• Analytical Science and Technology
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• v.22 no.2
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• pp.152-158
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• 2009

In this study, we made a new discharge source improving previous SPI source to ionize softly organic compounds. The new SPI source consists of two electrodes as a hollow mesh cathode of half cylindrical shape and a hollow anode. We optimized the geometrical parameter of the SPI source by investigating the I-V curves at the various distance between the cathode and the anode. As the results, we found stable conditions of the soft plasma on broad range of the current and the voltage. The new SPI source attached to quadrupole mass spectrometer (QMS), and we obtained the mass spectra of dichloromethane (DCM). The fragment patterns of DCM appeared similarly with the pattern of electron ionization (EI).

• Journal of the Korean Vacuum Society
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• v.5 no.3
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• pp.251-257
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• 1996

The present paper represents the results of development and first experimental tests of a new ionized cluster beam (ICB) source. The novelty of ICB source lies in the fact that the crucible and ionization parts are spaced in one cylindrical shell but are not divided in an electric circuit. The ICB source adapts permanent magnets to increase the ionization efficiency. The maximum obtained $Cu^+$ ion current denisity is $1.5{\mu}A/\textrm{cm}^2$, therewith the ionization rate amounts 3% under deposition rate is 0.2$\AA$/s and the acceleration voltage is 4 kV, the $Cu^+$ ion beam uniformity is better than 95%.

• Mass Spectrometry Letters
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• v.3 no.4
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• pp.87-92
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• 2012

In this study, we explored a new approach for generating ions of organics and biomolecules using contactless atmospheric pressure ionization (C-API). That is, a tapered capillary (~20 cm) was connected to a syringe, which was coupled to a syringe pump for providing a given flow rate to introduce sample solution to the proximity of a mass spectrometer. The gas phase ions derived from analytes were readily formed in the capillary outlet, which was very close to the mass spectrometer (~1 mm). No external electric connection was applied on the capillary emitter. This setup is very simple, but it can function as an ion source. This approach can be readily used for the analysis of small molecules such as amino acids and large molecules such as peptides and proteins. The limit of the detection of this approach was estimated to be ~10 pM when using bradykinin as the sample. Thus, we believe that this approach should be very useful for being used as an alternative ion source because of its low cost, high sensitivity, simplicity, and ease of operation.

• Mass Spectrometry Letters
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• v.10 no.4
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• pp.103-107
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• 2019

Low-temperature plasma (LTP) ionization is one of the ambient ionization methods typically used in mass spectrometry (MS) for fast screening of chemicals with minimal or no sample preparation. In spite of various advantages of LTP ionization method, including simple instrumentation and in-situ analysis, more general applications of the method are limited due to poor desorption of analytes with low volatilities and low ionization efficiencies in the negative ion mode. In order to overcome these limitations, an ultrasonic vibrator of a commercial hand-held humidifier was interfaced with an LTP ionization source, which generated microdroplets from sample solutions and assisted with LTP ionization. Ionization behaviors of various chemicals in microdroplet-assisted LTP (MA LTP) were tested and compared with typical LTP ionization from dried samples applied on a surface. MA LTP efficiently ionized small organic, amino, and fatty acids with low volatilities and high polarities, which were hardly ionized using the standard LTP method. Facile interaction of LTP with ultrafine droplets generated by ultrasonic resonator allows efficient ionization of relatively non-volatile and polar analytes both in the positive and negative ion modes.

• Journal of radiological science and technology
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• v.30 no.2
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• pp.147-151
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• 2007

AAPM TG43 report has recommended to measure air kerma strength with the strength of source. Main purpose of this study is to verify the accuracy of air kerma strength provided by manufacturer. Materials for this study were MAX-4001 Electrometer, HDR 1000 Plus of the corporation of standard imaging, and 6 french bronchial Applicator with 1000 mm. we measured ionization current in 10-90 mm range from the bottom of the central axis of chamber. The reference point of calibration displayed by the maximum ionization current in the ionization current curve was measured, and air kerma strength was computed from the maximum ionization current. we acquired 50 mm distance to correspond with the maximum ionization current in the ionization current curve. Its distance has perfectly fitted to the source reference point of calibration certificate of UW-ADCL. Air kerma strength computed value has measured about 0.5% more than calibration value provided by manufacturer. Air kerma strength of calibration certificate provided by manufacturer has acquired reliable results. This study shows that considering the move error of dwell position of source and the dead space length in well-type chamber is a good way to get an accurate result.

