Miniature ring-orbitron getter ion pumps have been proposed for supplying high vacuums to advanced scientific instruments expected to be developed in the next few years. Examples of such instruments include electron microscopes, ion mass spectrometers, and instruments based on electron probes.
A conventional orbitron getter ion pump (shown in the top part of the figure) includes a positively biased rod electrode on the axis of a cylindrical cavity with typical dimensions of tens of centimeters. Electrons are injected into the cavity, where they collide with and thereby ionize residual gas molecules. The resulting ions are accelerated toward, and become buried in, an ion-getter material on cavity surfaces. Because of the positively biased rod, the injected electrons get caught in orbits around the rod. The orbiting confines the electrons in a region away from the walls, thus increasing the electron path lengths and the probability that the electrons collide with the gas molecules, leading to increased efficiency of pumping.
In a conventional large orbitron getter ion pump, a negative bias is applied to the flat end walls of the cylindrical cavity to deflect the approaching electrons back into the cavity. However, the required relatively large voltage becomes increasingly impractical as the size of the pump is reduced. Thus, miniaturization must entail elimination of negative bias on the end walls; this makes it necessary to find another way to confine electrons in the cavity.
The proposed ring orbitron configuration would provide the needed confinement. The rod electrode of the conventional orbitron would be replaced with a wire ring electrode, as shown in the bottom part of the figure. As in the case of the rod electrode, positive bias on the ring electrode would create a potential well, causing the electrons to spiral around the ring, and the electrons would be injected slightly off-ring to give them enough angular momentum to go into the orbits.
Unlike a conventional orbitron, a ring orbitron would be scalable to subcentimeter dimensions. In the fabrication of miniature orbitron pumps, bulk and surface micromachining and lithography could be used to define ring electrodes, ring-supporting posts, and electron emitters. Cavities could be fabricated from stacks of micromachined wafers.
This work was done by Jaroslava Z. Wilcox, Thomas George, and Jason Feldman of Caltech for NASA's Jet Propulsion Laboratory. NPO-20436
This Brief includes a Technical Support Package (TSP).
Miniature ring-orbitron getter ion vacuum pumps
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Overview
The document is a technical support package from NASA detailing the Miniature Ring-Orbitron Getter Ion Vacuum Pumps, developed by inventors Jaroslava Z. Wilcox, Thomas George, and Jason Feldman. It is part of a broader effort to enhance the capabilities of scientific instruments used in space exploration and other applications.
The introduction highlights the significance of miniaturization in instrumentation, particularly for NASA missions, where reduced size and power consumption can lead to lower costs and improved mission capabilities. The document emphasizes the potential for integrating these miniature pumps with various microinstruments, such as mass spectrometers, to facilitate advanced scientific measurements.
The technical tasks outlined in the document include determining the pumping requirements for a self-contained electron microprobe. This involves measuring leak rates for different gases as they diffuse through thin electron-transparent membranes, which is crucial for understanding the performance of the vacuum pumps in practical applications.
The novelty of the Miniature Ring-Orbitron design lies in its ability to achieve high vacuum levels in a compact form factor, which is essential for modern scientific instruments that require precise control of their operating environments. The document suggests that the advancements in microfabrication techniques have made it feasible to create such miniaturized devices, which can significantly enhance the efficiency and effectiveness of space exploration missions.
The document also includes a notice stating that neither the U.S. Government nor NASA makes any warranties regarding the accuracy or completeness of the information provided, nor do they assume liability for any damages resulting from its use. This disclaimer underscores the experimental nature of the technology and the importance of further research and validation.
Overall, the technical support package serves as a foundational document for understanding the development and application of Miniature Ring-Orbitron Getter Ion Vacuum Pumps, highlighting their potential impact on future scientific research and exploration endeavors. The work is expected to generate valuable experimental data that will contribute to a deeper understanding of electron-ion interactions in micromachined structures, ultimately advancing the field of microfabricated instrumentation.
