A theoretical upper limit for the density in an ohmically heated tokamak discharge follows from the requirement that the ohmic heating power deposited in the central current-carrying channel exceed the impurity radiative cooling in this critical region. A compact summary of our results gives this limit n/sub M/ for the central density as n/sub M/ = (Z/sub e//(Z/sub e/-1)/sup 1/2/n/sub eo/ (B/sub T//1T)(1m/R) where n/sub eo/ depends strongly on the impurity species and is remarkably independent of the central electron temperature T/sub e/(0). For T/sub e/(0) approx. 1 keV, we have n/sub eo/ = 1.5 x 10/sup 14/ cm/sup -3/ …
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A theoretical upper limit for the density in an ohmically heated tokamak discharge follows from the requirement that the ohmic heating power deposited in the central current-carrying channel exceed the impurity radiative cooling in this critical region. A compact summary of our results gives this limit n/sub M/ for the central density as n/sub M/ = (Z/sub e//(Z/sub e/-1)/sup 1/2/n/sub eo/ (B/sub T//1T)(1m/R) where n/sub eo/ depends strongly on the impurity species and is remarkably independent of the central electron temperature T/sub e/(0). For T/sub e/(0) approx. 1 keV, we have n/sub eo/ = 1.5 x 10/sup 14/ cm/sup -3/ for beryllium, n/sub eo/ = 5 x 10/sup 13/ cm/sup -3/ for oxygen, n/sub eo/ = 1.0 x 10/sup 13/ cm/sup -3/ for iron, and n/sub eo/ = 0.5 x 10/sup 13/ cm/sup -3/ for tungsten. The results agree quantitatively with Murakami's original observations. A similar density limit, known as the I/N limit, exists for reversed-field pinch devices and this limit has also been evaluated for a variety of impurity species.
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Perkins, F.W. & Hulse, R.A.Murakami density limit in tokamaks and reversed-field pinches,
report,
March 1, 1984;
New Jersey.
(https://digital.library.unt.edu/ark:/67531/metadc1055147/:
accessed May 30, 2024),
University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu;
crediting UNT Libraries Government Documents Department.
