To accurately monitor the degree of vacuum in a vacuum airtight container.
An ionizing electron emitting part 112 constituted of an field emission array is formed on a cathode base plate 101, an anode electrode 106, an electron accelerating electrode 110 and an ion collector electrode 111 are formed on an anode base plate 108 so arranged as to face the cathode base plate 101, and an electrons emitted from the ionizing electron emitting part 112 collide with remaining gas in a container, so as to generate ions. The amount of ions is proportional to the concentration of the remaining gas, and positive ions of generated ions are drawn by the ion collector electrode 111 to which the specified negative electric potential is applied. Accordingly, the concentration of the remaining gas in the container, namely, the degree of vacuum is measured by measuring the current to flow to the ion collector electrode 111.
TONEGAWA TAKESHI
YOKOYAMA MIKIO
UCHIDA YUJI
