Related Experiment Video
Updated: Jun 5, 2026
06:46
Applying X-ray Imaging Crystal Spectroscopy for Use as a High Temperature Plasma Diagnostic
Published on: August 25, 2016
"Snowflake" H mode in a tokamak plasma
1Ecole Polytechnique Fédérale de Lausanne, Centre de Recherches en Physique des Plasmas, Association Euratom-Confédération Suisse, Station 13, CH-1015 Lausanne, Switzerland. francesco.piras@epfl.ch
Physical Review Letters
|January 15, 2011
Summary
Researchers achieved a stable edge-localized mode (ELM) H-mode using a novel snowflake divertor in the TCV tokamak. This new configuration significantly reduces ELM frequency and enhances energy confinement compared to standard H-mode operations.
Area of Science:
- Plasma Physics
- Fusion Energy Research
- Tokamak Operations
Background:
- Edge-localized modes (ELMs) are crucial for tokamak performance but can disrupt plasma stability.
- The H-mode regime offers improved confinement but requires careful control of edge plasma conditions.
- Divertor configurations play a key role in managing heat and particle exhaust in fusion devices.
Purpose of the Study:
- To establish and investigate an edge-localized mode (ELM) H-mode regime in a novel "snowflake" divertor configuration.
- To compare the ELM characteristics and stability of the snowflake divertor regime with conventional single-null diverted H-mode.
- To experimentally validate the power redistribution capabilities of the snowflake divertor.
Main Methods:
- Successful establishment of ELM H-mode using electron cyclotron heating in a TCV tokamak snowflake divertor.
- Comparative analysis of ELM frequency and normalized ELM energy between snowflake and conventional single-null diverted H-mode.
- Experimental confirmation of power redistribution to additional strike points in the snowflake configuration.
Main Results:
- The snowflake divertor regime demonstrated 2-3 times lower ELM frequency compared to conventional H-mode.
- A 20%-30% increase in normalized ELM energy (ΔWELM/Wp) was observed in the snowflake regime.
- Enhanced stability of mid- to high-toroidal-mode-number ideal modes was consistent with snowflake ELM phenomenology.
Conclusions:
- The snowflake divertor configuration offers a promising pathway for improved ELM control and enhanced plasma stability in tokamaks.
- This configuration facilitates effective redistribution of edge power, mitigating heat loads on divertor components.
- The findings represent a significant advancement in optimizing tokamak operational regimes for future fusion reactors.
Related Concept Videos
01:14Atomic Nuclei: Nuclear Spin State Population Distribution
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
02:45Nuclear Fusion
The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process called fusion. The principal source of energy in the sun is a net fusion reaction in which four hydrogen nuclei fuse and ultimately produce one helium nucleus and two positrons.
A helium nucleus has a mass that is 0.7% less than that of four hydrogen nuclei; this lost mass is converted into energy during the fusion. This reaction produces about...
A helium nucleus has a mass that is 0.7% less than that of four hydrogen nuclei; this lost mass is converted into energy during the fusion. This reaction produces about...
01:08Hückel's Rule Diagram of π MOs: Frost Circle
The Frost circle or the inscribed polygon method is a graphical method for determining the relative energies of π molecular orbitals (MOs) for planar, fully conjugated, and monocyclic compounds. This method was first described by A. A. Frost and Boris Musulin in 1953.
A Frost circle is constructed by drawing a polygon whose number of edges is equal to the number of carbons of the given cyclic system, with one of the vertices pointing down. Then, a circle is drawn enclosing the polygon so that...
A Frost circle is constructed by drawing a polygon whose number of edges is equal to the number of carbons of the given cyclic system, with one of the vertices pointing down. Then, a circle is drawn enclosing the polygon so that...
02:39Phase Transitions: Melting and Freezing
Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
01:23Atomic Nuclei: Nuclear Relaxation Processes
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis. This...
01:12Fermi Level Dynamics
The vacuum level denotes the energy threshold required for an electron to escape from a material surface. It is usually positioned above the conduction band of a semiconductor and acts as a benchmark for comparing electron energies within various materials.
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...