Patent ID: 7619375

Claim:
An electromagnetic wave generating device, comprising: a hollow annular vacuum chamber, the chamber being hermetically sealed to be kept under vacuum; an electron gun for emitting an electron beam into the vacuum chamber; an electromagnet including: a pair of discoid combinations each composed of a cylindrical accelerating magnet pole and an annular focusing magnet pole with a rectangular cross section, arranged in this order from the inner side to the outer side of the discoid combination, and disposed concentrically and symmetrically with each other on both sides of the vacuum chamber, and the center axis of the each discoid combination being made coaxial with that of the chamber; and a return yoke disposed outside around both the accelerating and focusing magnet poles, and the vacuum chamber; a pair of accelerating coils each wound around the accelerating magnet poles, for exciting the accelerating magnet poles; a pair of focusing coils each wound around the focusing magnet poles, for exciting the focusing magnet poles; a through hole formed along the center axis of the accelerating magnet poles; and power supply wires led out through the through hole, to be connected to an accelerating power supply, for supplying electric power to the accelerating coils.