Showing papers by "Varian Associates published in 1975"

Solar energy converter with waste heat engine

Abstract: A solar energy converter uses gallium arsenide photovoltaic cells to convert light to direct current. Optical concentrators reduce the needed area of cells. Gallium arsenide retains high conversion efficiency up to several hundred degrees, so the waste heat may be used to produce mechanical power in a Rankine cycle engine.

Through-substrate source contact for microwave fet

Abstract: A microwave field effect transistor (FET) comprises source, gate, and drain electrodes deposited on an epitaxial layer grown on a semi-insulating substrate. The FET has lowered thermal resistance, lowered source lead inductance, and lowered gate series resistance, together with concomitant performance improvements, through the use of a novel source electrode connection which comprises a deposited or plated through metallic contact extending from the bottom of the wafer, through a hole in the substrate and epitaxial layer, to the underside of the source or other electrode which is deposited on the top side of the epitaxial layer. The chip, comprising the substrate, epitaxial layer, and top electrodes, is mounted on a heat sink. The chip's underside, including the bottom surface of the plated through source contact, is conductively bonded to the top surface of the heat sink.

Apparatus and method for reconstructing data

Abstract: In an apparatus and method for reconstructing data, a beam of radiation in the shape of a fan is passed through an object lying in the same quasi plane as the radiation source and non-absorption and non-scatter thereof is recorded on oppositely situated detectors aligned with said source of radiation. There is relative rotation between the source-detector configuration and the object within the quasi-plane. Periodic values of the detected radiation are taken, convolved with certain functions, and back-projected to produce a two-dimensional output picture on a visual display illustrating a facsimile of the object slice. A series of two-dimensional pictures obtained simultaneously or serially can be combined to produce a three-dimensional portrayal of the entire object. The invention is the first device which uses a fan beam source of radiation coupled with the application of a convolution method of data reduction with no intervening reordering of fan beam rays, thereby eliminating errors and delays in computation time which would be involved in such reordering. The invention is the first method for providing an exact reconstruction of a two-dimensional picture of an object slice from a series of one-dimensional projections of radiation not absorbed by the slice when the superior fan beam source is employed.

The quantitative measurement of rotational motion of the subfragment-1 region of myosin by saturation transfer epr spectroscopy.

Abstract: According to current models of muscle contraction (Huxley, H. E., Science 164: 1356-1366 [1969]), motion of flexible myosin crossbridges is essential to the contractile cycle. Using a spin-label analog of iodoacetamide bound to the subfragment No. 1 (S1) region of myosin, we have obtained rotational correlation times (tau 2) for this region of the molecule with the ultimate goal of making quantitative measurements of the motion of the crossbridges under conditions comparable to those in living, contracting muscle. We used the newly developed technique of saturation transfer electron paramagnetic resonance spectroscopy (Hyde, J.S., and Thomas, D.D., Ann. N.Y. Acad Sci. 22:680-692 [1973]), which is uniquely sensitive to rotational motion in the range of 10(-7)-10(-3) sec. Our results indicate that the spin label is rigidly bound to S1 (tau 2 for isolated S1 is 2 X 10(-7) sec) and that the motion of the label reflects the motion of the S1 region of myosin. the value of tau 2 for the S1 segment of myosin is less than twice that for isolated S1, while the molecular weights differ by a factor of 4, indicating flexibility of myosin in agreement with the conclusions of Mendelson et al. (Biochemistry 12:2250-2255 [1973]). Adding F-actin increses tau 2 in either myosin or isolated S1 by a factor of mearly 103, indicating rigid immobilization of S1 by actin. Formation of myosin filaments (at an ionic strength of 0.15 or less) increses tau 2 by a factor of 10-30, depending on the ionic strength, indicating a decrease of the rotational mobility of S1 in these agregates. The remaining motion is at least a factor of 10 faster than would be expected for the filament itself, suggesting motion of the S1 region independent of the filament backbone but slower than in a single molecule. F-actin has a strong immobilizing effect on labeled S1 in myosin filaments (in 0.137 M KC1), but the immobilization is less complete than that observed when F-actin is added to labeled myosin monomers (in 0.5 M KC1). A spin-label analog of maleimide, attached to the SH-2 thiol groups of S1, is immobilized to a much lesser extent by F-actin than is the label on SH-1 groups. The maleimide label also was attached directly to F-actin and was sufficiently immobilized to suggest rigid binding to actin.

