PURPOSE: To enable to prevent leakage of a microwave generated by vibration of a coil, by a method wherein a modulating coil is surrounded with conductive member which has an enough thickness to shut off the microwave and to enable a modulating high frequency to pass.
CONSTITUTION: A conductor bar 2 pierces a cavity resonator 1 through holes 3 and 4, and is tightened to a resonator 1 by means of insulating bushes 5, 6 and nuts 7, 8 in a manner to maintain an insulation and a high-frequency current is supplied through feeding members 9 and 10. A copper film 12 with a thickness of about several μm is coated on an outer peripheral surface of a glass pipe 11 surrounding the conductor bar 2 with a gap between the gap and the glass fiber pipe. Thus, an electromagnetic field emanating from the conductor bar 2, can modulate a static magnetic field by the passage through the copper film 12. Besides, even if the conductor bar 2 vibrates violently thereupon, a microwave is shut off by the copper film 12, which does not vibrate, and does not reach surface of the conductor bar 2, and thereby the microwave is not modulated by the conductor bar 2.
FUJII KANAE
IIMA YOSHIO
