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An international ITB database has been constructed to address primarily power threshold scaling, confinement scaling and underlying physics in ITB plasmas. For the power threshold scaling, a precise definition of ITB is required. Either the temporal separation of temperatures in two neighbouring measurement channels or the discontinuity in gradients in temperature profiles is often used to judge the ITB formation. However, both of these criteria become unclear for low heating power approaching the threshold for the ITB formation. Given this uncertainty in determining ITB existence, parameters are sought which will better define the time and spatial location of ITB. A parameter frequently employed is R(geo)/L(T) where R(geo) is the plasma major radius and L(T)is the local temperature gradient scale length. Another parameter is rho(T)*=rho(s)/L(T) where rho(s) is the local ion gyroradius at the sound speed; rho(s) = (m(i)T(e)){l/2}/(Z(i)eB(t), m(i) is the ion mass, Z(i) is the ion charge number and B(t) is the toroidal field. This parameter has a strong B(t) dependence and no R(geo) dependence in contrast to R(geo)/L(T). The existence of ITB S in JET plasmas can be inferred in regions of space- time where rho(T)*>rho(ITB)* , where rho(ITB)* is some critical value. Interestingly, a constant value of rho(ITB)*, 0.014, is valid for a large variety of JET discharges heated by NB and IC with B(t) = 1.8-4.0 T when L(Te) is used as L(T). As a first step in finding a parameter or a key quantity that can be generally used to judge the ITB existence, the validity of rho(T)* is investigated for various devices in this paper.

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Authors: FUJITA T ET AL, JAERI, Naka Fusion Research Establishment, Naka (JP);ANIEL T ET AL, Association EURATOM -CEA, CEA Cadarache (FR);BARBATO E, Association EURATOM -ENEA, Frascati (IT);BEHN R, Association EURATOM-Confederation Suisse, Lausanne (CH);BELL R E, Princeton Plasma Physics Laboratory, Princeton (US);FIELD A R, EURATOM/UKAEA Fusion Association, Abingdon (GB);FUKADA T, Osaka University, Suita (JP);GOHIL P, General Atomics, San Diego (US);IDA K, NIFS, Toki (JP);KINERVA N A, RRC "Kurchatov Institute", Moscow (RU);RAZUMOVA K A, RRC "Kurchatov Institute", Moscow (RU);PENG Y-K M, Oak Ridge National Laboratory, Oak Ridge (US);RICE J E, Massachusetts Institute of Technology, Cambridge, USA;SIPS A C C, Max-Planck-Institut fur Plasmaphysik, EURATOM Association, Garching (DE)
Bibliographic Reference: An oral paper given at: 30th EPS Conference on Controlled Fusion and Plasma Physics Organised by: European Physical Society Held at: St. Petersburg, Russia, 7-11 July 2003 Paper No. P-2.131 Proceedings available online at: http://eps200
Availability: Available from Association EURATOM-CEA, Département de Recherches sur la Fusion Contrôlée, CEA Cadarache, F-13108 St Paul-Lez-Durance, France Tel:+33-4-42257001; Fax:+33-4-42256421 E-mail:
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