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Ion gauge tubes are one of the important scientific instruments. These glass ion gauge tubes have been evolved from triode radio tubes and have taken their place completely. In early designs of the ion gauge tubes, a filament was placed in the center of the tube with a grid surrounding the filament and a collector surrounding the grid. In this way the electrons were emitted from the hot filament and attracted by a positive electrical potential, which used to be inside the grid. The emitted electrons thus collided with gas molecules, forming positive ions. Thus in the ion gauge tube, the positive ions are attracted to the collector with an appropriate negative potential. In such cases, the ion current was proportional to pressure over a large range of pressures. Most common material for the ion gauge tube envelope is Nonex glass. The manufacturing process of this envelop involves attaching the side arm for system connection, sealing in the collector on the top of the bulb and sealing in the rest of the gauge structure in the bottom of the bulb. Some of the leading manufacturers of the ion gauge tubes are
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