High-pressure Argon Gas Research Articles

Control of the excited-to-ionized atoms ratio in a dense gas in the wake of an intense femtosecond laser pulse.

We demonstrate the sensitivity of the plasma composition in the filament wake channel in a dense gas to the temporal shape of the driving femtosecond laser pulse. During the pulse, the electrons released via strong-field ionization and driven by oscillating laser field are actively engaged in collisional processes with neutral neighbor atoms, including inverse Bremsstrahlung, impact ionization, and collisional excitation. By the end of the pulse, these collisional processes produce considerable numbers of additional free electrons (or ionized atoms) and excited atoms, and these contents of the filament wake channel determine its subsequent evolution dynamics. Addressing the case of high-pressure argon gas and using a kinetic model of these competing collisional processes, we explore the sensitivity of the resulting excited-to-ionized atoms number density ratio to the envelope shape of the driving laser pulse. By considering several families of pulses, we show that asymmetric pulse envelopes skewed toward the earlier time allow for efficient control of the ratio of excited atoms to ionized atoms. The pulse-shape control of the plasma composition in the immediate wake of the laser pulse projects into control of the wake channel evolution and of the associated transient electronic and optical nonlinearities.

Pulsed Discharge Plasma in High-Pressure Environment for Water Pollutant Degradation and Nanoparticle Synthesis

The application of high-voltage discharge plasma for water pollutant decomposition and the synthesis of nanoparticles under a high-pressure argon gas environment (~4 MPa) was demonstrated. The experiments were carried out in a batch-type system at room temperature with a pulsed DC power supply (15.4 to 18.6 kV) as a discharge plasma source. The results showed that the electrode materials, the pulsed repetition rates, the applied number of pulses, and the applied voltages had a significant effect on the degradation reactions of organic compounds. Furthermore, carbon solid materials from glycine decomposition were generated during the high-voltage discharge plasma treatment under high-pressure conditions, while Raman spectra and the HRTEM images indicated that titanium dioxide with a brookite structure and titanium carbide nanoparticles were also formed under these conditions. It was concluded that this process is applicable in practice and may lead to advanced organic compound decomposition and metal-based nanoparticle synthesis technologies.

Distributed Joule-Thomson effects and convective heat transfer of high-pressure argon gas flow in helically coiled mini-tubes

Helically coiled mini-tubes have compact structures and good heat transfer performance which attract wide attentions in applications of compact heat exchangers of miniature thermal systems. In this study, forced convection in the helically coiled mini-tubes is numerically studied for the high-pressure low-temperature argon gas. The distribution of temperature and velocity on the cross-section and the variations of the local Nusselt number along the length and periphery of helical coils are presented. The frictional factors and the average heat transfer coefficients h are obtained for Reynolds number in the range of 22500–82500. In the helical coil with tube diameter of 0.3 mm, the distributed Joule-Thomson effect becomes noticeable, and the secondary flow is more apparent at a large Reynolds number, leading to the enhancement of heat transfer compared with that of 0.5 mm tube. The proposed parametrization of Gnielinski correlation yields good consistency with the numerical results, and the deviations for predictions of friction factor and heat transfer coefficient are within ±10%.

Radio frequency and DC high voltage breakdown of high pressure helium, argon, and xenon

Motivated by the possibility of guiding daughter ions from double beta decay events to single-ion sensors for barium tagging, the NEXT collaboration is developing a program of R&D to test radio frequency (RF) carpets for ion transport in high pressure xenon gas. This would require carpet functionality in regimes at higher pressures than have been previously reported, implying correspondingly larger electrode voltages than in existing systems. This mode of operation appears plausible for contemporary RF-carpet geometries due to the higher predicted breakdown strength of high pressure xenon relative to low pressure helium, the working medium in most existing RF carpet devices. In this paper we present the first measurements of the high voltage dielectric strength of xenon gas at high pressure and at the relevant RF frequencies for ion transport (in the 10 MHz range), as well as new DC and RF measurements of the dielectric strengths of high pressure argon and helium gases at small gap sizes. We find breakdown voltages that are compatible with stable RF carpet operation given the gas, pressure, voltage, materials and geometry of interest.

