Metal Chamber Research Articles

A Theoretical Feasibility Study of a Source Stirring Reverberation Chamber

A novel theoretical feasibility study to reverberate a large metallic chamber is proposed. The method is based on the displacement of a radiating antenna inside the chamber, and the reverberating effect is obtained by coupling the antenna current in different ways with the cavity modes. This technique eliminates mechanical rotating paddles inside the chamber and offers the advantage of a continuous-wave operation compared with the frequency stirring method. The reverberating characteristics of the proposed technique are evaluated by calculating the field statistics. The analyzed situation concerns a real antenna, and its radiation into the reverberation chamber is modeled using Green's function of cavity. The numerical problem is solved by the method of moment. The model has been tested and is able to rigorously characterize the reverberating environment for the design and optimization of antenna configurations to be addressed in future studies.

Two-dimensional fluid model of a two-chamber plasma source

This study presents a two-dimensional fluid-plasma model developed for describing the cw regime operation of a tandem plasma source, consisting of a driver and an expansion plasma volume of different sizes. The moderate pressure range considered (tens to hundreds of milliTorr) allows a description within the drift–diffusion approximation, as employed in the model. Argon discharges maintained in a metal gas-discharge vessel are treated. The discussions stress charged-particle and electron-energy fluxes as well as the spatial distribution of their components. The main conclusions are for (i) different electron and ion fluxes resulting in a net current in the discharge; (ii) a radial ion flux prevailing over the axial one and an axial electron flux prevailing over the radial one; (iii) ion motion determined by the dc electric field and drift–diffusion electron motion influenced by thermal diffusion; (iv) plasma maintenance in the expansion plasma chamber due to charged-particle and electron-energy fluxes from the driver; (v) importance of the convective flux in the electron-energy balance; (vi) electron-energy losses for sustaining the dc electric field in the expansion plasma volume strongly predominating over the losses through collisions and (vii) electron cooling accompanied by a strong drop in the plasma density and in the potential of the dc electric field, due to the plasma expansion in a bigger volume. In general, the results show that the gas pressure range usually considered to be governed by ambipolar diffusion shows up in a different regime: a regime with a dc current, when the discharge is in a metal chamber with different dimensions in the transverse and longitudinal directions.

Blood processing

Blood processing

Surface cyclotron O-modes in planar waveguides of finite width with dielectric sheaths and transverse non-uniformity of plasma concentration

This paper studies the dispersion properties of slow electromagnetic surface O-modes propagating at the electron cyclotron frequency across an external magnetic field in planar metal chambers with dielectric coating and non-uniform plasma filling. Theoretical research into these modes is carried out using the kinetic description for the plasma particles. We investigate the effects of transverse plasma concentration inhomogeneity and finite transverse size of the plasma-filled waveguide on the frequency of electron surface cyclotron O-modes both analytically and numerically. Possible technological applications of these modes are discussed.

Coating techniques of metal chambers for remote catalytic chemical vapor deposition applications

To obtain information for remote catalytic chemical vapor deposition, the authors constructed a two-chamber system in which the decomposition and deposition areas were separated. H2 molecules were decomposed on a heated tungsten filament in the first area and the H atoms produced were carried to the second area, where the absolute H-atom densities were measured by a vacuum-ultraviolet laser absorption technique. The gas pressure in the decomposition area was maintained ten times higher than that in the deposition area by mounting a diffusion barrier to prevent the possible back-diffusion of the material gases. The inner walls of the decomposition area as well as the diffusion barrier were coated with SiO2 or polytetrafluoroethene to minimize the recombination of H atoms. The H-atom density could be increased by one order of magnitude by such coatings, and it is shown that H-atom densities in the order of 1012 cm−3 can be achieved in the deposition area in the present system.

