Improved confinement in HBTX with removal of tile limiters

The plasma energy confinement in CTX mesh flux conservers appears to be dominated by relaxation fluctuations which drive current in the resistive plasma edge region. Strong ion heating is expected from these relaxation processes. The paper presents new data, from previously studied decaying discharges, which show impurity oxygen ion Doppler temperatures much above the Thomson scattering electron temperature. In addition, using the standard MHD equilibrium model by Knox et al., and the resistivity model previously described by Fernández et al., the contribution of relaxation fluctuations to spheromak current drive along the open magnetic field lines at the spheromak edge can be estimated.

Section: Discussionsupporting

confidence: 75%

Section: Ion Energy Correlationsmentioning

confidence: 99%

Ion heating and current drive from relaxation in decaying spheromaks in mesh flux conservers

Fernández¹,

Jarboe²,

Knox³

et al. 1990

“…Insertion of a movable limiter into the HBTX plasma resulted in an increase of the loop voltage and heating of ions [8]. The removal of tile limiters in HBTX [9,10] led to a reduction of the loop voltage by about one third, an increase of the electron temperature T e from 350 eV to 460 eV, and a decrease of the ion temperature Tj from 360 eV to 230 eV. In the ZT-40M experiment [11], the relation between T; and the fraction of the total input power absorbed by fluctuations was estimated using a modified Bessel function model.…”

Section: Introductionmentioning

confidence: 99%

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

Fujita¹,

Saito

Matsui

et al. 1991

Measurements of ion and electron temperatures on REPUTE-1 ultra-low q (ULQ) and reversed field pinch (RFP) plasmas have revealed that the ion temperature is higher than the electron temperature and that the impurity ion temperature exceeds the hydrogen ion temperature. In ULQ plasmas the impurity ion temperature is correlated with the amplitude of the magnetic field fluctuations observed outside the plasma. A model on ion heating by fluctuations is found to explain the experimental results.

“…Alternatively, we could attribute R p I p completely to V s without introducing V . We showed a global scaling of Z * in equation (8), which showed an increase of Z * with I p . In particular cases in TPE-1RM15 and TPE-1RM20, Z * increases from ∼4 at I p = 100 kA to ∼8 at I p = 220 kA: namely, Z * increases approximately proportionally to I p , which is consistent with the global scaling in equation (8).…”

Section: Critical Input Power In the I P -Scanmentioning

confidence: 76%

Characteristics of global confinement properties in TPE-series reversed-field pinch devices

Yagi¹,

Maejima²,

Hirano³

et al. 2003

A confinement database of the reversed-field pinch (RFP) devices of the toroidal pinch experiment (TPE) series has been established. The TPE database contains global confinement properties under various experimental conditions for four different devices and seven different cases, which cover two decades of experiments. Characteristics of the TPE database have been extracted under consistent experimental conditions of conventional RFP discharges, and scaling laws of the poloidal beta, βp and energy confinement time, τ E, are given against independent parameters that include the size of the plasma and the pinch parameter Θ. Scaling laws of and are obtained for a set of scans, where a is the plasma minor radius, Ip the plasma current and N the column density. The scaling of τ E on a, Ip, and I/N is similar to that dominated by the transport under tearing instability. Another scaling shows that τ E is inversely proportional to the Joule input power. The scaling for the apparent effective charge shows a positive correlation both with Ip and I/N.