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A measurement technique for a commercial four-terminal (4 T) air-dielectric capacitance standard set (Keysight 16380A) for frequencies from 1 kHz up to 13 MHz was developed for the accurate calibration of impedance analyzers. The technique consists of a measurement of capacitance at 1 kHz using a precision bridge, seven measurements of one-port driving point impedance (DPI) over 30 MHz using a vector network analyzer (VNA), and various numerical calculation procedures for parasitic component estimation and uncertainty propagation. The contribution from parasitic components in the frequency range of interest (FRI) from 1 to 13 MHz was estimated by extrapolation from the measured impedance using a VNA. A linear model for parasitic components was employed to extrapolate DPIs for a reliable estimation. The uncertainty of the calibration was estimated using Monte-Carlo (MC) simulation. The developed technique demonstrated better efficacy than others for the calibration of 100 pF and 1000 pF standards in FRI by applying simple, but reliable linear extrapolation models and Monte-Carlo (MC) simulation for uncertainty evaluation.

This paper describes the calibration of a 10 nF capacitance standard traced to the DC quantum Hall resistance primary standard using a multi-purpose digital impedance bridge. The bridge can directly compare the unlike impedances in the fully digital (FD) mode, so the capacitance standard can be calibrated by a direct comparison against the AC resistance standard. The measurement ability of the bridge in the FD mode was evaluated in various angles, and the bridge voltage dependencies were improved by selecting appropriate impedances for the high current arms and also by using an additional injection circuit. Thereby, the measurement accuracy could reach up to 10−7 in relative terms. Based on the bridge evaluation, a 10 nF capacitance standard was calibrated against a 10 kΩ resistance standard, and the measurement value agreed with a reference value in the level of 10−7.

A national traceability chain from dc quantum Hall resistance (QHR) to capacitance has been established at Korea Research Institute of Standards and Science using various impedance standards and coaxial bridges. An ac–dc calculable resistance standard of nominal value of 12.9 $\text{k}\Omega $ was used as a transfer standard from dc to ac at the frequency of 1.541 kHz. Two ac coaxial bridges, developed by INRiM, were employed: a ratio bridge, linking the 103- $\text{k}\Omega $ ac resistor to the 12.9- $\text{k}\Omega $ ac–dc calculable resistor calibrated in terms of the dc QHR and a quadrature bridge, calibrating the 1000 pF capacitors versus the 103- $\text{k}\Omega $ ac resistors. The ratio bridge defines the 103- $\text{k}\Omega $ resistor as a two-terminal-pair (2TP) standard and the 12.9- $\text{k}\Omega $ resistor as a four-terminal-pair standard; a cable correction was applied to the 2TP defined standard. The stability of all standards has been monitored for more than 3 years to be within a few parts in 106. The capacitance value, obtained with the new traceability chain, shows an agreement (a few parts in 107) in a comparison with the reference values, traced from the National Institute for Standards and Technology (USA).

To make a graphene quantum Hall resistance (QHR) standard, there are many issues to overcome, such as the fabrication process and long-term stability. This paper shows the recent progress of graphene-based QHR at Korea Research Institute of Standards and Science on the graphene growth and the device fabrication. We synthesized high-quality epitaxial graphene (EG) grown on silicon carbide (SiC) substrate and introduced the high temperature annealing process between the fabrication process for making the Hall bar structure and the doping process for reducing the carrier concentration. By comparing the electrical property of graphene devices with the different quality, we show that these steps are crucial to make graphene-based QHR standard.

A digitally assisted coaxial bridge—mainly consisted of a ratio transformer and digital voltage sources—was set up in a 4-terminal-pair (4-TP) configuration for the precision capacitance measurements. The 10: 1 capacitance ratio was measured in the range of 1 pF $\sim 1\ \mu\mathrm{F}$ mainly at 1 kHz using the 4-TP bridge. The measurement results show a degree of equivalence from a few parts in 108 to 105 when compared with those obtained using 2-terminal-pair/3-terminal bridges. Moreover, the measurement frequency of the 4-TP bridge was varied from 50 Hz to 20 kHz. The Allan deviation measurements imply that the statistical uncertainty could be achieved a level of 10−9 at 1 kHz.

