High Background Pressure Research Articles

A simple numerical simulation model can elucidate the key factors for designing a miniaturized ion trap mass spectrometer

BackgroundMiniature ion trap mass spectrometer enables mass-to-charge ratio analysis of ions via quadrupole field in a low vacuum environment. It plays an important role in on-site detection due to its portability and specificity. In order to gain a deeper understanding of the analysis mechanism of miniature ion trap mass spectrometers, a quadrupole MS ion trajectory numerical simulation model (QITNS) is established in this paper for ions trajectory calculation under the action of quadrupole field, exciting field and neutral gas molecule collision. Compared with the existing methods, the model in this paper is simpler and more direct, which effectively explored the effects of dipole excitation and quadrupole excitation on ion manipulation under high background pressure. ResultsThe simulation results demonstrate that high RF amplitude, low auxiliary AC amplitude and quadrupole excitation can effectively improve the isolation resolution. Besides, it clarified the difference between the analysis mechanism of ion trap mass spectrometers under high background pressure (above 13.332 Pa) and absolute vacuum conditions. The relevant results are consistent with the conclusions of previous experiments and other theories, proving the applicability and accuracy of the proposed calculation model and solution method. SignificanceThis research bears the guiding significance for further understanding the mechanism of quadrupole mass spectrometry as well as designing and developing miniature mass spectrometers.

Exploring morphological variation in bismuth ferrite nanostructures by pulsed laser deposition: synthesis, structural and electrochemical properties.

Structural and electrochemical properties of bismuth ferrite nanostructures produced by pulsed laser deposition with various morphologies are reported. The nanostructures are also explored as electrode materials for high-performance supercapacitors. Scanning electron microscopy images revealed that various bismuth ferrite morphologies were produced by varying the background pressure (10-6, 0.01, 0.10, 0.25, 0.50, 1.0, 2.0 and 4.0 Torr) in the deposition chamber and submitting them to a thermal treatment after deposition at 500◦C. The as-deposited bismuth ferrite nanostructures range from very compact thin-film (10-6, 0.01, 0.10 Torr), to clustered nanoparticles (0.25, 0.50, 1.0 Torr), to very dispersed arrangement of nanoparticles (2.0 and 4.0 Torr). The electrochemical characteristic of the electrodes was investigated through cyclic voltammetry process. The increase in the specific surface area of the nanostructures as background pressure in the chamber increases does not lead to an increase in interfacial capacitance. This is likely due to the wakening of electrical contact between nanoparticles with increasing porosity of the nanostructures. The thermal treatment increased the contact between nanoparticles, which caused an increase in the interfacial capacitance of the nanostructure deposited under high background pressure in the chamber.

Kinetic simulation of ion thruster plume neutralization in a vacuum chamber

The electrical environment of a ground vacuum testing chamber creates facility effects for gridded ion thrusters. For example, it is well known that the plume from the thruster generates current paths that are very different from what occurs in space, and the neutralization of this plume is also different. For reasons such as this, it is important to clarify how the experimental testing environment affects plasma flows, but understanding this effect solely through ground experiments is difficult. To that end, this study utilizes particle-in-cell and direct simulation Monte Carlo methods to simulate xenon beam ions and electrons emitted from a neutralizer. First, we compare simulations conducted within the chamber to those conducted in space, demonstrating that grounded chamber walls increase the electric potential and electron temperature. Next, we investigate the impact of the neutralizer’s position and the background pressure on the plume in the vacuum chamber. We find that as the neutralizer position moves closer to the location of maximum potential, more electrons are extracted, resulting in increased neutralization of the plume. We also observe that high background pressure generates slow charge-exchange ions, creating ion sheaths on the side walls that alter ion current paths. Finally, we discuss how the potential at the thruster and neutralizer exits affects the plume. The relative potential of the neutralizer to the vacuum chamber wall is observed to significantly influence the behavior of the electrons, thereby altering the degree of plume neutralization. These findings are shown to be consistent with experimental results in the literature and demonstrate the promise of high-performance simulation.

