtai...In this paper,the singular value decomposition（SVD） method as a filter is applied before the tomographic inversion of soft-X-ray emission.Series of ＇filtered＇ signals including specific chronos and topos are obtained.（Here,chronos and topos are the decomposed spatial vectors and the decomposed temporal vectors,respectively）.Given specific magnetic flux function with coupling m = 1 and m = 2 modes,the line-integrated soft-X-ray signals at all chords have been obtained.Then m = 1 and m = 2 modes have been identified by tomography of simulated ＇filtered＇ signals extracted by the SVD method.Finaly,using the experimental line-integrated soft-X-ray signals,m = 2 competent mode of complex magnetohydrodynamics（MHD） activities during internal soft disruption is observed.This result demonstrates that m = 2 mode plays an important role in internal disruption（Here,m is the poloidal mode number）.展开更多
Operation of HT-7 tokamak in a multicycle alternating square wave plasma current regime is reported. A set of AC operation experiments, including LHW heating to enhance plasma ionization during the current transition ...Operation of HT-7 tokamak in a multicycle alternating square wave plasma current regime is reported. A set of AC operation experiments, including LHW heating to enhance plasma ionization during the current transition and current sustainment, is described. The behaviour of runaway electrons is analysed by four HXR detectors tangentially viewing the plasma in the equatorial plane, within energy ranges 0.3-1.2 MeV and 0.3-7 MeV, separately. High energy runaway electrons （~MeV） axe found to circulate predominantly in the opposite direction to the plasma current, while the number of low energy runaway electrons （~tens to hundreds of keV） circulating along the plasma current is comparable to that in the direction opposite to the plasma current. AC operation with lower hybrid current drive （LHCD） is observed to have an additional benefit of suppressing the runaway electrons if the drop of the loop voltage is large enough.展开更多
In EAST,synchrotron radiation is emitted by runaway electrons in the infrared band,which can be observed by infrared cameras.This synchrotron radiation is mainly emitted by passing runaway electrons with tens of MeV e...In EAST,synchrotron radiation is emitted by runaway electrons in the infrared band,which can be observed by infrared cameras.This synchrotron radiation is mainly emitted by passing runaway electrons with tens of MeV energy.A common feature of radiation dominated by passing runaway electrons is that it is strongest on the high field side.However,the deeply trapped runaway electrons cannot reach the high field side in principle.Therefore,in this case,the high field side radiation is expected to be weak.This paper reports for the first time that the synchrotron radiation from trapped runaway electrons dominates that from passing runaway electrons and is identifiable in an image.Although the synchrotron radiation dominated by trapped runaway electrons can be observed in experiment,the proportion of trapped runaway electrons is very low.展开更多
The runaway electron phenomenon caused by dis- ruptions is one of the challenging conditions on the ITER Tokamak, which may destroy the vacuum ves- sel. To avoid runaway electrons hitting the fist wall, there must be ...The runaway electron phenomenon caused by dis- ruptions is one of the challenging conditions on the ITER Tokamak, which may destroy the vacuum ves- sel. To avoid runaway electrons hitting the fist wall, there must be some monitor systems which can pro- vide position information of the runaway electron beam. Hard x-ray camera is the most conventional di- agnostic system to monitor the runaway electrons. While there is no hard x-ray camera working for the entire ITER operation phase even for D-D phase of ITER, there must be some systems playing the role of observation of the runaway electrons. In this case, with some international experiences from other Toka- mak devices, the soft x-ray camera can share the role of runaway electron observation. On JET and some other Tokamak devices, the runaway electron current generated by disruption has been observed by the soft x-ray camera system.展开更多
基金Project partly supported by the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2021445)the Science Foundation of Institute of Plasma Physics of Chinese Academy of Sciences(Grant No.DSJJ-2022-05)partly supported by the Comprehensive Research Facility for Fusion Technology Program of China(Grant No.2018-000052-73-01-001228).
文摘The effect of tearing modes on the confinement of runaway electrons is studied in Experimental Advanced Superconducting Tokamak(EAST).The general tendency of the radial diffusion coefficient of runaway electrons(REs)Dr is derived based on the time response relation between the tearing modes and runaway electrons.The results indicate that,the magnetic fluctuations of tearing modes will enhance the radial diffusion of runaway electrons when the magnetic island is small.Following the increasing of the magnetic fluctuations of the tearing modes,the formed large magnetic island may weaken the radial diffusion of runaway electrons.The results can be important to understand the confinement of runaway electrons when large magnetic islands exist in the plasma.