This paper describes a calibration method for 10 nF capacitance standard from the primary standard of dc quantum Hall resistance using a multi-purpose digital coaxial bridge. The capacitance standard of 10 nF was calibrated by a direct comparison against the ac resistance standard of $10\ \mathrm{k}\Omega$ —its resistance value is traced to the quantum Hall resistance—using the digital bridge in the fully digital quadrature mode. The preliminary calibration value of the 10 nF was confirmed by comparing with a reference capacitance standard within uncertainty level of 10−6.

Interlaboratory comparisons of the quantized Hall resistance (QHR) are essential to verify the international coherence of primary impedance standards. Here, we report on the investigation of the stability of p-doped graphene-based QHR devices at direct and alternating currents at CMI, KRISS, and PTB. To improve the stability of the electronic transport properties of the polymer-encapsulated devices, they were shipped in an over-pressurized transport chamber. The agreement of the quantized resistance with R K/2 at direct current was on the order of 1 nΩ Ω−1 between 3.5 and 7.5 T at a temperature of 4.2 K despite changes in the carrier density during the shipping of the devices. At alternating current, the quantized resistance was realized in a double-shielded graphene Hall device. Preliminary measurements with digital impedance bridges demonstrate the good reproducibility of the quantized resistance near the frequency of 1 kHz within 0.1 μΩ Ω−1 throughout the international delivery.

Mass spectrometry (MS) with low temperature plasma (LTP) as an ionization source is one of the widely used ambient methods in analyzing various bio-chemical samples for their detection, identification, differentiation, etc. While the LTP-MS allows selective analysis of a sample with low-molecular weight without thermal damages, it has difficulties desorbing a target molecule from the sample surface with a low volatility. Hence, for the purpose of enhancing the desorption and ionization efficiencies of the LTP-MS when analyzing the fatty acids, two methods were compared: directly heating the sample surface and increasing the vapor pressure of the fatty acid itself by derivatization. In addition, the fatty acids in Drosophila were directly analyzed with the LTP-MS. As a result, it was found that the LTP-MS detection efficiency was enhanced with the derivatization as much as with the heating condition while there was little synergy in employing both of the heating and derivatization together.

In this work, the effect of relative humidity (RH) on two commercial four-terminal-pair (4TP) air-dielectric capacitance standards has been measured and analyzed. The capacitance is linearly proportional to the RH under 50% owing to the dependence of the dielectric constant of air on the RH. Over 50%, a clear dielectric dispersion has been observed. It is probable that this dispersion is caused by the interfacial polarization of the adsorbed water molecules on the oxidized aluminum electrodes. In calibration aspect, it is recommended to store at least for a day to stabilize the RH inside the standard and calibrate it at RH lower than 50%. The RH coefficient of the capacitance under 50% was estimated as 3 (μF/F)/% from the measurement.

A national traceability chain from dc quantum Hall resistance (QHR) to capacitance has been established at KRISS using various impedance standards and ac coaxial bridges. Two bridges developed by INRiM, were employed: a quadrature bridge, calibrating 1000 pF capacitors versus 103 kΩ ac resistors and a ratio bridge, linking the ac resistor values to an ac-dc calculable resistor calibrated in terms of the dc QHR. The capacitance value obtained with the new traceability chain showed an agreement (a few parts in ${10}^{7}$ ) in a comparison with the scale maintained at National Institute for Standards and Technology (NIST, USA).

Although the low temperature plasma mass spectrometry (LTP-MS) is widely used as an analysis tool for many biochemical samples, its application window is somehow limited to the analytes of low molecular mass and high volatility. For this reason, there have been attempts to enhance the ionization/desorption efficiencies with extra heating, for instance. In this study, another enhancement method was suggested using the photocatalytic nano-particles (NPs). In order to assess the NP effects on the LTP-MS, two fatty acid ethyl ester samples of ethyl myristate and ethyl palmitate were used, and the NP of titanium dioxide (TiO2) was mainly employed. The results showed that the signal intensities of the LTP-MS were largely increased with the TiO2 addition for both samples. In addition, the cholesterol sample was analyzed using the TiO2 assisted LTP-MS, also resulting in the enhancement of the signal intensity. The overall results inferred that the photocatalytic NP confirmed its role as an effective assist tool for the LTP-MS, especially suitable because of the facile method and the heat-free nature.

