A potential mechanism for the creation of reversed-magnetic-shear transport barriers in tokamaks
| dc.contributor.author | Throumoulopoulos, G. N. | en |
| dc.contributor.author | Pfirsch, D. | en |
| dc.date.accessioned | 2015-11-24T18:33:38Z | |
| dc.date.available | 2015-11-24T18:33:38Z | |
| dc.identifier.issn | 1070-664X | - |
| dc.identifier.uri | https://olympias.lib.uoi.gr/jspui/handle/123456789/16767 | |
| dc.rights | Default Licence | - |
| dc.subject | negative-energy perturbations | en |
| dc.subject | deuterium-tritium plasmas | en |
| dc.subject | maxwell-vlasov equilibria | en |
| dc.subject | radial electric-field | en |
| dc.subject | drift kinetic-theory | en |
| dc.subject | cylindrical equilibria | en |
| dc.subject | waves | en |
| dc.subject | modes | en |
| dc.subject | stability | en |
| dc.subject | framework | en |
| dc.title | A potential mechanism for the creation of reversed-magnetic-shear transport barriers in tokamaks | en |
| heal.abstract | The impact of reversed magnetic shear (s < 0) along with a radial electric field E-r on negative-energy perturbations (NEP's) is investigated for the case of cylindrical tokamak-like equilibria. NEP's can imply instabilities leading to anomalous transport [G. N. Throumoulopoulos and D. Pfirsch, Phys. Rev. E 56, 5979 (1997) and references therein]. For equilibria with E-r corresponding to \e(nu)phi\much less than beta T-nu and eta(nu)< 4/3 (phi is the electrostatic potential, beta equivalent to 8 pi P/B-2, eta(nu)equivalent to partial derivative lnT(nu)/partial derivative lnN(nu) and nu denotes the particle species) s < 0 results in a reduction of the fraction of particles associated with NEP's (active particles) as compared with equilibria with s > 0, by making the pressure profile steeper. The reduction is stronger the closer the minimum of the safety factor (q(min)) to the plasma center and the lower the negative value of s. For equilibria with \e(nu)phi\much less than beta T-nu and eta(nu)> 4/3 the fraction of active particles decreases as the magnetic tension B-theta(2)/r becomes larger. For E-r< 0 corresponding to \e(nu)phi\approximate to beta T-nu the electric field leads to a reduction of the fraction of active ions for eta(i)< 4/3 and of the fraction of active electrons for eta(e)> 4/3 in addition to that caused by s < 0 and B-theta(2)/r, respectively. For T(nu)greater than or equal to\e(nu)phi\much greater than beta T-nu, which corresponds to experimental observations, the reduction of active particles caused by E-r< 0 is insensitive to the sign and the value of s, the position of q(min), and the value of B-theta(2)/r. In addition, it is shown that the experimentally evidenced facts that (a) s < 0 is associated with a steepness of the pressure profile and (b) the position of q(min) is displaced towards the plasma edge as the toroidal current is increased are consistent with equilibrium considerations. It is emphasized that these results cannot yet give a complete picture, since the present paper still neglects toroidal effects. (C) 1999 American Institute of Physics. [S1070-664X(99)03208-5]. | en |
| heal.access | campus | - |
| heal.fullTextAvailability | TRUE | - |
| heal.identifier.secondary | <Go to ISI>://000081587100030 | - |
| heal.identifier.secondary | http://link.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PHPAEN000006000008003226000001 | - |
| heal.journalName | Physics of Plasmas | en |
| heal.journalType | peer reviewed | - |
| heal.language | en | - |
| heal.publicationDate | 1999 | - |
| heal.recordProvider | Πανεπιστήμιο Ιωαννίνων. Σχολή Επιστημών και Τεχνολογιών. Τμήμα Βιολογικών Εφαρμογών και Τεχνολογιών | el |
| heal.type | journalArticle | - |
| heal.type.el | Άρθρο Περιοδικού | el |
| heal.type.en | Journal article | en |
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