基金supported by the Key Program of the National Natural Science Foundation of China (No. 10775041)the National Magaetic Confinement Fusion Science Program of China (Nos. 2010GB106000, 2010GB106004)
文摘Neutron emission in EAST was investigated by a time-resolved monitor system which consists of four 3He proportional counters and a 235U fission chamber. The D-D neutron flux increased approximately an order of magnitude during the 27 MHz ion-cyclotron radio frequency （ICRF） heating, demonstrating that the ICRF wave heated the plasma effectively. In addition in lower hybrid wave （LHW） experiment with higher plasma parameters D-D neutrons were also detected. However, masses of photoneutrons were generated in Ohmic discharges with low plasma density. Effect of plasma density on the production of photoneutrons was studied, and it is found that LHW can suppress the generation of the runaway electrons and reduce the share of the photoneutrons effectively.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11775263 and 11405219)the JSPS-NRF-NSFC A3 Foresight Program in the Field of Plasma Physics,China(Grant No.11261140328)the National Magnetic Confnement Fusion Science Program of China(Grant No.2015GB102004)
文摘A detailed analysis of the synchrotron radiation intensity and energy of runaway electrons is presented for the Experimental Advanced Superconducting Tokamak（EAST）. In order to make the energy of the calculated runaway electrons more accurate, we take the Shafranov shift into account. The results of the analysis show that the synchrotron radiation intensity and energy of runaway electrons did not reach the maximum at the same time. The energy of the runaway electrons reached the maximum first, and then the synchrotron radiation intensity of the runaway electrons reached the maximum.We also analyze the runaway electrons density, and find that the density of runaway electrons continuously increased. For this reason, although the energy of the runaway electrons dropped but the synchrotron radiation intensity of the runaway electrons would continue rising for a while.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10935004)
文摘In this paper,the singular value decomposition（SVD） method as a filter is applied before the tomographic inversion of soft-X-ray emission.Series of ＇filtered＇ signals including specific chronos and topos are obtained.（Here,chronos and topos are the decomposed spatial vectors and the decomposed temporal vectors,respectively）.Given specific magnetic flux function with coupling m = 1 and m = 2 modes,the line-integrated soft-X-ray signals at all chords have been obtained.Then m = 1 and m = 2 modes have been identified by tomography of simulated ＇filtered＇ signals extracted by the SVD method.Finaly,using the experimental line-integrated soft-X-ray signals,m = 2 competent mode of complex magnetohydrodynamics（MHD） activities during internal soft disruption is observed.This result demonstrates that m = 2 mode plays an important role in internal disruption（Here,m is the poloidal mode number）.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10935004 and 10775041)
文摘Operation of HT-7 tokamak in a multicycle alternating square wave plasma current regime is reported. A set of AC operation experiments, including LHW heating to enhance plasma ionization during the current transition and current sustainment, is described. The behaviour of runaway electrons is analysed by four HXR detectors tangentially viewing the plasma in the equatorial plane, within energy ranges 0.3-1.2 MeV and 0.3-7 MeV, separately. High energy runaway electrons （~MeV） axe found to circulate predominantly in the opposite direction to the plasma current, while the number of low energy runaway electrons （~tens to hundreds of keV） circulating along the plasma current is comparable to that in the direction opposite to the plasma current. AC operation with lower hybrid current drive （LHCD） is observed to have an additional benefit of suppressing the runaway electrons if the drop of the loop voltage is large enough.
基金the National Natural Science Foundation of China(Grant No.11775263)the National Magnetic Confinement Fusion Energy Research Project of China(Grant No.2015GB111003).
文摘In EAST,synchrotron radiation is emitted by runaway electrons in the infrared band,which can be observed by infrared cameras.This synchrotron radiation is mainly emitted by passing runaway electrons with tens of MeV energy.A common feature of radiation dominated by passing runaway electrons is that it is strongest on the high field side.However,the deeply trapped runaway electrons cannot reach the high field side in principle.Therefore,in this case,the high field side radiation is expected to be weak.This paper reports for the first time that the synchrotron radiation from trapped runaway electrons dominates that from passing runaway electrons and is identifiable in an image.Although the synchrotron radiation dominated by trapped runaway electrons can be observed in experiment,the proportion of trapped runaway electrons is very low.
文摘The runaway electron phenomenon caused by dis- ruptions is one of the challenging conditions on the ITER Tokamak, which may destroy the vacuum ves- sel. To avoid runaway electrons hitting the fist wall, there must be some monitor systems which can pro- vide position information of the runaway electron beam. Hard x-ray camera is the most conventional di- agnostic system to monitor the runaway electrons. While there is no hard x-ray camera working for the entire ITER operation phase even for D-D phase of ITER, there must be some systems playing the role of observation of the runaway electrons. In this case, with some international experiences from other Toka- mak devices, the soft x-ray camera can share the role of runaway electron observation. On JET and some other Tokamak devices, the runaway electron current generated by disruption has been observed by the soft x-ray camera system.