Predictive analysis of surface roughness in argon-assisted EDM using semiempirical and ANN techniques

This experimentation explores the utilization of argon-assisted electrical discharge machining (AAEDM) of high-carbon high-chromium die steel. High-pressure argon gas in conventional EDM was utilized to assess the surface roughness (SR). Analysis of variance was connected to decide the critical parameters influencing SR. In this study, a mathematical model has been instigated to get to know SR by using Buckingham pi-theorem while applying the AAEDM process. The fit summary confirmed that the quadratic model is statistically appropriate, and the lack-of-fit is insignificant. Root-mean-square error and absolute standard deviation, obtained through response surface method, were also used for developing the model and for its predicting abilities through ANN. The experiment and anticipated estimates of SR during the process, obtained by dimensional analysis and ANN, were found to be in accord with each other. However, the ANN technique proved to be more fitting to the response as compared to the dimensional analysis.

High voltage insulation and gas absorption of polymers in high pressure argon and xenon gases

High pressure gas time projection chambers (HPGTPCs) are made with a variety of materials, many of which still await proper characterization in high pressure noble gas environments. As HPGTPCs increase in size toward ton-scale detectors, assemblies become larger and more complex, creating a need for detailed understanding of how structural supports and high voltage insulators behave. This includes identification of materials with predictable mechanical properties and without surface charge accumulation that may lead to field deformation or sparking. This paper explores the mechanical and electrical effects of high pressure gas environments on insulating polymers PTFE, HDPE, PEEK, POM and UHMW in argon and xenon, including studying gas absorption, swelling and high voltage insulation strength.

Optical observation of the ballooning and burst of E110 and E110G cladding tubes

Abstract During the last decades several experiments revealed interesting details of the ballooning and burst of nuclear cladding tubes in accident conditions involving high temperature and high pressure. To further investigate this phenomenon, a new set of experiments was conducted at MTA EK. A large tube furnace was fitted with two optical telescopes on opposite sides to observe the ballooning and burst of Russian E110 and E110G (sponge based E110) fuel cladding samples. The experiments were recorded using regular and high-speed cameras. Based on the captured images we developed a method to separate the contours of the cladding tubes during the ballooning to measure the change in diameter. Two successive modes of ballooning were observed, the uniform growth of the samples was followed by an asymmetrical, local ballooning (bulge formation) 2 s before the burst. It was found that the samples have bent by approximately 5° relative to their original axis in the latter phase and this was not caused by the jet effect of the high pressure argon gas escaping after the burst. Every sample opened up on the convex side of the bend. Axial grooves have formed on the surface of the E110G samples under tension. The high-speed camera was used to capture the cracking and the burst. Prior to the burst, a high temperature spot was observed at the position where the crack would initiate. The timescale of the crack propagation was 0.2 ms, the crack tip was estimated to be at least 100 °C hotter than the rest of the sample. The burst pressure was determined between 700 °C and 900 °C at different pressurization rates.

Microstructural characterisation of CuAgZr powder particles produced by argon gas atomisation

ABSTRACTCuAgZr alloy is known for its high strength and high conductivity, which are reasons for its wide application. In this work, CuAgZr powder alloys were produced by high-pressure argon gas atomisation. The results indicate that the surface morphology of the powder is a cellular crystal structure with a pentagonal crystal structure, with a ‘rose-like’ lattice and cross-shaped dendrites. A three-dimensional model of the primary dendritic changes in the CuAgZr alloy powder with different powder diameters was established by studying the surface morphology and internal microstructure of the powder. The relationship between the powder diameter and the powder cooling rate was established as the function of the primary dendritic length (PDL), the primary dendritic volume fraction (PDVF), the secondary dendrite arm spacing (SDAS) and the secondary dendritic volume fraction (SDVF). A confidence validation was performed, and the function fitting error is within 10%. The results establish that the function is meaningful.

Influence of Atomizing Gas and Cooling Rate on Solidification Characterization of Nickel-based Superalloy Powders

Nickel-based superalloy powders have been produced by high pressure argon gas and nitrogen gas atomization, separately. The microstructural characterization of nickel-based alloy powders has been performed by a scanning electron microscope equipped with an EDS microanalysis unit. Based on a Newtonian cooling model, the flight speed and the cooling rate of two kinds of alloy droplets were calculated. The results show that the droplet cooling rate, which depends on atomization medium and droplet size, has an effect on the solidification microstructure. For argon-gas atomized powders, the developed dendrite structure is predominant at a lower cooling rate and a mixed microstructure composed of dendrite structure and cellular structure is observed at a higher cooling rate. For nitrogen-gas atomized powders, the dendrite structure is predominant at a lower cooling rate and a full cellular structure can be observed at a higher cooling rate. According to calculation, the cooling rate of argon-gas atomized droplets is in a range from 1.0×105 K·s−1 to 4.24×106 K·s−1, while the cooling rate of nitrogen-gas atomized droplets is from 1.0×105 K·s−1 to 4.8×106 K·s−1. The cooling rate increases with decreasing of droplets diameter. Two kinds of atomizing gases have a slight influence on the cooling rate of droplets. The dendrite axis is rich in elements such as Cr, Co, W, Ni and Al while the inter-dendrite region is rich in Ti element.