Three-Dimensional Kinetic Simulations of Carbon Backsputtering in Vacuum Chambers from Ion Thruster Plumes

Gridded ion thrusters are tested in ground vacuum chambers to verify their performance when deployed in space. However, the presence of high background pressure and conductive walls in the chamber leads to facility effects that increase uncertainty in the performance of the thruster in space. To address this issue, this study utilizes a fully kinetic simulation to investigate the facility effects on the thruster plume. The in-chamber condition shows a downstream neutral particle density 100 times larger than the in-space case due to ion neutralization at the wall and limited vacuum pump capability, resulting in a significant difference in the density and distribution of charge-exchange ions. The flux, energy, and angle of charge-exchange ions incident on the chamber wall are found to be altered by the electron sheath, which can only be simulated by the fully kinetic approach, as opposed to the conventionally used quasi-neutral Boltzmann approach. We also examine the effect of backsputtering, another important facility effect, and find that it does not necessarily require a fully kinetic simulation as the incident flux and energy of the sampled charge-exchange ion are negligibly small. Finally, we demonstrate that the carbon deposition rate on the thruster is significantly influenced by the angular dependence of the sputtered carbon, with a nearly 50% effect.

A Numerical Investigation of Supercavitation Vehicle’s Hydrodynamic Noise

This paper presents the simulation results of the acoustic field around an underwater supercavitation vehicle under various operating conditions and analyzes the cavitation phenomenon and the hydrodynamic noise spectrum. Regarding the ventilated cavitation phenomenon, the simulation shows that low vehicle speed can reduce the threshold of the ventilated supercavitation, and high background pressure can enhance the stability of the supercavitation structure. As for hydrodynamic noise, firstly, the simulation results reveal that when cavitation occurs, the noise spectrum exhibits several characteristic peaks near 1 kHz and between 3 and 10 kHz. The overall noise amplitude demonstrates a descending trend between 10 and 40 kHz. Further, under natural cavitation conditions, a characteristic peak is detectable between 40 and 80 kHz. The influence of the operating conditions on the noise is essentially achieved by altering the scale of the cavitation flow: with the growth of the bubble flow scale, the noise between 3 and 10 kHz first increases and then decreases due to its own pulsation and the masking effect, while the noise between 10 to 40 kHz substantially reduces. On the other hand, if the scale expansion of bubble flow is related to the increase of ventilation flow, the noise amplitude near 1 kHz will increase significantly. These results provide theoretical support for studying the supercavitation vehicles’ noise and applying the ventilated supercavitation technology.

Densification of a polymer glass under high-pressure shear flow

The properties of glasses can change significantly as they evolve toward equilibrium. Mechanical deformation appears to influence this physical aging process in conflicting ways, with experiments and simulations showing both effects associated with rejuvenation away from and overaging toward the equilibrium state. Here we report a significant densification effect in a polymer undergoing shear flow under high pressure. We used the high-aspect ratio geometry of the layer compression test to measure the uniform and homogeneous accumulation of plastic strain during isothermal confined compression of a deeply quenched film of polystyrene glass. Combined scanning transmission x-ray microscopy (STXM) and atomic force microscopy confirmed defect-free deformation leaving up to 1.2% residual densification under conditions of confined uniaxial strain. At higher peak strain, plastic shear flow extruded glass from below the compressing punch under conditions of a high background pressure. A further density increase of 2% was observed by STXM for a highly thinned residual thickness of polymer that nevertheless showed no signs of crystallization or internal strain localization. While the confined uniaxial densification can be accounted for by a simple elastic--plastic constitutive model, the high-pressure extrusion densification cannot.

New Insight into the Gas Phase Reaction Dynamics in Pulsed Laser Deposition of Multi-Elemental Oxides.

The gas-phase reaction dynamics and kinetics in a laser induced plasma are very much dependent on the interactions of the evaporated target material and the background gas. For metal (M) and metal–oxygen (MO) species ablated in an Ar and O2 background, the expansion dynamics in O2 are similar to the expansion dynamics in Ar for M+ ions with an MO+ dissociation energy smaller than O2. This is different for metal ions with an MO+ dissociation energy larger than for O2. This study shows that the plume expansion in O2 differentiates itself from the expansion in Ar due to the formation of MO+ species. It also shows that at a high oxygen background pressure, the preferred kinetic energy range to form MO species as a result of chemical reactions in an expanding plasma, is up to 5 eV.

