| 摘要 |
G2 electrode is mounted so as to be movable along the beam line and, optionally, perpendicular to it as well. G1 and G2 are curved with a constant gap between G1 and G2 in the radial direction (so that the two electrodes are concentric). This contrasts with the prior art where G1 and G2 were equidistantly spaced along the beam line direction instead. G1 is made re-entrant adjacent the slit so as to improve extraction efficiency from the plasma. Finally, a lens such as a quadrupole lens is formed downstream of G3.
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