We developed a calibration software based on the Suzuki method for the calibration of a commercial four terminal pair air dielectric capacitance standard. The uncertainty of the calibration has been evaluated using the Monte-Carlo method. The calibration results showed good agreement with those of Keysight technologies.

Unlike large area plasmas, small size plasma jets could be useful in treating localized regions. For this reason, we developed a micro plasma jet having a polytetrafluoroethylene (PTFE) part exposed to the discharge inside the plasma source. As the helium gas flow rate was raised from 0.1 to 6.0 slpm, the plasma exhibited a change in characteristic from laminar to turbulent and an abrupt change of appearance at a certain flow rate (2.0–3.0 slpm). The measured rotational temperature was above 500K under laminar flow conditions, which was a sufficiently high temperature for the pyrolysis of PTFE, and the excitation temperature of the laminar flowwas higher than that of the turbulent flow. The corresponding optical emission spectra were different (CN, C2, F I, Ha dominated for laminar conditions while N þ 2 , OH, O I dominated for turbulent flow conditions). These different plasma characteristics were obtained by simply controlling the gas flow rate. A feasibility study of surface modification demonstrated a change of the surface wettability from hydrophobic to hydrophilic (and vice versa) depending only on the gas flow rate.

This paper details a plasma surface treatment feasibility study conducted for different driving frequencies of low frequency (LF, 50 kHz) and radio-frequency (RF, 13.56 MHz) sources by adding a target plate to a single pin electrode plasma jet system. The plasmas were generated in ambient air with a helium gas supply. The electrical characteristics of the plasmas were studied and compared for cases with and without a plane electrode. The LF plasma was more affected by the presence of the dielectric plate than was the RF plasma, showing a larger increase in its current. In addition, pork samples were treated to assess the electrical and thermal safety of plasma biomaterial surface treatments. The LF plasma conduction current and temperature during the pork treatment were 0.5 mA and 22 °C, and those of the RF plasma were 40 mA and 31 °C at maximum.

The objective of this study was to investigate the effect of atmospheric pressure plasma (APP) on Listeria monocytogenes inoculated onto disposable food containers including disposable plastic trays, aluminum foil, and paper cups. The parameters considered in APP processing were input power (75, 100, 125, and 150 W) and exposure time (60, 90, and 120 s). The bacterial reduction in the disposable plastic trays, aluminum foil, and paper cups was associated with increased input power and exposure time of APP. The D10 values were calculated as 49.3, 47.7, 36.2, and 17.9 s in disposable plastic trays, 133, 111, 76.9, and 31.6 s in aluminum foil and 526, 65.8, 51.8, and 41.7 s in paper cups at 75, 100, 125, and 150 W of input power, respectively. There were no viable cells detected after 90 and 120 s of APP treatment at 150 W in disposable plastic trays. However, only three decimal reductions of viable cells were achieved in aluminum foil and paper cups at 150 W for 120 s. These results demonstrate that APP treatment is effective for inactivation of L. monocytogenes and applicable for disposable food containers. However, the type of material is crucial and appropriate treatment conditions should be considered for achieving satisfactory inactivation level.

Both atmospheric pressure plasma and photo-catalyst metal oxide titanium dioxide (TiO2) are well known for their microorganism inactivation and chemical material decomposition abilities. In this work, radio-frequency atmospheric pressure plasma and TiO2 are used together to inactivate Bacillus subtilis spores that have a very high degree of environmental resistance to ultra-violet (UV) photons and heat. The combinational use of the plasma and TiO2 demonstrates an enhanced performance of B. subtilis spore inactivation by showing a decrease in the decimal reduction time of as large as 40% compared with the use of plasma alone. A significant increase of hydroxyl (OH) and excited oxygen atomic emission line (O I) intensities in the presence of TiO2 suggests that the atmospheric pressure plasma assisted by TiO2 is very effective at generating reactive oxygen radicals, which is known to be a dominant factor in bacterial spore inactivation. Possible TiO2 activation mechanism by the plasma is investigated.

