Compare the electron-ion collision frequency in two very different plasmas

PHYSICS · Multi-part · Fermi University Physics · Plasma Physics · Kinetic theory, collisions and transport · Kinetic theory, collisions and transport

Plasma Physics, Ch What makes an ionised gas a plasma: shielding, the plasma parameter and the natural frequencies

Problem

Compare the electron-ion collision frequency in two very different plasmas, using the quoted estimate νei≈2.91×10−12 neln⁡Λ Te[eV]−3/2 s−1\nu_{ei} \approx 2.91\times10^{-12}\,n_e\ln\Lambda\,T_e[\mathrm{eV}]^{-3/2}\,\mathrm{s^{-1}} (density nen_e in m−3\mathrm{m^{-3}}). ((a)) An argon processing discharge has ne=1.0×1016 m−3n_e = 1.0\times10^{16}\,\mathrm{m^{-3}}, Te=2 eVT_e = 2\,\mathrm{eV} and ln⁡Λ=13\ln\Lambda = 13. Find νei\nu_{ei}. ((b)) The solar corona has ne=1.0×1015 m−3n_e = 1.0\times10^{15}\,\mathrm{m^{-3}}, Te=100 eVT_e = 100\,\mathrm{eV} and ln⁡Λ=20\ln\Lambda = 20. Find νei\nu_{ei}. ((c)) Which plasma is more collisional, and how does this bear on the idea that a hotter plasma must be more collisional?

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