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On the frequency bifurcations of the MHD startup modes in NSTX
The observed bifurcations of the low frequency ( < 50 kHz) and low toroidal periodicity (n
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| Published in: | Physics of plasmas 2023-06, Vol.30 (6) |
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| cites | cdi_FETCH-LOGICAL-c389t-8607661b94d41eba80ac45e12f970e14f04fa9ae5d8f6ee4da891ae88ffbf7273 |
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| container_issue | 6 |
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| container_title | Physics of plasmas |
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| creator | Munaretto, S. Ferraro, N. M. Fredrickson, E. D. |
| description | The observed bifurcations of the low frequency (
<
50
kHz) and low toroidal periodicity (n |
| doi_str_mv | 10.1063/5.0147928 |
| format | article |
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<
50
kHz) and low toroidal periodicity (n < 5) magnetohydrodynamic (MHD) activity often present in the initial part of the National Spherical Tokamak Experiment (NSTX) discharges can be explained by the evolution of the radial profile of the safety factor (
q
=
r
B
ϕ
/
R
B
θ) crossing multiple rational surfaces in the core. Important performance limiting instability mechanisms in the NSTX spherical tokamak are often linked to low frequency and low-n MHD activity. They are quite common in long-pulse NSTX plasmas. They can be present at the beginning of the plasma current flat-top, at the end of the discharge or during the whole duration, and they have been observed to deleteriously impact performance over a wide range of q95. An interesting feature observed in some NSTX discharges is the presence of a bifurcation in the frequency of the low n modes, as low as n = 1, that have frequencies comparable to the plasma core rotation divided by n. Equilibrium reconstructions constrained by magnetic diagnostics data and motional stark effect pitch angle radial profiles suggest that the observed bifurcations are linked to a fast evolving minimum value of q. 3D non-linear resistive MHD simulations show that these modes are ideal and exist as non-resonant before the correspondent rational surface enters the plasma.</description><identifier>ISSN: 1070-664X</identifier><identifier>EISSN: 1089-7674</identifier><identifier>DOI: 10.1063/5.0147928</identifier><identifier>CODEN: PHPAEN</identifier><language>eng</language><publisher>Melville: American Institute of Physics</publisher><subject>70 PLASMA PHYSICS AND FUSION TECHNOLOGY ; Bifurcations ; Discharge ; Low frequencies ; magnetic confinement fusion ; Magnetohydrodynamics ; Pitch (inclination) ; plasma confinement ; Plasma currents ; plasma instabilities ; Plasma physics ; Rotating plasmas ; Safety factors ; Stark effect ; Tokamak devices ; tokamaks</subject><ispartof>Physics of plasmas, 2023-06, Vol.30 (6)</ispartof><rights>Author(s)</rights><rights>2023 Author(s). Published under an exclusive license by AIP Publishing.</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c389t-8607661b94d41eba80ac45e12f970e14f04fa9ae5d8f6ee4da891ae88ffbf7273</citedby><cites>FETCH-LOGICAL-c389t-8607661b94d41eba80ac45e12f970e14f04fa9ae5d8f6ee4da891ae88ffbf7273</cites><orcidid>0000-0003-1465-0971 ; 0000-0002-6348-7827 ; 0000-0002-2439-4089 ; 0000000263487827 ; 0000000224394089 ; 0000000314650971</orcidid></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><linktohtml>$$Uhttps://pubs.aip.org/pop/article-lookup/doi/10.1063/5.0147928$$EHTML$$P50$$Gscitation$$H</linktohtml><link.rule.ids>230,315,783,785,787,798,888,27936,27937,76718</link.rule.ids><backlink>$$Uhttps://www.osti.gov/servlets/purl/1986325$$D View this record in Osti.gov$$Hfree_for_read</backlink></links><search><creatorcontrib>Munaretto, S.</creatorcontrib><creatorcontrib>Ferraro, N. M.</creatorcontrib><creatorcontrib>Fredrickson, E. D.</creatorcontrib><creatorcontrib>Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)</creatorcontrib><title>On the frequency bifurcations of the MHD startup modes in NSTX</title><title>Physics of plasmas</title><description>The observed bifurcations of the low frequency (