Dimethyl methylphosphonate (DMMP), a chemical simulant of the nerve gas GB, was decontaminated with a nonthermal atmospheric pressure plasma. The decontamination efficiency was measured qualitatively by means of Fourier transform spectroscopy and quantitatively by means of gas chromatography. With helium gas only, 10 g/m 2 of DMMP on an aluminum surface was 99.9% decontaminated in 2 min, furthermore, with the addition of 5% of oxygen gas, it was 99.99% decontaminated in 10 min. Given the low input power (

Current–voltage characteristics of α- and γ-modes were investigated in moderate and atmospheric pressure capacitive discharges. The α- and γ-modes, the co-existence of both modes, and the α- to γ- and γ- to α-mode transitions were observed with the changes in voltage, current, and plasma volume. Changing of gas pressure, (100–760) Torr, the α to γ and the γ to α transition occurred with respect to input power increasing and decreasing, respectively. The hysteresis in current and voltage curve was observed and became more evident at higher pressure. Using a simple electrical circuit model, the relation between the gas pressure and the α-sheath thickness before mode transition was described.

This paper describes the realization of a two-terminal-pair digital impedance bridge and the test measurements performed with it. The bridge, with a very simple architecture, is based on a commercial two-channel digital signal synthesizer and a synchronous detector. The bridge can perform comparisons between the impedances having arbitrary phase and magnitude ratio. The bridge balance is achieved automatically in less than 1 min. $R$ – $C$ comparisons with calibrated standards, at kilohertz frequencies and 100- $\text{k}\Omega $ magnitude level, give ratio errors of the order of $10^{-6}$ , with potential for further improvements.

Progress in the development of an evaluation system for thermal-transfer standard based on a Josephson waveform synthesizer at KRISS. The synthesizer adopting a Josephson junction array, which can generate arbitrary stepwise waveforms with a number of the quantum-voltage steps up to 2.5-V level amplitude. With the synthesizer, we have built a sampling voltmeter that measures the differential voltages between a sinusoidal waveform produced by a semiconductor-based ac source and the Josephson waveforms. We will present in the conference that the developed sampling voltmeter can be utilized as a reference for ac-dc difference measurements of a thermal transfer standard.

Two terminal dual source impedance bridge was configured using commercial voltage calibrators. The bridge performance was evaluated by measuring 1 to 1 resistance ratio at 1 kHz using 1 kΩ and 10 kΩ resistors. The same bridge was used for the resistance (R) to the inductor (L) and the capacitor (C) ratio measurements by adjusting the phase between the voltage sources. Then, the AC resistance value was found from the R : C ratio. This simple two terminal dual source impedance bridge proved its reliable and versatile measurement capability.

Impedance measurements are wildly required for most of the electrical metrology laboratories. Therefore, it is needed to establish different measurement systems with different levels of accuracy to meet all demands. So, a simple impedance bridge is presented through this paper. It is more suitable for routine calibrations of impedance. Theory of operation, construction, and basic balance equations are demonstrated. To verify this new established impedance system, some of the measurements related to the resistance have been carried out. Therefore, the optimum operating voltage at the commonly used 1 kHz frequency has been specified to the achieved relative error which is in the order of 10−5.

Summary form only given. A feasibility study of plasma cancer cell treatment was performed using a pin-type plasma jet. A 50 kHz AC power was used to generate the plasma in the ambient air assisted by the helium flow. The plasma gas temperature was maintained at the room temperature of 25degC to eliminate the thermal damages to the cell. The liver cancer cells of HEPG-2 and SK-HEP-1 were used as the treatment samples. The sample cells were prepared on the fibronectin coated slide glass for the sake of convenience of the microscopic observation process. The input voltage and the treatment time were controlled in the range of (750-1000) V and (30-120) s, respectively. After the plasma treatments, the sample cells were stained with the viability assay (ethidium homodimer and calcein AM) to make discrimination between live and dead cells. Then, the microscopy scan was performed from the plasma center up to about 1 cm. The necrotized cells as well as a void or cell free zone appeared starting at the input voltage of 800 V and the treatment time of 60 s, . The necrotized zone and the void were well matched to the plasma profile. Normal liver cell, THLE-2, was then treated for comparison with the liver cancer cells.

