Capillary Discharge Research Articles

Excitation and ionization of a diagnosis gas in front of the flexible μ tube plasma and in a diagnosis tube

The noble gases Helium, Argon, Krypton and even Xeon have been applied as discharge gases for the flexible μ tube plasma (FμTP) with comparable ionization efficiencies. It was assumed that a temporally and spatially limited potential plays a major role in the generation of reactant ions responsible for protonation in the surrounding air. However, the excited and ionized species of ambient air cannot be detected directly by emission spectroscopy because there is no known emission wavelength within the detectable range. In this work, a diagnosis gas was introduced as a substitute for the surrounding air to understand the excitation and ionization outside the discharge capillary. It was found that with Ne, Ar, Kr, Xe as plasma gases the diagnosis gas He can be excited during the positive half cycle. The emission of He 706 nm and N2+ 391 nm propagate with and against diagnosis gas flow directions in case of He and Ne driven plasmas. In case of Ar, Kr, and Xe driven plasmas, the emission of both species mainly develops against the diagnosis gas and the shapes of He 706 nm are wide. Further on, the diagnosis gas He is also excited even though there is a glass wall between the plasma gas flow and diagnosis gas flow. These findings demonstrate that the transient potential is responsible for the excitation of the diagnosis gas, not penning ionization or charge transfer between discharge plasma and diagnosis gas.

A repetitive pulsed electrothermal plasma jet ignition system based on capillary discharge.

Plasma ignition and combustion enhancement is a promising technology in applications of engines, industrial burners, pollutant emissions controls, etc. A new repetitive electrothermal plasma jet ignition system based on ablated capillary discharge under atmospheric pressure is presented in this paper. It consists of a capillary discharge module, a pulse current circuit, a pulse voltage circuit, a current release unit, an LC series resonant circuit, and a control system. The effects of the energy storage capacitor's voltage and resistance in the current release unit on the electrical parameters are investigated. Increasing the capacitor voltage helps to shorten the discharge delay and increase the energy deposition efficiency in the main discharge process. The increase of the resistance in the current release unit leads to a longer discharge delay and higher energy deposition efficiency in the main discharge process. Balanced parameters between the delay of discharge in 66 µs and the energy deposition efficiency in 84% are achieved through optimization, with a peak radiative heat flux of 23MWm-2 and a maximum jet length of 17cm. Repetitive capillary discharge at 20Hz under atmospheric pressure is achieved with the dispersion of energy storage capacitor charging voltage and energy deposition efficiency of 0.3% and 9.6%, respectively. Simplified circuit topology and control logic contribute to the miniaturization of the ignition system.

A novel micro-capillary discharge plasma jet triggered gas switch.

To reduce the working coefficient and jitter of the three-electrode gas switch used in linear transformer drivers, a novel trigger method that uses a nanosecond pulse in cooperation with the microplasma jet generated by capillary discharge was developed. A microplasma jet was generated by the nanosecond trigger pulse and injected into the follow-up breakdown gap of the gas switch to decrease the working coefficient. The influence of capillary parameters on the development of the microplasma jet was simulated. The results showed that the microplasma jet significantly reduced the breakdown delay time, jitter, and working coefficient. Increasing the capillary length and decreasing the diameter results in better triggered breakdown performance. Furthermore, the gas switch triggered by a positive pulse exhibits a lower breakdown delay and jitter. Combined with the intensified charge coupled device's shooting results, it can be concluded that the microplasma jet has a distinct influence on streamer formation, which is important for improving the working performance of the gas switch.

