Alumina Capillary Research Articles

Short rise- and decay-time Z-pinch currents for soft x-ray laser excitation

The article addresses how to create inductance-free plasma and use it to excite soft x-ray lasers. The method employs a bifilar phenomenon in which one part of the pulsed current flows via the plasma column while the other part runs in the opposite direction via the closely placed external conductor. The electromagnetic fields formed by the plasma and return conductor are adjusted by lowering the distance between them to neutralize the magnetic field of the bifilar. Because the net transient magnetic field is drastically reduced, the plasma-conductor mutual inductance is near zero during current rise and decay. The inductance-free (L ∼ 2 nH) 35 cm-long Z pinches in a 3.1 mm-diameter argon-filled alumina capillary with current rise and decay times of 15 ns, dI/dt > 1012 A/s, and amplitudes up to 17 kA were predicted, realized, and verified to be suitable for pumping soft x-ray Ar+8 lasers. Without the bifilar phenomenon, the 35 cm Z pinches obey a 200 nH inductance that restricts the rise and decay durations of currents to 150 ns. The 35 cm Z pinches with 2 nH inductance generated 46.9 nm laser pulses with up to 4 μJ of energy and a beam divergence of 2 mrad at a low operating voltage of 35–45 kV, compared to 0.1–0.8 MV for similar lasers. The bifilar method could find applications in many research and technological fields, where the rise and decay times of discharge currents play a key role.

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.

Numerical simulation of Ne-like Ar plasma dynamics and laser beam characteristics of 46.9 nm laser excited by capillary discharge

In this work, we performed computer modeling of high electrical discharge in an Ar filled alumina capillary in order to investigate the parameters of the discharge system that may lead to achieve an intense laser beam. One-dimensional magnetohydrodynamics (MHD) simulations were used to study the parameters of discharge produced Ar plasma. The radial evolution of plasma parameters such as electron temperature, electron density, and Ne-like argon density was estimated from MHD simulations. Additionally, the influence of the main discharge current on the pinching time and plasma radius was analyzed with the one-dimensional MHD model. The active medium for lasing is created by a high amplitude main pulse and pre-pulse. Specifically, we investigated the optimum main discharge current and Ar filling pressure. The main discharge current of 30 kA was declared as the best current to obtain the 46.9 nm laser with a 4 mm alumina capillary. The influence of the main discharge current and lasing pressure on laser beam intensity and beam characteristics has been studied theoretically and experimentally. The saturated laser intensity was obtained with a main discharge current of 30 kA. A severe reduction in laser intensity was observed above the main discharge current of 30 kA due to capillary wall ablation. The laser beam divergence was observed to be less than 3.5 mrad. The theoretical results obtained from MHD simulations are in good agreement with the experimental results of laser intensity and laser beam characteristics.

Impact of pre-pulse current and delay time on 46.9 nm laser with larger inner diameter alumina capillary

In this Letter, we firstly, to the best of our knowledge, demonstrated the influence of pre-pulse current and delay time on the intensity of a discharge pumped Ne-like Ar soft X-ray laser operating at 46.9 nm by employing an alumina capillary having an inner diameter of 4.8 mm. Specifically, the delay time was changed from 8 to 520 μs in small intervals. The pre-discharge current was increased from 25 A to 250 A through small steps, while keeping the main discharge current constant. Usually, a small pre-discharge current is applied to an Ar-filled capillary to attain a plasma column having sufficient pre-ionization before the injection of the main current. The pre-discharge current of 140 A was declared the best current to obtain lasing with a 4.8 mm diameter capillary. The laser spots were captured at best time delays for the pre-discharge currents of 25, 45, 80, 140, and 250 A, which support the experimental results. We observed that by applying the pre-discharge current of 140 A, the laser spot exhibits small divergence, higher symmetry, and uniformity, which is clear evidence of strong amplification. The laser spot obtained at 140 A is cylindrically symmetric and has a better structure than those reported by all other groups in the literature. Hence, the laser spot indicates that the laser beam is highly focusable and beneficial for the applications of the 46.9 nm laser. Results of this Letter might open a new way to enhance applications of a 46.9 nm capillary discharge soft X-ray laser.