Experimental results of the treatment of dimethyl methylphosphonate (DMMP), which is a chemical stimulant of the sarin gas, are reported. The plasma used for the experiment was a large area non-thermal RF atmospheric pressure plasma produced in the ambient air, of which size was 15times100 mm2. Previously measured current and gas temperature were low enough for thermally-sensitive material treatments, and actual applications to a pork sample and human skin proved its electrical and thermal safety. 100 muliter of the liquid DMMP was dropped on copper and glass plates then treated by the plasma at the input power of 100 W for several tens of minutes. Fourier transform infrared spectroscopy showed that several minute long treatment was enough to significantly affect the DMMP characteristic infrared spectrum. On the other hand, gas chromatography was used for quantitative measurements. The treated copper and glass plates were placed in methane chloride solvent to collect the remaining DMMP. Then, the DMMP concentration of each solution was measured. After 10 minutes of the treatment, 99.05% of DMMP on the copper plate was gone, and 99.96% DMMP on the glass plate was decontaminated after 16 minutes of the treatment. These decontamination rates are far good compared to other conventional methods such as heat, chemical catalyst etc.

Summary form only given. Non-thermal atmospheric pressure micro jet plasmas were generated in a single electrode system using either LF (several tens of kHz) or RF (13.56 MHz) power sources, and the characteristics of the produced plasmas were compared. A copper electrode with radius of about 360 mum was placed in a glass tube with radius of 3 mm, and the main gas was helium. The plasma characteristics, such as physical appearance, electrical properties, and temperature, were measured by various means. The LF plasma shown to be about 50 mm long on the average, and its temperature, measured using a thermocouple, was about the room temperature. When the helium flow rate was 3 l/min, the breakdown voltage was less than 1000 V. Also, the plasma was maintained with up to 1 % of oxygen gas mixed. On the other hand, the RF plasma was about 5 mm long at the most, but it was thicker in radius than the LF plasma. The measured rotational temperature was between 300 K and 380 K, which was higher than the LF plasma temperature. The emission spectrum was more intense with a larger number of He I lines. Both plasmas exhibited different characteristics, and a further study would define their advantages and disadvantages and thus match appropriate applications for each.

Summary form only given. Plasma characteristics were studied through electrical and optical diagnostics for a volumetric (105 times 40 times 4 mm) RF plasma (MyPL; www.applasma.com) produced at the atmospheric pressure in the ambient air. The main discharge device has a conducting rod as a powered electrode, which is covered with a dielectric material and placed between two ground electrodes. A flow of the main supply gas is provided onto the conducting rod. The plasma length is extendable by having a longer rod. The plasma was produced at the peak to peak voltage of about 90 V with an ignition. The spatial uniformity of the visible emission was obtained through an image processing of the plasma image captured by a CCD camera. Varying the gas flow and the applied power, the uniformity along the length direction was maintained less than 10%. The gas temperature measured by a thermocouple and a fiber probe was between 300 and 400 K for the input power range of 40 and 100 W. The feasibility of plasma sterilization was also studied. An E-coli sample was treated with the plasma by varying treatment time, gas flow rate, treatment position etc. After the plasma treatment, the E-coli sample was cultured for 12 hours to study the plasma effects. So far, 30 s of treatment time is enough to kill every E-coli that there was none survived after the plasma treatment.

When treated by atmospheric pressure plasma, human liver cancer cells (SK-HEP-1) and normal cells (THLE-2) exhibited distinctive cellular responses, especially in relation to their adhesion behavior. We discovered the critical threshold voltage of 950 V, biased at the electrode of the micro-plasma jet source, above which SK-HEP-1 started to detach from the substrate while THLE-2 remained intact. Our mechanical and biochemical analyses confirmed the presence of intrinsic differences in the adhesion properties between the cancer and the normal liver cells, which provide a clue to the differential detachment characteristics of cancer and normal cells to the atmospheric pressure plasma.

