Calibration Of Vacuum Gauges Research Articles

Investigation of outgassing properties of CuZr alloy for vacuum chamber structural materials

CuZr alloy is considered for the structural material of the vacuum chamber of the Hefei Advanced Light Facility (HALF) storage ring. In order to test the outgassing properties of CuZr alloy, we designed and constructed a vacuum gauge calibration device and an outgassing rate test system. The outgassing rates of CuZr alloy and Stainless Steel (SS) were tested and compared at different temperatures after a rigorous ultra-high vacuum cleaning process. It can be seen that the outgassing rate of CuZr alloy can be reduced to 3.85 × 10−11 Pa L/s·cm2 after baking at 120 °C for 48h, which is lower than that of SS after baking at 180 °C. The outgassing rate of CuZr alloy can reach 2.69 × 10−11 Pa L/s·cm2 after baking at 180 °C for 48h, which is more than one order of magnitude lower than that of SS. These results indicate that CuZr alloy is easier to degas by baking at lower temperatures and is a material with very low outgassing rates. Moreover, it is a highly competitive structural material for future accelerator vacuum chamber based on its good electrical conductivity, high strength and hardness.

On the Possibility of Using the Strain-Frequency Method for Measuring the Absolute Gas Pressure in Reference Vacuum Gauges

An especially important direction in metrological science is ensuring the accuracy of vacuum measurements, which is crucial for industry. In Russia, predominantly foreign vacuum gauges with a vacuum measurement range PNPI – PVPI 0.1–1000 Pa are used as reference vacuum gauges for verification and calibration of vacuum gauges. On the basis of the analysis of the characteristics of reference vacuum gauges used in Russia based on various methods for measuring gas pressure, it can be argued that the most accurate and common measurement method among reference vacuum gauges is the strain method. However, the strain method has a number of limitations associated with the need to introduce the following corrections: correction for the residual pressure in the comparative chamber, correction for the influence of temperature effects during temperature control of the primary measuring transducer. The purpose of this work was to study the compliance of the metrological characteristics of a vacuum gauge based on a new strain-frequency method for measuring the absolute gas pressure with the requirements for reference vacuum gauges given in state verification schemes in the field of vacuum measurements.The main research methods were the study of the metrological characteristics of the strain-frequency vacuum gauge, taking into account the correction for the residual pressure in the comparative chamber; corrections for the influence of temperature effects during temperature control of the primary measuring transducer, as well as for the compliance of the method with the requirements of state verification schemes in the field of vacuum measurements. An assessment of the accuracy indicators of the strain-frequency method for measuring the absolute gas pressure based on the analysis of the measurement equation, taking into account the assessment of the components of the uncertainty sources, is given. The obtained results have shown the possibility of using the strain-frequency method of pressure measurement, with the exception of the correction for the residual pressure in the comparative chamber, corrections for the influence of temperature effects during temperature control of the primary measuring transducer in reference vacuum gauges that meet the requirements of state verification schemes in the field of vacuum measurements.As a result of the study, it was found that the expanded uncertainty of the result of measuring pressure with a vacuum gauge based on the new strain-frequency method does not exceed 2 %. This makes it possible to use this method in reference vacuum gauges.The practical significance of the developed scientific and methodological principles, and technological solutions for calculating and manufacturing the primary measuring transducer of a vacuum gauge based on a new method for measuring low absolute pressure lies in the possibility to manufacture the primary measuring transducer at Russian enterprises using domestic technologies of microsystem technology.

Modernization of the hardware and software complex of the national standards service in the area of pressure measurement technology for the calibration of vacuum gauges and development of a calibration simulator

The article provides information about the functions and the algorithm of modernization of the software and hardware complex for automating the calibration process of vacuum gauges, offers software as a simulator for learning the procedure for calibrating vacuum gauges and effective training of testers. It is shown that in the department for national standards in the field of pressure measurement of D. I. Mendeleyev Institute for Metrology VNIIM. The modernization makes it possible to reduce the work intensity of the test procedure, to reduce the influence of the "human factor", to increase the work productivity of the inspector and to reduce the training time for inspectors in the field of vacuum measurements.

