A new scaling for divertor detachment

doi:10.1088/1361-6587/aa5e6e

Title: A new scaling for divertor detachment

Article Details
Other Related Research

The ITER design, and future reactor designs, depend on divertor `detachment,'whether partial, pronounced or complete, to limit heat flux to plasma-facing components and to limit surface erosion due to sputtering. It would be valuable to have a measure of the difficulty of achieving detachment as a function of machine parameters, such as input power, magnetic field, major radius, etc. Frequently the parallel heat flux, estimated typically as proportional to P-sep/R or PsepB/R, is used as a proxy for this difficulty. Here we argue that impurity cooling is dependent on the upstream density, which itself must be limited by a Greenwald-like scaling. Taking this into account self-consistently, we find the impurity fraction required for detachment scales dominantly as power divided by poloidal magnetic field. The absence of any explicit scaling with machine size is concerning, as P-sep surely must increase greatly for an economic fusion system, while increases in the poloidal field strength are limited by coil technology and plasma physics. This result should be challenged by comparison with 2D divertor codes and with measurements on existing experiments. Nonetheless, it suggests that higher magnetic field, stronger shaping, double-null operation, `advanced' divertor configurations, as well as alternate means to handle heat fluxmore »

Authors:

; ;

Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Publication Date:: 2017-03-29

Grant/Contract Number:: AC02-09CH11466; AC05-00OR22725

Type:: Accepted Manuscript

Journal Name:: Plasma Physics and Controlled Fusion

Additional Journal Information:: Journal Volume: 59; Journal Issue: 5; Journal ID: ISSN 0741-3335

Publisher:: IOP Science

Research Org:: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Sponsoring Org:: USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)

Country of Publication:: United States

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Divertor; Detachment; Radiation; Impurities

OSTI Identifier:: 1353398


                    Goldston, R. J., Reinke, M. L., and Schwartz, J. A.. A new scaling for divertor detachment.  United States: N. p.,  
        Web.  doi:10.1088/1361-6587/aa5e6e.

Copy to clipboard


                    Goldston, R. J., Reinke, M. L., & Schwartz, J. A.. A new scaling for divertor detachment.  United States.  doi:10.1088/1361-6587/aa5e6e.

Copy to clipboard


                    Goldston, R. J., Reinke, M. L., and Schwartz, J. A.. 2017.  
        "A new scaling for divertor detachment".  United States.  
        doi:10.1088/1361-6587/aa5e6e.  https://www.osti.gov/servlets/purl/1353398.

Copy to clipboard


                    
@article{osti_1353398,

  title        = {A new scaling for divertor detachment},

  author       = {Goldston, R. J. and Reinke, M. L. and Schwartz, J. A.},

  abstractNote = {The ITER design, and future reactor designs, depend on divertor `detachment,'whether partial, pronounced or complete, to limit heat flux to plasma-facing components and to limit surface erosion due to sputtering. It would be valuable to have a measure of the difficulty of achieving detachment as a function of machine parameters, such as input power, magnetic field, major radius, etc. Frequently the parallel heat flux, estimated typically as proportional to P-sep/R or PsepB/R, is used as a proxy for this difficulty. Here we argue that impurity cooling is dependent on the upstream density, which itself must be limited by a Greenwald-like scaling. Taking this into account self-consistently, we find the impurity fraction required for detachment scales dominantly as power divided by poloidal magnetic field. The absence of any explicit scaling with machine size is concerning, as P-sep surely must increase greatly for an economic fusion system, while increases in the poloidal field strength are limited by coil technology and plasma physics. This result should be challenged by comparison with 2D divertor codes and with measurements on existing experiments. Nonetheless, it suggests that higher magnetic field, stronger shaping, double-null operation, `advanced' divertor configurations, as well as alternate means to handle heat flux such as metallic liquid and/or vapor targets merit greater attention.},

  doi          = {10.1088/1361-6587/aa5e6e},

  journal      = {Plasma Physics and Controlled Fusion},

  number       = 5,

  volume       = 59,

  place        = {United States},

  year         = {2017},

  month        = {3}

}

Copy to clipboard

Free Publicly Accessible Full Text
Accepted Manuscript (DOE)
Publisher's Version of Record
10.1088/1361-6587/aa5e6e
https://doi.org/10.1088/1361-6587/aa5e6e

Citation Metrics
Cited by: 5works
Citation information provided by
Web of Science

Save / Share this Record
Export Metadata
- Endnote
- RIS
- Excel
- CSV
- XML
Save to My Library
Send to Email