Impact of discharge currents on the intensity of 46.9 nm capillary discharge soft X-ray laser.

In this article, capillary discharge Ne-like argon 46.9nm soft X-ray laser has been firstly manifested with 4.8mm inner diameter alumina capillary for higher discharge currents. We have designed and installed capillary discharge setup for 4.8mm inner diameter alumina capillary to achieve intense 46.9nm laser. One dimensional Langragian Magneto-hydrodynamics (MHD) code was used to simulate the plasma conditions at the lasing time. The MHD code was used to perform the parametric studies of Z-pinch argon plasma, such as electron temperature, electron density and Ne-like argon ion density. The intensities of capillary discharge 46.9nm laser emitted from 4.8mm inner diameter alumina capillary were measured at 30, 36 and 40kA main discharge currents. According to the results, when the main current amplitude was increased from 30kA to 36kA and 40kA, the intensity of laser produced at optimum pressure increased up to 1.5 and 2 times, respectively. Moreover, we also studied the influence of predischarge current by increasing the predischarge current from 25 to 250A and investigated 140A as the best predischarge current for lasing. Hence, increasing the amplitude of main current using a comparatively larger inner diameter capillary is an effective way to improve intensity of capillary discharge 46.9nm soft X-ray laser. The maximum energy of 46.9nm laser was observed approximately 1.5mJ under best discharge conditions. The discussion has been made on the enhancement of 46.9nm laser intensity for higher main discharge currents and best predischarge current with experimental and simulated results. This is the first observation of 46.9nm laser with 4.8mm inner diameter alumina capillary.

High-Temperature Interaction Between Molten AlSr10 Alloy and Glass-Like Carbon Substrate

Wettability of glass-like carbon substrate (Cglc) by molten Al-10 wt.% Sr alloy (AlSr10) has been examined by a sessile drop method at 700-800 °C for 120 min under vacuum. Non-contact heating to the test temperature combined with the removal of oxide film from the alloy drop was done using capillary purification procedure by squeezing the liquid alloy from a capillary. The influence of the type of capillary on wetting behavior of AlSr10/Cglc couples was noticed. Molten AlSr10 alloy does not wet Cglc at about 700 °C forming the contact angles of 111° with graphite capillary and 141° with alumina capillary. At 800 °C with alumina capillary, non-wetting-to-wetting transition takes place resulting in a final contact angle of 70°. After testing at 800 °C, the AlSr10/Cglc interface was revealed at the test temperature directly in the vacuum chamber by the drop suction procedure. Structural characterization of the interfaces by scanning and transmission electron microscopy combined with energy-dispersive x-ray spectroscopy and by scanning probe microscopy combined with Auger electron spectrometry did not show any new phases formed with Sr. It suggests that the dominant role in wettability improvement by alloying Al with 10 wt.% Sr was related with significant lowering of the surface tension of liquid metal and adsorption of Sr at the interface.

Demonstration of soft X-ray laser generated in highly saturated capillary discharge amplifier with 4.0 mm and 3.2 mm inner diameter alumina capillaries

Capillary discharge highly saturated Ne-like Ar 46.9 nm laser had been firstly demonstrated with a 4.0 mm inner diameter alumina capillary. The intensity of laser is greater for the 4.0 mm inner diameter capillary than for the conventional 3.2 mm inner diameter capillary. The gain coefficients have been enhanced to 0.86 cm −1 and 1.3 −1 , for the 4.0 mm and 3.2 mm inner diameter alumina capillaries, respectively. Furthermore, an alumina capillary with a 4.0 mm or larger inner diameter possesses crucial advantages to achieve more intense or shorter wavelength soft X-ray laser.

