1 k。/ev en 1.018 deby =69 1m)~69,/3×110 =24×105m=24um 3×103 If wall not biased (insulator) evs -kTe In. / m 8=5d~3d For sheath in front of extractor grid, Vs-1000V18=78dD 6=1.9mm asma This approximately sizes the extractor holes 16.522, Space P pessan Lecture 15 Prof. Manuel martinez Page 4 of 1116.522, Space Propulsion Lecture 15 Prof. Manuel Martinez-Sanchez Page 4 of 11 sh sh 3 3 2 2 2 0s 0 e s 2 e e e e 42 1 42 V kT eV = 9 n 9 kT ekT e n ε ε ⎛ ⎞ δ ⎜ ⎟ ⎝ ⎠  e e sh -1 n = n exp 2 ∞ ⎛ ⎞ ⎜ ⎟ ⎝ ⎠ 1 3 2 4 0e s -1 2 2 e e 4 2 kT eV e n kT 9e ∞ ε ⎛ ⎞ δ ⎜ ⎟ ⎝ ⎠  1.018 dDebye ( ) ( ) e -5 Debye -3 17 e T K 3×11600 d 69 69 = 2.4×10 m = 24 m n m 3×10 = ∼ µ If wall not biased (insulator), i 3 4 se DD e m eV kT ln 5 d 3d m ⎛ ⎞ ∼ →δ ∼ ⎜ ⎟ ⎜ ⎟ ⎝ ⎠  For sheath in front of extractor grid, V 1000V s ∼ 78dD δ  kTe 3V e ∼ δ  1.9 mm This approximately sizes the extractor holes