Omegatron for Total and Partial Pressure Measurement Available to Purchase

Partly because of a supposed simplicity, omegatrons have been used frequently in applications requiring a light-weight or low-volume mass spectrometer. The present gauge was suggested by the Klopfer ionization gauge, which is similar to an omegatron in its electrode arrangement. The design, construction, and operation of an omegatron is reported here which was designed for operation either as a total or partial pressure instrument. It has a low x-ray limit, low electron current, and a sensitivity for nitrogen of $25 Torr−1$⁠. As a total pressure gauge, the ionizing electrons have a more nearly constant energy than other gauges, making it in effect a crude ionization cross-section measuring device. Internal shielding of the ion collector and choice of operating parameters to avoid important spurious effects are considered. The performance is compared to other gauges in argon and nitrogen.