Study of high-frequency electrodeless mercury capillary discharge in the magnetic field

Study of high-frequency electrodeless mercury capillary discharge in the magnetic field

Modelling of Capillary Discharge in Repetition Mode for Short Capillary Systems with Various Filling Methods

Modelling of Capillary Discharge in Repetition Mode for Short Capillary Systems with Various Filling Methods

Investigation of the Emission Spectrum of a Fast Capillary Discharge in the “Water Window” Region

Investigation of the Emission Spectrum of a Fast Capillary Discharge in the “Water Window” Region

Capillary Point Discharge-Optical Emission Spectrometer: field portable mercury analyzer

Environmental mercury pollution poses a serious threat to public health and ecosystems, underscoring the value of rapid and accurate on-site mercury measurement technologies. Therefore, a portable mercury analyzer was developed with capillary point discharge for excitation and cold vapor generation for sample introduction. A limit of detection (LOD) of 0.23 μg L−1 for mercury was achieved, relative standard deviations below 5 % were maintained in a 10-hour testing period. This method was successfully used for mercury determination of spiked water samples, fish meat, and laboratory wastewater. Powered by several power banks, it can be used to monitor mercury levels in water samples continuously over a working day. Compared with traditional technology, this one greatly reduces the size of the instrument, the consumption of working gas, and the construction cost, making it suitable for rapid field analysis of many types of samples for trace mercury.

Analysis of Plasma Dynamics in He-Ne Lasers with Different Gas Ratios

He-Ne lasers play a crucial role in ultra-precision measurement and optical sensing across various fields. For many applications based on He-Ne lasers, a higher output power is required to enhance the accuracy and signal-to-noise ratios of the associated optical measurements. However, conventional methods to increase the output power by reducing the diameter of the He-Ne laser discharge capillary inevitably result in higher diffraction losses and constrain the lasing performance. Here, we propose an approach to enhance laser pumping efficiency and output power through optimizing the ratios of He and Ne gasses. The validity of our proposal has been confirmed by both numerical simulations of He-Ne laser plasma discharge processes and experimental demonstrations, showing that the optimal gas ratio increases with the capillary diameter and total gas pressure.

Capillary discharge in the high repetition rate regime

Capillary discharge in the high repetition rate regime

Azimuthally extreme-ultraviolet focal splitter by modified spiral photon sieves

Extreme Ultraviolet (EUV) radiation is a short-wavelength light source that has important applications in many fields, such as optical communication, particle manipulation, and ultrahigh resolution imaging. However, the highly absorptive nature of EUV light makes it challenging to design suitable focusing optics, such as focal splitters, to properly manipulate the energetic light. Here, we propose modified spiral photon sieves to transform EUV laser light into azimuthally splitting focusing. A genetic algorithm was used to design and optimize the azimuthally focal splitters. A capillary discharge EUV laser at 46.9 nm was used to verify the effectiveness of our proposed method, and PMMA targets were used to record the focused laser spot. The profile of the recorded patterns measured by atomic force microscopy shows that the focal spots in the experiment are diffraction-limited and agreed with the theoretical analysis. The proposed technique provides a new way for manipulating EUV light and further extends the applications ranging from EUV to soft x rays.

Absolute calibration of the ratio of Xe/O two-photon absorption cross-sections for O-TALIF applications

The paper presents a calibration of the ratio of two-photon absorption cross-sections, σXe(2)/σO(2) , necessary for the absolute O-atom density measurements by two-photon absorption laser-induced fluorescence (TALIF) technique. To calibrate the ratio of the cross-sections, a special discharge with 100% dissociation of molecular oxygen, and so with a known ‘reference’ density of O-atom [O] ref=2⋅ [O2] was suggested. This is a nanosecond capillary discharge in N2:O2 mixtures with a few percent of oxygen at a reduced electric field of a few hundred of Townsend and specific deposited energy of about 1 eV mol−1. Voltage at the electrodes, electrical current in the plasma, longitudinal electric field and energy delivered to the gas were measured with 0.2 ns synchronisation. Additionally, radial distribution of emission of excited nitrogen molecules and gas temperature in the discharge and afterglow were obtained experimentally. Detailed 1D kinetic modeling was suggested to confirm complete O2 dissociation and to analyse the main reactions. By comparing the data measured by TALIF technique with the ‘reference’ density of oxygen atoms [O] ref , the ratio of the two-photon absorption cross-sections σXe(2)/σO(2) was determined.