Rf plasma system as an atomic oxygen exposure facility

The materials of spacecraft external surfaces in low Earth orbit (LEO) are exposed to the various constituents of the space environment, including atomic oxygen (AO) and solar ultra violet (UV) radiation. Material degradation and erosion by LEO are simulated in ground laboratories using a variety of experimental facilities, each with their respective limitations. rf oxygen plasma is a simulation facility widely used for materials screening for LEO application. However, the complex plasma environment, which contains, in addition to the neutral oxygen atoms, excited species, electrons, and ions as well as vacuum ultraviolet (VUV) radiation, might lead to erroneous determination of materials reactivity with respect to LEO. This paper describes the development of a simple, low cost rf plasma system to produce a well-defined AO and VUV environment. The new system constrained the afterglow flow through two right-angle turns. The afterglow was characterized at three specific locations by (i) optical emission spectroscopy for assessment of electronically excited states, (ii) current measurements, and (iii) UV radiation measurements. KaptonR samples were exposed at the three specific locations in the system and characterized by mass loss for etch rate evaluation, and atomic force microscopy for surface modification. It was found that there is a significant reduction in ionic species, excited species, and UV radiation as the afterglow advances through the right-angle turns. The reduction in charged particle flux is due to recombination within the afterglow as well as neutralization by colliding with the grounded metal chamber walls; similar decrease in UV radiation flux occurs through radiation absorption by the chamber walls. Finally, it is shown that the ground state AO is the dominant reactive specie of the plasma afterglow after passing through the two right-angle turns.

Modeling of Induction Heating in Oxide Czochralski Systems—Advantages and Problems

Two mathematical models of induction heating for oxide Czochralski crystal growth systems are reviewed, and additional results of electromagnetic field and volumetric heat generation have been computed for both models using a finite element method (ENTWIFE package). In the first model, the eddy current in the RF coil (i.e., the self-inductance effect) has been neglected while for the second model, it is taken into account. For the calculations, the electrical current input and total voltage of induction coil are set to be 1000 A and 200 ν, respectively, with a frequency of 10 kHz; the heat generation in all metallic parts, that is, crucible, afterheater, RF coil, and chamber, has been calculated for a real Czochralski setup. It has been found that by including the self-inductance effect in the RF coil the results change dramatically. Also, it was shown that the spatial distribution of the heat generation in the crucible is more realistic in the second model than in the first model. Concerning the distribu...

Savings on natural gas consumption by doubling thermal efficiencies of balanced-flue space heaters

Natural gas is a relatively clean fossil fuel for space heating. However, when it is not used efficiently high consumption can become an environmental problem. In Argentina, individual balanced-flue space heaters are the most extensively used in temperate and cold regions. This furnace is a simple device with a burner set into a metal chamber, separated from the indoor ambient by an enclosing cabinet, and both inlet and outgas chimneys are connected to the outdoor ambient. In previous studies, we measured the performance of these commercial devices, and found very low thermal efficiency (in the range of 39–63% depending on the chimney configuration). The extensive use of these devices is possible due to the availability of unlimited amount of subsidised natural gas to households and businesses. In the present work, we developed a prototype with simple and low cost modifications made on commercial models, and measured the improvements on the thermal efficiency. Findings showed better infrared radiation, enhanced indoor air convection, and passive chimney flow regulation leading to thermal efficiency in the range of 75–85%. These values represent an improvement of 100% when compared to marketed models, and hence, the specific cost of the heater per unit of useful heating power delivered was actually reduced. Considering the large market presence of these furnaces in both residential and business sectors in Argentina, the potential benefits related to gas consumption and environmental emissions are very significant.

Use of hybrid vibrations for measuring the amount of liquid in tanks with mobile displacers

The possibility is considered of using the resonance properties of metal chambers for measuring their volume and the amount of liquid contained in them. Basic calculation relationships are obtained for a system of coupled chamber resonators. An algorithm and functional scheme are proposed for processing resonance frequencies with measurement of the amount of liquid in long tanks. Results are presented for experimental studies.

Aerosol Therapy by Pressured Metered-Dose Inhaler-Spacer in Sleeping Young Children: To Do or Not to Do?

