The effect of plasma beta on high-n ballooning stability at low magnetic shear

  title={The effect of plasma beta on high-n ballooning stability at low magnetic shear},
  author={J. W. Connor and C J Ham and R. J. Hastie},
  journal={Plasma Physics and Controlled Fusion},
An explanation of the observed improvement in H-mode pedestal characteristics with increasing core plasma pressure or poloidal beta, βpol, as observed in MAST and JET, is sought in terms of the impact of the Shafranov shift, Δ′, on ideal ballooning MHD stability. To illustrate this succinctly, a self-consistent treatment of the low magnetic shear region of the ‘s−α’ stability diagram is presented using the large aspect ratio Shafranov equilibrium, but enhancing both α   and Δ′ so that they… 

Effect of pressure gradient in the connection region on the stability of the edge pedestal

We have numerically investigated the dependence of pedestal properties such as the pedestal height and the pedestal width on the normalized pressure gradient ( α) in the connection region, αc. We

Analytic study on low-n external ideal infernal modes in tokamaks with large edge pressure gradients

The problem of pressure driven infernal type perturbations near the plasma edge is addressed analytically for a circular limited tokamak configuration which presents an edge flattened safety factor.

Dependence of pedestal properties on plasma parameters

We have numerically investigated the dependence of pedestal properties such as the pedestal height and the pedestal width on various global parameters using the EURO-DEMO as the reference

Long-lived coupled peeling ballooning modes preceding ELMs on JET

In some JET discharges, type-I edge localised modes (ELMs) are preceded by a class of low-frequency oscillations (Perez et al 2004 Nucl. Fusion 44 609). While in many cases the ELM is triggered

Plasma shaping and its impact on the pedestal of ASDEX Upgrade: edge stability and inter-ELM dynamics at varied triangularity

The plasma shape, in particular the triangularity (δ), impacts on the pedestal stability. A scan of δ including a variation of heating power (Pheat) and gas puff was performed to study the behaviour

On energy confinement following the onset of ‘stiff’ transport

The dependence of confinement on input power for a tokamak plasma with regions having a stiff temperature profile is explored. The resilience of the confinement of the core energy to increasing power

On hybrid scenarios in KSTAR

We report the status of hybrid scenario experiments in Korea Superconducting Tokamak Advanced Research (KSTAR). The hybrid scenario is defined as stationary discharges with βN ⩾ 2.4 and H89 ⩾ 2.0 at



The stabilizing effect of core pressure on the edge pedestal in MAST plasmas

The pedestal pressure measured in Mega Ampere Spherical Tokamak plasmas has been shown to increase as the global plasma pressure increases. By deliberately suppressing the transition into the

Impact of the edge pedestal characteristics on the integrated performance in advanced tokamak operation modes in JT-60U

Characteristics of the edge pedestal has been studied for the high βp ELMy H mode and the reversed shear ELMy H mode in JT-60U. The contribution of the pedestal is around 20% for the confinement

The second region of stability against ballooning modes

A new type of axisymmetric magnetohydrodynamic equilibrium is presented. It is characterized by a region of pressure and safety factor variation with a short scale length imposed as a perturbation.

Impact of plasma core profiles on MHD stability at tokamak edge pedestal

Impact of plasma core profiles on magnetohydrodynamics (MHD) stability at tokamak edge pedestal is investigated numerically to extend an operation regime for small amplitude grassy edge localized

Ideal magnetohydrodynamic stability of the tokamak high-confinement-mode edge region

The ideal magnetohydrodynamic (MHD) stability of the tokamak edge is analyzed, with particular emphasis on radially localized instabilities; it is proposed that these are responsible for edge

High mode number stability of an axisymmetric toroidal plasma

In the investigation of stability of a plasma confined by magnetic fields some of the most important modes of oscillation are those with long wavelength parallel to the magnetic field and short

Influence of global beta, shape, and rotation on the H-mode pedestal structure in DIII-D

The scaling of pedestal pressure with global beta, shaping, and toroidal rotation is examined. The pedestal pressure is observed to increase with higher global beta and increased shaping, but is not

Comparison of hybrid and baseline ELMy H-mode confinement in JET with the carbon wall

The confinement in JET baseline type I ELMy H-mode plasmas is compared to that in so-called hybrid H-modes in a database study of 112 plasmas in JET with the carbon fibre composite (CFC) wall. The

Thermal energy confinement properties of ELMy H mode plasmas in JT-60U

The dominant causes of the reduction in the enhancement factor of thermal energy confinement with increasing plasma density in ELMy H mode plasmas in JT-60U were analysed by separating the thermal

Identification of plasma-edge-related operational regime boundaries and the effect of edge instability on confinement in ASDEX Upgrade

Local edge parameters on the ASDEX Upgrade tokamak are investigated at the L-mode to H-mode transition, during phases with various types of edge-localized modes (ELMs), and at the density limit. A