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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Field emission assisted micro plasma discharges at vacuum and atmospheric pressures
摘要： Spatially confined non-equilibrium plasmas at vacuum and atmospheric pressure in the dimensions from a few microns to one millimeter are a promising approach to the generation and maintenance of stable glow discharges. The realization of these micro-discharges or micro-plasmas enable more accurate investigations in the field of micro plasma research. We report on field emission assisted micro plasmas excited by an alternating current with frequencies up to 1 kHz. Due to the field enhancement caused by an array of Si nano-tip structures the ignition voltage of stable plasma discharges can be reduced by 30%.
关键词： low-temperature plasma,field emission array,dielectric barrier discharge,plasma discharge
更新于2025-09-23 15:21:21
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Clinical efficacy comparison of low-temperature plasma radiofrequency ablation and Nd:YAG laser in treating recurrent acquired nasolacrimal duct obstruction
摘要： To evaluate the effectiveness and safety of low-temperature plasma radiofrequency ablation (coblation) and Nd:YAG laser in treating recurrent nasolacrimal duct obstruction. A prospective study was performed on patients who agreed to be treated with coblation or Nd:YAG laser for recurrent nasolacrimal duct obstruction after failed lacrimal Nd:YAG laser combined with silicone intubation. The visual analogue scale (VAS) pain grade was assessed at baseline, immediately, and 3 and 7 days after surgery. The degree of watering, lacrimal passage irrigation, and complications were also evaluated 1 week and 1, 3, and 6 months after surgery. Ninety-five patients who met the criteria for recurrent nasolacrimal duct obstruction from February 2018 to February 2019 were included in this study, with 46 patients receiving coblation and 49 patients Nd:YAG laser. The intraoperative and postoperative (3 days after surgery) VAS pain grades of the patients who received coblation were significantly lower than those who received Nd:YAG laser (P < 0.001). The number of patients in the coblation group who achieved complete clinical relief (no epiphora symptoms with fluent lacrimal passage irrigation) was significantly larger than that in the lacrimal Nd:YAG laser group at 1, 3, and 6 months after surgery (P = 0.033, P = 0.006, P = 0.003, respectively). During the follow-up period, there were no unexpected complications in either group. Compared with Nd:YAG laser, coblation performed well in alleviating pain and maintaining sustained disease relief and may therefore be an alternative to conventional laser or dacryocystorhinostomy surgery in the management of recurrent nasolacrimal duct obstruction.
关键词： Nd:YAG laser,Recurrent acquired nasolacrimal duct obstruction,Low-temperature plasma radiofrequency ablation,VAS pain grade
更新于2025-09-23 15:19:57
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Mass spectrometry imaging of thin-layer chromatography plates using laser desorption/low-temperature plasma ionisation
摘要： Thin-layer chromatography (TLC) is a classic method for the separation and analysis of complex mixtures. Biological assays, chemical derivatisation and spectroscopy techniques are compatible with TLC and provide extra information about isolated compounds. However, coupling TLC to mass spectrometry is hampered by the difficulty to desorb the analytes from the silica surfaces. In this study, we used a multimodal ion source for laser desorption (LD) and low-temperature plasma (LTP) post-ionisation. Efficient desorption was reached by covering the TLC plates with activated carbon. Regions of interest can be analysed by spots, by lines or by area. We show the separation of methylxanthines from coffee, tea and cocoa preparations by TLC, with subsequent mass spectrometry imaging (MSI). Using a lateral resolution of 400 mm × 400 mm, allowed the acquisition of 21,895 spectra in 2.4 h (2.5 pixels/s). Further, we demonstrate the possibility of direct mass fragmentation studies and quantification. We mounted the system on an Open LabBot with a theoretical lateral resolution of 12.5 mm and performed the visualisation of ions of interest and the pixel-wise review of mass spectra with our free software RmsiGUI (https://bitbucket.org/lababi/rmsigui). This non-proprietary and modular platform enables the cost-efficient adaption of the system and further development by the community.