From Groundwork to Efficient Solar Cells: On the Importance of the Substrate Material in Co‐Evaporated Perovskite Solar Cells

Adv. Funct. Mater. 2021, 31, 2104482 The originally published article contains an error in the calculation of the mean free path of methylammonium iodine (MAI) according to equation (2) in the main manuscript (wrong diameter for the MAI molecule), which also resulted in too low values for the mean free path of MAI in Figure 1b and a wrong explanation in the introductory part of the manuscript in section 2.1. The corrected Figure 1b is as follows: Relating to this change, a short paragraph starting on page 4 in the main manuscript, left column second-to-last line (“Due to the larger diameter of the MAI molecule compared to PbI2 […] resulting in a loss of the directed effusive flux and a transition to a more CVD-like evaporation behavior.”) is not completely correct. The mean free paths of MAI and PbI2 are rather similar after correction. Therefore, the conclusion that the loss in the effusive component of the MAI evaporation is due to the increased number of collisions between MAI molecules is unlikely. However, the clear indications that the MAI evaporation in the employed process is not fully effusive, but at least in part of CVD-like nature (e.g., the high background pressure and the conversion of a PbI2 film in presence of the background MAI atmosphere as discussed in the supporting information) remains valid, but must have another primary cause. As mentioned in the original manuscript and shown by others, the decomposition of MAI into more volatile compounds is expected to be one reason for the strong rise in background pressure as well as the CVD-like evaporation characteristic. Given the fact that a strong CVD-like evaporation characteristic of MAI is observed in our process, the description of the employed process as well as its challenges are still valid in the original manuscript. Most importantly, the influence of the substrate material (here polarity) on the film formation is not influenced by this initially wrong interpretation of our process since the substrate dependency is linked to the interaction of the substrate surface and the condensing molecules in this complex mixed process environment as shown throughout the manuscript. The authors apologize for any inconvenience this error may have caused and thank Tomas Leijtens for making us aware of it.

Background Pressure Induced Structural and Chemical Change in NiV/B4C Multilayers Prepared by Magnetron Sputtering

NiV/B4C multilayers with a small d-spacing are suitable for multilayer monochromator working at a photon energy region from 5 to 8 keV, or photon energy region from 10 to 100 keV. To investigate the influence of background pressure during fabrication, NiV/B4C multilayers with a d-spacing of 3.0 nm were fabricated by magnetron sputtering with different background pressures. The grazing incidence x-ray reflectivity (GIXR) and transmission electron microscopy (TEM) measurement illustrated the structural change that happened in NiV/B4C multilayers when background pressure is high. The electron dispersive x-ray spectroscopy (EDX) of NiV/B4C multilayer deposited with a high background pressure suggests a gradient distribution of oxygen, which corresponds to the gradient thickness change. The detailed x-ray absorption near edge spectroscopy (XANES) comparison of NiV/B4C multilayers, NiV coating, and B4C coating showed the chemical state change induced by background pressure. We concluded that during the deposition, vanadium oxide promoted the oxidation of boron. In order to fabricate a good performance of NiV/B4C multilayers, the background pressure needs lower than 1 × 10−4 Pa.

Well-adhered hydrogenated amorphous carbon thin films on ferrous alloy using silicon-containing interlayers at low temperatures

Si-containing interlayers are commonly used to overcome the low adhesion of DLC films to steel. However, a relatively high deposition temperature of 300 °C is necessary to deposit interlayers that ensure adhesion when tetramethylsilane is used as precursor. Moreover, oxygen impairs the adhesion between thin films and ferrous alloys. This work aims to verify the influence of low background pressure in the deposition of a-SiCx:H interlayers using tetramethylsilane at low deposition temperatures. Also, this letter contains a systematic study of the physicochemical properties of the interlayer and its influence on the film's structure. The results show that a background pressure of 0.8 Pa suits the formation of well-adhered a-C:H thin films even at temperatures as low as 85 °C. Chemical analysis associates this outstanding increase in adhesion with fewer oxygen found within the interlayer and at both interfaces when compared to previous results at high background pressures.