Signal processor for ultrasonic imaging

Abstract: A signal processor for an ultrasonic imaging system permits the selection of scan angles and focusing distances. The system includes an ultrasonic receiver comprising an array of electromechanical transducers, with the individual transducers being coupled to phase selection circuitry whereby non-continuous delay values can be introduced between adjacent transducers. Proper selection of the delay values between adjacent transducers can accomplish preferential ultrasonic reception or transmission in particular directions. An optimized switching arrangement minimizes the number of electronic components required to provide the desired delay values.

High pressure liquid chromatography system

Abstract: A high pressure liquid chromatography system including a reservoir for a liquid mobile phase, an LC column and detector, a high pressure reciprocating pump for enabling flow from said reservoir through the column, and a positively actuated inlet valve for controlling flow from the reservoir to the pump chamber. The pump is driven by motor means, such as a stepping motor, directly coupled thereto; and the inlet valve is actuated by the power train of the motor and pump, e.g., by an eccentric carried by the pump crank shaft. The pump piston is similarly driven by an eccentric, the pump and inlet valve eccentrics being angularly displaced in their respective positions at the crank shaft, as to delay opening of the inlet valve for a predetermined period following a pump stroke, so as to enable decompression of the liquid in the pump chamber.

Liquid chromatography pumping system with compensation means for liquid compressibility

Abstract: In a liquid chromatography system including a chromatographic column, a reservoir for a slightly compressible liquid mobile phase, piston means cooperating with the reservoir for pumping the liquid phase through the chromatographic column, and means for displacing the piston at a pre-selected velocity, an improvement is disclosed enabling maintenance of a constant flow in the presence of flow resistance changes at the chromatographic column. Such flow resistance changes may arise, for example, in consequence of viscosity changes occurring in the liquid phase during the course of gradient elution operation. According to the improvement, pressure control means are provided in the flow path between the reservoir and column, the pressure control means being adapted for maintaining a substantially constant pressure at the reservoir. In consequence, flow rate changes arising from expansion or contraction of the liquid phase in consequence of compressibility are precluded.

Standing-wave linear accelerator

Abstract: A standing-wave linear charged particle accelerator is disclosed which comprises a plurality of interlaced substructures, with each substructure having a plurality of accelerating cavities disposed along the particle beam path and having side cavities disposed away from the beam path for electromagnetically coupling the accelerating cavities. A standing radio-frequency electromagnetic wave is supported in each substructure, with the wave in each substructure being phase with respect to the wave in every other substructure so that the particle beam will experience a maximum energy gain throughout its path through the accelerator. This interlaced substructure configuration minimizes the transit time of the particles across the gap of each accelerating cavity and makes it possible to operate the accelerator without radio-frequency breakdown at a power level that provides a substantially higher average value of the accelerating electric field along the beam path than has heretofore been obtainable.

X-ray treatment machine having means for reducing secondary electron skin dose

Abstract: In an x-ray treatment machine a charged particle accelerator or cobalt source is provided for producing a field of high energy x-ray radiation for application to a body, for treatment thereof. The radiation machine includes collimators and field shaping structures for shaping the field of x-ray radiation applied to the body. The high energy x-ray radiation intercepted by the field shaping and collimating structures produces high energy secondary electrons by a number of different atomic processes. These energetic secondaries contaminate the shaped radiation field applied to the body being treated. The contaminating high energy electrons, if not eliminated, substantially increase the dosage of radiation delivered to the surface of the body. However, electron deflecting means, such as magnet structures, are provided for interposing in the electron contaminated field of x-ray radiation, so as to provide an electron deflecting flux for deflecting the contaminating electrons and reducing the dose due to these electrons by spreading them out more uniformly over the treated surface. In addition, an electron absorbing screen is interposed in the secondary electron contaminated radiation field for further absorbing the unwanted high energy secondary electrons.