Study of the transfer and matching line for a PWFA-driven FEL

The development of compact accelerator facilities providing high-brightness beams is one of the most challenging tasks in the field of next-generation compact and cost affordable particle accelerators. Recent results obtained at SPARC_LAB show evidence of the FEL laser by a compact (3 cm) particle driven plasma-based accelerator. This work is carried out in the framework of the SPARC_LAB activities concerning the R&D on plasma wakefield accelerators for the realization of new compact plasma based facilities, i.e EuPRAXIA@SPARC_LAB. The work here presented is a theoretical study demonstrating a possible scheme concerning the implementation of an innovative array of discharge capillaries, operating as active-plasma lenses, and one collimator to build an unconventional transport line for bunches outgoing from plasma accelerating module. Taking advantage of the symmetric and linear focusing provided by an active-plasma lens, the witness is captured and transported along the array without affecting its quality at the exit of the plasma module. At the same time the driver, being over-focused in the same array, can be removed by means of a collimator.

Study of demixing in C–F plasma produced in a capillary discharge

The spatial distribution of chemical elements in plasma produced by a pulsed discharge in a capillary made of polytetrafluoroethylene has been studied by methods and means of optical spectroscopy. It has been found that the ratio of the molar fractions of fluorine and carbon differs significantly from that in the polymer wall and varies nonmonotonically along the radius of the plasma jet emerging from the capillary. The performed qualitative analysis of the intensity and direction of a number of competing diffusion fluxes involving C, C+, F, and F+ indicates both the possibility of the slowdown in the fluorine and carbon demixing, which start from the peripheral zone, and a change in the direction of some of these fluxes in the central zone of the discharge, which is reflected in the measured mole fraction profiles of these elements.

Thermal and oxidative disintegration of anaerobic digested sludge by solution plasma process

Solution plasma process (SPP) is promising for sludge disintegration, since the SPP only uses electric power and induces strongly oxidizing environments. In this study, the SPP using a capillary discharge that generating reactive oxygen species and heating solution was developed to assess the disintegration performance of anaerobic digested sludge. The SPP was compared with the thermal process (TP) which has only thermal contributions to evaluate the contributions of thermal and oxidative disintegration of sludge. Compared to the TP, under all tested conditions, the improved solubilization performance (up to 1.41, 1.84, and 6.55 times higher for overall COD, proteins, and carbohydrates, respectively) by the SPP was attributed to the oxidative effect (statistically significant, p < 0.01) with the thermal effect on the sludge disintegration. This oxidative effect became less significant as the temperature and incubation time without further plasma discharge increased. According to the particle size distributions and detailed characterization of dissolved organic matters, an increased release of biopolymers (proteins and carbohydrates), low molecular weight (LMW) substances (building blocks and neutrals), and the significant particle size reduction, suggested that the SPP induced floc disruption, cell lysis, and disintegration of sludge flocs even at the temperature of between 60 and 80 °C, while the TP was not favorable for releasing intracellular LMW substances and reducing the sludge floc size. Therefore, the SPP showed a synergistic impact of thermal and oxidative effects for improving the sludge disintegration. This study provides comprehensive insights for understanding the SPP and its possible application to sludge treatment.

Evolution of tungsten degradation under different cyclic ELM-like high heat flux plasma

A millisecond pulsed repetitive plasma generator based on capillary discharge is utilized to produce ELM-like heat load. Based on this device, the evolution of tungsten degradation under heat loads with different heat fluxes, pulses, and frequencies is investigated. With an increase of heat flux and pulse, the tungsten surface experiences an increasing melting and cracking damage. The cross-sections of samples are analyzed to investigate the mechanisms of crack formation and propagation. There are numerous small cracks of ∼20 μm length in the melting layer, which may extend to form the primary cracks under further stress. Among the primary cracks, the central crack in the heat-affected layer initially propagates perpendicularly to the surface and grows parallel to the surface, converging with the edge cracks under cyclic high heat loads. And the microstructures near cracks also reveal the mechanism of crack formation, including the intergranular primary cracks and partial transgranular secondary cracks. This work provides a novel approach to simulating ELM-like thermal load and corresponding tungsten cracking behavior under repetitive high heat flux plasma.

