Compact Plasma and Focused Ion Beams

296 Compact Plasma and Focused Ion Beams

near the center of the MC. The trend is the same at other values of the mag-

netic eld away from the center of the MC. Here, t = 0 implies the end of

the pulse and D

⊥

= eT

e

/(m

v

en

+ M

υ

in

)(1 +

γ

B

2

), where

v

en

and

υ

in

are electron–

and ion–neutral collision frequency, m and M are electron and ion mass,

and

γ

= e

2

/(mM

v

en

υ

in

). It is observed that

τ

ed

~ 10–40 μs, calculated by taking

T

e

(t) and n

e

(t) proles for t

w

= 20 and 100 μs. However, while it increases

almost linearly for t

w

= 100 μs, the increase is more like an exponential for

t

w

= 20 μs until t ~ 200 μs, after which both get converged. Higher value of

τ

ed

for t

w

= 20 μs just after t = 0 indicates longer connement of electrons in

interpulse plasmas ...