Study on heat transfer process during leaks of high pressure argon through a realistic crack

This paper proposes a method for simulating the heat transfer process of high pressure argon gas leaking through a narrow crack which causes the Joule-Thomson cooling effect (JT cooling effect). A once-through (decoupled) model was developed to firstly calculate the gas pressure drop at different crack depth, followed by the temperature drop. A MATLAB code was also developed to iteratively calculate the properties of leaking gas in a crack which was fitted as formula as boundary conditions in heat transfer simulation in COMSOL program. The simulated lowest temperature of the test plate in the vicinity of the crack is 13.8 °C after decreasing from the temperature of 30 °C with initial argon gas pressure of 91 bar. An experiment test rig designed and tested under the same conditions showed a good agreement between the simulation and experiment at the obtained lowest temperature in the test plate. The method is useful for predicting the lowest temperature in the vicinity of the crack caused by the JT cooling effect.

Laser ion source for multi-nucleon transfer reaction products

We have developed a laser ion source for the target-like fragments (TLFs) produced in multi-nucleon transfer (MNT) reactions. The operation principle of the source is based on the in-gas laser ionization and spectroscopy (IGLIS) approach. In the source TLFs are thermalized and neutralized in high pressure and high purity argon gas, and are extracted after being selectively re-ionized in a multi-step laser resonance ionization process. The laser ion source has been implemented at the KEK Isotope Separation System (KISS) for β-decay spectroscopy of neutron-rich isotopes with N=126 of nuclear astrophysical interest. The simulations of gas flow and ion-beam optics have been performed to optimize the gas cell for efficient thermalization and fast transporting the TLFs, and the mass-separator for efficient transport with high mass-resolving power, respectively. To confirm the performances expected at the design stage, off-line experiments have been performed by using 56Fe atoms evaporated from a filament in the gas cell. The gas-transport time of 230ms in the argon cell and the measured KISS mass-resolving power of 900 are consistent with the designed values. The high purity of the gas-cell system, which is extremely important for efficient and highly-selective production of laser ions, was achieved and confirmed from the mass distribution of the extracted ions. After the off-line tests, on-line experiments were conducted by directly injecting energetic 56Fe beam into the gas cell. After thermalization of the injected 56Fe beam, laser-produced singly-charged 56Fe+ ions were extracted. The extraction efficiency and selectivity of the gas cell in the presence of plasma induced by 56Fe beam injection as well as the time profile of the extracted ions were investigated; extraction efficiency of 0.25%, a beam purity of >99% and an extraction time of 270ms. It has been confirmed that the performance of the KISS laser ion source is satisfactory to start the measurements of lifetimes of the β-decayed nuclei with N=126.

High-harmonic generation and spherically confined hydrogen atom

The dynamics of a hydrogen atom in a spherical box under the action of a strong infrared femtosecond laser is numerically investigated. The spherical box is introduced to model collisions of ionized electrons with neighboring atoms to model their influence on high-order harmonic generation. The physical situation appropriate for such application is considered in detail. The presence of tunneling in the process is investigated. In the strong field limit this consideration is extended including a dressing approach in the calculation. The harmonic spectrum is calculated for a small radius of the sphere assuming a high gas pressure. The intensities of the harmonic lines are reduced and the envelope of the spectrum is strongly modified with respect to the plateau of harmonics. The inclusion of the dressing approach in the calculation can significantly modify this result. The situation is changed if a kicking electric field is added at the moment when ionization probability has local maximum. The electron kinetic energy is drastically increased, and as a consequence of the dynamic Stark shifts in the kicking field, and an unusual electron recombination is possible. The odd harmonics of a very high-order and a somewhat different form of plateau of harmonics appear. The intensities of so obtained single-atom harmonic emission are dramatically enhanced. To check the reliability of the model with an impenetrable spherical box, high-pressure argon gas is also considered in relation to the single atom high-order harmonic generation.

