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Spherical Tori (ST TCP)

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Enabling benchmarks of fusion physics

The ST TCP supports co-operation among spherical torus research programmes and facilities worldwide in order to advance the scientific and technology knowledge of plasma confinement. A new, small, inexpensive device measures turbulence and the energy contained in the plasma across several devices in order to establish benchmarks and enable comparative analysis. 

Proton and triton data gathered from experiments on the new charged fusion production detector.*

While much research in fusion science has focused on tokamak devices, the ball-shaped spherical tori (ST) have recently emerged as an innovative approach to fusion confinement. As the STs are smaller than tokamaks they offer particular advantages including lower construction and operating costs and facilitating control of the physics parameters of the plasma.

In addition, due to the improved stability of an ST device, the plasma has a higher plasma pressure relative to the magnetic field pressure, an important element in fusion science. Higher plasma pressure combined with a significantly smaller magnetic field result in greater power output as less electricity is required to create the magnetic field.

Further research is required to understand how modifications in the magnetic field impact the stability and confinement of the plasma in ST fusion reactors. Additional research is also needed to assess the effectiveness of STs in using external sources of heat to maintain the plasma. 

The plasma in STs is heated by injecting fuel using neutral beam injection (NBI). As the neutral particles are injected they collide and transfer energy to the plasma particles. NBI also helps sustain the plasma by pushing the flow (current) and spinning the plasma which suppresses turbulence and increases the plasma temperature. Therefore, measuring and understanding how NBI particles are deposited, transported or lost from the plasma is critical.

For these reasons the ST TCP set out to increase the knowledge and understanding of ST physics through improved measurements of the turbulent fluctuations and the energy contained in the plasma.

A new “charged fusion product detector” developed by participants from Florida International University (FIU) in collaboration with the Princeton Plasma Physics Laboratory (United States) measures the production of protons and tritons from NBI-induced fusion reactions. The particles are measured as they pass through the detector. The new detector was successfully installed and tested on the Mega Ampere Spherical Tokamak (MAST) device (United Kingdom) for the first time during its final experimental campaign in 2013.

The resulting data were found to be consistent with results of other devices installed in fusion devices, thereby validating the new detector’s capabilities. In addition, as the new detector is more compact, less expensive and easier to implement, it may be easily installed for use on other devices, providing further data sets which may be compared to those obtained on MAST. These and other results are available in the ST TCP Annual Report 2014. 

* Graph adapted from data provided by the ST TCP

Activities

  • Physics and technologies
  • Science and R&D
  • Steady-state operation

Participants

  IEA member 
countries
 Partner 
 countries 
Reg./Int. 
orgs.
Contracting Parties  2 -  1
Sponsors - -  -

For more information: http://iea-st.pppl.gov 

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