S. S. Hong

Hot cathode ionization gauge calibration with the KRISS ultra-high vacuum standards

The calibration system for ultra-high vacuum standards at the Korea Research Institute of Standards and Science (KRISS) uses a restriction in the range 5 × 10-7 Pa to 2 × 10-3 Pa. Using this system, we have calibrated for argon two commercially available gauges, an extractor gauge and a stabil-ion gauge. The correction factor of the extractor gauge in the lower pressure range was about 1.07 but it rose by 4%, reaching 1.11 at 2 × 10-5 Pa, while that of the stabil-ion gauge slowly decreased from 1.04 to 1.02 over four decades of the pressure range.

The static expansion system as a new medium vacuum primary standard in KRISS

A new medium vacuum primary standard using the static expansion method was developed in Korea Research Institute of Standards and Technology. We compared the system with an ultrasonic interferometer manometer using two capacitance diaphragm gauges with full-scale ranges of 133 Pa and 1333 Pa. The results showed that the two standards are coincident with each other within the range of uncertainty at calibrated pressures 3 Pa to 100 Pa.

Results of a bilateral comparison of the high-vacuum primary standards at the Korea Research Institute of Standards and Science and the UK National Physical Laboratory

The high-vacuum standards of the Korea Research Institute of Standards and Science (KRISS) and the National Physical Laboratory (NPL) in the UK have been compared over the pressure range 4.5 × 10-3 Pa to 1.25 × 10-2 Pa using argon as the reference gas. Despite large instabilities in the characteristics of the transfer standards, the maximum difference between the data obtained at the KRISS and those obtained at the NPL is less than the combined uncertainty (k = 2) for the two standards.

Development of an in situ vacuum gauge calibration system

A low-vacuum standard, which is based on the static expansion method and can generate vacuum in the wide range of 1 Pa–100 kPa, has been developed. The largest chamber of this system, in which the known pressures are generated, has an orifice-flow pressure generator for gauge calibration. This dual function for the largest chamber permits a more efficient routine calibration of gauges than a traditional chamber as follows: reference gauges attached to the largest chamber are calibrated by the static expansion method which generates known pressures; these gauges are then left in place in the calibration chamber; other gauges to be calibrated can be attached to the large chamber and calibrated against the reference gauges by the comparison method. The reference gauges only need to be recalibrated infrequently.

Extending the Pressure Limit for Turbomolecular Pump up to 133 Pa by using Conductance-Reducer and Measuring the Pressure Differences in Vacuum Chamber

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.

Fabrication of an electron-stimulated desorption apparatus and a study on desorbed hydrogen on the cold surface of Cu and rare-gas solid

An electron-stimulated desorption (ESD) system was assembled in order to study ESD ions desorbed from the cold surface of materials. We have investigated electronically stimulated ions desorbed from physisorbed hydrogen on Cu and rare-gas solid. The desorption yield showed a dependence on incident electron energy. Desorbed H+ and H+2 ions of exposed H2 on the surface of rare-gas solid were much higher than H2 exposed directly to the surface of Cu. The kinetic energy of desorbed H+ and H+2 ions depends on incident electron energy. When the incident electron energy was 200 eV, the kinetic energies of H+ and H+2 were 5.0044 eV and 0.8405 eV, respectively.

Measurement Uncertainties for Vacuum Standards from a Low to an Ultra-high Vacuum

The Korea Research Institute of Standards and Science (KRISS) has three major vacuum systems: an ultrasonic interferometer manometer (UIM; Section II, Figs. 1 and 2) for a low vacuum, a static expansion system (SES; Section III, Figs. 3 and 4) for a medium vacuum, and an orifice-type dynamic expansion system (DES, Section IV, Figs. 5 and 6) for high and ultra-high vacuum systems. For each system, explicit measurement model equations with multiple variables are given. According to ISO standards, all of these system variable errors were used to calculate the expanded uncertainty (U). For each system, the expanded uncertainties (k = 1, confidence level = 95%) and relative expanded uncertainty (expanded uncertainty/generated pressure) levels are summarized in Table 4. Within the uncertainty limits, our bilateral and key comparisons [CCM.P-K4 (10 Pa to 1 kPa)] are extensive and in good agreement with those of other nations (Fig. 8 and Table 5).

The study of new vacuum pressure measurement technique using ultrasonic acoustic impedance transducers.

Ultrasonic sensors of 500 kHz frequency have been used to study the measuring of gas pressure in the range 1.33 × 10(3)-2.026 × 10(5) Pa. From the experimental data it was observed that amplitude of the transmitted ultrasound was dependent on gas pressure. The results confirm that by using appropriate instruments including sensors and electronic devices, pressure of the gas can be successfully measured by measuring the magnitude of the received signal. The proposed method is expected to be applied to develop as new vacuum pressure measurement instrument.

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.

A Study of Non-uniform Pressure Distribution in Vacuum Chamber during Dynamic Gas Flow

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.