Send to Email

Email address:

Content:

Similar Records

Similar records in DOE PAGES and OSTI.GOV collections:

Effects of divertor geometry on H-mode pedestal structure in attached and detached plasmas in the DIII-D tokamak [Effects of divertor geometry on H-mode pedestal structure near divertor detachment in the DIII-D tokamak]

Journal Article Wang, H. Q. ; Guo, H. Y. ; Leonard, A. W. ; ... July 2018 - Nuclear Fusion

Dedicated experiments have been performed in the DIII-D tokamak to assess the influence of divertor geometry on the H-mode pedestal structure. It has been found that in both attached and detached plasmas, compared to the open divertor, the more closed divertor traps more neutrals in the divertor region, leading to lower pedestal fueling and thus results in lower density and higher temperature at the pedestal top. In addition, approaching divertor detachment by increasing the gas-puffing rate, for different divertor geometries, the pedestal width exhibits different trends. In the attached plasma, the pedestal width agrees well with the theoretical and empiricalmore »« less
A review of radiative detachment studies in tokamak advanced magnetic divertor configurations

Journal Article Soukhanovskii, V. A. April 2017 - Plasma Physics and Controlled Fusion

The present vision for a plasma–material interface in the tokamak is an axisymmetric poloidal magnetic X-point divertor. Four tasks are accomplished by the standard poloidal X-point divertor: plasma power exhaust; particle control (D/T and He pumping); reduction of impurity production (source); and impurity screening by the divertor scrape-off layer. A low-temperature, low heat flux divertor operating regime called radiative detachment is viewed as the main option that addresses these tasks for present and future tokamaks. Advanced magnetic divertor configuration has the capability to modify divertor parallel and cross-field transport, radiative and dissipative losses, and detachment front stability. Advanced magnetic divertormore »« less
Cited by 2Full Text Available
SOLPS modeling of the effect on plasma detachment of closing the lower divertor in DIII-D

Journal Article Sang, C. F. ; Stangeby, P. C. ; Guo, H. Y. ; ... December 2016 - Plasma Physics and Controlled Fusion

SOLPS modeling has been carried out to assess the effect of tightly closing the lower divertor in DIII-D, which at present is almost fully open, on the achievement of cold dissipative/detached divertor conditions. To isolate the impact of other factors on the divertor plasma solution and to make direct comparisons, most of the parameters including the meshes were kept as similar as possible. Only the neutral baffling was modified to compare a fully open divertor with a tightly closed one. The modeling shows that the tightly closed divertor greatly improves trapping of recycling neutrals, thereby increasing radiative and charge exchangemore »« less
Full Text Available
Effects of low-Z and high-Z impurities on divertor detachment and plasma confinement

Journal Article Wang, H. Q. ; Guo, Houyang Y. ; Petrie, Thomas W. ; ... March 2017 - Nuclear Materials and Energy

The impurity-seeded detached divertor is essential for heat exhaust in ITER and other reactor-relevant devices. Dedicated experiments with injection of N ₂, Ne and Ar have been performed in DIII-D to assess the impact of the different impurities on divertor detachment and confinement. Seeding with N ₂, Ne and Ar all promote divertor detachment, greatly reducing heat flux near the strike point. The upstream plasma density at the onset of detachment decreases with increasing impurity-puffing flow rates. For all injected impurity species, the confinement and pedestal pressure are correlated with the impurity content and the ratio of separatrix loss powermore »« less
Full Text Available
Increased heat dissipation with the X-divertor geometry facilitating detachment onset at lower density in DIII-D

Journal Article Covele, Brent ; Kotschenreuther, M. ; Mahajan, S. ; ... June 2017 - Nuclear Fusion

The X-Divertor geometry on DIII-D has demonstrated reduced particle and heat fluxes to the target, facilitating detachment onset at ~20% lower upstream density and higher H-mode pedestal pressure than a standard divertor. SOLPS modeling suggests that this effect cannot be explained by an increase in total connection length alone, but rather by the addition of connection length specifically in the power-dissipating volume near the target, via poloidal flux expansion and flaring. But, poloidal flaring must work synergistically with divertor closure to most effectively reduce the detachment density threshold. Furthermore, the model also points to carbon radiation as the primary drivermore »« less
Cited by 5Full Text Available

Access journal articles and accepted manuscripts resulting from DOE research funding

Title: A new scaling for divertor detachment

Access journal articles and accepted manuscripts
resulting from DOE research funding