Murakami density limit in tokamaks and reversed-field pinches
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.
- Research Organization:
- Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
- DOE Contract Number:
- AC02-76CH03073
- OSTI ID:
- 5194209
- Report Number(s):
- PPPL-2087; ON: DE84009353
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
REVERSE-FIELD PINCH
PLASMA DENSITY
TOKAMAK DEVICES
ELECTRON TEMPERATURE
IMPURITIES
JOULE HEATING
CLOSED PLASMA DEVICES
ELECTRIC HEATING
HEATING
PINCH EFFECT
PLASMA HEATING
RESISTANCE HEATING
THERMONUCLEAR DEVICES
700105* - Fusion Energy- Plasma Research- Plasma Kinetics-Theoretical- (-1987)