关键词： mass spectrometry imaging,thin-layer chromatography,low-temperature plasma,laser desorption,ambient ionisation
更新于2025-09-19 17:13:59
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Influence of External Input Parameters on Species Production in a Dual-Frequency Capacitively Coupled Radio-frequency Oxygen Plasma
摘要： The impact of some external input parameters on electron, ozone O3, negative O? and positive O2+ ions, metastable singlet delta-state O2(a1Δg) molecule and atomic oxygen O formation is investigated using a numerical simulation. A one-dimensional, self-consistent fluid model of a dual radio-frequency capacitively coupled discharge operating on pure oxygen is developed to explore the evolution of the species density profiles as functions of gas pressure pg, driving high-frequency fhf, inter-electrode gap distance d and driving voltage waveform Vhf. The proposed model incorporates five main species and 24 dominant reaction channels. Simulation results show that the time-averaged density profiles of electron, ozone O3, negative O? and positive O2+ ions decrease when the gas pressure increases. However, the density of the metastable singlet delta-state O2(a1Δg) molecule and atomic oxygen O increase when the gas pressure increases. The electron density significantly increases with increased fhf until a maximum peak is reached at 40.68 MHz, and then it drops almost linearly at frequencies greater than 40.68 MHz. However, the negative ions O? density increases over a range of frequencies from 27.12 to 67.80 MHz, then it decreases slightly as fhf increases further. Therefore, when fhf increases, it does enhance the production of the metastable O2(a1Δg) and the oxygen O atoms, whereas the O2+ density is decreased. It is also shown that an increase in the inter-electrode gap distance causes a noticeably decrease in the formation of the various species in the discharge. Furthermore, a significant increase in the atomic oxygen O and the metastable singlet delta-state O2(a1Δg) densities is displayed as Vhf increases. Comparisons are made with recent simulation models and experimental data, and a qualitative agreement is obtained.
关键词： Low-temperature plasma,Dual capacitively coupled oxygen plasma,Species production
更新于2025-09-12 10:27:22
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Laser diagnostics for the electron density of helium low temperature plasmas using saturated absorption spectroscopy
摘要： Helium (He) low temperature plasma with an electron density higher than 10^11 cm^-3 was produced using an inductively coupled plasma source, and the electron density of this plasma was determined using a high-resolution laser spectroscopic technique. To remove the Doppler broadening which is the most dominant line broadening in low temperature plasmas, a saturated absorption spectroscopy system was configured. The Lamb dip was successfully separated from the Doppler broadening for the 2^1S - 4^1P transition of the He plasma using a high-resolution laser beam with a narrow spectral line width (below 1 MHz) at 396.5 nm. The estimated spectral line widths of natural broadening, van der Waals broadening, resonance broadening, and Stark broadening were 40.14 MHz, 0.93 MHz, 0.15 MHz, and 12.60 MHz, respectively, when the He gas pressure was 30 mTorr and 1 kW RF power was applied. The electron density of the He plasmas was determined to be ~3 x 10^11 cm^-3, which was comparable with those determined by a Langmuir probe and optical emission spectroscopy combined with a collisional-radiative model.
关键词： Low temperature plasma,Spectral line broadening,Saturated absorption spectroscopy,Helium
更新于2025-09-11 14:15:04
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Experimental Characterization of Polymer Surfaces Subject to Corona Discharges in Controlled Atmospheres
摘要： Polymeric dielectrics are employed extensively in the power transmission industry, thanks to their excellent properties; however, under normal operating conditions these materials tend to degrade and fail. In this study, samples of low-density polyethylene, polypropylene, polymethyl methacrylate, and polytetrafluoroethylene were subjected to corona discharges under nitrogen and air atmospheres. The discharges introduced structural modifications over the polymer surface. From a chemical perspective, the alterations are analogous among the non-fluorinated polymers (i.e., polyethylene (PE), polypropylene (PP), and polymethyl methacrylate (PMMA)). A simulation of the corona discharge allowed the identification of highly reactive species in the proximity of the surface. The results are consistent with the degradation of insulating polymers in high-voltage applications due to internal partial discharges that ultimately lead to the breakdown of the material.
关键词： partial discharges,chemical characterization,polymer surface degradation,morphological characterization,low-temperature plasma
更新于2025-09-11 14:15:04