Ionization Gauge Research Articles

Design and testing of an internal hot-cathode-type PIG ion source for superconducting cyclotron

The superconducting cyclotron SC200 is intended to generate a 200 MeV, 400 nA proton beam for future particle therapy. The internal hot-cathode-type Penning ionization gauge (PIG) ion source for the SC200 is designed for the generation of hydrogen ions. A brief description of the design of ion source and test bench, which are used in SC200, is given in this paper. The ion source has been verified on the test bench, and the results indicated that the designed ion source meets the expected requirements. The lifetime of the filament exceeded 100 h in the test. In addition, the extraction voltage and the gas flow that influence the extracted ion current intensity have been tested in the experiment.

3D-Simulation of a Bayard Alpert ionisation gauge using SIMION program

Numerical simulation of a Bayard-Alpert ionisation gauge using SIMION 8.1 software is presented. Gauge sensitivity, being the most important parameter of an ionisation gauge, has been derived using two different approaches. In the first one, SIMION is used to determine mean length of electron trajectories, and ion collection efficiency. From these values, known ionisation cross sections and the gas temperature, the sensitivity can be readily calculated. In the second and more detailed approach, a Monte Carlo method was implemented in the Lua programming language to simulate electron impact ionisation of the gas. The Lua code is incorporated in the SIMION trajectory simulations, in which the ionisation event is modelled by transforming a primary electron into an ion. This approach evaluates the contribution of each trajectory to the gas ionisation. It considers energy dependence of the ionisation probability and the contribution of the electrons backscattered from the grid to the sensitivity. The simulation approaches were tested on the gauge geometry, recently modelled by the CERN group. Very good quantitative agreement with the CERN simulations was obtained using both approaches. Monte Carlo simulations reveal that the relative contribution of electrons backscattered from molybdenum grid to the sensitivity is about 14%.

Experimental exploration of the upper measuring limit of pressure gauges for ITER by variation of instrumental parameters

Hot cathode ionization gauges are intended to be the only in-situ diagnostic for neutral gas pressures in the vacuum vessel of ITER. The development bases on the well established ASDEX pressure gauge. The upper measuring limit for ITER is required to be at least 20 Pa in hydrogen at a magnetic flux density of up to 8 T. The objective of the presented study is to find parameter and design settings that allow to satisfy this specification. At the same time, the sensitivity shall be high and only weakly dependent on the magnetic field strength. Gauge parameters, specifically the electron emission current, the electrode potentials and the transparency of the acceleration grid, were varied consecutively to assess their impact on the calibration characteristics. The ratio of ion to electron current as a function of pressure and magnetic flux density was obtained for each parameter set.A monotonic progression of the signal in dependence of the pressure was proven even up to 30 Pa. This was achieved by a low grid transparency and high electric field strength at the cathode. While the former leads to a lower sensitivity, which is unfavorable for measurements in the low pressure range, this can be compensated by a higher electron current.

Analysis on the Sensitivity of the ASDEX Type Ionization Gauge in Mixed Radiator Gases of Divertor Simulators

Analysis on the Sensitivity of the ASDEX Type Ionization Gauge in Mixed Radiator Gases of Divertor Simulators

Исследование нестационарного воздушного потока в большой вакуумной камере с помощью стандартного ионизационного манометра

AbstractA method for creating a pressure gradient by pulsed injection of air into a large vacuum chamber for laboratory simulation of plasma phenomena in a vertically nonuniform atmosphere is proposed. The dynamics of subsonic and transonic air flows at different background chamber pressures is studied. The feasibility of creating and detecting instantaneous pressure drops by more than two orders of magnitude on a scale of about one meter is shown. Features of the operation of the PMI-10-2 ionization gauge used for pressure measurements in a pulsed gas flow are discussed.

Study of a Pulsed Air Flow in a Large Vacuum Chamber by Means of a Commercial Ionization Gauge

A method for creating a pressure gradient by pulsed injection of air into a large vacuum chamber for laboratory simulation of plasma phenomena in a vertically nonuniform atmosphere is proposed. The dynamics of subsonic and transonic air flows at different background chamber pressures is studied. The feasibility of creating and detecting instantaneous pressure drops by more than two orders of magnitude on a scale of about one meter is shown. Features of the operation of the PMI-10-2 ionization gauge used for pressure measurements in a pulsed gas flow are discussed.