Numerical Study on the Temporal Evolution of a Helicon Discharge

A numerical model is developed to study the temporal evolution of helicon discharge. The initiation of helicon discharge is first presented in terms of time-dependent electron density and temperature, electric and magnetic fields, and power deposition; then, their steady-state values are compared with experimental data and previous simulations for benchmark. It is found that the evolutions of electron density and temperature arrive steady state around 100 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.5~\mu \text{s}$ </tex-math></inline-formula> , respectively, while electric and magnetic fields become steady prior to 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> . The spatial distributions of power deposition indicate that RF power is absorbed mostly near the edge, similar to those of electron temperature. Parameter studies show that high background pressure, confining magnetic field strength, and RF power are beneficial to obtaining high-density helicon plasma, while the driving frequency has little effect. These findings are interesting for the design and optimization of helicon plasma source.

Characterization of a Multicusp Ion Source With Two-Grid Extraction System for Studying Extraction and Transport of Ion Beam

A low-energy multipole line cusp ion source with two-grid extraction system has been developed and characterized for studying the role of the charge exchange processes on ion beam extraction, transport, and neutralization. The ion source is operated for extraction of Ar <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ion beam of current 50–240 mA at energies 850–1650 eV. The characterization of the ion beam is carried out at various axial positions along a 200–815-mm beam path with a background pressure of 4– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$20\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−5</sup> Torr. An 11-channel Faraday cup array is used to measure the radial profiles of ion current density and angular beam divergence at these positions. The beam divergences are found to be in the range of 6°–15° for beam perveance of 0.50– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.75\times10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−9</sup> AV <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3/2</sup> . The attenuation of ion beam current along the beam path is observed due to the charge exchange neutralization of the energetic ions in the presence of high background pressure. Since ion current density along the beam path can be reduced by both the charge exchange processes and beam divergence, the accounting of beam particles, i.e., energetic ions and neutrals, at larger distances is difficult by the measurements of ion current density using the Faraday cup alone. The flux of energetic particles (energetic ions and fast neutrals) is therefore obtained by a thrust measurements on a beam target fixed at a distance of 800 mm from the ion source. The neutralization of the ion beam obtained by the emission of electrons from a hot filament neutralizer is also investigated in the presence of the charge exchange processes. Space-charge neutralization is provided initially by the secondary electrons emitted from the vessel walls or by the charge exchange processes even without the neutralizer operating at the desired temperature. However, the current neutralization is achieved only by the electrons emitted from the hot filament neutralizer operating in a space-charge-limited mode.

Interfacial Properties of a PEM Water Electrolysis Pt Electrode Probed by Operando Tender Ambient Pressure X-Ray Photoelectron Spectroscopy

The probe of the chemical, structural, and electronic properties at the electrode-electrolyte interfaces under operational conditions is critical for the mechanistic study and optimization of all the electrochemical systems and has therefore been at the center of numerous studies [1]. Soft X-ray Ambient pressure X-ray photoelectron spectroscopy (APXPS) has been known as a promising in-situ/operando technique, but its applications in the probe of a realistic solid/liquid interface under ambient conditions has been limited by the short inelastic mean free path (IMFP) of photoelectrons in the liquid medium. Here, inspired by prior work [2,3] and taking advantage of the synchrotron tender X-ray source (Beamline 9.3.1) at the Advanced Light Source of the Lawrence Berkeley National Laboratory [4], the IMFP can be significantly increased. A larger IMFP enables interfacial characterization under higher background pressures and through liquid overlayer greater than 30 nm in thickness. We have designed and built a graphene sealed operando electrolysis electrochemical cell that is compatible with an existing tender X-ray APXPS setup for the investigation of electrode-electrolyte interfaces under operational conditions. The present setup will be utilized to probe various systems involving solid/liquid interfaces, including but not limited to the interactions of ions, the solvation of salts, and electrocatalysis.In this work, the utilization of tender X-rays (2000 – 6000 eV) facilitates investigations of the electrode-electrolyte interface with a liquid-layer thickness of tens of nanometers, which can be preserved within the sandwiched region between the topmost graphene and the Pt nanoparticle loaded proton exchange membrane (PEM). In addition, the environmental water vapor pressure within the analysis chamber was kept at the water vapor pressure at 298 K (~15 Torr). The setup allows the study of a water splitting electrolyzer under real working conditions, where the electrocatalytic performance and the operando photoemission spectroscopy can be simultaneous investigated. As a proof-of-concept, Pt nanoparticle-catalyzed oxygen evolution reaction (OER) was investigated under operando conditions. The electrochemistry and detailed analysis of the photoemission spectra demonstrating the evolution of the chemical, structural, and electronic properties at the H2O/Pt interface under the influence of external electrical field will be presented.

