| 摘要 |
PROBLEM TO BE SOLVED: To switch the frequency of a parabolic current flowing through a quadrupole coil for correcting the beam shape of an electron beam by using an electronic switch. SOLUTION: An auxiliary coil L3 is connected in parallel to the quadrupole coil L2. Diodes D3 and D2 connected to the coil L3 have opposite continuity directions, and a PNP-type transistor Tr2 is connected to the diode D3 and an NPN-type transistor Tr3 is connected to the diode D2. The transistors Tr2 and Tr3 are controlled so as to be simultaneously turned on/off by a frequency switching drive circuit 12, and, when the transistors Tr2 and Tr3 are turned on, the coil L3 conducts. At this time, either the transistor Tr2 or Tr3 conducts in response to the direction of the current flowing through the coil L3. COPYRIGHT: (C)2004,JPO
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