Optimization of a Water Window Capillary Discharge Radiation Source

Computer modeling of a fast electrical discharge in a nitrogen-filled alumina capillary was performed in order to discover discharge system parameters that lead to high radiation intensity in the so-called water window range of wavelengths (2–4 nm). The modeling was performed by means of the two-dimensional RMHD code Z*. The time and spatial distribution of plasma quantities were used for calculating the ion level populations and for estimating the absorption of the 2.88 nm radiation line in the capillary plasma, using the FLYCHK code. Optimum discharge parameters for the capillary discharge water window source are suggested. The heating of the electrodes and the role of capillary channel shielding were analyzed according to the Z* code.

Pinching capillary discharge as a water window radiation source

Our aim is to develop a tabletop monochromatic incoherent water window radiation source based on the pinching capillary discharge in nitrogen. We have performed experiments with alumina capillary filled by nitrogen. Strong spectral line at 2.88 nm, corresponding to the quantum transition 1s2p → 1s 2 of the helium-like nitrogen ions, was observed. Spatial and time evolutions of pinching plasma quantities as well as the water window emission were modeled by means of RHMD code Z *. Computer and laboratory experimental results correspond each other. Computer optimization of the device has been done by varying capillary geometry, charging voltage and initial pressure. Reasonable capillary shortening has been suggested.

Observations of extreme ultraviolet emission from plasma produced by capillary discharges

This study reports the results of a pilot experiment concerning observations of extreme ultraviolet emission from plasma produced by the capillary discharges. A few kA current was applied across the gas-filled alumina capillary (1 mm diameter and 8 mm long) to generate radiation in the EUV region (12–63 nm). Spectroscopic studies were carried out by means of a XEUV spectrometer which was upgraded for special lithography purposes. The results obtained from the EUV spectroscopic measurements provided information about the radiation processes from xenon and argon plasma and testifies that given capillary is an effective source of EUV emission. Additionally we showed a simulation which describes plasma dynamics parameters and dynamics of various ionization stages in capillary discharge. Our computer simulation confirmed the presence of ions, which spectra was registered in the experiment.

Nanostructural characterizations of hydrogen-permselective Si–Co–O membranes by transmission electron microscopy

Nanostructural characterizations of liquid metal–organic precursors-derived cobalt-doped amorphous silica (Si–Co–O) membranes supported on a mesoporous anodic alumina capillary (MAAC) tube were performed to study their unique high-temperature hydrogen gas permeation properties. Cross-sectional scanning transmission electron microscopy images and selected-area electron diffraction patterns indicated that the metal cobalt and the different oxidation states of cobalt oxides (CoO and Co3O4) nanocrystallites having a size range of 5–20 nm were in situ formed in the mesopore channels of the MAAC tube. In addition, high-resolution transmission electron microscopy micrographs and electron energy loss spectroscopy elemental mapping images indicated that the highly dense Co-doped amorphous Si–O formed within the mesopore channels of the MAAC tube. These nanostructural features could contribute to the hydrogen-selective permeation properties observed for the membranes.

Estimation of thermal shock resistance of fine porous alumina by infrared radiation heating method

The thermal shock resistance of α-alumina porous capillary, the support material for hydrogen-permselective microporous ceramic membrane was studied. To study the effect of porosity on the thermal shock resistance systematically, porous alumina with different porosities was fabricated, and the thermal shock resistance of the fabricated samples as well as the porous capillary was estimated by the infrared radiation heating method. The mechanical and thermal properties concerned to the thermal shock resistance were also measured and the effect of the porosity on the properties was carefully examined. The fracture strength was not changed with temperature, but decreased with the porosity. The fracture toughness, Young's modulus and thermal conductivity were also decreased with porosity. Thermal shock resistance of porous alumina was estimated quantitively by the experimental thermal shock parameters, thermal shock strength, R1c and thermal shock fracture toughness, R2c. The thermal shock parameters of porous alumina were much lower than dense alumina, and decreased with porosity due to the decreasing of fracture strength and thermal conductivity. The experimental thermal shock strength was good accordance with that calculated from the material properties in this study. Thermal shock strength of porous alumina capillary at service temperature could be estimated by the comparison experimental and calculated thermal shock strength.

