Compact Plasma and Focused Ion Beams

331Basic Beam Studies

Al, Cu, and SS are approximately 3.8, 1.9, and 1.7, respectively [10]. From the

secondary electron yield data, the true ion current density, J

ion

, is deduced to

be ~2 A/cm

2

at –5 kV.

From J

ion

, we can estimate the reduced-source side brightness, B

rs

of the

plasma ion source, which is related to the ion temperature, T

i

(in eV), by [12,13]

BeJTAm sr V

rs ioni

=

−−−

/

211

.

(21.4)

From the above results, considering a J

ion

~2 A/cm

2

for 1 mm PE aperture

and a T

i

of ~0.2 eV, a reduced source side brightness B

rs

of ~10

5

Am

−2

sr

−1

V

−1

may be predicted, which is close to that of LMIS [13].

350

Krypton

Argon

Hydrogen

300

J

i

(mA/cm

2

)

250

200

150