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Title: Upgrade of Langmuir probe diagnostic in ITER-like tungsten mono-block divertor on experimental advanced superconducting tokamak

Abstract

In order to withstand rapid increase in particle and power impact onto the divertor and demonstrate the feasibility of the ITER design under long pulse operation, the upper divertor of the EAST tokamak has been upgraded to actively water-cooled, ITER-like tungsten mono-block structure since the 2014 campaign, which is the first attempt for ITER on the tokamak devices. Therefore, a new divertor Langmuir probe diagnostic system (DivLP) was designed and successfully upgraded on the tungsten divertor to obtain the plasma parameters in the divertor region such as electron temperature, electron density, particle and heat fluxes. More specifically, two identical triple probe arrays have been installed at two ports of different toroidal positions (112.5-deg separated toroidally), which can provide fundamental data to study the toroidal asymmetry of divertor power deposition and related 3-dimension (3D) physics, as induced by resonant magnetic perturbations, lower hybrid wave, and so on. The shape of graphite tip and fixed structure of the probe are designed according to the structure of the upper tungsten divertor. The ceramic support, small graphite tip, and proper connector installed make it possible to be successfully installed in the very narrow interval between the cassette body and tungsten mono-block, i.e., 13.5 mm.more » It was demonstrated during the 2014 and 2015 commissioning campaigns that the newly upgraded divertor Langmuir probe diagnostic system is successful. Representative experimental data are given and discussed for the DivLP measurements, then proving its availability and reliability.« less

Authors:
; ; ;  [1];  [2]; ; ; ; ; ; ; ; ; ; ; ; ; ;  [1];  [1] more »;  [3] « less
  1. Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)
  2. (China)
  3. (United States)
Publication Date:
OSTI Identifier:
22597679
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 87; Journal Issue: 8; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CONNECTORS; DESIGN; DIVERTORS; ELECTRON DENSITY; ELECTRON TEMPERATURE; ELECTRONS; GRAPHITE; HEAT; HEAT FLUX; HT-7U TOKAMAK; ITER TOKAMAK; LANGMUIR PROBE; LOWER HYBRID CURRENT DRIVE; LOWER HYBRID HEATING; OPERATION; PARTICLES; PERTURBATION THEORY; TUNGSTEN; WATER; WATER COOLED REACTORS