Esposito-Festen J, Ijsselstijn H, Hop W, van Vliet F, de Jongste J, Tiddens H. Chest. 2006;130:487–492 PURPOSE OF THE STUDY. To determine the feasibility of aerosol administration with a metered-dose inhaler (MDI) spacer in sleeping young children. STUDY POPULATION. Thirty children (18 boys) from the Netherlands between 6 and 23 months of age were treated with inhalation therapy twice per day for recurrent wheezing in the previous month. METHODS. Parents were trained to use a metal chamber (NebuChamber) with a face mask to administer 200 μg of budesonide aerosol. A filter was placed between the spacer and face mask to trap and then measure the aerosol inhaled from the spacer. The study included 1 run-in week and 2 test weeks. The families were visited at home 4 times in the 3 weeks. At the 1-week run-in, the parents practiced the procedure with a placebo MDI while the child was awake. In weeks 2 and 3, they administered 1 puff while the child was awake (awake administration), 1 puff before bedtime, and 1 puff while the child was asleep (sleep administration). Parents then were asked to score the child's asthma symptoms and degree of cooperation and the feasibility of administration. Filters were washed, and budesonide amounts were measured by high-performance liquid chromatography and spectrophotometry. RESULTS. Twenty-one children fully completed the study, and a total of 350 awake-administration filters and 331 sleep-administration filters were collected. The mean filter dose was significantly higher for awake administration (47% ± 26%) than that for sleep administration (16% ± 13%). The median variability dose for awake administration was 50%, whereas it was 110% for sleep administration. Poor cooperation was noted for 29% of the awake administrations. In 69% of the sleep administrations, the child woke up, and in 75% of these cases, the child was distressed. Twenty-two percent of parents reported mask-positioning problems while the child was sleeping. Mean symptoms scores were 1.4 ± 2.2 (0 = no symptoms, 4 = severe symptoms; maximum score = 12 for sum of cough, wheeze, and shortness of breath). CONCLUSIONS. Administering aerosol therapy during sleep has been suggested as a way to overcome cooperation problems in young children, but this study suggests that this is not the answer. REVIEWER COMMENTS. The study included 30 children, and only 21 completed the study; a larger study would need to be performed with design modifications. One significant concern about the study design is that the children did not receive active drug during the study because the design required capturing the drug in a filter to determine drug delivery (which may explain the high drop-out rate). Furthermore, the design of the study did not allow for a means to determine clinical efficacy or lung deposition of the drug. In the interim, pediatricians may want to reconsider recommending dosing of aerosolized medications during sleep.

Thermal efficiency of natural gas balanced-flue space heaters: Measurements for commercial devices

The performance of the most common gas space heater used in residences in Argentina was experimentally investigated. The furnace is a simple device with a burner (ranging from 2 to 7 kW according to the model) set into a metal chamber, and this separated from the ambient by an enclosing cabinet. This type of individual gas heater is installed indoors with both inlet and outgases chimneys connected to the outside. For the same furnace, two chimney configurations are regularly provided: a vertical one that intakes and exhausts through the roof, and a horizontal one with short concentric tubes connected to outdoors through the wall. To assess the thermal efficiency of the equipment, we have measured several running parameters, like temperatures, airflows, and gas consumption. Thermal efficiencies for indoor heating in the range of 40–60% were found, for vertical and horizontal chimneys, respectively. The main design characteristics leading to the poor performance were identified: low emissivity of the combustion chamber surface (leading to poor radiation transfer), tight enclosing cabinet (affecting radiation and convection transfer), and no chimney flow control (leading to large outgas losses). The findings are in agreement with previous works on the excessive amount of natural gas consumed in residences in the area studied.

Diffusion and Not Active Transport Underlies and Limits ERK1/2 Synapse-to-Nucleus Signaling in Hippocampal Neurons

The propagation of signals from synapses and dendrites to the nucleus is crucial for long lasting adaptive changes in the nervous system. The ERK-MAPK pathway can link neuronal activity and cell surface receptor activation to the regulation of gene transcription, and it is often considered the principal mediator of synapse-to-nucleus communication in late-phase plasticity and learning. However, the mechanisms underlying ERK1/2 trafficking in dendrites and nuclear translocation in neurons remain to be determined leaving it unclear whether ERK1/2 activated at the synapse can contribute to nuclear signaling and transcriptional regulation. Using the photobleachable and photoactivable fluorescent tag Dronpa on ERK1 and ERK2, we show here that ERK1/2 translocation to the nucleus of hippocampal neurons is induced by the stimulation of N-methyl-D-aspartate receptors or TrkB stimulation and is apparently mediated by facilitated diffusion. In contrast, ERK1/2 trafficking within dendrites is not signal-regulated and is mediated by passive diffusion. Within dendrites, the reach of a locally activated pool of ERK1/2 is very limited and follows an exponential decay with distance. These results indicate that successful signal propagation to the nucleus by the ERK-MAPK pathway depends on the distance of the nucleus from the site of ERK1/2 activation. ERK1/2 activated within or near the soma may rapidly reach the nucleus to induce gene expression, whereas ERK1/2 activated at distal synapses may only contribute to local signaling.

