Use of refrigerator-cooled cryopumps in sputtering plants

A theory of gas tungsten arc welding (GTAW) arcs that treats the tungsten electrode, the arc, and the workpiece as a unified system has been applied to make predictions in two dimensions of the temperature distributions in the arc, the tungsten cathode, and the workpiece, for any given arc current and gas mixture. Predictions of arc temperatures, radii, and voltages are compared for argon and mixtures of argon and hydrogen. It is found that arcs in gas mixtures containing hydrogen are more constricted and have a higher maximum temperature and arc voltage than arcs in pure argon. The addition of hydrogen also significantly increases the volume of molten material in the weld pool due to the higher thermal conductivity of argon-hydrogen mixtures at temperatures at which molecules of hydrogen dissociate. Predictions are also compared for workpieces of steel and aluminum. The volume of molten material is very much less for aluminum, despite its lower melting point, because of the higher thermal conductivity of aluminum. Predicted arc voltages as a function of current for a mixture of 10% hydrogen in argon are in good agreement with experimental results.

Measurements are described of the velocity of ultrasonics in mixtures of argon, helium and hydrogen at a frequency of 524 kc./sec. as a function of pressure and at fixed temperatures near 90° and 20° absolute. From these data, information about the interaction between the gases in the mixtures is deduced, using the equation of state of Kamerlingh Onnes.

Producing hot, high rate, high pressure wells can subject tubing threads to compression and tensile forces that exceed the scope of current published data and specifications. Mobil Oil Indonesia, contractor to Pertamina, Indonesia's National Oil Company initiated the development of test apparatus and test procedures to simulate actual downhole stresses on tubulars. Mobil's intention was to fill the gap in the published data and to determine the cause of thread leaks in Aran wells. It was postulated that the leaks were the result of extreme compression and tensile forces acting on the tubing threads. Weils completed in the Arun Limestone are capable of producing 250 MMSCFD at well-head pressures and temperatures of 4000 psi and 347° F. Forces on the tubing string varying from 350,000 lbs compression to nearly 500.000 lbs tension during pressure and temperature reversals between conditions of shut-in, producing and stimulating. The test apparatus and procedure can detect thread leaks while subjecting test specimens to: 7500 psi internal pressureCompression and tensile loads up to 500,000 lbs.Temperatures up to 350° F.Quenching of internal pin surface such that the temperature is reduced from 350° F to 150° in Application of the equipment and test procedures confirmed the failure mechanism and helped evaluate other thread designs for use in the harsh Aran wellhore environment.

Porous copper with elongated cylindrical pores were fabricated by a unidirectional solidification method in a mixture of hydrogen and argon with high pressures. The porous copper with longitudinal pores and radial pores were compared on structure. The effect of both hydrogen pressure and argon pressure on structure of the porous copper including pore size, pore density, and porosity was investigated. The reason for the effect is explained.

Focus on cryogenics and vacuum

Summary form only given, as follows. A high-density large volume plasma of air constituent (N/sub 2/, O/sub 2/, Air and Argon mixtures) is created using a high power (1-25 kW) pulsed radio frequency source at high gas pressures. Such high-Pressure air plasmas are finding increasing application in plasma processing industry, as plasma reactors, as light source and as biological decontaminants. One of the major issues particular to such plasma is the high power required to initiate and sustain the discharge. The power requirement to create and sustain the discharge can be reduced by mixing noble gas with air constituents. Initial experiments reveal that noble gas mix of nitrogen, argon and oxygen improves the antenna loading and is beneficial for the break down of air constituents. It also leads to a lower recombination rate. A tangentially injected high-speed swirl gas flow improves the plasma confinement. It also keeps the plasma off the inside walls of the Pyrex chamber and reduces the excessive heating of the plasma chamber. Radio frequency power is coupled through a five turn helical antenna using a capacitive matching network.. A large volume plasma in argon at 20 Torr at moderate radio frequency power 1.5 kW has been produced. Recent results with high power pulsed unit in high-pressure range (100-200 Torr of argon, nitrogen, oxygen and their mixture) will be presented.