Development of a low current discharge-driven soft x-ray laser

We report the output characteristics of a saturated capillary discharge 46.9 nm Ne-like Ar soft x-ray laser obtained with relatively low main discharge current of less than 20 kA, with the lowest being 9 kA. The 20 cm long and 3 mm diameter alumina capillary channel was filled with argon in the region 0.1–0.4 mbar and was driven by a current pulse with a quarter-cycle duration of about 40 ns. The laser pulse duration generated was about 1.3 ns, with a gain coefficient of 1.2 cm−1.

Influence of Sulphur Impurities on the Interfacial Tension between Aluminium and Cryolite Alumina Melts

The interfacial tension (IFT) between aluminium and cryolite melts containing different salt additions (AlF3, NaF,Na2SO4) has been measured during electrolysis by the capillary depression method. The technique is based on the measurement of the capillary depression occurring when a capillary, which is moved vertically down through the molten salt layer, passes through the metal/salt interface. The depression is measured by simultaneous video recording of the immersion height of the alumina capillary. The interfacial tension is strongly dependent on the n(NaF)/n(AlF3) ratio. The addition of Na2SO4 decreases the IFT of the aluminium/electrolyte interface. We also found the different influence of the conditions of electrolysis on the IFT in systems with and without Na2SO4. In systems without Na2SO4 the IFT decreases with increasing current density, and in systems with Na2SO4 it increases.

Population inversion during pinch decay in nitrogen capillary discharge

We summarise the results of computer modelling of the capillary discharge in nitrogen for the device recently developed in the Department of Physics, Technion-Israel Institute of Technology, Haifa. We performed computer modelling of a fast electrical discharge in a nitrogen-filled alumina capillary. Discharge system parameters that may lead to efficient recombination pumping of soft X-ray laser with active medium created by H-like nitrogen ions were determined.

Interfacial tension between aluminum and cryolite melts during electrolysis of the systems Na3AlF6–AlF3 (NaF)–Al2O3

The interfacial tension between aluminum and cryolite melts containing different salt additions has been measured by the capillary depression method. The technique is based on the measurement of the capillary depression occurring when the capillary, which is moved vertically down through the molten salt layer, passes through the salt/metal interface. The depression is measured by simultaneous video recording of the immersion height of the alumina capillary. The interfacial tension was found to be strongly dependent on the n(NaF)/n(AlF3) ratio (cryolite ratio, CR). At the cryolite ratio 2.28 (80 wt.% Na3AlF6 + 10 wt.% AlF3 + 10 wt.% Al2O3 // Al, t = 1000 °C) the interfacial tension was 546 mN m−1, while it was 450 mN m−1 at the cryolite ratio 4.43 (80 wt.% Na3AlF6 + 10 wt.% NaF + 10 wt.% Al2O3 // Al, t = 1000 °C). Experiments under current flow conditions were also performed. During the electrolysis the interfacial tension at n(NaF)/n(AlF3) ratio 2.28 decreased from 546 mN m−1 at zero current to 518 mN m−1 at 0.112 A cm−2. The same trend was observed in the system with a cryolite ratio 4.43. The interfacial tension decreased from 450 mN m−1 at zero current to 400 mN m−1 at 0.112 A cm−2. The consequent increase in interfacial tension of these systems caused by interruption of electrolysis was observed. Electrolysis of the system 25 wt.% NaF + 75 wt.% NaCl (eutectic mixture)/Al indicated no influence of applied current on the interfacial tension at 850 °C.