Fluidized Bed Device for Plastic Granules Triboelectrification

The study of the triboelectrification process is the key factor to the successful industrial application of electrostatic separation in the field of plastics recycling. Therefore, the aim of the present work is to evaluate an original device for the laboratory study of this process. The original design of the fluidized bed type triboelectrification device has the following distinctive features: (i) transparent walls to observe the fluidization process and the particles moving in the triboelectrification module; (ii) air distributors with different mesh apertures correlated with granule size; (iii) quick replacement of the triboelectrification Plexiglas chamber with other metallic (aluminium, copper) or nonmetallic chambers (polyvinyl chloride—PVC, polyethylene—PE, and polyethylene terephthalate—PET); (iv) possibility of independent operation, for granule charge measurement or integrated operation, for the electrostatic separation experiments using a free-fall electrostatic separator. The results of charge measurement experiments pointed out the different triboelectric behaviour of two types of granules (polystyrene and low-density polyethylene) in contact with the walls of the device. The electrostatic separation experiments carried out on a binary mixture of mm-size polystyrene/polyethylene granules confirmed the effectiveness of the triboelectrification device.

Review of relaxation oscillations in plasma processing discharges

Relaxation oscillations due to plasma instabilities at frequencies ranging from a few Hz to tens of kHz have been observed in various types of plasma processing discharges. Relaxation oscillations have been observed in electropositive capacitive discharges between a powered anode and a metallic chamber whose periphery is grounded through a slot with dielectric spacers. The oscillations of time-varying optical emission from the main discharge chamber show, for example, a high-frequency (~ 40?kHz) relaxation oscillation at 13.33Pa, with an absorbed power being nearly the peripheral breakdown power, and a low-frequency (~ 3 Hz) oscillation, with an even higher absorbed power. The high-frequency oscillation is found to ignite plasma in the slot, but usually not in the peripheral chamber. The kilohertz oscillations are modelled using an electromagnetic model of the slot impedance, coupled to a circuit analysis of the system including the matching network. The model results are in general agreement with the experimental observations, and indicate a variety of behaviours dependent on the matching conditions. In low-pressure inductive discharges, oscillations appear in the transition between low-density capacitively driven and high-density inductively driven discharges when attaching gases such as SF6 and Ar/SF6 mixtures are used. Oscillations of charged particles, plasma potential, and light, at frequencies ranging from a few Hz to tens of kHz, are seen for gas pressures between 0.133 Pa and 13.33 Pa and discharge powers in a range of 75?1200 W. The region of instability increases as the plasma becomes more electronegative, and the frequency of plasma oscillation increases as the power, pressure, and gas flow rate increase. A volume-averaged (global) model of the kilohertz instability has been developed; the results obtained from the model agree well with the experimental observations.

A theory for formation of a low pressure, current-free double layer

A theory is developed for the formation of a low pressure, current-free double layer just inside an upstream dielectric source chamber connected to a larger diameter, downstream metallic expansion chamber. The double layer is described using four groups of charged particle: thermal ions, mono-energetic accelerated ions flowing downstream, accelerated electrons flowing upstream and thermal electrons. The accelerated electrons are formed downstream from an initially nearly half-Maxwellian electron distribution. A fifth group of counter-streaming electrons formed by the reflection of the accelerated electrons from the sheath at the insulated end wall of the source chamber is used to enforce the condition that the double layer be current-free. The condition of particle balance upstream is found to determine the double layer potential. The double layer is found to disappear at very low pressures due to loss of ionization balance upstream and due to energy relaxation processes for ionizing electrons at higher pressures. The theory is found to be in good agreement with the experiments.

Use of Hyperbaric Oxygenation in Small Bowel Preservation for Transplant

Introduction The aim of this work was to study the effects of hyperbaric oxygenation as a preservation technique for small bowel transplantation. Methods Twenty 2-month-old male Wistar rats weighting 250 g were divided into two groups: group A ( n = 10) in which the small bowel was preserved for 12 hours, and group B ( n = 10) in which the small bowel was preserved for 24 hours. After vascular and intraluminal perfusion, 3-cm segments were maintained in Ringer’s solution at temperatures between 2°C to 4°C and in normobaric O 2 conditions (groups A 1, B 1) or conditioned in an hyperbaric O 2 metal chamber (100% oxygen at 5.5 absolute atmospheres) (groups A 2, B 2). After this preservation time, we studied intestinal tissue injury and morphometric analysis of the villi. Results Mucosal injury was significantly greater among group A 1 compared to group A 2 animals. The grade of the lesions was greater among group B 1 compared to group B 2 animals. Group A 1 showed no difference from Group B 1. For lesion grade, the range was smaller in group A 2 and group B 2 animals. The villi height was significantly smaller in groups A 1 and B 1 compared to the other groups; whereas it was higher in group A 2 as compared with B 2. Conclusion Hyperbaric oxygenation may play a role as a preservation technique. Further research is necessary.