Observations of Reduced Turbulence and Wave Activity in the Arctic Middle Atmosphere Following the January 2015 Sudden Stratospheric Warming.

Measurements of turbulence and waves were made as part of the Mesosphere-Lower Thermosphere Turbulence Experiment (MTeX) on the night of 25–26 January 2015 at Poker Flat Research Range, Chatanika, Alaska (65°N, 147°W). Rocket-borne ionization gauge measurements revealed turbulence in the 70- to 88-km altitude region with energy dissipation rates between 0.1 and 24 mW/kg with an average value of 2.6 mW/kg. The eddy diffusion coefficient varied between 0.3 and 134 m2/s with an average value of 10 m2/s. Turbulence was detected around mesospheric inversion layers (MILs) in both the topside and bottomside of the MILs. These low levels of turbulence were measured after a minor sudden stratospheric warming when the circulation continued to be disturbed by planetary waves and winds remained weak in the stratosphere and mesosphere. Ground-based lidar measurements characterized the ensemble of inertia-gravity waves and monochromatic gravity waves. The ensemble of inertia-gravity waves had a specific potential energy of 0.8 J/kg over the 40- to 50-km altitude region, one of the lowest values recorded at Chatanika. The turbulence measurements coincided with the overturning of a 2.5-hr monochromatic gravity wave in a depth of 3 km at 85 km. The energy dissipation rates were estimated to be 3 mW/kg for the ensemble of waves and 18 mW/kg for the monochromatic wave. The MTeX observations reveal low levels of turbulence associated with low levels of gravity wave activity. In the light of other Arctic observations and model studies, these observations suggest that there may be reduced turbulence during disturbed winters.

Design and Simulation of Hot Cathode Ionization Vacuum Gauge with no X-Ray Limitations

In this paper, the MEMS type ionization gauge with no X-Ray limitations has been presented. Having the dimensions of 2.4 mm× 0.8mm × 1.4 mm, the designed gauge is 9000 times smaller than the conventional type and can operate in HV and UHV pressures up to 5×10-9 torr. Operating at the temperature of 750°C, the cathode of proposed gauge is implemented using nickel and works in a way in which its temperature, independent of the peripheral gas pressure, remains constant throughout it. The total power consumption of the designed scheme is 430 times less than the conventional type. The electrical, thermal, mechanical, ionization collisions and elastic collisions have been performed using COMSOL5 program, and the output data from COMSOL were analyzed by MATLAB. The simulation results have been employed in implementation of cathode and other parts’ dimensions and based on these results the sensitivity factor of 0.2 1/torr was obtained.

Real-time adjustable, 11 μs FWHM, 5 kHz, piezo electric pulsed atomic beam source.

This paper provides a detailed description of how to construct a pulsed atomic beam source [including a fast ionization gauge (FIG) for characterization] with a unique combination of characteristics. We include technical drawings for a real-time adjustable piezo electric actuated pulsed valve capable of generating a 11 μs duration pulse of gas at a repetition rate of >5 KHz, with a shot-to-shot stability of 0.6%, and maximum densities of 1015 particles/cm3. We also include details on how to construct a FIG, with a 4 μs rise time, to measure the pulse. We report a 3D density map of a supersonic expansion of helium gas with a speed ratio S = 46 and a calculated longitudinal temperature of 0.3 K. Finally, the results of a laser ionization test are provided in order to verify the performance of the pulsed valve in a typical experimental configuration.

Development of an CNT field emission UHV ionization gauge with customized electronics

An ionization vacuum gauge with carbon nanotube (CNT) cathode was designed for measurement of ultra high vacuum (UHV). The sensor was constructed based on Bayard-Alpert type gauge. The key index of the control unit is determined by theoretical analysis and experimental results. A customized detection circuit was designed considering the characteristics of the output ion current of the sensor, the performance of which, such as linearity, noise, bandwidth and gain, were determined by a series of tests and calibrations. At last, the vacuum measurement range and uncertainty of this gauge were determined. The test results showed that the lower limit of the CNT-cathode ionization vacuum gauge enters 10-8Pa, The measurement uncertainty is about 4.0% in the pressure range of 10-4Pa-10-7Pa. This work can provide a new solution for UHV measurement.