Grid controlled electron source and method of making same

Abstract: A grid-controlled electron source comprises an apertured grid spaced in front of a thermionic cathode. Areas of the cathode directly behind the grid conductors are made non-emissive by a bonded surface layer of non-emissive material such as zirconium. On porous metal cathodes impregnated with active emitting material the metal surface may be sealed with a dense layer of inactive metal under the non-emissive layer to prevent chemical reaction of the latter with the emitting material. Methods of depositing the surface layers in the desired pattern include coating the cathode's entire large-scale surface contour, followed by machining small concave dimples into the surface, thereby removing the non-emissive layer from the dimpled surfaces from which small beamlets of electrons are focused between the grid conductors without grid interception. Another method is to mask the desired non-emissive areas with an apertured mask having solid elements registered with the desired positions of the grid conductors. The surface behind the mask apertures is coated with an inactive powder, then the mask is removed and the non-emissive layer or layers deposited in the uncoated, previously masked paths. Lastly, the inactive powder is removed, uncovering the emissive surface areas.

Spectrometer means employing linear synthesized RF excitation

Abstract: Broadband RF excitation for a Fourier transform spectrometer is obtained by synthesizing the time domain excitation from the desired frequency spectrum of RF excitation. Means are provided to Fourier transform the desired spectral data from the frequency domain into the time domain to obtain a modulation output for modulating an RF carrier signal to generate the desired sideband of RF excitation. In a preferred embodiment, the desired frequency domain data, as tabled in the computer, has a pseudorandom phase shift added to each component for scrambling the phases of the RF excitation. The excited RF resonance signals in the time domain are detected, time-averaged, Fourier transformed to the frequency domain and, in the case of phase scrambling, unscrambled by the pseudorandom phase angle sequence, and displayed.

Noise figure of the MCP image intensifier tube

Abstract: Expressions are obtained for the noise figure of the photoelectric image intensifier type of tube using a microchannel plate in the linear gain mode, including effects of dark current and ionic or optical feedback in the MCP, and of the same device using the MCP in an electron-counting mode. Comparison shows that the latter should be a preferable mode of operation, if practical problems can be overcome.

Spectrosorptance measuring system and method

Abstract: Apparatus and method for measuring the absolute absorptance of a relatively thin sample displaying both reflecting and transmitting characteristics. An integrating sphere is provided, and monochromatic reference and sample beams are projected into the sphere from a pair of angularly-spaced ports. Detector means are positioned at the sphere to receive illumination from the internal sphere wall, including the illumination arising from the first reflectance from that portion of the sphere directly illuminated by the sample and reference beams. The reference and sample electrical signals proceeding from the detector are equalized over the wavelength range of the instrument to establish a relatively flat baseline with the sample withdrawn from the sample beam. The sample is then repositioned within the sample beam. By virtue of the position of the detector and the thinness of the sample, the detector views the illumination of the sphere wall, but substantially excludes the first reflectance and scattered energy from the sample. The light falling on the detector due to illumination of the sphere via the sample is compared with the light falling on the detector due to illumination of the sphere by the reference beam, the ratio between the two providing a direct measure of the quantity of incident sample beam energy transmitted and reflected by said sample. By subtracting the thus determined reflectance and transmittance of the sample from unity, the absorptance of the sample may be directly indicated.

