PLASMA PROPERTIES

• Plasma species: ions, radicals, neutrals, molecules, electrons
  • plasma is neutral as a total, thus: n_e = n_i = n, i.e. the number of electrons is equal to the number of ions
  • a degree of ionization can be defined to characterise plasma efficiency:, where n₀ is the concentration of neutrals
• Temperatures and energies
  • Electrons are more energetic than ions, because of their smaller mass (2 eV - 0.04 eV)
  • Temperature (23000 K - 500 K) of electrons/ions is defined as the energy of the particle divided by Boltzmann constant, therefore the temperature is an indicative of the electron/ion energy
  • Energy depends on a number of factors, includin the pressure; at high pressure, there are more collisions and electrons loose their energies, at low pressure there are'nt sufficient collisions to ignite and sustain the plasma