An RF-only ion-funnel for extraction from high-pressure gases

An RF ion-funnel technique has been developed to extract ions from a high-pressure (10bar) noble-gas environment into a vacuum (10−6mbar). Detailed simulations have been performed and a prototype has been developed for the purpose of extracting 136Ba ions from Xe gas with high efficiency. With this prototype, ions have been extracted for the first time from high-pressure xenon gas and argon gas. Systematic studies have been carried out and compared to simulations. This demonstration of extraction of ions, with mass comparable to that of the gas generating the high-pressure, has applications to Ba tagging from a Xe-gas time-projection chamber for double-beta decay, as well as to the general problem of recovering trace amounts of an ionized element in a heavy (m>40u) carrier gas.

Numerical Study on the Heat Transfer in the Leakage of Pressure Vessels Considering the Joule-Thomson Cooling Effect

The cooling effect caused by the Joule-Thomson (JT) effect in the leakage of pressure vessels has gained more and more attention and worries from natural gas transportation industries as it may influence the validity of the conventional leak-before-break approach. Currently, leak-before-break (LBB) design codes for pressure vessels do not take into account of the subsequent low temperature depression and the drop in fracture toughness in the aftermath of a leak. This study is to ensure the integrity of the compressed natural gas (CNG) containment in marine transportation vessels being proposed to transport the gas in highly pressurized (up to 250bar) cylinders. A numerical method was proposed to simulate the heat transfer between the high pressure argon gas leaking through a narrow crack and the surrounding metal which is caused by the Joule-Thomson cooling effect of the leaking argon. A one-way coupling model was developed to calculate the gas pressure drop at different crack depth, followed by the temperature drop. A heat transfer simulation then calculated the temperature in the metal in the vicinity of the crack. The Redlich-Kwong (RK) equation with a relatively high accuracy was adopted to evaluate the temperature change of the leaking argon. The modified Petukhov correlation by Adams et al. was employed to evaluate the heat transfer coefficient of leaking argon. A MATLAB code was developed to iteratively calculate the properties of leaking gas in a crack which was fitted as formula as boundary conditions in heat transfer simulation of COMSOL program. Under the maximum internal pressure of 91bar, the simulated temperature drop of the test plate in the vicinity of the crack caused by the Joule-Thomson cooling effect is 16.2°C. An experiment rig designed and tested under the same conditions showed a good agreement between the simulation and experiment at the obtained lowest temperature in the test plate.

The LAGUNA/LBNO potential for Long Baseline neutrino physics

The LAGUNA/LBNO collaboration proposes a new generation neutrino experiment to address fundamental questions in particle and astroparticle physics. The experiment consists of a far detector, Liquid Argon (LAr) double phase Time TPC (Time Projection Chamber), the fiducial mass of the detector is set to 20 kt in its first stage. The detector will be situated at 2300 km from CERN: this long baseline provides a unique opportunity to study the neutrino flavour oscillations over the first and second oscillation maxima and to explore the L/E (Length over energy) behaviour. The near detector is based on a high-pressure argon gas TPC situated at CERN. I will detail the physics potential of this experiment for determining without ambiguity the mass hierarchy (MH) in its first stage and discovering CP violation (CPV) using the CERN SPS beam with a power of 750 kw. The impact of the assumptions on the knowledge of the oscillation parameters and the systematic errors are very important and will be shown in detail to prove the force of the experiment assuming realistic and conservative parameter values.

The mass-hierarchy and CP-violation discovery reach of the LBNO long-baseline neutrino experiment

The next generation neutrino observatory proposed by the LBNO collaboration will address fundamental questions in particle and astroparticle physics. The experiment consists of a far detector, in its first stage a 20 kt LAr double phase TPC and a magnetised iron calorimeter, situated at 2300 km from CERN and a near detector based on a high-pressure argon gas TPC. The long baseline provides a unique opportunity to study neutrino flavour oscillations over their 1st and 2nd oscillation maxima exploring the $L/E$ behaviour, and distinguishing effects arising from $\delta_{CP}$ and matter. In this paper we have reevaluated the physics potential of this setup for determining the mass hierarchy (MH) and discovering CP-violation (CPV), using a conventional neutrino beam from the CERN SPS with a power of 750 kW. We use conservative assumptions on the knowledge of oscillation parameter priors and systematic uncertainties. The impact of each systematic error and the precision of oscillation prior is shown. We demonstrate that the first stage of LBNO can determine unambiguously the MH to $>5\sigma$C.L. over the whole phase space. We show that the statistical treatment of the experiment is of very high importance, resulting in the conclusion that LBNO has 100% probability to determine the MH in at most 4-5 years of running. Since the knowledge of MH is indispensable to extract $\delta_{CP}$ from the data, the first LBNO phase can convincingly give evidence for CPV on the $3\sigma$C.L. using today's knowledge on oscillation parameters and realistic assumptions on the systematic uncertainties.