Measurement of transient neutral gas puff pressure in the NUDT_IPPTx by a fast ionization gauge

A gas injector was designed for the 400 J/pulse prototype of the planar inductive pulsed plasma thruster (IPPT) developed by the National University of Defense Technology (NUDT_IPPTx). As the gas puff distribution over the coil surface is critical to the NUDT_IPPTx functioning efficiently, a fast ionization gauge was developed to investigate the neutral gas pressure profiles to seek the critical time when the thruster is ignited. The gauge was calibrated for argon by using a capacitance manometer. Time-resolved pressure profiles have been acquired in the condition of the gas puff mass matching with the discharge energy and the drive coil parameters of the NUDT_IPPTx. It is demonstrated that the gas injector can supply a gas puff with a sufficiently steep (dp/dt ≈ 770 kPa s−1) leading and trailing edge, and the gas puff can be compressed against the drive coil as expected. The critical ignition moment is considered to appear at some instant between 525 μs and 650 μs after the valve trigger.

Experimental research on beam current extraction of PIG negative hydrogen ion source for neutron tube

A new structure of the Penning ion gauge (PIG) ion source used for neutron tube is designed, and the experiments on beam current extraction of the PIG negative hydrogen (H−) ion source are performed. The influences of the magnetic field of the ion source, different cathode materials and the aperture size of the extraction cathode on the negative hydrogen ion flow are studied. The neutron experiments are performed with a PIG negative hydrogen (H−PIG) ion source D–D neutron tube, and the experimental data demonstrate that this sort of negative hydrogen ion source can be used to produce neutron tubes with good performance.

The Mochi LabJet Experiment for Measurements of Canonical Helicity Injection in a Laboratory Astrophysical Jet

Abstract The Mochi device is a new pulsed power plasma experiment designed to produce long, collimated, stable, magnetized plasma jets when set up in the LabJet configuration. The LabJet configuration aims to simulate an astrophysical jet in the laboratory by mimicking an accretion disk threaded by a poloidal magnetic field with concentric planar electrodes in front of a solenoidal coil. The unique setup consists of three electrodes, each with azimuthally symmetric gas slits. Two of the electrodes are biased independently with respect to the third electrode to control the radial electric field profile across the poloidal bias magnetic field. This design approximates a shear azimuthal rotation profile in an accretion disk. The azimuthally symmetric gas slits provide a continuously symmetric mass source at the footpoint of the plasma jet, so any azimuthal rotation of the plasma jet is not hindered by a discrete number of gas holes. The initial set of diagnostics consists of current Rogowski coils, voltage probes, magnetic field probe arrays, an interferometer and ion Doppler spectroscopy, supplemented by a fast ion gauge and a retarding grid energy analyzer. The measured parameters of the first plasmas are ∼1022 m−3, ∼0.4 T, and 5–25 eV, with velocities of ∼20–80 km s−1. The combination of a controllable electric field profile, a flared poloidal magnetic field, and azimuthally symmetric mass sources in the experiment successfully produces short-lived (∼10 μs, ≳5 Alfvén times) collimated magnetic jets with a ∼10:1 aspect ratio and long-lived (∼100 μs, ≳40 Alfvén times) flow-stabilized, collimated, magnetic jets with a ∼30:1 aspect ratio.

Recommended practice for calibrating vacuum gauges of the ionization type.

This article represents a recommended practice for the calibration of ionization gauges using the comparison method. In this method, ionization gauges are compared to a working standard that has an SI traceable calibration. The ionization gauge is either of the hot-cathode ionization type or the cold-cathode ionization type. Details of the calibration apparatus, the principle of operation of the gauges, data analysis, uncertainty budget, and reporting the uncertainty are given.

