Low Vacuum Region Research Articles

The Electric Discharge Detection Method in the Low Vacuum Region of Vacuum Interrupter

SUMMARYThe vacuum circuit breaker (VCB) achieves the high current interrupting capability in the pressure lower than 10 Pa to 5 Pa. When gas pressure increases, the breakdown voltage of a VCB decreases according to Paschen's law, and in the case of small leak, the partial discharge will occur in the VCB and the high frequency electromagnetic waves are radiated. So, we have developed the partial discharge detection system using an antenna with the region from 200 MHz to 300 MHz placed inside the VCB. However, if the partial discharge occurs outside the VCB, the detection system leads to misdetection as the partial discharge inside the VCB. In order to improve the performance of partial discharge detection, the outputs of antenna voltages inside and outside the VCB are investigated.

真空バルブ内真空度低下時における放電検知手法の検討

真空バルブ内真空度低下時における放電検知手法の検討

Suprathermal plasma analyzer for the measurement of low-energy electron distribution in the ionosphere

It is commonly believed that an energy transfer from thermal to suprathermal electrons (<several eV) greatly affects the energy budget of the ionosphere. However, observation of electron energy spectrum in this energy range is quite limited because of technical difficulties of measurement. We have developed an instrument to measure electron energy distribution from thermal to suprathermal energy continuously with high-energy resolution of about 0.15 eV. The measurement principle is based on the combination of a retarding potential analyzer with a channel electron multiplier (CEM) and the Druyvesteyn method, which derives energy distribution from the current-voltage characteristics. The capability of detecting plasma space potential enables absolute calibration of electron energy. The instrument with a small vacuum pump, which is required for the CEM to work in low-vacuum region, was first successfully tested by a sounding rocket S-310-37 in the ionospheric E region. The instrument is expected to provide new opportunities to measure energy distribution of thermal and non-thermal electrons in low-density plasma, where a Langmuir probe cannot measure electron temperature because of low plasma density.

Precision vacuum pumping speed measurement using sonic nozzles

Constant volume flow meter systems were developed for measuring pumping speeds of dry vacuum pumps. Their capability to measure throughput in the low vacuum region was exploited to calibrate 0.03, 0.2, and 1.6 mm throat diameter sonic nozzles. It was demonstrated that the calibrated sonic nozzles enabled the precise measurement of the pumping speed of a dry vacuum pump under test as the constant volume flow meter systems. To examine the measurement capability of both approaches considered in this study, the expanded measurement uncertainty, as well as the detailed measurement uncertainty budget, is presented. The proposed pumping speed measurement method has potential application for a new “in situ and portable” pumping speed tester or analyzer for the Korean semiconductor and flat display process industry.

低真空領域における密閉ボイドの部分放電特性

低真空領域における密閉ボイドの部分放電特性

Determination of gas pressure in vacuum interrupter based on partial discharge

Partial discharge characteristics in air under a low vacuum region were studied to develop a diagnosis technique to determine the gas pressure in a vacuum interrupter. The pressures were set at from 1.3 Pa to 2.6 kPa in order to simulate the leakage of gas into the vacuum interrupter. The structure of the vacuum interrupter, the measurement and the circuit construction for the experimental setup were described. The measurement of partial discharge occurring inside the vacuum interrupter was performed with a current transformer, intensified charge coupled device (1CCD) camera and photomultiplier tube. The measurement of partial discharge light intensity with a photomultiplier tube was more sensitive compared with that measured with a current transformer. From this result, an attempt has been made to distinguish the pressure below and above 260 Pa on the basis of the rise time and peak intensity of discharge light pulses. A relatively longer rise time (2 mus) with a smaller magnitude (less than 0.5 mA) was attributed to a Townsend-like discharge at pressures below 260 Pa, while a sharper rise time ~(10-100 ns) with a larger magnitude (greater than 1 mA) was characterized as a streamer-like discharge above 260 Pa. In addition, the estimation of gas pressure in a vacuum interrupter was made based on phase-resolved discharge characteristics utilizing an artificial neural network.

Discharge Properties in Low Vacuum Region of Vacuum Interrupter Filled with SF6 Gas

This paper deals with the discharge properties in low vacuum region of practical vacuum interrupter filled with SF6 gas. In field, the vacuum interrupter inside the cubicle-gas insulated switchgear is surrounded by SF6 gas. If the leakages occur, the surrounding gas may invade the vacuum interrupter and increase the internal pressure. Thus, the pressures are set at 1.3 Pa to 2.6 kPa to simulate the leakage. The measurement of discharge occurring inside the vacuum interrupter was performed with a photomultiplier tube. From the result of the experiment, it is found that the pressure of vacuum interrupter below and above 50 Pa can be distinguished on the basis of the rise time, peak intensity and width of the discharge light pulse. The result reveals that the discharge pulses at pressures below 50 Pa have the relatively larger rise time of 100ns order, and larger pulse width of 2μs order. While, for pressures above 50 Pa, the rise time have relatively smaller value of 10 ns and pulse width of 0.1μs order. The result also shows significant difference in discharge characteristics compared with those in low vacuum of vacuum interrupter filled with air that we have investigated previously.