R.f. transistor package having an isolated common lead

Abstract: In a radio frequency transistor package, a layer of metallization is deposited on an electrically insulative thermally conductive ceramic substrate member serving as a heat sink An insular region of the metallization serves as a pad for receiving a transistor die with the collector region of the transistor bonded to the insular region of metallization The region of the metallization surrounding the pad comprises a ground plane An apertured ceramic insulative spacer is bonded over the ground plane metallization with the aperture in registration over the transistor Input, output and a pair of common lead metal strips are bonded to the upper surface of the spacer in generally coplanar configuration The two common leads extend across the spacer adjacent opposite sides of the aperture in generally tangential relation thereto The input and output leads are disposed in between the common leads and are interrupted by the central aperture in the spacer The common leads are electrically interconnected to the ground plane metallization layer via conductive means extending through the aperture in the spacer The input lead is connected to one of the base or emitter regions of the transistor die via wire bonding leads extending through the aperture in the spacer The other base or emitter region of the transistor die is connected via parallel wire bonding leads to the surrounding ground plane metallization The output lead is connected via a set of parallel wire bond leads through the central aperture to the transistor pad

Photovoltaic cell employing lattice matched quaternary passivating layer

Abstract: A photovoltaic cell has an active portion comprising at least one active layer of a IIIA-VA compound having a p-n junction adjacent an upper surface thereof and an overlying epitaxially grown passivating layer of the quaternary alloy AlGaAsP. The passivating layer has a substantially higher bandgap than the active layer so that it is transparent to photons to which the active layer is sensitive. The lattice constant of this passivating layer can be made the same as that of the active layer, thereby to improve efficiency and device performance by reducing surface recombinations of generated carriers, such that a greater percentage of generated carriers will reach the p-n junction and provide useful output electrical energy. The active portion comprises a GaAs layer covered by an AlGaAsP passivating layer, and the AlGaAsP passivating layer can be lattice matched to the GaAs layer.

Device for selecting computer operational mode and labeling input controls accordingly

Abstract: The device is a translucent plastic mask or overlay which fits over the keyboard of the computer input/output station to label the keys with their functions according to the selected mode of operation. A projecting portion along one of the edges of the mask extends into a slot adjacent the keyboard where a series of code segments forms an optical code which is read by a corresponding series of lamp and photocell pairs to provide the computer with the information to cause its mode of operation to correspond with the keyboard legends.

Magnetic stirrer improvement

Abstract: Improved magnetic stirring means for use with an optical absorption cell of the type characterized by a non-magnetic container for fluidic samples to be analyzed, which container has a rectangular cross-section of interior dimensions A × B, where A is relatively large compared with B. The stirrer comprises a magnetically responsive body positioned at the bottom of the container, for effecting agitation of the sample in response to a rotating magnetic field applied by field sources which rotate about a vertical axis beneath the container. The stirrer body is of generally cylindrical cross-section, of axial length slightly less than the dimension A, and of diameter slightly less than dimension B. The stirrer body is oriented with its axis in a horizontal plane, and thus its lateral periphery lies closely adjacent to the internal container walls. The body carries permanent magnet means toward one end thereof, which provide a pair of opposite magnetic poles displaced to alternate sides of the body axis. The externally applied rotating magnetic field, alternately attracts and repels the magnetic poles, and the body, by virtue of the constraints imposed by the cell walls, rotates about its horizontal axis. The body preferably carries surface portions which are parallel to the body axis, whereby rotation about said axis drives the surfaces through the sample, to promote the desired agitation. These surface portions may be defined at longitudinally extending notches formed into the cylinder.

Machine for treating wafer-form items

Abstract: A machine which processes discrete wafer-form items in a chamber is provided with a slot-form channel along which the items move between points inside and outside the chamber, a lateral opening exposing the channel from its side, exposed walls of the channel defining a sealing margin directed toward that opening. A resilient sealing member is movable through the opening between an open position, in which the channel is not obstructed, and a sealing position, in which the sealing member resiliently engages the sealing margin. The machine shown is an ion implanter in which a beam of ions strikes the exposed item in the chamber. Features include a channel which makes an angle with the horizontal for gravity movement of the items; the sealing member serving as a stop to position an item along the length of the channel; and a plurality of openings and associated sealing members to provide locks on the sides of the chamber. The sealing member, preferably of cylindrical form, comprises an elongated resilient element disposed in the direction of the width of the slot and having a corresponding dimension greater than the thickness of the slot.