Lately, the atmospheric pressure jet type corona plasma, which has been typically driven by dc to low frequency (LF: several tens of kHz), is often generated by using radio frequency of 13.56 MHz. Yet, the relationship between the plasma and its driving frequency has seldom been investigated. Hence, in this study, dependence of the atmospheric pressure corona plasma characteristics on the driving frequency was explored experimentally from LF to rf (5 kHz–13.56 MHz). The plasmas generated by the driving frequency under 2 MHz were cylindrical shape of several tens of millimeters long while the 13.56 MHz plasma is spherical and a few millimeters long. As the driving frequency was increased, the plasma length became shortened. At the lower driving frequencies (below 2 MHz), the plasmas existed as positive streamer and negative glow for each half period of the applied voltage, but the discharge was more continuous in time for the 13.56 MHz plasma. It was inferred from the measured I–V curves that the higher dr...

Time-resolved images of an atmospheric pressure corona discharge, generated at 50 kHz in a single pin electrode source, show unique positive and negative corona discharge features: a streamer for the positive period and a glow for the negative period. However, unlike in previous reports of dc pulse and low frequency corona discharges, multistreamers were observed at the initial time stage of the positive corona. A possible physical mechanism for the multistreamers is suggested.

Radio frequency mixing of 2 and 13.56 MHz was investigated by performing experimental measurements on the atmospheric pressure corona plasma. As a result of the dual frequency, length, current density, and electron excitation temperature of the plasma were increased, while the gas temperature was maintained at roughly the same level when compared to the respective single frequency plasmas. Moreover, observation of time-resolved images revealed that the dual frequency plasma has a discharge mode of 2 MHz positive streamer, 2 MHz negative glow, and 13.56 MHz continuous glow.

Atmospheric pressure helium plasma treated human hepatocytes exhibit distinctive zones of necrotic and live cells separated by a void. We propose that plasma induced necrosis is attributed to plasma species such as oxygen radicals, charged particles, metastables and/or severe disruption of charged cytoskeletal proteins. Interestingly, uncharged cytoskeletal intermediate filaments are only minimally disturbed by plasma, elucidating the possibility of plasma induced electrostatic effects selectively destroying charged proteins. These bona fide plasma effects, which inflict alterations in specific subcellular structures leading to necrosis and cellular detachment, were not observed by application of helium flow or electric field alone.

Atmospheric pressure helium discharge characteristics were investigated for varying driving radio frequencies in the range between 1.86 and 27.1 MHz. As the driving frequency is raised, both gas breakdown and α-γ transition voltages decrease due to the reduction in the electron drift loss. In addition, different discharge features such as normal, abnormal, α, and γ modes show certain dependences on the frequency. Using a simple circuit model, the changes in sheath thickness from 2.35 to 0.11 mm, electron density from 0.26 to 15.6×1011 cm−3 was obtained by raising the frequency from 1.86 to 27.1 MHz.

Atmospheric pressure of helium (He) and methane (CH4) mixture discharge characteristics are investigated using emission spectroscopic methods. Plasmas are produced in a radio frequency capacitively coupled device at atmospheric pressure in the ambient air. Without the CH4 gas introduced in the plasma, the emission spectrum exhibits typical helium discharge characteristics showing helium atomic lines with nitrogen molecular bands and oxygen atomic lines resulting from air impurities. Addition of a small amount (

Microsize jet-type plasmas were generated in a single pin electrode structure source for two separate input frequencies of 50kHz and 13.56MHz in the ambient air. The copper pin electrode radius was 360μm, and it was placed in a Pyrex tube with a radius of 3mm for helium gas supply. Due to the input frequency difference, the generated plasmas showed distinct discharge characteristics for their plasma physical appearances, electrical properties, gas temperatures, and optical properties. Strengths and weaknesses of both plasmas were discussed for further applications.

Controllability of small size atmospheric pressure plasma generated at low frequency in a pin to dielectric plane electrode configuration was studied. It was shown that the plasma characteristics could be controlled by geometrical and operational parameters of the experiment. Under most circumstances, continuous glow discharges were observed, but both the corona and/or the dielectric barrier discharge characteristics were observed depending on the position of the pin electrode. The plasma size and the rotational temperature were also varied by the parameters. The rotational temperature was between 300 and 490K, being low enough to treat thermally sensitive materials.