Multiple ion temperature gradient driven modes in transport barriers

The ion temperature gradient (ITG) modes in transport barriers (TBs) of tokamak plasmas are numerically studied with a code solving gyrokinetic integral eigenvalue equations in toroidal configurations. It is found that multiple ITG modes with conventional and unconventional ballooning mode structure...

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Published in:Nuclear fusion 2017-04, Vol.57 (4), p.46019
Main Authors: Han, M.K., Wang, Zheng-Xiong, Dong, J.Q., Du, Huarong
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Language:English
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ion temperature gradient instability
transport barriers
turbulence
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description The ion temperature gradient (ITG) modes in transport barriers (TBs) of tokamak plasmas are numerically studied with a code solving gyrokinetic integral eigenvalue equations in toroidal configurations. It is found that multiple ITG modes with conventional and unconventional ballooning mode structures can be excited simultaneously in TBs with steep gradients of ion temperature and density. The characteristics of the modes, including the dependence of the mode frequencies, growth rate and structure on plasma parameters, are systematically investigated. Unconventional modes with large mode-number l (where l denotes a certain parity and peak number in ballooning space) dominate in the large kθρs region (kθρs 1.2), while the conventional mode with l=0 dominates in the medium kθρs region (0.4 kθρs
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It is found that multiple ITG modes with conventional and unconventional ballooning mode structures can be excited simultaneously in TBs with steep gradients of ion temperature and density. The characteristics of the modes, including the dependence of the mode frequencies, growth rate and structure on plasma parameters, are systematically investigated. Unconventional modes with large mode-number l (where l denotes a certain parity and peak number in ballooning space) dominate in the large kθρs region (kθρs 1.2), while the conventional mode with l=0 dominates in the medium kθρs region (0.4 kθρs&lt;1.2), and unconventional modes with small mode-number l dominate in the small kθρs region (kθρs&lt;0.4). Thus, the kθρs spectra of these conventional and unconventional modes at steep gradients are qualitatively different from those of the conventional ITG modes at small or medium gradients, in which the growth rate of the only ITG mode with l=0 reaches maximum at the medium value kθρs=0.6. Through scanning ion temperature gradient εTi and density gradient εn separately, it is proven that the synergetic effect of εTi and εn, rather than εTi alone, drives the unconventional ITG modes in TBs. Moreover, it is found that the critical value of εn for driving the unconventional ITG modes with large l number increases with increasing kθρs. In addition, the effects of magnetic shear on conventional and unconventional ITG modes in the high confinement regime (H-mode) are analyzed in detail, and compared with equivalent effects on conventional modes in the low and intermediate gradient regimes (L- and I- modes). Finally, the effects of the poloidal wave number and gradients of ion temperature and density on radial transport are analyzed based on quasi-linear mixing length estimations.</description><identifier>ISSN: 0029-5515</identifier><identifier>EISSN: 1741-4326</identifier><identifier>DOI: 10.1088/1741-4326/aa5d02</identifier><identifier>CODEN: NUFUAU</identifier><language>eng</language><publisher>IOP Publishing</publisher><subject>ion temperature gradient instability ; transport barriers ; turbulence</subject><ispartof>Nuclear fusion, 2017-04, Vol.57 (4), p.46019</ispartof><rights>2017 IAEA, Vienna</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c322t-d692ba47dfdf673ad013f2ee7c853355f00159f084000eb0785f1d1715c9724b3</citedby><cites>FETCH-LOGICAL-c322t-d692ba47dfdf673ad013f2ee7c853355f00159f084000eb0785f1d1715c9724b3</cites></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,780,784,27924,27925</link.rule.ids></links><search><creatorcontrib>Han, M.K.</creatorcontrib><creatorcontrib>Wang, Zheng-Xiong</creatorcontrib><creatorcontrib>Dong, J.Q.</creatorcontrib><creatorcontrib>Du, Huarong</creatorcontrib><title>Multiple ion temperature gradient driven modes in transport barriers</title><title>Nuclear fusion</title><addtitle>NF</addtitle><addtitle>Nucl. Fusion</addtitle><description>The ion temperature gradient (ITG) modes in transport barriers (TBs) of tokamak plasmas are numerically studied with a code solving gyrokinetic integral eigenvalue equations in toroidal configurations. It is found that multiple ITG modes with conventional and unconventional ballooning mode structures can be excited simultaneously in TBs with steep gradients of ion temperature and density. The characteristics of the modes, including the dependence of the mode frequencies, growth rate and structure on plasma parameters, are systematically investigated. Unconventional modes with large mode-number l (where l denotes a certain parity and peak number in ballooning space) dominate in the large kθρs region (kθρs 1.2), while the conventional mode with l=0 dominates in the medium kθρs region (0.4 kθρs&lt;1.2), and unconventional modes with small mode-number l dominate in the small kθρs region (kθρs&lt;0.4). Thus, the kθρs spectra of these conventional and unconventional modes at steep gradients are qualitatively different from those of the conventional ITG modes at small