Patent ID: 8729465

Claim:
A vacuum measurement device comprising: a grid ( 10 ); and an electron source ( 20 ) provided inside a vacuum vessel, wherein the electron source ( 20 ) emits electrons to ionize gas molecules flying into the grid ( 10 ), so that an ion extractor electrode ( 30 ) extracts the ions as an ion beam ( 100 ) from an ion outlet ( 11 ) of the grid, and an ion collector ( 40 ) captures and converts the ion beam ( 100 ) into a current signal, the grid ( 10 ) is formed in a substantially circular columnar cylinder or a polygonal columnar cylinder of more than a pentagonal shape so that the electrons emitted from the electron source pass therethrough, the ion outlet ( 11 ) is opened and elongated in a longitudinal direction thereof along a side surface of the grid ( 10 ), the ion outlet ( 11 ) is formed so that a longitudinal length of an opening is equal or substantially equal to a longitudinal length of the side surface of the grid ( 10 ), the ion extractor electrode ( 30 ) includes an ion beam passage slit ( 31 ) through which the ion beam ( 100 ) passes, the ion beam passage slit ( 31 ) is formed in a shape the same or substantially the same as that of the ion outlet ( 11 ), the ion outlet ( 11 ) and the ion beam passage slit ( 31 ) are disposed to face each other with a gap in between so that the shapes thereof match each other, the ion collector ( 40 ) is formed in a shape the same or substantially the same as that of the ion beam passage slit ( 31 ), and the ion beam passage slit ( 31 ) and the ion collector ( 40 ) are disposed with a gap in between so that the shapes thereof match each other.