High vacuum pump

Abstract: The pressure range, pumping speed and through-put of a high-vacuum pump can be significantly improved, particularly with respect to the pumping of hydrogen, by making pump components that are exposed to the vacuum from an alloy that is metallurgically stabilized to maintain a body-centered cubic crystal lattice structure throughout the range of temperatures usually experienced by the pump. In a sputter-ion pump, the cathode especially should be made from an alloy stabilized in the body-centered cubic crystal lattice form. A suitable alloy, which is so stabilized in the body-centered cubic crystal lattice form, has a major constituent comprising one or more elements selected from Group IV B of the conventional long form of the Periodic Chart of the Elements, and a minor constituent comprising one or more elements selected from Groups III B, V B, VI B and VII B of the Chart, with the minor constituent constituting at least 10% but not more than 50% by weight of the alloy. The alloy may have an additional constituent comprising one or more elements selected from Group III A or from any other Group of the Chart, provided that this additional constituent does not constitute more than 5% by weight of the alloy. Particular commercially available alloys that are suitable according to this invention include Ti-13V-11Cr-3Al and Ti-11.5Mo-6Zr-4.5Sn.

Magnetic shield for image intensifier tube

Abstract: Intensifier tubes for x-rays or low-light levels form an image of photoelectrons which is focused on a fluorescent viewing screen. Stray magnetic fields, including the earth's field, bend the electron trajectories and distort the image. Magnetic shielding has been used around the tube, leaving the image-receiving end open. Magnetic field leaking through the open end is reduced by extending the end of the shield around the image-receiving aperture inward and forward of the edge of the tube.

Automatic baseline compensator for optical absorption spectroscopy

Abstract: Apparatus and method are disclosed enabling automatic baseline compensation in a dual beam spectrophotometer. The wavelength adjustment mechanism of the instrument monochromator, is driven in step-wise fashion by a stepping motor or the like, which also drives the tape advance means of a magnetic tape recorder, whereby the tape is advanced past a read/write head in incremental steps with the advance of the wavelength adjustment mechanism. During a calibration run an error signal is generated, which signal indicates at each discrete wavelength whether the imbalance between the reference and sample signals is in a first (or "+") direction, or in a second (or "-" direction). The information conveyed by the error signal is written as a single "+" or "-" bit upon the tape during each step-wise movement of same. The signal comprised by the stream of successive bits is also integrated, and applied to an attenuator in the reference or sample signal channel, to reduce the imbalance, thereby flattening the baseline throughout the spectrophotometer range. During the sample run the bit stream is read-out from the tape and applied to the integrator, to adjust the attenuation in the selected channel, as to duplicate the baseline adjustments effected during writing of the bit stream upon the tape.

Two dimensional gyromagnetic resonance spectroscopy

Abstract: The multiplet spectral structure produced by coupled gyromagnetic resonators, such as heteronuclear coupling, is resolved by inducing a train of transient free induction decay (FID) resonances of a first group of gyromagnetic bodies, such as carbon-13 nuclei coupled to a second group of gyromagnetic bodies, such as protons, and detecting the FID resonance. A decoupling r.f. magnetic field is applied to the second group during free induction decay resonance of the first group for decoupling the spins of the first and second groups during detection of resonance of the first group. The duration of the decoupling effect is changed from one successive free induction decay resonance to the next and the detected resonance data is stored as a function of the change in the decoupling effect. The detected resonance data which is a function of two time intervals is then double Fourier transformed into the frequency domain and displayed as a two dimensional plot for resolving the multiplet structure of the spectra of the first group of gyromagnetic bodies.

Sputter-ion pump having improved cooling and improved magnetic circuitry

Abstract: In a magnetically confined sputter-ion vacuum pump a multi-apertured anode electrode is interposed between a pair of reactive cathode electrode plates. An evacuable envelope encloses the anode and cathode electrodes and a magnetic circuit surrounds the vacuum envelope for producing a glow discharge confining magnetic field extending axially of the apertures in the anode. The reactive cathode plates include peripheral sealing flanges for compressing a sealing gasket into sealing engagement with a pair of sealing surfaces at opposite ends of a tubular main body portion of the envelope. A clamping ring structure, having a bolt circle formed therein, serves to clamp the two reactive cathode plates to the main body and also serves as an integral part of the magnetic circuit. Water coolant channels are brazed to the outer surfaces of the cathode plates for cooling same in use. The magnetic circuit includes a pair of ferrite magnets disposed outside the envelope on opposite sides of the cathodes and enclosed by a magnetic yoke to minimize the size and weight of the magnet and to reduce unwanted stray magnetic fields.