Discharge properties in low vacuum region of vacuum interrupter at open contact of main electrode

Discharge properties in low vacuum region of vacuum interrupter at open contact of main electrode

Solution‐phase deuterium/hydrogen exchange at a specific residue using nozzle‐skimmer and electron capture dissociation mass spectrometry

Information about protein conformation can be obtained with hydrogen/deuterium exchange (HDX) mass spectrometry. The isotopic solution-phase exchange of specific amide hydrogen atoms can be followed using low-vacuum nozzle-skimmer collision-induced dissociation (CID). In this study, the nozzle-skimmer technique was complemented by electron capture dissociation (ECD) Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS). The solution-phase exchange at a specific residue is monitored by comparing isotopic distributions of two consecutive b- or c-type ions. While nozzle-skimmer fragmentation takes place in the low-vacuum region of the mass spectrometer, ECD occurs at ultra-high vacuum within the mass analyzer cell of the FTICR mass spectrometer. The dissociations take place at 10(-4) and 10(-9) mbar, respectively. Low-vacuum nozzle-skimmer fragmentation can result in intramolecular exchange between product ions and solvent molecules in the gas phase. Consequently, the solution-phase information about protein or peptide conformation is lost. It was not possible to monitor isotopic solution-phase exchange at the eighth residue in substance P, (Phe)8, with nozzle-skimmer CID. By using the in-cell ECD fragmentation method, the solution-phase exchange at the (Phe)8 residue was preserved during mass spectrometric analysis. This result shows the complementary aspects of applying fragmentation at low and at high vacuum, when studying isotopic exchange in solution at specific residues using FTICRMS.

Discharge Properties and Emitted Electromagnetic Wave Spectrum in Low Vacuum Region of Vacuum Interrupter

Study on reliability of vacuum interrupter (VI) such as detection method of the slow leak has been extensively carried out, while study on discharge properties in low vacuum of VI is still insufficient. In this report, we experimentally investigated discharge properties inside VI under closed contact and open contact conditions of main contactors in low vacuum of VI to simulate vacuum leakage. We also measured current waveforms and spectrum of electromagnetic wave (EMW) emitted by discharges in VI. Furthermore, we discussed the relationship between partial discharge against the product of pressure and gap spacing, and compared the results with the Paschen's curve of air. We also discussed flowing path of the discharge current in an experimental circuit including VI.

Photothermal vibration for a cantilever placed near a planar wall in low-vacuum region

The pressure dependence of the resonant frequency of a cantilever type solid membrane which was vibrated photothermally in air in low-vacuum was investigated, and a linear response was observed. When a planar wall was placed near the membrane, the effect of the wall on the frequency response was also investigated. The resonant frequency decreased corresponding to the narrowing of the space between the wall and the membrane. These experimental results are discussed theoretically with a vibration model for the membrane

Dependence of Resonance Frequency of a Membrane Vibrated Photothermally on Pressure and Geometry in a Low-Vacuum Region

An experimental study of resonance frequency for a membrane vibrated photothermally in a low-vacuum region is described. The resonance frequency is decreased by the reaction force from gases around the vibrating membrane. Experimental values of resonance frequencies for various types of rectangular membranes in several kinds of gases agree well with theoretical ones.

周波数計測による低真空領域の光学式圧力センシング

The optical sensing system has been proposed for measuring the pressure in the low-vacuum region from the resonance frequency of a photothermal vibration of a thin glass plate. Resonance frequency decreased with increasing pressure in the above region, and its shift was relatively large as compared with that of the quartz oscillator gauge. By using the string-of-beads model, it was clarified that the thin plate is more effective than thick one for obtaining large value of the resonance frequency shift.

Gas Flow in Slit-Rectangular Tube in Low Vacuum Region

Gas Flow in Slit-Rectangular Tube in Low Vacuum Region

Electrical clean-up phenomena in electron tube

The electrical clean-up phenomena as well as the gettering phenomena of active metals have been measured. The electrical clean-up phenomena are more striking than the gettering ones in the high vacuum ( –4 mmHg). The effect of electrical clean-up depends on the anode current, vacuum degree and electron path fixed by the voltage of electrodes. The rate of clean-up accords with the value of calculation in the low-vacuum region (10 –2 to 10 –4 mmHg), but it does not accord with the line calculated, decreasing in the high vacuum (10 –5 to 10 –6 mmHg). The differences of values (litre-micron Hg) between the calculation and measurement are nearly equal at each stage. So, these differences seem to show gases desorped from the wall, and the vacuum degree of the tube is fixed as result of equilibrium of sorption and desorption. The gases cleaned-up are not found on the surfaces of the cathode and positive electrode, and the small quantity of gases are found at the negative electrode, the gases are sorped on the surface of the decontaminated glass bulb by which there are many electron paths. The high vacuum in the electron tube is done very fast by making use of the electrical clean-up phenomenon and the chemical gettering action at the same time.