TÜBİTAK UME vacuum laboratory capabilities and activities

TÜBİTAK National Metrology Institute (TÜBİTAK UME) is a research and development institute that operates under the Scientific and Technological Research Council of Turkey (TÜBİTAK). TÜBİTAK UME Vacuum laboratory takes part in under the mechanics group among the groups of physics, mechanics and chemistry group laboratories. TUBITAK UME Vacuum Laboratory aims to develop and maintain national measurement standards, to establish vacuum pressure traceability to SI units and to disseminate this to industry, science and research in Turkey. The laboratory was founded in 1996 and started to provide secondary level calibration services with Vacuum Gauge Calibration System (VGCS-200). Primary vacuum standard called Multi-Stage Static Expansion System (MSSE1) was established in 2000. Commercially available secondary vacuum gauge calibration system was improved with the addition of automation under the name Vacuum Gauge Metrology System (VGMS) in 2010. The main activities of the Vacuum Laboratory are conducted in the following working fields: Primary and secondary vacuum measurements and calibrations, secondary calibrations of leak standards, primary constant pressure flowmeter (CPFM) standard establishment works, renewal works of existing primary static expansion system, European Metrology Research and Innovation Projects, Quadrupole Mass Spectrometer (QMS) characterization measurements on Dynamic Vacuum System (DVS), training and consultancy services in the field of vacuum metrology. In this paper, the Vacuum Laboratory capabilities and activities will be briefly introduced.

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.

Development of a transportable apparatus for vacuum gauge calibration

A new ultrahigh vacuum transportable apparatus for vacuum gauge calibration in the pressure range from 10−5 Pa–105 Pa is developed. On the basis of modularization design, it can be easily extended and assembled. A standard pressure pstd with various gas species can be generated by means of pressure attenuation module which is easy to introduce the corresponding calibration gas through an orifice. The standard pressure pstd in the range from 10−5 Pa to 10−2 Pa could be obtained by changing the upstream pressure from 1 Pa to 103 Pa with an uncertainty of approximately 2.4%. At the same time, calibration can also be performed by direct comparison with a reference gauge either in static or stationary equilibrium. The ultimate pressure could be in the level of 10−6 Pa typically. The pumpdown characteristic and outgassing rate of the apparatus after exposing to atmospheric pressure are presented. The main metrological characteristics of the apparatus are given. The size and weight of this apparatus are 475 mm × 420 mm × 800 mm and 37.8 kg, respectively. Its calibration range is from 1.96 × 10−5 Pa to 1.03 × 105 Pa with the relative combined standard uncertainty from 2.8% to 0.40%.

The KRISS Primary Vacuum Gauge Calibration Standards: A Review

The KRISS Primary Vacuum Gauge Calibration Standards: A Review

Generation of a medium vacuum pressure by using two different pumping methods in the KRISS dynamic flow-control system

Pumping systems with large vacuum chambers have numerous applications in the process industry: for example, mixing of various types of gases as in the semiconductor industry, the calibration of vacuum gauges, the measurement of outgassing rates of various materials in the field of space technology, etc. Most often, these systems are used in the medium vacuum range (10−1 Pa–102 Pa) and in the dynamically-generated pressure mode. We have designed and developed a new dynamic flow system at the KRISS (Korea Research Institute of Standards and Science) that can be used for such applications with reliability in the range from 0.1 Pa – 133 Pa. In this report, the design philosophy, operational procedure and experimental data for the generated stable pressure points in the chamber of the system are discussed. The data consist the pressure points generated in the medium vacuum range while pumping the chamber of the system by using two different methods: first by using a dry scroll pump and then by using a combination of a turbomolecular pump backed by the same scroll pump. The relative standard deviations in the pressure points were calculated and were found to be greater than 1.5% for the scroll pump and less than 0.5% for the turbomolecular pump.

