High-confinement mode#H-mode scaling: IPB98(y,2)

{{Short description|Type of plasma state achievable in tokamak research}}

In plasma physics and magnetic confinement fusion, the high-confinement mode (H-mode) is a phenomenon observed in toroidal fusion plasmas such as tokamaks. In general, plasma energy confinement degrades as the applied heating power is increased. Above a certain characteristic power threshold, the plasma transitions from L-(low-confinement) to H-mode regime, where the particle and energy confinement is significantly enhanced.

The H-mode was discovered by Friedrich Wagner and team in 1982 on the ASDEX diverted tokamak.[http://www.iter.org/newsline/86/659 How Fritz Wagner "discovered" the H-Mode]. It has since been reproduced in all major toroidal confinement devices, and is foreseen to be the standard operational scenario of many future reactors, such as ITER.

Physical properties

= L-H transition =

Plasma confinement degrades as the applied heating power is increased (referred to as the low-confinement mode, or the L-mode). Above a critical power threshold that crosses the plasma boundary, the plasma transitions to H-mode where the confinement time approximately doubles.

= Edge transport barrier =

In the H-mode, an edge transport barrier forms where turbulent transport is reduced and the pressure gradient is increased.

= Edge-localized modes =

The steep pressure gradients in the edge pedestal region leads to a new type of magnetohydrodynamic instability called the edge-localized modes (ELMs), which appear as fast periodic bursts of particle and energy in the plasma edge.

= Energy confinement scaling =

{{nobr|H-mode}} is the foreseen operating regime for most future tokamak reactor designs. The physics basis of ITER rely on the empirical ELMy H-mode energy confinement time scaling.{{cite journal |last1=ITER Physics Expert Group on Confinement and Transport |last2=ITER Physics Expert Group on Confinement Modelling and Database |last3=ITER Physics Basis Editors |title=Chapter 2: Plasma confinement and transport |journal=Nuclear Fusion |date=December 1999 |volume=39 |issue=12 |pages=2175–2249 |doi=10.1088/0029-5515/39/12/302|bibcode= 1999NucFu..39.2175I}} One such scaling named IPB98(y,2) reads:

: $\tau_{E}^{\text{IPB98(y,2)}}=0.0562 M^{0.19} I_{\text{P}}^{0.93} R^{1.97} \epsilon^{0.58} \kappa^{0.78} n^{0.41} B^{0.15} P^{-0.69}$

where

$M$ is the hydrogen isotopic mass number
$I_{\text{P}}$ is the plasma current in $\text{MA}$
$R$ is the major radius in $\text{m}$
$\epsilon$ is the inverse aspect ratio
$\kappa$ is the plasma elongation
$n$ is the line-averaged plasma density in $10^{19} \text{m}^{-3}$
$B$ is the toroidal magnetic field in $\text{T}$
$P$ is the total heating power in $\text{MW}$

References

Category:Magnetic confinement fusion