Svenska ElektronikForumet

When the X-ray image intensifier is used in a state where a very small amount of X-ray is input, a relatively small number of electrons are generated from the input screen and the amount of gas generated in the vacuum vessel is also small. It is therefore possible to maintain the vessel in a high vacuum for a long period of time merely by incorporating a predetermined amount of getters in the vessel, so that a stable operation can be obtained.
However, when the X-ray image intensifier is exposed to a relatively large amount of X-ray, as in a non-destructive inspection, a large amount of electrons are generated from the input screen and a large amount of gas is generated from the electrodes in the vessel, the output screen, the other elements in the vessel, and the vacuum vessel itself. As a result, the electron emitting performance of the input screen may be degraded or an abnormal discharge may occur in the vessel.

SUMMARY OF THE INVENTION
An object of the present invention to provide an X-ray intensifier wherein a vacuum vessel can be maintained in a high vacuum for a long period of time.
According to the present invention, there is provided an X-ray image intensifier having a vacuum vessel which incorporates an ion pump constituted by a pair of electrodes opposed to each other and an element for applying a magnetic field across the opposed electrodes, at least one of the opposed electrodes of the ion pump electrically connected to a focusing electrode in the vacuum vessel.
In the X-ray image intensifier of the present invention, the ion pump incorporated in the vacuum vessel is operated as soon as the image intensifier starts operating, and absorbs gas generated in the vessel. Hence, even when the image intensifier is operated in a state where a relatively large amount of X-ray is to be input to the input screen, the vessel is kept in a high vacuum and discharge is suppressed, so that a stable operation can be maintained. In addition, since terminals for applying a voltage to the ion pump are reduced, the structure can be simplified and the image intensifier can be assembled easily.