Observation of ultra low q equilibrium

Abstract

LETTERS by sputtering at the divertor target may not be retained within the divertor and contamination of the core plasma may result.Peak target temperatures below ~50 eV imply that the flow will be reversed at the separatrix and forward at the wall. While this may help to remove impurities produced at the first wall, it is likely to have a detrimental effect on the particle removal rate. Coupling of core and edge plasma codes [8] has shown that the stagnated flow in the upstream scrape-off layer caused by the high recycling conditions in the divertor leads to a flattening of the radial density profile near the edge of the core plasma. Flow reversal at the separatrix is expected to increase this tendency which has the effect of increasing the particle confinement time in the core plasma. Removal of the fusion generated alpha particles may thus pose a problem leading to a higher fraction of helium in the core plasma than is desirable and a reduction of the fuel density and fusion power if the plasma is operating at its 0 limit.

Minimum dissipative relaxed states applied to laboratory and space plasmas

“…Pressure profile peaks at the center and goes to zero at the edge. Some of these results have been observed in the SINP tokamak [Lahiri et al, 1996] and were also reported earlier in REPUTE-1 [Yoshida et al, 1986] and in TORIUT-6 [Yamada et al, 1987].…”

Tokamak, reversed field pinch and intermediate structures as minimum-dissipative relaxed states

“…Such observations of low q-equilibria have also been reported earlier in Repute-1 17 as well as in Toriut-6. 20 An effort to understand the equilibrium of a cylindrical plasma in the ULQ regime was earlier made by Yoshida et al, 21 by solving the force-free equation by assuming a nonconstant Lagrange multiplier . The present work is an attempt to understand the relaxation mechanisms that are operative in these low-q type of toroidal discharges as well as to present the different configurations within the framework of a single relaxation model as is often indicated by the experimental results.…”

Anomalous ion heating in REPUTE-1 ultra-low q and reversed field pinch plasmas

“…Substituting E o = V A B into Eq. ( 10), we have W = mV A g 2Bl (14) and so the heating power is proportional to B 2 .…”

“…In the ULQ configuration, q(r) lies between two m = 1 rational surfaces and it is a decreasing function of r in the major part of plasma, which results in a minimum of the pitch near the periphery. Such a profile is formed through MHD relaxation [14][15][16] or fast current rise. The linear stability of ULQ configurations has been studied theoretically and numerically [17].…”