Electrostatic recorder with a recording head which floats on a fluid cushion

Abstract: In a method and apparatus for electrostatically recording on a dielectric coated sheet, a recording head carrying a stylus array is spaced apart from the sheet to form an ionization gap. A charge image is transferred to the sheet by applying an activating voltage between selected styli and a back-up electrode. All styli receive a D.C. bias voltage and selected styli additionally receive "write" pulse voltage. The sum of the bias and write pulse voltages exceeds the threshold breakdown voltage of the gap to ionize the air in the gap under the selected styli. The charge image, created by the ionized air, is subsequently toned to form a visible image. The magnitude of the threshold breakdown voltage is dependent on the length of the gap and the required magnitude of the write pulses depends in part on how accurately the length of the gap is maintained constant. In order to accurately establish gap length and thereby minimize the required magnitude of the "write" pulses, an air cushion between the recording head and sheet is established by fluid jets of air emanating from apertures along the bottom of the recording head. The gap length is controlled by adjusting the air pressure forming the air jets. By adding moisture to the air, the humidity of the ionization gap is also controlled.

Flame photometric detector employing premixed hydrogen and oxygen gases

Abstract: A flame photometric detector including a burner assembly having a first passageway leading to the burner tip so that a mixture of the hydrogen fuel gas and the combustion supporting gas such as oxygen may be delivered via the passageway to the burner tip to produce a hydrogen rich reducing flame. The sample to be analyzed is delivered via a second passageway and directed by a sample guide to the peripheral region of the reducing flame where the sample is burned in a relatively low temperature, hydrogen rich region whereby the interfering light emission from interfering substances is maintained at a low level. SP This is a division of application Ser. No. 389,614 filed on Aug. 20, 1973, now U.S. Pat. No. 3,879,126, which was a continuation of application Ser. No. 232,926 filed on Mar. 8, 1972 abandoned.

Permanent magnet structure for crossed-field tubes

Abstract: A permanent magnet structure particularly beneficial for generating the interaction field in coaxial, crossed field electron tubes is designed such that the normal iron flux return path is not required. Substantial reduction in weight results. A further benefit is that a magnetron interaction structure including the magnets may be built as a unit replaceable in the field in a stabilizing cavity structure. Since the cavity structure contains no iron, the magnets are not demagnetized in the replacement process and there are no mechanical mounting problems caused by magnetic forces.

Cold cathode ionization gauge control for vacuum measurement

Abstract: A cold cathode ionization gauge controller utilizing a periodically varying potential across the gauge tube at higher pressure and substantially constant potential at low pressure provides a wide-range pressure measurement capability from about 10 - 1 to about 10 - 7 torr.

III-V Compound heterojunction solar cells

Abstract: Silicon has been used for most solar cell applications in the past, owing to the availability of the necessary technology. But from a fundamental materials standpoint, Si is a poor choice. It has a lower-than-optimum bandgap for highest efficiency, a low optical absorption coefficient requiring long lifetime material which is sensitive to radiation damage, and no material with which it forms a high quality heterojunction. III-V semiconductors have properties which avoid these problems and permit greatly improved solar cell performance. High quality heterojunctions have been demonstrated in several III-V systems including In 1-x Ga x AS 1-y P y (1) and Al 1-x Ga x As 1-y P y (2). Direct bangap materials with hlgh optical absorption coefficients are available with bandgaps from 0.4 to 2.1 eV. These advantages have long been known, but the AlGaAs/GaAs heterojunction cell was the first to demonstrate them experimentally.