Soft x-ray Ar + 8 laser excited by low-voltage capillary discharge.

We demonstrated the operation of a 46.9-nm capillary discharge Ar + 8-laser excited by electrical pulses at a very low voltage (35 - 45 kV), which is approximately two times lower than previously reported. The decrease in pulse voltage not only allows for further reduction in the size of the laser's excitation part, but also a principal shift to the experimental methods, techniques, and technologies used in ordinary pulsed gas lasers operating in the ultraviolet, visible, and infrared regions of the spectra. In an argon-filled alumina capillary with an inner diameter of 3.1 mm and a length of 22 cm, laser pulses with an energy of 4 µJ and a duration of 1.6 ns were generated. The laser produces a beam with a Gaussian intensity distribution and an FWHM divergence of 1.9 mrad. The results could be particularly useful in the development of compact, practical soft x-ray capillary lasers for use in small laboratories at educational and research institutions.

Investigation of the Radiative Properties of Fast Capillary Discharge Plasma in the Soft X-Ray Range

Investigation of the Radiative Properties of Fast Capillary Discharge Plasma in the Soft X-Ray Range

INVESTIGATION OF PARAMETERS OF ELECTRON AND POSITRON BUNCHES IN A PLASMA-DIELECTRIC WAKEFIELD ACCELERATOR

The results of numerical PIC-simulation of the dynamics of accelerated positron and drive electron bunches under wake acceleration in a dielectric waveguide filled with plasma with a vacuum channel are presented. The wake field was excited by an electron bunch in a quartz dielectric tube inserted into a cylindrical metal waveguide. The inner region of the dielectric tube was filled with plasma with a vacuum channel along the waveguide axis. The difference in the energy and spatial characteristics, acceleration efficiency, emittance, and energy spread for positron and electron bunches is studied for different radii of the vacuum channel and two models of the plasma density dependence on the radius: a homogeneous and an inhomogeneous dependence characteristic of a capillary discharge.

Different elements, same results: time-resolved temperature determination by oxygen and nitrogen elements

The core purpose of this research is to use optical emission spectroscopy to determine the electron temperature (Te ) of a hydrogen plasma generated in a capillary discharge plasma, with a focus on its temporal variation. The plasma density (ne ) is first determined using the Stark broadening technique, which measures the broadening of spectral lines as a result of the electric field in the plasma. Subsequently, a passive spectroscopic technique is employed to estimate the electron plasma temperature by detecting the emitted light from the plasma. This spectral detection is performed using a visible range spectrometer. In this study, two elements, oxygen and nitrogen, are specifically selected based on the chemical composition of the capillary. The electron plasma temperature is estimated using the line ratio method, which involves comparing the intensities of two specific spectral lines emitted by the selected elements. By analyzing these line ratios, the electron plasma temperature can be inferred. The combination of the Stark broadening technique and line ratio method provides valuable insights into the plasma's physical characteristics, specifically its density and temperature.

Computational and Experimental Modeling in Magnetoplasma Aerodynamics and High-Speed Gas and Plasma Flows (A Review)

This paper provides an overview of modern research on magnetoplasma methods of influencing gas-dynamic and plasma flows. The main physical mechanisms that control the interaction of plasma discharges with gaseous moving media are indicated. The ways of organizing pulsed energy input, characteristic of plasma aerodynamics, are briefly described: linearly stabilized discharge, magnetoplasma compressor, capillary discharge, laser-microwave action, electron beam action, nanosecond surface barrier discharges, pulsed spark discharges, and nanosecond optical discharges. A description of the physical mechanism of heating the gas-plasma flow at high values of electric fields, which are realized in high-current and nanosecond (ultrafast heating) electric discharges, is performed. Methods for magnetoplasma control of the configuration and gas-dynamic characteristics of shock waves arising in front of promising and advanced aircraft (AA) are described. Approaches to the control of quasi-stationary separated flows, laminar–turbulent transitions, and static and dynamic separation of the boundary layer (for large PA angles of attack) are presented.