Compact Plasma and Focused Ion Beams

96 Compact Plasma and Focused Ion Beams

plasma density (N

e

) with pressure as a function of three different powers.

For all powers, the “O-like” mode showed a bump in N

e

. The maximum N

e

at

200 W was 2 × 10

10

cm

l3

. No such peaks were observed in the “X-like” mode

at any pressure. Figure 6.7 shows the space potential (V

s

) measured as a func-

tion of p for different powers. The V

s

also has a fairly sharp increase around

0.2 mTorr, with values in the range 55–65 V.

70

E || B

Solid symbol: P

r

/P

f

Open symbol: P

r

40

35

30

25

20

15

10

5

0

60

50

×10

×10

2.1 × 10

–4

Torr

1.5 × 10

–4

Torr

2.7 × 10

–4

Torr

40

30

P

r

(W)

P

r

/P

f

(%)

P

f

(W)

20

10

0

100 150 200 250 300

FIGURE 6.5

Relation bet