TEM observation of hydrogen permeable Si-M-O (M = Ni or Sc) membranes synthesized on mesoporous anodic alumina capillary tubes

Microstructures of Si-M-O (M = Ni or Sc; M/Si = 0.5) membranes synthesized on a mesoporous anodic alumina capillary (MAAC) tube using chemical processing techniques were characterized by transmission electron microscopy. The chemical composition of the membranes was analyzed by energy-dispersive X-ray spectroscopy. An as-synthesized Si-Ni-O membrane was found to be formed as a thin amorphous layer with a thickness of 400 nm on the MAAC tube, and in the mesopore channels of the MAAC tube, amorphous Si-Ni-O was also formed. The EDS analysis indicated a compositional gradient of Ni/Si for the Si-Ni-O membrane. The ratio of Ni/Si increased the further in depth from the surface of the membrane. After heat treatment in a hydrogen flow, a multilayered structure was formed, and nickel and nickel oxides were precipitated in the membrane. In the Si-Sc-O membrane, neither precipitation nor compositional gradient of Sc/Si were observed. The compositional change and precipitating behaviors of the Si-Ni-O and Si-Sc-O membrane are discussed in terms of the stability of the silica-dopant metal network and the hydrogen permselectivity of the membranes.

Modelling of a nitrogen x-ray laser pumped by capillary discharge

Abstract We performed computer modelling of a fast electrical discharge in a nitrogen-filled alumina capillary in order to discover discharge system parameters that may lead to efficient recombination pumping of soft X-ray laser with active medium created by H-like nitrogen ions. The space-time dependences of pinch plasma quantities were found by means of a one-dimensional MHD code. Time dependences of populations of all ionisation states and populations of selected energy levels of lithium-, helium- and hydrogen-like nitrogen ions were evaluated using the FLY code as a post-processor. The population inversion was found at the quantum transition corresponding to the Balmer α-line of N6+ ions and the resulting gain factor was evaluated for different capillary radii, initial pressure, electric current peaks and periods. A gain factor of 1 cm−1 spanning the time interval of 1 ns was found for an optimised arrangement with capillary radius 1.5 mm, peak current 50 kA, quarter period 40 ns and filling gas pressure 0.5 kPa. It is pointed out that even higher values of the gain factor may be achieved with thinner capillaries and shorter current pulses, e.g. a gain factor of 6 cm−1 is achieved if the capillary radius is 0.5 mm, peak current 56 kA, quarter period 15 ns, and filling nitrogen pressure 3.9 kPa.

Plasma jet emission in fast-pulsed capillary discharges

The properties of a plasma jet generated in low-pressure pulsed capillary discharge have been measured. The discharge operates in a 5 cm long and 1.6-mm-inner diameter alumina capillary, with argon in a pressure range between 20 and 100 Torr, at 11-kV applied voltage. The temporal and spatial evolutions of the plasma density in the plasma jets are measured close to the capillary end with a Michelson interferometry based on a 10-ns-pulse Nd:yttrium aluminum garnet laser. The maximum on-axis plasma density is of the order of 1017cm−3 at the capillary output, with an ∼6‐ns rise time to reach a significative electron density. At lower pressure the plasma density is seen to decay in a time scale of 50 ns and over an axial distance of the order of 0.5 mm, whereas at the higher pressure, 100 Torr, it remains more or less stationary for up to ∼300ns. The discharge is characterized by a high efficiency in energy coupling, as the local-stored energy is much less than 1 J per pulse.

Effect of pre-pulses on capillary discharge soft x-ray laser

On a capillary discharge setup lasing in Ne-like Ar at 46.9nm, the ablation of c apillary wall was investigated for polythene and alumina material at both of inh erent 2—5kA-pre-pulse of setup and separate pre-pulse of 20A by measuring soft x ray emission from the capillary discharged. For inherent pre-pulse and polythe ne capillary, the ablation is too large to create uniform plasma columns and it is impossible to obtain lasing. In the case of 20A-pre-pulse and alumina capilla ry, the ablation decreased remarkably and the laser spike pulse was distinguishe d on an x-ray diode because the uniform Z-Pinch plasma column had formed.