Compact Plasma and Focused Ion Beams

115Comparison of Square and Near-Circular Multicusp Waveguides

with a short wavelength, much smaller than the wavelength of microwaves in

free space, the radial plasma extent, and the scale of magnetic nonuniformity

B/(dB/dr) = 0.08 cm. The wavelength of the waves can be estimated from [3]

k

k

j

jj

k

o

o













=













=−

−−

{}

−−−−

−

2

2

22

222

1

1

11

λ

l

ada

dbad

()

() ()

cc

o

k













2

,

(7.17)

where k, k

o

, and k

c

are the wave numbers in the magnetized plasma in a

waveguide, that in free space, and the cutoff wave number in the wave-

guide without plasma, respectively.

δ

= v

e

/

ω

, where v

e

is the electron neu-

tral collision frequency and j

2

= −1. As a typical example, the wa ...