A modified numerical method for the accurate calculation of molecular flow transmission probabilities and density distributions of cylindrical tubes

Accurate numerical calculations of molecular flow transmission probabilities and density distributions of tubes are important to the benchmark problems of Monte Carlo solutions, dynamic expansion vacuum gauge calibration systems, and molecular beam formation studies. Although Nawyn and Meyer [published by van Essen and Heerens. J Vac Sci Technol 1976; 13:1183] have solved cylindrical tube problems by using the numerical method based on Clausing's equations, perhaps the calculated results still lack sufficient accuracy. In this paper, we propose a modified method that could achieve calculation accuracies of transmission probabilities as high as 10−11–10−13 in the range of L′/R ≤ 100 (where L′ is the tube length, R is the tube radius), which are more accurate than the results recently reported by Mohan et al. [J Vac Sci Technol A 2007; 25:758] and Gómez-Goñi et al. [J Vac Sci Technol A 2003; 21:1452].

Spinning rotor gauge based vacuum gauge calibration system at the Institute for Plasma Research (IPR)

The Steady-state Superconducting Tokamak (SST-1) is an indigenously built medium sized fusion device at IPR designed for plasma duration of 1000 seconds. It consists of two large vacuum chambers – Vacuum Vessel (16 m3) and Cryostat (39 m3) which will be pumped to UHV and HV pressures respectively using a set of turbo molecular pumps, Cryo-pumps and Roots pumps. The total as well as the partial pressure measurement in these chambers will be carried out using a set of Pirani gauges, Bayard Alpert type gauges, Capacitance manometers and Residual Gas Analyzers (RGA). A reliable and accurate pressure measurement is essential for successful operation of SST-1 machine. For this purpose a gauge calibration system is set up in SST-1 Vacuum laboratory based on Spinning Rotor Gauge which can measure absolute pressure in the range 1.0 mbar to 1.0 × 10−7 mbar. This system is designed to calibrate up to five gauges simultaneously for different gases in different operating pressure ranges of the gauges. This paper discusses the experimental set-up and the procedure adopted for the calibration of such vacuum gauges.

Analysis of pressure distribution for the various gas flow vacuum system in the range from 1 Pa to 133 Pa

The measurement and control of gas flow are critical in many manufacturing processes. Semiconductor manufacturers, in particular, require a number of different process gases for etching, deposition, oxidation, doping and inerting applications. In many of these, as well as other industrial and research processes including measurement of partial pressures with residual gas analyzers (RGAs), calibration of vacuum gauges, and conductance of a conductance-reducer , accurate measurement and stability of the gas pressure within the reaction vacuum chamber is essential. In the present work, pressure distribution in the chamber of a newly developed flow control system was investigated for three gases (Ar, N2, and He) range from 1Pa to 133Pa. For all the gases, the relative deviations in pressure distribution near the gas inlet and outlet were in the range of −1.3% and 1.2% respectively.

Development of a new dynamic gas flow-control system in the pressure range of 1 Pa–133 Pa

A new flow-control system (FCS-705) has been developed at Korea Research Institute of Standards and Science. The system is intended for calibration of vacuum gauges in the pressure range of 1 Pa-133 Pa by comparison method. This paper describes some basic characteristics of the system including; (1) the design and construction of the system, (2) the generation of stable pressures in the chamber, (3) achieving high upstream pressure limit by installing a short duct in the by-pass pumping line, and (4) investigation of the gas flow regimes within the short duct.

Newly developed standard conductance element for in situ calibration of high vacuum gauges

A new leak element, which is named as “standard conductance element (SCE)”, has been developed for in situ calibration of ionization gauges (IGs) and quadrupole mass spectrometers (QMSs). The SCE is made of a stainless-steel sintered filter with the pore size of less than 1μm. Since the gas flow through the SCE satisfies the molecular flow condition even at the pressure up to 104Pa, some useful characteristics of molecular flow are available. The SCE is supplied to users with a calibration certificate described its molecular conductance. Users can introduce optional test gases with the known flow rate to their vacuum chamber through the SCE in their laboratories. The overview of the SCE, the calibration method and recommended practices are introduced.

