In the ultra-high vacuum chamber for field emission electron guns used in conventional electron microscopes, two vacuum valves are installed between the rough exhaust pipe and the main vacuum pump (SIP). They are used to exhaust both the electron gun chamber and the intermediate chamber. This arrangement requires space to install rough exhaust pipes in the chamber and the exhaust pump, and to satisfy this condition, the entire electron gun becomes large. In addition, there is a distance between the chamber and the pump, and the exhaust efficiency is not good.
By DIY-like method, we have developed a new compact electron gun chamber ( Fig. 1) that solves this problem in one fell swoop. We will introduce it in this talk.
We have devised a chamber-integrated roughing valve with a structure in which holes are provided on the same plane in the chamber body that connect to the electron gun chamber and the intermediate chamber, and these two holes are opened and closed by a single round plate, in addition to the exhaust pipes for the exhaust pumps for the electron gun chamber and the intermediate chamber. This eliminates the need for an external roughing valve, resulting in a smart field structure. In conventional field emission electron gun chambers, the airlock valve between the intermediate chamber and the electron microscope column was designed inside the intermediate chamber to face the O-ring surface downward to prevent damage to the O-ring by the electron beam. This design increased the load on the intermediate chamber when evacuating it to vacuum.
Fig. 1.
Cross sectional of the valve-integrated compact electron gun chamber and its external view.
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