Citation Formats

Xu, J. C., Jia, M. N., Feng, W., Deng, G. Z., Science Island Branch of Graduate School, University of Science and Technology of China, Hefei 230031, Wang, L., E-mail: wliang@ipp.ac.cn, Xu, G. S., Luo, G. N., Yao, D. M., Li, Q., Cao, L., Chen, L., Zhang, W., Liu, S. C., Wang, H. Q., Hu, L. Q., Wan, B. N., Li, J., Sun, Y. W., Guo, H. Y., and General Atomics, P.O. Box 85608, San Diego, California 92186. Upgrade of Langmuir probe diagnostic in ITER-like tungsten mono-block divertor on experimental advanced superconducting tokamak. United States: N. p., 2016. Web. doi:10.1063/1.4960181.
Xu, J. C., Jia, M. N., Feng, W., Deng, G. Z., Science Island Branch of Graduate School, University of Science and Technology of China, Hefei 230031, Wang, L., E-mail: wliang@ipp.ac.cn, Xu, G. S., Luo, G. N., Yao, D. M., Li, Q., Cao, L., Chen, L., Zhang, W., Liu, S. C., Wang, H. Q., Hu, L. Q., Wan, B. N., Li, J., Sun, Y. W., Guo, H. Y., & General Atomics, P.O. Box 85608, San Diego, California 92186. Upgrade of Langmuir probe diagnostic in ITER-like tungsten mono-block divertor on experimental advanced superconducting tokamak. United States. doi:10.1063/1.4960181.
Xu, J. C., Jia, M. N., Feng, W., Deng, G. Z., Science Island Branch of Graduate School, University of Science and Technology of China, Hefei 230031, Wang, L., E-mail: wliang@ipp.ac.cn, Xu, G. S., Luo, G. N., Yao, D. M., Li, Q., Cao, L., Chen, L., Zhang, W., Liu, S. C., Wang, H. Q., Hu, L. Q., Wan, B. N., Li, J., Sun, Y. W., Guo, H. Y., and General Atomics, P.O. Box 85608, San Diego, California 92186. 2016. "Upgrade of Langmuir probe diagnostic in ITER-like tungsten mono-block divertor on experimental advanced superconducting tokamak". United States. doi:10.1063/1.4960181.
@article{osti_22597679,
title = {Upgrade of Langmuir probe diagnostic in ITER-like tungsten mono-block divertor on experimental advanced superconducting tokamak},
author = {Xu, J. C. and Jia, M. N. and Feng, W. and Deng, G. Z. and Science Island Branch of Graduate School, University of Science and Technology of China, Hefei 230031 and Wang, L., E-mail: wliang@ipp.ac.cn and Xu, G. S. and Luo, G. N. and Yao, D. M. and Li, Q. and Cao, L. and Chen, L. and Zhang, W. and Liu, S. C. and Wang, H. Q. and Hu, L. Q. and Wan, B. N. and Li, J. and Sun, Y. W. and Guo, H. Y. and General Atomics, P.O. Box 85608, San Diego, California 92186},
abstractNote = {In order to withstand rapid increase in particle and power impact onto the divertor and demonstrate the feasibility of the ITER design under long pulse operation, the upper divertor of the EAST tokamak has been upgraded to actively water-cooled, ITER-like tungsten mono-block structure since the 2014 campaign, which is the first attempt for ITER on the tokamak devices. Therefore, a new divertor Langmuir probe diagnostic system (DivLP) was designed and successfully upgraded on the tungsten divertor to obtain the plasma parameters in the divertor region such as electron temperature, electron density, particle and heat fluxes. More specifically, two identical triple probe arrays have been installed at two ports of different toroidal positions (112.5-deg separated toroidally), which can provide fundamental data to study the toroidal asymmetry of divertor power deposition and related 3-dimension (3D) physics, as induced by resonant magnetic perturbations, lower hybrid wave, and so on. The shape of graphite tip and fixed structure of the probe are designed according to the structure of the upper tungsten divertor. The ceramic support, small graphite tip, and proper connector installed make it possible to be successfully installed in the very narrow interval between the cassette body and tungsten mono-block, i.e., 13.5 mm. It was demonstrated during the 2014 and 2015 commissioning campaigns that the newly upgraded divertor Langmuir probe diagnostic system is successful. Representative experimental data are given and discussed for the DivLP measurements, then proving its availability and reliability.},
doi = {10.1063/1.4960181},
journal = {Review of Scientific Instruments},
number = 8,
volume = 87,
place = {United States},
year = 2016,
month = 8
}
  • Heat exhaust is one of the most challenging issues to be addressed for tokamak magnetic confinement fusion research. Detailed modeling with SOLPS5.0/B2.5-Eirene code package is carried out to examine an alternative advanced divertor configuration, i.e., quasi snowflake (QSF), for long pulse operation in EAST. Comparison is also made with the lower single null (LSN) divertor configuration. SOLPS predicts that the quasi snowflake configuration significantly reduces the peak heat flux at the lower divertor outer target, by a factor of 2–3, owing to the magnetic flux expansion. Furthermore, the density threshold for detachment is much lower for QSF, compared to LSNmore » under the same upstream conditions. This indicates that QSF provides a promising tool for controlling heat flux at divertor target while maintaining a lower separatrix density, which is highly desirable for current drive, thus greatly facilitating long-pulse operation in EAST.« less