Gas Pressure Measurements in Pure and Mixed Gases at Around 1.0 Pa by Using ASDEX Type Fast Ionization Gauge

Gas Pressure Measurements in Pure and Mixed Gases at Around 1.0 Pa by Using ASDEX Type Fast Ionization Gauge

Quantitative measurements of various gases in high and ultrahigh vacuum

Two calibration methods for ionization gauges, a measurement method for the effective pumping speed of turbomolecular pumps, and a method for introducing low gas flow rates into vacuum chambers were examined. Twenty-four gases were used, including inert gases, hydrocarbons, oxygen, carbon oxide, chlorofluorocarbons, and liquid vapors. Direct comparison with a reference spinning rotor gauge and incorporation of the standard conductance element into the conductance modulation methods were tested as calibration methods in the range from 10−6 to 10−3 Pa. The effective pumping speed of a turbomolecular pump with a nominal pumping speed of 0.37 m3/s for N2 was measured using the modified conductance modulation method. A standard conductance element, which is a porous plug fabricated from sintered stainless steel, was tested in the range of 10−8 to 10−4 Pa m3/s to quantitatively introduce gas into a vacuum chamber. The obtained results were compared with previously reported values.

Experimental validation of thermo-mechanical simulations of ITER diagnostic pressure gauges

Diagnostic Pressure Gauges (DPG) shall provide measurements of the neutral gas pressure in ITER in 4 lower ports, 4 divertor cassettes and 2 equatorial ports. The DPG is a hot cathode ionization gauge where the filament (hot cathode) is heated up by a high electric current in order to reach a temperature sufficient for emission of electrons. The DPG will operate in an environment with strong magnetic field (up to 8 T). Hence, under mentioned operational conditions the filament of the gauge will be under high thermal stress and the influence of j→×B→ forces. Finite element analyses (FEA) of the DPG sensor have been executed with the aim to determine the temperature distribution and to assess stress level and structural integrity of the filament and other gauge components. In cases where boundary conditions and material constants were not exactly defined, assumptions have been made accordingly. This, however, reduces the reliability of simulation results. In order to gain benchmarking data for validation of the performed simulations, experimental investigation of the filament temperature profile has been executed. Reliability tests are envisaged to investigate the operational margin of the gauge by identifying the minimum heating current required to produce sufficient emission current over a long period of time and the maximum current in a high magnetic field causing structural damage to the filament. Results of these tests allow measuring the accurateness of FEA, which delivers predictions of stability thresholds with respect to the heating current and magnetic field. Comparison of experimental data with results of FEA simulations are discussed in this paper.

Concept for a MEMS-type vacuum sensor based on electrical conductivity measurements

Abstract. The concept of the micro-structured vacuum sensor presented in this article is the measurement of the electrical conductivity of thinned gases in order to develop a small, economical and quite a simple type of vacuum sensor. There are already some approaches for small vacuum sensors. Most of them are based on conservative measurement principles similar to those used in macroscopic vacuum gauges. Ionization gauges use additional sources of energy, like hot cathodes, ultraviolet radiation or high voltage for example, for ionizing gas molecules and thereby increasing the number of charge carriers for measuring low pressures. In contrast, the concept discussed here cannot be found in macroscopic sensor systems because it depends on the microscopic dimension of a gas volume defined by two electrodes. Here we present the concept and the production of a micro-structured vacuum sensor chip, followed by the electrical characterization. Reference measurements with electrodes at a distance of about 1 mm showed currents in the size of picoampere and a conductivity depending on ambient pressure. In comparison with these preliminary measurements, fundamental differences regarding pressure dependence of the conductivity are monitored in the electrical characterization of the micro-structured sensor chip. Finally the future perspectives of this sensor concept are discussed.

An ionization gauge for ultrahigh vacuum measurement based on a carbon nanotube cathode.

This work reports on the complete design and the properties of an ionization gauge based on a carbon nanotube cathode, which can measure ultrahigh vacuum without thermal effects. The gauge is composed of a pressure sensor and an electronic controller. This pressure sensor is constructed based on a hot-cathode ionization gauge, where the traditional hot filament is replaced by an electron source prepared with multi-wall nanotubes. Besides, an electronic controller was developed for bias voltage supply, low current detection, and pressure indication. The gauge was calibrated in the pressure range of 10-8 to 10-4 Pa in a XHV/UHV calibration apparatus. The gauge shows good linear characteristics in different gases. The calibrated sensitivity is 0.035 Pa-1 in N2, and the standard deviation of the sensitivity is about 1.1%. In addition, the stability of the sensitivity was learned in a long period. The standard deviation of the sensitivity factor "S" during one year is 2.0% for Ar and 1.6% for N2.

Focus on materials, semiconductors, vacuum, and cryogenics

Focus on materials, semiconductors, vacuum, and cryogenics