The characterization of new VGMS (vacuum gauge metrology system) by the traceability of multi stage static expansion system

In this study, the design and characterization of vacuum gauge calibration system which was upgraded is described. A capacitance diaphragm manometer is used to characterize the system performance. 1Torr and 10Torr CDGs are available to compare the performance of VGMS system which is traceable to the static expansion system generating calibration pressures in the range of 9×10−4Pa up to 1×103Pa. The working pressure range of VGMS system is 1×10−4–1.3×105Pa. It is used a comparison method as a calibration process. After making the system description and process, the results of calibrations included uncertainty values are given to determine long term instability and show the performance of the system.

Comparison of an ultrasonic interferometer manometer and a new dynamic flow control system in the pressure range 1–133 Pa

This work is concerned with comparison of two low-pressure calibration systems at the Korea Research Institute of Standards and Science (KRISS). The ultrasonic interferometer manometer (UIM) which is a national primary standard and the dynamic flow control system (FCS) which can be used for the calibration of vacuum gauges by comparison method by generating precise and stable pressure in the range 1–133 Pa. For this comparison, a capacitance diaphragm gauge (CDG) of 133 Pa full-scale range was used as transfer standard in the overlapping range of 1–133 Pa. The behavior of two systems in the pressure range 1.37–11.5 Pa had large variations which gradually reduced above 11.5 Pa. In the range 1.37–11.5 Pa, the difference in calibration factors for the two systems was 0.0114 with relative deviations of 5.177%. However above 11.5 Pa the corresponding values were 0.0056 and 1.197%, respectively. Since in vacuum metrology, UIM is world-wide recognized as a national calibration standard, the results of this comparison will be used to validate the FCS for calibration of low vacuum gauges.

Calibration of ultrahigh vacuum gauge from 10 −9 Pa to 10 −5 Pa by the two-stage flow-dividing system

A new two-stage flow-dividing system has been developed for the calibration of ultrahigh vacuum gauges from 10 −9 Pa to 10 −5 Pa for N 2, Ar, and H 2. This system is designed based on the techniques for our previously developed calibration system in the range from 10 −7 Pa to 10 −2 Pa. Three modifications were performed to extend the calibration pressure to a lower range. The relative standard uncertainty of the generated pressure ( k = 1) is in the range from 2.3% to 2.6%, from 10 −9 Pa to 10 −5 Pa. The characteristics of ultrahigh vacuum gauges were also examined by using this system. The stabilities of the pressure reading, the linearity, the temperature dependence, and the long-term stability were examined. These results show that the calibration of ultrahigh vacuum gauges is possible in the range from 10 −9 Pa to 10 −5 Pa for N 2, Ar, and H 2 with the uncertainty of about 6.0% ( k = 2) by this new system.

확장한 진공용기 내부의 압력구배 측정

진공게이지의 비교교정 방법으로 교정이 가능하고-비교교정은, 2차표준기라고 부르는 교정되어진 게이지와 교정할 다른 게이지의 지시값을 읽어 비교는 방법- 다른 진공관련 실험을 할 수 있는 기체 유량 시스템을 개발하였다. 교정시스템에의 진공용기는 터보분자펌프(TMP)에 의해서 배기하고, 후면에 스크롤펌프를 배치하여 배기시스템을 꾸몄다. 터보분자펌프의 최대허용가능 압력은 펌프의 주입구에서 0.1 Pa까지이며, 이보다 압력이 높아지면 배기속도가 감소하며 압력대 이하의 환경을 조절하기가 매우 어렵게 된다. 현재 133 Pa까지의 높은 압력을 발생시킬 수 있는 새롭게 개발된 기체유량조절시스템은 바이패스 라인에 맞도록 설계된 컨덕턴스-리듀서를 설치하여 터보분자펌프를 안전하게 운용할 수 있도록 하였다. 추가로 진공용기안에 전체압력 범위(0.1 Pa ~ 133 Pa)의 압력을 생성하며 기체 주입과 압력구배를 연구하였다. 압력의 최대 편차는 용기의 위쪽 방향에 위치한 가스 주입구에서 가까운 위치 C에서 1.6%로 나타났다. A dynamic flow system has been developed which can be used for vacuum gauge calibration by comparison method - a calibration method in which the reading of the gauge under calibration is compared to another calibrated vacuum gauge called the "secondary standard" - and other vacuum-related experiments. The chamber of the calibration system is pumped by a turbomolecular pump (TMP), backed by a scroll pump. As maximum acceptable pressure at the inlet of a TMP is 0.1 Pa, above which the TMP decelerates, the pumping speed decreases and it becomes more difficult to adjust pressure under such circumstances. In the present work, high pressures of up to 133 Pa have been generated in the chamber of the newly developed dynamic flow control system by installing a well-designed conductance-reducer in the by-pass line and, at the same time, operating the TMP in safe mode. In addition, the gas flow and pressure distribution within the chamber have been investigated for the entire pressure range (0.1 Pa ~ 133 Pa) while generating pressure dynamically. Maximum deviations in pressure (1.6 %) were observed at point C on the chamber, which is close to the gas inlet port on the top of the chamber.

