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In plasma physics of tokamaks, collisionality is a dimensionless parameter which expresses the ratio of the electron-ion collision frequency to the banana orbit frequency.


The plasma collisionality \nu^* is defined as[1][2]

\nu^* = \nu_\mathrm{ei}\,\sqrt{\frac{m_\mathrm{i}}{k_\mathrm{B} T_\mathrm{i}}}\,\epsilon^{-3/2}\,qR,

where \nu_\mathrm{ei} denotes the electron-ion collision frequency, R is the plasma major radius, \epsilon is the inverse aspect-ratio, and q is the safety factor. The plasma parameters m_\mathrm{i} and T_\mathrm{i} denote, respectively, the mass and temperature of the ions, and k_\mathrm{B} is the Boltzmann constant.

See also[edit]


  1. ^ Nucl. Fusion, Vol. 39, No. 12 (1999)
  2. ^ Wenzel, K and Sigmar, D.. Nucl. Fusion 30, 1117 (1990)