<
50
kHz) and low toroidal periodicity (n < 5) magnetohydrodynamic (MHD) activity often present in the initial part of the National Spherical Tokamak Experiment (NSTX) discharges can be explained by the evolution of the radial profile of the safety factor (
q
=
r
B
ϕ
/
R
B
θ) crossing multiple rational surfaces in the core. Important performance limiting instability mechanisms in the NSTX spherical tokamak are often linked to low frequency and low-n MHD activity. They are quite common in long-pulse NSTX plasmas. They can be present at the beginning of the plasma current flat-top, at the end of the discharge or during the whole duration, and they have been observed to deleteriously impact performance over a wide range of q95. An interesting feature observed in some NSTX discharges is the presence of a bifurcation in the frequency of the low n modes, as low as n = 1, that have frequencies comparable to the plasma core rotation divided by n. Equilibrium reconstructions constrained by magnetic diagnostics data and motional stark effect pitch angle radial profiles suggest that the observed bifurcations are linked to a fast evolving minimum value of q. 3D non-linear resistive MHD simulations show that these modes are ideal and exist as non-resonant before the correspondent rational surface enters the plasma.</description><subject>70 PLASMA PHYSICS AND FUSION TECHNOLOGY</subject><subject>Bifurcations</subject><subject>Discharge</subject><subject>Low frequencies</subject><subject>magnetic confinement fusion</subject><subject>Magnetohydrodynamics</subject><subject>Pitch (inclination)</subject><subject>plasma confinement</subject><subject>Plasma currents</subject><subject>plasma instabilities</subject><subject>Plasma physics</subject><subject>Rotating plasmas</subject><subject>Safety factors</subject><subject>Stark effect</subject><subject>Tokamak devices</subject><subject>tokamaks</subject><issn>1070-664X</issn><issn>1089-7674</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2023</creationdate><recordtype>article</recordtype><recordid>eNqd0E1LwzAYB_AgCs7pwW8Q9KTQmbRpXi6CzJcJ0x2csFtI04R1uKYmqbBvb7sOvHvKA_nxvPwBuMRoghHN7vIJwoSJlB-BEUZcJIwyctzXDCWUktUpOAthgxAiNOcjcL-oYVwbaL35bk2td7CobOu1ipWrA3R2__s2e4QhKh_bBm5daQKsavj-sVydgxOrvoK5OLxj8Pn8tJzOkvni5XX6ME90xkVMOEWMUlwIUhJsCsWR0iQ3OLWCIYOJRcQqoUxeckuNIaXiAivDubWFZSnLxuBq6OtCrGTQVTR6rV1dGx0lFpxmad6h6wE13nXHhCg3rvV1t5dMeYpJnmWMdupmUNq7ELyxsvHVVvmdxEj2GcpcHjLs7O1g-4n7SP6Hf5z_g7IpbfYLobB93w</recordid><startdate>202306</startdate><enddate>202306</enddate><creator>Munaretto, S.</creator><creator>Ferraro, N. M.</creator><creator>Fredrickson, E. D.</creator><general>American Institute of Physics</general><general>American Institute of Physics (AIP)</general><scope>AAYXX</scope><scope>CITATION</scope><scope>8FD</scope><scope>H8D</scope><scope>L7M</scope><scope>OIOZB</scope><scope>OTOTI</scope><orcidid>https://orcid.org/0000-0003-1465-0971</orcidid><orcidid>https://orcid.org/0000-0002-6348-7827</orcidid><orcidid>https://orcid.org/0000-0002-2439-4089</orcidid><orcidid>https://orcid.org/0000000263487827</orcidid><orcidid>https://orcid.org/0000000224394089</orcidid><orcidid>https://orcid.org/0000000314650971</orcidid></search><sort><creationdate>202306</creationdate><title>On the frequency bifurcations of the MHD startup modes in NSTX</title><author>Munaretto, S. ; Ferraro, N. M. ; Fredrickson, E. D.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c389t-8607661b94d41eba80ac45e12f970e14f04fa9ae5d8f6ee4da891ae88ffbf7273</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2023</creationdate><topic>70 PLASMA PHYSICS AND FUSION TECHNOLOGY</topic><topic>Bifurcations</topic><topic>Discharge</topic><topic>Low frequencies</topic><topic>magnetic confinement fusion</topic><topic>Magnetohydrodynamics</topic><topic>Pitch (inclination)</topic><topic>plasma confinement</topic><topic>Plasma currents</topic><topic>plasma instabilities</topic><topic>Plasma physics</topic><topic>Rotating plasmas</topic><topic>Safety factors</topic><topic>Stark effect</topic><topic>Tokamak devices</topic><topic>tokamaks</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Munaretto, S.