J0320303 低温焼結により作製されたチタン多孔質体のカプセルフリーHIP処理とその評価([J032-03]ポリマー・セラミックス・メタル多孔質材料の開発と応用(3),材料力学部門)

The low elastic modulus titanium alloy used for implant has been investigated, and the conflicting problem of strength and porosity has been challenged. Manufacturing of porous material by capsule-free hot isostatic pressing (HIP) can be expected for simultaneous control of porosity and mechanical strength. In this study, commercial pure titanium powders were sieved below 150μm and 106μm, and the sieved powders were compacted by hydraulic hand operated pressing machine. Then, the compacts were sintered by electric furnace under atmospheric pressure argon gas at 823K, and finally capsule-free HIPed under high-pressure argon gas (150MPa) at 1523K. Results showed that the HIPed compacts maintained pores sufficiently, and the character was affected by compaction load. The aspect of pore forming was, however, considered to be different in the surface and the inside.

Study on Characteristics of Nanopowders Synthesized by Nanosecond Electrical Explosion of Thin Aluminum Wire in the Argon Gas

As a new gas-phase synthesis method for the production of nanosize powders, the wire electrical explosion method has the advantages of high energy efficiency and high product purity through production under pure inert gas conditions and has been applied to the continuous industrial production of nanopowders. In this paper, an experimental device based on the electrical explosion of metallic wires for nanopowder production and collection is designed and built. Also, aluminum nanopowders were produced by electrically exploding an aluminum wire and collected by the microporous membrane filter successfully under different pressures of argon gas. Moreover, the influence of the argon gas pressure on the characteristics of the aluminum nanopowders was analyzed by a transmission electron microscope. The results showed that the particle shape, size, and distribution of the aluminum nanopowders could be controlled by the pressure of argon gas. The aluminum nanoparticles produced in the high-pressure argon gas had better spherical particle shape; meanwhile, the count mean diameter of the aluminum nanopowders increased obviously with the rise of the argon gas pressure. A higher pressure of argon gas could broaden the range of the aluminum nanoparticle size distribution evidently.

An accurate loading experimental measurement device for superplastic free bulging

Superplastic alloy has very strong structure sensitivity. Superplastic bulging with a die of the plate is related not only to stress state but also closely to loading paths. It is an important basis for bulging forming with a die to study deformation law and experimental apparatus for superplastic free bulging, because the boundary of test piece is fixed and friction is insignificant for free bulging. In the paper, a pure high-pressure argon gas source is used as the loading media after it is heated by the heating system outside the furnace, which improves the heating efficiency and temperature uniformity of the test piece. The photoelectric non-contact measurement device can avoid negative influence on the additional stress and uneven temperature at the peak of bulging part caused by push rod in the contact measurement. The temperature and pressure of the test piece in cylindrical insulation furnace with blank holder give feedback control to improve the control precision. In loading gas channels, the pressure is adjusted by accurately measuring and controlling the rotation angle of the stepping motor, and is loaded by an electromagnetic valve. It significantly increases the response characteristics of the control pressure. This paper also introduces steps and methods to realize several typical loading paths, such as constant pressure, jump pressure and additional back & differential pressure loading. These provide a new way to measure the strain rate sensitivity index m value and improve the deformation speed of superplastic free bulging.

Mechanical behavior of cellular borosilicate glass with pressurized Ar-filled closed pores

High strength borosilicate foams were fabricated by melting glass powder under high-pressure argon gas and subsequent heat treatment of the glass bulk at atmospheric pressure. In the first step, borosilicate glass powder was melted at 1100°C for 1h by capsule-free hot isostatic pressing (HIPing) under a high gas pressure of 10–70MPa. Pressurized Ar-filled spherical pores were introduced into the glass, and argon atoms were dissolved in the glass network structure. The expansion of argon-filled pores and the release of the dissolved Ar gas resulted in the formation of pressurized Ar-filled closed pores by isothermal heat treatment at 800°C for 10min. A high porosity of up to 80% with a bimodal distribution of micro-size cells was obtained for the resultant cellular borosilicate glass. By increasing the total gas pressure from 10 to 70MPa, the compressive strength and the Young’s modulus were increased considerably from 15 to 52MPa and from 4.1 to 12.6GPa, respectively, which can be substantially attributed to the high collapse stress from the high enclosed gas pressure. The cellular glass with a high porosity showed a large failure strain under uniaxial compression.