Study on Lifted Flame Stabilization Under Different Background Pressures

Abstract A numerical experimental investigation is presented for a steady methane lifted flame and a nonreaction jet flow in a co-flow of hot combustion products from lean premixed air-hydrogen combustion. The main objective has been to analyze the dependence of methane jet flame stability on the background pressure: a pressurized vitiated co-flow burner (PVCB) has been used to study the methane lifted flame and nonreaction jet flow under different background pressures (1–1.5 bars). The lifted flame is characterized by a liftoff height, which has been measured with a high-speed camera, and a central jet flow defined by the jet velocity, which has been measured by means of a high-sensitivity Schlieren imaging system. The experimental results show that the liftoff height decreases for an increment in the background pressure (from 1 to 1.5 bar at 1073 K) and in the co-flow temperature (from 1058 K to 1118 K at 1 bar). The standard deviation of the liftoff height also reduces for an increase in either the background pressure or the co-flow temperature, which indicates that the liftoff height is more stable at higher background pressures and co-flow temperatures. As far as the experimental tests on the nonreaction jet flow is concerned, the jet velocity becomes extinct faster as the background pressure rises, which is consistent with the decrease in the liftoff height as the background pressure grows. The evolution of the jet velocity has been proved to be another important factor that affects the liftoff height under different background pressures (physical factor), in addition to the fuel autoignition delay (chemical factor). The simulation data led with a Reynolds-averaged Navier–Stokes (RANS)/probability density function (PDF) model show that an increment in the background pressure makes the temperatures increase and induces a brighter yellow part of lifted flame, which leads to more soot production. This proves that the flame is not completely premixed. On the other hand, the Schlieren images of the non-reaction jet flow highlight that the flame is partially premixed, since the edge of the jet is not well defined, as the jet penetration increases with time. The liftoff height values of the flame in the numerical simulations were found to be generally higher than those measured in the corresponding experiments. This discrepancy was caused by an appreciable radiation heat loss at the thermocouple. A correlation was therefore developed for the thermocouple temperature measurement in order to correct the inaccuracy.

Propagation of microwave breakdown in argon induced by a 28 GHz gyrotron beam

An atmospheric argon discharge plasma was induced by a high-power microwave beam using a 28 GHz gyrotron and investigated at pressures of 40 kPa–100 kPa and Gaussian peak intensities of 0.115 GW/m2 (0.204 MV/cm) and 0.168 GW/m2 (0.246 MV/cm). According to high-speed imaging results, the propagation velocity of the discharge front increased with the backpressure to maintain a range of 600 m/s–1000 m/s. The propagation velocity was 25 times larger in argon than in air. Applying the collisional-radiative (CR) model to the spectroscopic results showed that the electron density increases with the pressure from 5.0×1021 m−3 at 40 kPa to 5.0×1022 m−3 at 100 kPa and lies on the critical density curve. The electron temperature decreases as the background pressure increases from 2 eV to 0.5 eV, and the gas temperature was 300–400 K. According to CR analysis, the population densities of 3dn and 2sn excitation levels in the fast velocity condition are much lower than that in any other conditions. The results revealed that the energy transfer from electrons to ionized particles is more remarkable in the high background pressure and the fast velocity condition.

Investigation of multi-event spark discharge strategy for lean methane-air combustion

The characterization of the single-coil repetitive discharge and the dual-coil offset discharge was conducted in a constant volume combustion chamber to better understand the operating principle of the multi-event spark ignition strategies. A parametric study of the dual-coil offset discharge was carried out through electric and optical diagnosis to identify the effective operational parameters, including coil working frequency, charging voltage, and coil inductances. Combustion tests under both quiescent and flow conditions with methane-air mixture were performed to demonstrate the ignition capability of the dual-coil offset strategy. Test results have shown that constantly depositing spark energy through offset discharge is beneficial to secure flame kernel. However, the offset discharge strategy requires a high working frequency, an elevated charging voltage, and fast reacting coils to maintain the spark plasma channel under high background pressure and intensified flow conditions.