</creatorcontrib><creatorcontrib>Ferraro, N. M.</creatorcontrib><creatorcontrib>Fredrickson, E. D.</creatorcontrib><creatorcontrib>Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)</creatorcontrib><collection>CrossRef</collection><collection>Technology Research Database</collection><collection>Aerospace Database</collection><collection>Advanced Technologies Database with Aerospace</collection><collection>OSTI.GOV - Hybrid</collection><collection>OSTI.GOV</collection><jtitle>Physics of plasmas</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Munaretto, S.</au><au>Ferraro, N. M.</au><au>Fredrickson, E. D.</au><aucorp>Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)</aucorp><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>On the frequency bifurcations of the MHD startup modes in NSTX</atitle><jtitle>Physics of plasmas</jtitle><date>2023-06</date><risdate>2023</risdate><volume>30</volume><issue>6</issue><issn>1070-664X</issn><eissn>1089-7674</eissn><coden>PHPAEN</coden><abstract>The observed bifurcations of the low frequency (
<
50
kHz) and low toroidal periodicity (n < 5) magnetohydrodynamic (MHD) activity often present in the initial part of the National Spherical Tokamak Experiment (NSTX) discharges can be explained by the evolution of the radial profile of the safety factor (
q
=
r
B
ϕ
/
R
B
θ) crossing multiple rational surfaces in the core. Important performance limiting instability mechanisms in the NSTX spherical tokamak are often linked to low frequency and low-n MHD activity. They are quite common in long-pulse NSTX plasmas. They can be present at the beginning of the plasma current flat-top, at the end of the discharge or during the whole duration, and they have been observed to deleteriously impact performance over a wide range of q95. An interesting feature observed in some NSTX discharges is the presence of a bifurcation in the frequency of the low n modes, as low as n = 1, that have frequencies comparable to the plasma core rotation divided by n. Equilibrium reconstructions constrained by magnetic diagnostics data and motional stark effect pitch angle radial profiles suggest that the observed bifurcations are linked to a fast evolving minimum value of q. 3D non-linear resistive MHD simulations show that these modes are ideal and exist as non-resonant before the correspondent rational surface enters the plasma.</abstract><cop>Melville</cop><pub>American Institute of Physics</pub><doi>10.1063/5.0147928</doi><tpages>9</tpages><orcidid>https://orcid.org/0000-0003-1465-0971</orcidid><orcidid>https://orcid.org/0000-0002-6348-7827</orcidid><orcidid>https://orcid.org/0000-0002-2439-4089</orcidid><orcidid>https://orcid.org/0000000263487827</orcidid><orcidid>https://orcid.org/0000000224394089</orcidid><orcidid>https://orcid.org/0000000314650971</orcidid><oa>free_for_read</oa></addata></record> |
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| ispartof | Physics of plasmas, 2023-06, Vol.30 (6) |
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| language | eng |
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| source | American Institute of Physics:Jisc Collections:Transitional Journals Agreement 2021-23 (Reading list); American Institute of Physics |
| subjects | 70 PLASMA PHYSICS AND FUSION TECHNOLOGY Bifurcations Discharge Low frequencies magnetic confinement fusion Magnetohydrodynamics Pitch (inclination) plasma confinement Plasma currents plasma instabilities Plasma physics Rotating plasmas Safety factors Stark effect Tokamak devices tokamaks |
| title | On the frequency bifurcations of the MHD startup modes in NSTX |
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