• Bulletin of the Korean Chemical Society
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• v.24 no.8
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• pp.1163-1168
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• 2003

The structures of molecular species of galactolipids, such as monogalactosyl diacylglycerol (MGDG) and digalactosyl diacylglycerol (DGDG), isolated from wheat flour have been investigated using negative-ion electrospray ionization (ESI) mass spectrometry interfaced with high performance liquid chromatography (HPLC). According to the result of HPLC analysis, MGDG and DGDG were found to consist of mixtures of five and four molecular species, respectively. The galactolipids have been also analyzed to determine their fatty acid compositions, using HPLC/ESI-MS combined with in-source (or cone voltage) fragmentation. HPLC/ ESI-MS is very useful for one-step analysis of mixtures of galactolipids with a small sample quantity. Especially, the carboxylate anions produced in in-source fragmentations of the negative-ion of each component separated by HPLC provide valuable information on the composition of its fatty acyl chains.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.23-27
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• 2002

Two $^{192}$ Ir HDR brachytherapy sources were calibrated with a Farmer ionization chamber in air method and in a PMMA cylindrical phantom. The calibration air method used ionization chamber with buildup cap, and 8 variation distances for center-to-center of the source to chamber. In the optimum distance the measured activity, especially for the high activity source, deviation was 0.3% from the activity provided by manufacturer. Calibration with a PMMA cylindrical phantom was less sensitive, and suitable for quick check method with accuracy less than 10%.

• Journal of Photoscience
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• v.8 no.2
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• pp.83-86
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• 2001

Structural analyses of oligosaccharide-malononitrile derivatives were conducted by matrix-assisted laser desorption/ionization post-source decay (MALDI-PSD) analysis in positive ion mode. The malononitrile derivatives of oligosaccharides, which were developed for highly sensitive detection of multi-component oligosaccharides by negative ion electrospray ionization mass spectrometry (ESI MS), were detected by positive-ion MALDI with the detection limit of 2 pmol level from the crude derivatization sample. The used matrix affected drastically the analytical results of oligosaccharide-malononitrile derivative by matrix-assisted laser desoprtion/ionization mass spectrometry (MALDI MS). The malononitrile derivatization of oligosaccharide also affect the patterns of MALDI-PSD spectra and give much more structural information than the free oligosaccharide.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.71.2-71.2
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• 2010

Cooling hot gas sets a floor on the ionization level for diffuse gas in the ISM in general and the galactic halo. Many high galactic latitude sight lines, cooling hot gas is the dominant source of the ionization. Such sites are prime regions for the formation of both C IV and Si IV ions at a temperature of T~105K. To study of the ISM that have the 104.5~6K ionization state by ionization or photoionization by the collision, searching for the radiation energy that is emitted at far ultra violet range is required. In this paper, we report the analysis of NGP( North Galactic Pole, $l:270^{\circ},b:90^{\circ},rad:40^{\circ}$) region by fuv($1350{\sim}1750{\AA}$) data that are surveyed with FIMS. After making the FIMS FUV image of the NGP region, we divided up into 50 small regions for that and got the spectrum emission lines from each one.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.70.2-70.2
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• 2010

Cooling hot gas sets a floor on the ionization level for diffuse gas in the ISM in general and the galactic halo. Many high galactic latitude sight lines, cooling hot gas is the dominant source of the ionization. Such sites are prime regions for the formation of both C IV and Si IV ions at a temperature of T~105K. To study of the ISM that have the 104.5~6K ionization state by ionization or photoionization by the collision, searching for the radiation energy that is emitted at far ultra violet range is required. In this paper, we report the analysis of NGP(North Galactic Pole, $l:0^{\circ},b:90^{\circ}$,rad: $40^{\circ}$) region by fuv($1350\sim1750\AA$) data that are surveyed with FIMS. After making the FIMS FUV image of the NGP region, we divided up into some small regions for that and got the spectrum emission lines from each one.