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Projeto de investigação
Manómetro de ionização de elevada estabilidade provisório
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Cylindrical hot cathode ionisation gauge
Publication . Silva, Ricardo A. S.; Bundaleski, Nenad; Teodoro, Orlando M. D. N.; CeFITec – Centro de Física e Investigação Tecnológica; DF – Departamento de Física; Elsevier
A novel design of an ionisation vacuum gauge is presented, aiming to achieve predictable sensitivity and high accuracy in high and the ultra-high vacuum range. The proposed design features a belt-like electron beam emitted from a linear filament, following a circular trajectory between two cylindrical electrodes, resembling a cylindrical analyser. The proposed design offers several key upsides: a precisely defined electron beam trajectory with reduced susceptibility to path variations, effective electron collection in a Faraday cup able to contain secondary emissions and backscattered electrons, and the inclusion of a suppressor grid in front of the ion collector to eliminate ion-induced secondary electron emission. These features are expected to secure high stability of the gauge and the low pressure limit. An in-depth description of the design is presented, along with the discussions on simulations of the key components that provide the improved performance.
Effect of the magnetic field on the operation of ionisation gauges
Publication . Silva, Ricardo A. S.; Bundaleski, Nenad; Teodoro, Orlando M. N. D.; DF – Departamento de Física; CeFITec – Centro de Física e Investigação Tecnológica; Elsevier
Hot cathode ionisation gauges are the only reliable pressure measurement devices suitable for both high and ultra-high vacuum measurement. These devices are characterized by low accuracy that is hardly better than 20%. The sources of loss of accuracy are documented in the literature although their quantification and details are not fully understood. In the present work, simulations of Bayard-Alpert and extractor gauges were performed under the influence of uniform magnetic fields up to 30 Gs. Results are in qualitative agreement with measurements taken previously with the Bayard-Alpert gauge. Both gauges are sensitive to low intensity magnetic fields which may be present in vacuum chambers. However, the extractor gauge proved to be more stable in the presence of a magnetic field due to its ring-shaped cathode.
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Fundação para a Ciência e a Tecnologia
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UI/BD/150626/2020