or medium gradients, in which the growth rate of the only ITG mode with l=0 reaches maximum at the medium value kθρs=0.6. Through scanning ion temperature gradient εTi and density gradient εn separately, it is proven that the synergetic effect of εTi and εn, rather than εTi alone, drives the unconventional ITG modes in TBs. Moreover, it is found that the critical value of εn for driving the unconventional ITG modes with large l number increases with increasing kθρs. In addition, the effects of magnetic shear on conventional and unconventional ITG modes in the high confinement regime (H-mode) are analyzed in detail, and compared with equivalent effects on conventional modes in the low and intermediate gradient regimes (L- and I- modes). Finally, the effects of the poloidal wave number and gradients of ion temperature and density on radial transport are analyzed based on quasi-linear mixing length estimations.</description><subject>ion temperature gradient instability</subject><subject>transport barriers</subject><subject>turbulence</subject><issn>0029-5515</issn><issn>1741-4326</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2017</creationdate><recordtype>article</recordtype><recordid>eNp1UE1LxDAUDKLgunr3mB9g3ZekadqjrJ-w4kXPIW1eJEu_eGkF_71dVrx5Ghhmhplh7FrArYCy3AiTiyxXstg4pz3IE7b6o07ZCkBWmdZCn7OLlPYAIhdKrdj969xOcWyRx6HnE3YjkptmQv5JzkfsJ-4pfmHPu8Fj4nERkevTONDEa0cUkdIlOwuuTXj1i2v28fjwvn3Odm9PL9u7XdYoKafMF5WsXW588KEwynkQKkhE05RaKa3D0kpXAcocALAGU-ogvDBCN5WRea3WDI65DQ0pEQY7UuwcfVsB9vCCPUy2h8n2-MJiuTla4jDa_TBTvxT8X_4DNHheIw</recordid><startdate>20170401</startdate><enddate>20170401</enddate><creator>Han, M.K.</creator><creator>Wang, Zheng-Xiong</creator><creator>Dong, J.Q.</creator><creator>Du, Huarong</creator><general>IOP Publishing</general><scope>O3W</scope><scope>TSCCA</scope><scope>AAYXX</scope><scope>CITATION</scope></search><sort><creationdate>20170401</creationdate><title>Multiple ion temperature gradient driven modes in transport barriers</title><author>Han, M.K. ; Wang, Zheng-Xiong ; Dong, J.Q. ; Du, Huarong</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c322t-d692ba47dfdf673ad013f2ee7c853355f00159f084000eb0785f1d1715c9724b3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2017</creationdate><topic>ion temperature gradient instability</topic><topic>transport barriers</topic><topic>turbulence</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Han, M.K.</creatorcontrib><creatorcontrib>Wang, Zheng-Xiong</creatorcontrib><creatorcontrib>Dong, J.Q.</creatorcontrib><creatorcontrib>Du, Huarong</creatorcontrib><collection>Open Access: IOP Publishing Free Content</collection><collection>IOPscience (Open Access)</collection><collection>CrossRef</collection><jtitle>Nuclear fusion</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Han, M.K.</au><au>Wang, Zheng-Xiong</au><au>Dong, J.Q.</au><au>Du, Huarong</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Multiple ion temperature gradient driven modes in transport barriers</atitle><jtitle>Nuclear fusion</jtitle><stitle>NF</stitle><addtitle>Nucl. Fusion</addtitle><date>2017-04-01</date><risdate>2017</risdate><volume>57</volume><issue>4</issue><spage>46019</spage><pages>46019-</pages><issn>0029-5515</issn><eissn>1741-4326</eissn><coden>NUFUAU</coden><abstract>The ion temperature gradient (ITG) modes in transport barriers (TBs) of tokamak plasmas are numerically studied with a code solving gyrokinetic integral eigenvalue equations in toroidal configurations. It is found that multiple ITG modes with conventional and unconventional ballooning mode structures can be excited simultaneously in TBs with steep gradients of ion temperature and density. The characteristics of the modes, including the dependence of the mode frequencies, growth rate and structure on plasma parameters, are systematically investigated. Unconventional modes with large mode-number l (where l denotes a certain parity and peak number in ballooning space) dominate in the large kθρs region (kθρs 1.2), while the conventional mode with l=0 dominates in the medium kθρs region (0.4 kθρs&lt;1.2), and unconventional modes with small mode-number l dominate in the small kθρs region (kθρs&lt;0.4). Thus, the kθρs spectra of these conventional and unconventional modes at steep gradients are qualitatively different from those of the conventional ITG modes at small or medium gradients, in which the growth rate of the only ITG mode with l=0 reaches maximum at the medium value kθρs=0.6. Through scanning ion temperature gradient εTi and density gradient εn separately, it is proven that the synergetic effect of εTi and εn, rather than εTi alone, drives the unconventional ITG modes in TBs. Moreover, it is found that the critical value of εn for driving the unconventional ITG modes with large l number increases with increasing kθρs. In addition, the effects of magnetic shear on conventional and unconventional ITG modes in the high confinement regime (H-mode) are analyzed in detail, and compared with equivalent effects on conventional modes in the low and intermediate gradient regimes (L- and I- modes). Finally, the effects of the poloidal wave number and gradients of ion temperature and density on radial transport are analyzed based on quasi-linear mixing length estimations.</abstract><pub>IOP Publishing</pub><doi>10.1088/1741-4326/aa5d02</doi><tpages>14</tpages><oa>free_for_read</oa></addata></record>
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subjects ion temperature gradient instability
transport barriers
turbulence
title Multiple ion temperature gradient driven modes in transport barriers
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