physics 122 Lecture 02 October 1st 2013_final

Eav are so closely related it is customary in plasma

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Unformatted text preview: )dy −∞ The integral in the numerator is integrable by parts +∞ +∞ 1 1 2 − ∫ − exp(− y 2 )dy ∫ y exp(− y ) y dy = − 2 exp(− y ) y 2 −∞ −∞ [ 2 [ = 1 +∞ 2 ∫ exp(− y )dy 2 −∞ Canceling the integrals we have ⎛ྎ 1 3 ⎞ྏ ⎜ྎ mAvth ⎟ྏ 4 ⎠ྏ = 1 mv 2 = 1 kT Eav = ⎝ྎ th Avth 4 2 Temperature •  (in 3- D) Eav=3KT/2 •  Since T and Eav are so closely related, it is customary in plasma physics to give temperatures in units of energy. •  To avoid confusion on the number of dimensions involved it is not Eav but rather the energy corresponding to kT that is used to denote the temperature. •  For kT = 1 eV = 1.6 × 10- 19 J, we have T= 1.6 × 10 −19 1.38 ×10 − 23 = 11,600 Thus the conversion factor is 1 eV = 11,600 oK •  By a 2- eV plasma we mean that kT = 2 eV, or Eav = 3 eV in (3D) Debye Length •  DEBYE SHIELDING Debye L...
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