ISSN:
1089-7666
Source:
AIP Digital Archive
Topics:
Physics
Notes:
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 current-carrying channel exceed the impurity radiative cooling in this critical region. A compact summary of our results gives this limit nM for the central density as nM =[Ze/(Ze−1)]1/2 ne0 (BT /1T) (1m/R), where ne0 depends strongly on the impurity species and is remarkably independent of the central electron temperature Te(0). For Te(0) ∼1 keV, ne0 =1.5×1014 cm−3 for beryllium, ne0 =5.5×1013 cm−3 for oxygen, ne0 =1.0×1013 cm−3 for iron and, ne0 =0.5×1013 cm−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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.864927