기체유입이 되는 진공챔버 안의 불균등한 압력분포 연구

진공챔버는 진공게이지 교정, 산업에서의 재료처리 등 여러 가지 다양한 용도에 맞게 적용이 가능하다. 이 진공챔버 내부에서 가스가 유입되는 과정에서의 진공도는 일정하게 유지하기가 힘들다. 산업체 응용에서뿐만 아니라 연구과정에서도 진공챔버 내부에 가스가 유입되는 동안의 내부압력분포와 최대도달 평형압력을 아는 것이 매우 중요하다. 이러한 진공챔버 내부의 압력 불균형을 감소시키기 위해서 가스 주입구 부분에 baffle을 이용하는 방법이 있다. 현재 지속적인 기체흐름이 있는 진공챔버 내부의 기체흐름의 작용에 관해 0.1 Pa~133 Pa 영역에서 불규칙한 압력을 최소화하기 위한 baffle plate의 효과에 대해 연구하였다. 최대편차는 가스 주입구 부분에서 나타나는 압력으로 baffle plate가 전환흐름영역에서 큰 영향을 미치는 것으로 나타났다. Vacuum chambers have wide application for a variety of purposes such as material processing, vacuum gauge calibration, etc. As the dynamic pressure generated in such chamber is non-uniform, in many industrial as well as research processes, it is vital to know the non-uniform gas distribution with associated gas flow regimes and the ways of minimizing these pressure non-uniformities. In the present work, the behavior of gas flow in a vacuum chamber, during continuous gas flow, is described in the pressure range 0.1-133 Pa and the effect of baffle plate in minimizing the pressure non-uniformities is investigated. It was observed that maximum deviations in the pressure occur near the gas inlet point and that the effect of baffle plate in minimizing the pressure non-uniformities is more obvious in the transitional flow regime.

Accurate measurement of pressure differences and the effect of baffle on pressure distribution in vacuum chamber during dynamic gas flow

The need to know the pressure in relatively large vacuum chambers arises at different measurements (calibration of vacuum gauges, outgassing measurements, etc.) and investigating the ways to minimize these pressure differences are of equal importance in such industrial as well as research applications. The experimental determination of the pressure differences between various gauge positions in a chamber of cylindrical shape and the effect of a baffle on pressure distribution are described in the paper. The pressure in the chamber was generated dynamically in the pressure range 0.1–133 Pa through adjustable gas flow into the chamber. Five identical capacitance diaphragm gauges (CDGs) were used in which one CDG remained fixed at the central position of the chamber while the other four (in two pairs) were mutually interchanged. The differences on the order of several percent between positions at different levels were calculated and the effect of the baffle was investigated which are specific for this chamber.

Development and performance analysis of a standard orifice flow calibration system

An orifice flow system has been developed indigenously which is a primary standard for the calibration of high vacuum gauges in the range of 10(-3)-10(-6) mbar. It consists of a constant-volume flow meter, designed to generate a known flow rate of a particular gas to the vacuum chamber. This chamber is partitioned into two parts by a plate with an orifice of calculable conductance. The pressures, generated by this standard system, are compared with those of secondary standard, namely, spinning rotor gauge. Different uncertainties and correction factors are calculated. The maximum percentage deviation is from 1.16% to 0.97%. The combined uncertainties over the entire calibration range of the standard system are in the range of 4.0 x 10(-6) mbar.