Apoptosis and Nuclear Proliferation in Rat Small Bowel Submitted to Hypothermic Hyperbaric Oxygenation for Preservation

This study was conducted to assess apoptosis and nuclear proliferation in rat small bowel submitted to hypothermic hyperbaric oxygenation for preservation. Methods Twenty two-month-old, male Wistar rats, weighing 250 g were divided into two groups: group I ( n = 10), in which the small bowel was preserved for 12 hours, and group II ( n = 10) in which the small bowel was preserved for 24 hours. After vascular and intraluminal perfusion, 3-cm segments were maintained in Ringer’s solution at 2° to 4°C under normobaric conditions (groups Ia and IIa) or conditioned in a small hyperbaric metal chamber with 100% oxygen at 5.5 absolute atmospheres (groups Ib and IIb). After 12 or 24 hours, apoptotic and mitotic indices were evaluated by immunohistochemical methods. Results The apoptotic index was significantly higher in small bowel segments in groups Ia and IIa compared with groups Ib and IIb. The mitotic index was significantly higher among group IIb. Conclusion Hypothermic hyperbaric oxygenation reduced intestinal epithelial apoptosis and increased nuclear proliferation during rat small bowel preservation.

Design and Construction of the LEIR Extraction Septum

The Low Energy Ion Ring (LEIR) is part of the LHC injector chain for ions. The LEIR extraction will use a pulsed magnetic septum, clamped around a metallic vacuum chamber which plays an important role in separating the high vacuum in the LEIR ring (dynamic pressure ~10-12 mbar) from that in the transfer line to the PS, where the vacuum requirements are less stringent. The major technical challenges and novel solutions related to the design of this magnet will be presented

Probe Diagnostics of Expanding Plasmas at Low Gas Pressure

AbstractSummary: Results from tandem‐type probe diagnostics of a plasma source based on an inductive discharge are presented in this study. The driver region is in the classical form of a cylindrically shaped inductive discharge, with a coil positioned over a gas discharge tube, whereas a bigger metal chamber provides volume for plasma expansion. Low pressure argon discharges were studied. The axial profiles of the plasma parameters were measured in the discharge in the metal chamber. The results obtained show that decreasing electron temperature and plasma density with increasing distance from the driver characterizes the behavior of the expanding plasmas. Moreover, two regions with different rates of variation of the plasma parameters complete the plasma expansion volume: a faster drop close to the driver and slow axial changes away from it. The gas pressure and power applied for the discharge maintenance were the external parameters varied.Axial profiles of the electron concentration in the plasma expansion region of an inductive discharge.imageAxial profiles of the electron concentration in the plasma expansion region of an inductive discharge.

Electron Energy Distribution Function Measurements in an Inductively Driven Tandem Plasma Source

AbstractSummary: Electron energy distribution functions (EEDF) are obtained from probe measurement data along the axis of the metallic chamber of an inductively driven tandem plasma source. The numerical procedure for calculating the second derivative of the probe current combines Savitzky‐Golay smoothing filter and the three‐point differentiator with a varying step. The EEDF is obtained through the Druyvesteyn formula from the calculated second derivative. The shape of the EEDFs in argon gas at low pressures is investigated for the case of a tandem plasma source. Experimental EEDFs are compared with Maxwellian distributions, and deviations in the tail are observed at higher pressures, which are explained in terms of the ratio between the electron‐electron collision frequency and the excitation frequency. Axial variations of the slope and of the area below the EEDF curve result in electron temperature and concentration decrease along the axis.Electron energy distribution function (EEDF) measured for gas pressure of 26 mTorr, at an axial position of 12 cm.imageElectron energy distribution function (EEDF) measured for gas pressure of 26 mTorr, at an axial position of 12 cm.