120 Compact Plasma and Focused Ion Beams
length of the waveguide. The radial measurement of the magnetic eld
inside the waveguide clearly demonstrated the minimum-B (bucket) eld
structure, with a distance of about 1 cm from the center being almost eld
free. The ECR condition was realized all along the waveguide at a distance
of 0.75 cm from the inner wall. The electron temperature was 5–11 eV with
slightly higher values near the ECR region, and the space potential was
found to have a peak at the center of the waveguide with a value of about
70 V. Special characteristics such as an optimum pressure at 2.5−3.5 × 10
−4
Torr, where the density became a maximum, the presence of hysteresis in
the ion current, and density jumps were observed dependi ...