Evaluation and metrological performance of a novel ionisation vacuum gauge suitable as reference standard

Funding Information: This work has received funding from the EMPIR programme (projects 16NRM05 and 20SIP01) co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme and the Portuguese National Funding Agency for Science, Research and Technology in the framework of the project UIDB/FIS/ 00068/2020. Publisher Copyright: © 2023 The Author(s)Recently, a new type of ionization vacuum gauge was introduced, which was proposed as a reference and transfer standard in the range of 10-6 Pa to 10-2 Pa because of its excellent stability and linearity. In contrast to present models of ionisation vacuum gauges, all electrons have a well-defined path length through the ionisation space. This even allows one to predict the sensitivity for a gas species provided that the ionisation cross section of the gas molecules for electrons between 50 eV and 200 eV is known. Following the development of this gauge we investigated its metrological performance in terms of linearity, resolution, repeatability, reproducibility, transport and long-term stability, disturbances by magnetic fields, influence of the surrounding earth potential and so on. The gauge demonstrated excellent metrological properties and is indeed suitable as an accurate reference and transfer standard, but can also provide important economic benefits to manufacturers and users.publishersversionpublishe

Development of a design for an ionisation vacuum gauge suitable as a reference standard

UID/FIS/00068/2019The EURAMET EMPIR project “16NRM05 - Ion gauge” aims to develop an ionisation vacuum gauge suitable as a reference vacuum standard. In such a gauge the electron trajectories and their kinetic energy inside the ionisation volume should be well defined and stable. In the search for a suitable design, a series of simulations on different ionisation gauge concepts that have the potential to meet stringent stability requirements have been carried out. Different software packages were used for this purpose. This paper focuses on the design aspects and the performance of the different ionisation gauge concepts that have been investigated by simulation. Parameters such as ionisation gauge sensitivity, ion collection efficiency and electron transmission efficiency, have been determined as a function of emission current, pressure and electron source alignment.publishersversionpublishe

Sub-monolayer adsorption isotherms and gas propagation of H2 and He in cryogenic copper tubes

A presentation given within the Vacuum Group Seminars at CERN on the 6th December 2021 about the current status of adsorption measurements performed for the PUMA project. The measurements focus on the sub-monolayer adsorption behavior of hydrogen and helium on copper at 5 to 20 Kelvin. The data is fitted to the Dubinin-Radushkevich-Kaganer isotherm model and the fit is tested via propagation measurements in a copper tube and a cross-checked with COMSOL simulations. A prognosis is made for the vacuum condition in the PUMA cryostat

Comparison of ionization vacuum gauges close to their low pressure limit

Parts of CERN’s accelerator complex and experiments, especially in the antimatter field, require a vacuum in the  $10^{-12}$ mbar range or better. Thus gauges are needed to reliably measure XHV during experimental operation and in order to study the vacuum science needed for those experiments. We therefore built a setup to reach $1⋅10^{-13}$mbar  in order to simultaneously compare different hot cathode ionization gauges with the ability to measure high UHV and XHV close to their lower pressure limit: Barion extended, Extractor IE514, a modulated Bayard–Alpert gauge and two Improved Helmer gauges. All gauges but the Extractor behave similarly with respect to small pressure variations around the limit pressure, while the Extractor seems to overestimate high UHV hydrogen pressure. We show how gauge operation determines our ultimate achievable pressure due to outgassing, which was comparable for all gauges and in the order of $Q∼10^{-10}$mbar l s$^{-1}$. Further we show the disturbances caused in the static system due to gauge pumping (visible only as electronic pumping), and report some of the possible difficulties and origins of noise when measuring pressures in the XHV range, including the thermoelectric effect