To reduce combustion noise significantly and improve torque curve a new control strategy is presented. The new control strategy is based on solenoid-valve-controlled high pressure common rail (CR) injection system, which is one in which the high injection pressure is available at all times and not only during the injection periods. The system layout, which includes high pressure pump, rail and pipes, injector, ECU, and sensors, is drawn and every part is described in detail. Three control functions are carried out: rail pressure set point, rail pressure control and rail pressure monitoring. In addition, a block diagram of the high pressure control function is shown. Finally, a few applications are made: low pressure system with filtering, design of a CR system by simulation, and rail pressure. Besides, start- times controlled by CR system and by conventional high distributor pump (VP44 and VP37) are compared. Finally, schematic of the test bench configuration and engine specification are showed. Cylinder pressures and the corresponding heat release rates with variation of injection timing are compared with experimental data. It gives the theory and method about control strategy exactly in directed-injection diesel engine.

Numerical simulations are carried out for detonation initiation behind reflected shock waves in a shock tube. The two-dimensional thin-layer Navier-Stokes equations with chemical effects are numerically solved by use of a combined method consisting of the Flux-Corrected Transport scheme, the Crank-Nicolson scheme, and a chemical calculation step. Effects of chemical reactions occurring in a shock-heated hydrogen, oxygen, and argon mixture are estimated by using a simplified reaction model: two progress parameters are introduced to take account of induction reactions as well as exothermic reactions. Simulations are carried out referring to several experiments: generation of multidimensional and unstable reaction shock waves; strong and mild ignitions; and reacting shock waves in hydrogen and oxygen diluted in argon mixture. Introduction A reflected shock technique has been often utilized to investigate initiation of detonation, a series of processes such that a reaction front, generated behind a reflected shock wave, develops to a reaction shock wave which overtakes the reflected shock wave. Remarks from some experimental investigations, relating to the present numerical investigations, can be found in the following. Gilbert and Strehlow explained the detonation initiation process as a one-dimensional phenomenon, comparing their one-dimensional analyses with experimentally-determined distance-time diagrams of the detonation initiation behind reflected shock waves in a hydrogen, oxygen, and Copyright ©1993 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. * Professor, Department of Mechanical Engineering 283

Dissociation mechanism of chlorosilane to silicon in low pressure microwave plasmas of argon and argon with hydrogen mixtures

A new type of cryopump with a metal cryopanel cooled below 3.6 K by a two-stage GM refrigerator

This work provides examples of some of the imaging capabilities of environmental scanning electron microscopy applied to easily charged samples relevant to particle analysis. Environmental SEM (also referred to as high pressure or low vacuum SEM) can address uncoated samples that are known to be difficult to image. Most of these specimens are difficult to image by conventional SEM even when coated with a conductive layer. Another area where environmental SEM is particularly applicable is for specimens not compatible with high vacuum, such as volatile specimens. Samples from which images were obtained that otherwise may not have been possible by conventional methods included fly ash particles on an oiled plastic membrane impactor substrate, a one micrometer diameter fiber mounted on the end of a wire, uranium oxide particles embedded in oil-bearing cellulose nitrate, teflon and polycarbonate filter materials with collected air particulate matter, polystyrene latex spheres on cellulosic filter paper, polystyrene latex spheres "loosely" sitting on a glass slide, and subsurface tracks in an etched nuclear track-etch detector. Surface charging problems experienced in high vacuum SEMs are virtually eliminated in the low vacuum SEM, extending imaging capabilities to samples previously difficult to use or incompatible with conventional methods.