The effect of high nitrogen pressures on the habitable zone and an appraisal of greenhouse states

ABSTRACT The habitable zone (HZ) is the main tool that mission architectures utilize to select potentially habitable planets for follow-up spectroscopic observation. Given its importance, the precise size and location of the HZ remains a hot topic, as many studies, using a hierarchy of models, have assessed various factors including: atmospheric composition, time, and planetary mass. However, little work has assessed how the HZ changes with variations in background nitrogen pressure, which is directly connected to the habitability and life-bearing potential of planets. Here, I use an advanced energy balance model with clouds to show that our Solar system's HZ is ∼0.9–1.7 au, assuming a 5-bar nitrogen background pressure and a maximum 100 per cent cloud cover at the inner edge. This width is ∼20 per cent wider than the conservative HZ estimate. Similar extensions are calculated for A–M stars. I also show that cooling clouds/hazes and high background pressures can decrease the runaway greenhouse threshold temperature to ∼300 K (or less) for planets orbiting any star type. This is because the associated increase in planetary albedo enables stable climates closer to the star, where rapid destabilization can be triggered from a lower mean surface temperature. Enhanced longwave emission for planets with very high stratospheric temperatures also permits stable climates at smaller orbital distances. The model predicts a runaway greenhouse above ∼330 K for planets orbiting the Sun, which is consistent with previous work. However, moist greenhouses only occur for planets orbiting A-stars.

Epitaxial Ge thin film Growth on Si Using a Cost-Effective Process in Simplified CVD Reactor

Germanium on silicon has the potential to enable growth of high quality group IV semiconductors for the field of silicon photonics by being used as virtual buffers. In addition Ge layers can be used in the fabrication of passive components such as waveguides and resonators. A cost-effective technology for the heteroepitaxial growth of Ge on Si will be highly beneficial. In this work, a simplified chemical vapor deposition reactor was assembled in-house to deposit Ge films. Epitaxial Ge film growth on Si (100) substrates was accomplished without requiring ultra-high vacuum conditions or a high temperature substrate pre-deposition bake thereby minimizing the economic and thermal budget of the process. Films were deposited using digermane (Ge2H6) precursor in a single step at a process temperature of 350 °C and chamber pressures of 1–10 Torr. Films were achieved at high chamber background pressures (>10−6 Torr) by implementing a thorough ex situ substrate cleaning process and optimizing times for wafer loading, chamber pumping and initiation of film deposition. Transmission electron microscopy and X-ray diffraction were used to confirm the epitaxial growth and crystalline quality of the obtained films. Optical properties of the films were characterized using Raman spectroscopy, Photoluminescence and Infra-red spectroscopy.

Oxygen in Complex Oxide Thin Films Grown by Pulsed Laser Deposition: a Perspective

For thin film synthesis of complex oxides, one of the most important issues has always been how to oxidise the material. For a technique like pulsed laser deposition, a key benefit is the relatively high oxygen background pressure one can operate at, and therefor oxidation should be relatively straightforward. However, understanding the microscopic oxidation mechanisms turns out to be rather difficult. In this perspective, we give a brief overview of the sources of oxidation for complex oxide thin films grown by pulsed laser deposition. While it is clear what these sources are, their role in the kinetics of the formation of the crystal structure and oxygen stoichiometry is not fully understood.

Effects of background pressure on the arc characteristics of gas spark gap

Gas spark gap is widely used in any pulsed power system as the key element which directly determines its repetitive performance and output characteristics. Among many factors of three-electrode gas spark gap, background pressure is of much importance in determining the gap performance parameters such as the delay and jitter, and relevant studies have been rarely performed. A magneto-hydrodynamic model of the arc in gas spark gap is built and the effects of background pressure on the arc characteristics are discussed in this paper. It is demonstrated that a higher background pressure may result in radial compression of the arc column, a higher arc voltage, and a lower declination rate of arc resistance in the first quarter cycle. Relevant simulation data would be helpful for the optimization of the design of gas spark gap.