  • In order to actively control power load on the divertor target plates and study the effect of radiative divertor on plasma parameters in divertor plasmas and heat fluxes to the targets, dedicated experiments with Ar impurity seeding have been performed on experimental advanced superconducting tokamak in typical L-mode discharge with single null divertor configuration, ohmic heating power of 0.5 MW, and lower hybrid wave heating power of 1.0 MW. Ar is puffed into the divertor plasma at the outer target plate near the separatrix strike point with the puffing rate 1.26 Multiplication-Sign 10{sup 20} s{sup -1}. The radiative divertor ismore » formed during the Ar puffing. The SOL/divertor plasma in the L-mode discharge with radiative divertor has been modelled by using SOLPS5.2 code package [V. Rozhansky et al., Nucl. Fusion 49, 025007 (2009)]. The modelling shows the cooling of the divertor plasma due to Ar seeding and is compared with the experimental measurement. The changes of peak electron temperature and heat fluxes at the targets with the shot time from the modelling results are similar to the experimental measurement before and during the Ar impurity seeding, but there is a major difference in time scales when Ar affects the plasma in between experiment and modelling.« less
  • Divertor asymmetries with helium puffing are investigated in various divertor configurations on Experimental Advanced Superconducting Tokamak (EAST). The outer divertor electron temperature decreases significantly during the gas injection at the outer midplane. As soon as the gas is injected into the edge plasma, the power deposition drops sharply at the lower outer target while increases gradually at the lower inner target in LSN configuration; the power deposition increases quickly at the upper outer target while remains unchanged at the upper inner target in upper single null configuration; the power deposition increases slightly at the outer targets while shows no obviousmore » variation at the inner targets in double null configuration. The radiated power measured by the extreme ultraviolet arrays increases significantly due to helium gas injection, especially in the outer divertor. The edge parameters are measured by reciprocating probes at the outer midplane, showing that the electron temperature and density increase but the parallel Mach number decreases significantly due to the gas injection. Effects of poloidal E × B drifts and parallel SOL flows on the divertor asymmetry observed in EAST are also discussed.« less
  • The dependence of divertor asymmetry and scrape-off layer (SOL) flow on heating power has been investigated in the Experimental Advanced Superconducting Tokamak (EAST). Divertor plasma exhibits an outboard-enhanced in-out asymmetry in heat flux in lower single null configuration for in reversed (ion ∇B drift direction toward the upper X-point) field directions. Upper single null exhibits an inboard-favored asymmetry in low heating power condition, while exhibits an outboard-favored asymmetry when increasing the heating power. Double null has the strongest in-out asymmetry in heat flux, favoring the outer divertor. The in-out asymmetry ratios of q{sub t,out}/q{sub t,in} and P{sub out}/P{sub total} increasemore » with the power across the separatrix P{sub loss}, which is probably induced by the enhanced radial particle transport due to a large pressure gradient. The characteristics of the measured SOL parallel flow under various discharge conditions are consistent with the Pfirsch-Schlüter (PS) flow with the parallel Mach number M{sub ∥} decreasing with the line averaged density but increasing with P{sub loss}, in the same direction as the PS flow. The contributions of both poloidal E×B drift and parallel flow on poloidal particle transport in SOL on EAST are also assessed.« less
  • For the new ITER-like wall at JET, two new infrared diagnostics (KL9B, KL3B) have been installed. These diagnostics can operate between 3.5 and 5 {mu}m and up to sampling frequencies of {approx}20 kHz. KL9B and KL3B image the horizontal and vertical tiles of the divertor. The divertor tiles are tungsten coated carbon fiber composite except the central tile which is bulk tungsten and consists of lamella segments. The thermal emission between lamellae affects the surface temperature measurement and therefore KL9A has been upgraded to achieve a higher spatial resolution (by a factor of 2). A technical description of KL9A, KL9B,more » and KL3B and cross correlation with a near infrared camera and a two-color pyrometer is presented.« less