Hydrogenated silicon (Si‐H) thin films were deposited from a mixture of pure silane (SiH4) and hydrogen (H2) gases in a home‐built plasma enhanced chemical vapour deposition (PECVD) system using the layer‐by‐layer (LBL) deposition technique. In the LBL process, the deposition was performed by periodically alternating the deposition of Si:H layer with the hydrogen treatment process of the growth surface. In this work, the effects of the H pasma treatment time to Si‐H layer growth time ratio on the film properties were studied. The LBL deposited Si‐H films studied in this work were deposited using different Si‐H layer growth times ranging from 2 minutes to 7 minutes with the hydrogen plasma treatment time on the growth surface fixed at 3 minutes. Optical transmission spectroscopy, X‐ray diffraction (XRD), micro‐Raman scattering spectroscopy, Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) measurements were done on these films to investigate the optical, structural and morphological properties of the films. The films deposited by this technique produced the highest deposition rate of 6.3 A/s when the growth time of the Si‐H layer was fixed at 5 minutes. These films were amorphous in structure and had large optical energy gaps irrespective of the Si‐H layer deposition time. High concentration of cone‐like structures was observed in the AFM images for the films deposited using the higher Si‐H layer deposition times.Hydrogenated silicon (Si‐H) thin films were deposited from a mixture of pure silane (SiH4) and hydrogen (H2) gases in a home‐built plasma enhanced chemical vapour deposition (PECVD) system using the layer‐by‐layer (LBL) deposition technique. In the LBL process, the deposition was performed by periodically alternating the deposition of Si:H layer with the hydrogen treatment process of the growth surface. In this work, the effects of the H pasma treatment time to Si‐H layer growth time ratio on the film properties were studied. The LBL deposited Si‐H films studied in this work were deposited using different Si‐H layer growth times ranging from 2 minutes to 7 minutes with the hydrogen plasma treatment time on the growth surface fixed at 3 minutes. Optical transmission spectroscopy, X‐ray diffraction (XRD), micro‐Raman scattering spectroscopy, Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) measurements were done on these films to investigate the optical, structural and morpho...

A novel type of an axial, piston-driven high pressure hydraulic pump with variable capacity marks a significant improvement in the area of the hydraulic machinery design. Total discharge from hydrostatic forces eliminates a need for a servomechanism, thus simplifying operation, reducing weight and introducing the possibility of the pump displacement control by computer. PWK-type pumps, invented in the Gdansk University of Technology, offer high efficiency for pressure levels up to 55 MPa, ability to work self sucking even at high speed. However, the heart of the new invention, the commutation unit, creates harmful pressure peaks. Those peaks can be mitigated by the introduction of a compensation chamber with elastic walls. Owing to the dynamic character of events taking place in the pump, a need for computer simulation arouse in order to understand phenomena leading to the occurrence of pressure peaks and choose compensation chamber parameters accordingly. A CFD package alone would not be sufficient to reliably represent the interaction between the compensation chamber wall and the working fluid. This paper presents Fluid Structure Interaction approach comparing 3 different models: 2 simplified models of the pump and a full pump model.

A high-speed drilling system has been developed which drills medium strength rocks at rates up to 1000 ft/hr (328 m/hr). This system uses special motors to operate high-pressure PDC bits at pressures up to 10,000 psi (69 MPa) and at speeds of 800 to 1000 RPM. High drilling rates were achieved due to the high rotary speeds and the use of PDC cutters to remove the rock ledges left on the hole bottom by the high-pressure jets.

Amorphous carbon films were obtained by remote microwave plasma enhanced chemical vapour deposition (RMPECVD). In this process, a mixture of argon and hydrogen is excited in the microwave discharge while methane is injected in the afterglow. The substrates are radio-frequency (RF) biased in order to improve the film properties. Three configurations have been compared: microwave, RF, and mixed microwave-RF coupling. Optical emission spectroscopy allowed to compare intensities of a few spectral lines in the afterglow (CH, C 2 , H, and Ar lines) as a function of process conditions. Films have been characterised by infra-red (IR) spectroscopy and electron recoil detection analysis (ERDA). Stress in the films is in the range of -0.7 to -0.3 GPa (compressive). The influence of the hydrogen presence in the plasma, microwave power and radio-frequency bias voltage is discussed.