Showing papers by "Varian Associates published in 1982"

The klystrode—An unusual transmitting tube with potential for UHF-TV

Abstract: Economic considerations, especially the increasing cost of energy, have forced electron power tube designers to revise current designs and to re-examine old ones. One result of this re-examination is the rebirth and improvement of a very old and largely forgotten device which appears to hold great promise as a generator of tens to hundreds of kilowatts in the UHF range, with special advantages in TV service. The device itself is described both theoretically and in practical terms, its performance to date and its calculated limits of power output are given, and examples of RF circuitry are shown.

Apparatus for thermal treatment of semiconductor wafers by gas conduction incorporating peripheral gas inlet

Abstract: An apparatus for the uniform thermal treatment of semiconductor wafers by gas conduction holds the wafer in place over a gas filled cavity in opposition to a thermal mass maintained at an appropriate temperature. Gas is introduced behind the semiconductor wafer adjacent its periphery to produce a near-constant gas pressure across the backside of the wafer. The constant pressure produces constant thermal conductivity. Consequently, heat conduction is uniform, the temperature of the wafer is uniform and uniform processing is accomplished across the wafer.

Apparatus for gas-assisted, solid-to-solid thermal transfer with a semiconductor wafer

Abstract: Apparatus and method are provided for effecting gas-assisted, solid-to-solid thermal transfer with a semiconductor wafer. A semiconductor wafer is loaded at its periphery onto a shaped platen. Sufficient contact pressure from the loading is produced between the wafer and the platen so that significant gas pressure may be accommodated against the back side of the wafer without having the wafer bow outwardly or break. Gas under pressure is introduced into the microscopic void region between the platen and the wafer. The gas fills the microscopic voids between the platen and semiconductor wafer. The gas pressure approaches that of the preloading contact pressure without any appreciable increase in the wafer-to-platen spacing. Since the gas pressure is significantly increased without any increase in the wafer-to-platen gap, the thermal resistance is reduced and solid-to-solid thermal transfer with gas assistance produces optimum results.

Transesophageal Phased Array for Imaging the Heart

Abstract: A 3.5 MHz phased array has been developed for imaging the heart through the esophagus. The ultrasonic probe is fitted on the distal end of an Olympus gastroscope. Transesophageal images of the heart were obtained on ten patients. This paper describes the design and realization of the phased array and presents some clinical results obtained on patients.

The organometallic vpe growth of GaSb and GaAsl−xSbx using trimethylantimony

Abstract: The organometallic vapor phase epitaxial (OMVPE) growth of GaSb and GaAsl−xSbx (0 ≤ × ≤ 0.26, 0 .64 ≤ × ≤1) is discussed. Trimethylgallium and trimethylantimony are used as the Ga and Sb source, respectively. Most GaAs1× Sbx growths are done using arsine, but the use of an alternate arsenic source, trimethylarsenic, is also discussed. In contrast to most arsenic-containing alloys, both GaSb and Sb-rich GaAs1−x Sbx are grown under Group III-rich conditions. The total input flux as well as the ratio of the input chemicals must be closely regulated. In particular, growth of GaAsl−xSbx requires careful control of the trimethylantimony-to-total Group V ratio, since arsenic preferentially incorporates into the crystal.

Ultrasound hyperthermia applicator with variable coherence by multi-spiral focusing

Abstract: An ultrasound hyperthermia applicator comprises a plurality of transducers which can be operated in different grouping modes so that the applicator is effectively provided with a variable number of elements having variable effective diameters transmitting coherent beams. The individually coherent beams from these elements are individually focused for incoherent superposition in the target volume according to a spiral or multi-spiral focusing scheme. Such an applicator is capable of uniformly heating without scanning a limited part of human body with volume greater than the inherent focal size of the individual transmitter element.

Optimum surface contour for conductive heat transfer with a thin flexible workpiece

Abstract: Conductive heat transfer between a thin deformable workpiece and heat sink is optimized by imposing a load over the workpiece resulting in a uniform contact pressure distribution in said workpiece which is also the maximum stress consistent with the elastic properties of the workpiece. The surface of the heat sink is given a contour determined by these criteria for a thin circular disk clamped thereto.

NMR System for the non-invasive study of phosphorus metabilism

Abstract: A nuclear magnetic resonance analytic apparatus for obtaining tissue metabolism information from a living body member. The apparatus consists of a large high-intensity electromagnet with an inner space having a uniform magnetic field, for receiving the body member. The space has a probe coil mounted therein with which the body member is engageable. For phosphorus-31 metabolite, there is provided a 24.33 MHz RF generator connected through a control logic section and a driver unit to the probe coil via a transmitter/receiver switching unit arranged to in effect switch the probe coil from a normal connection with a demodulation circuit to the driver unit responsive to a burst of RF pulse energy applied to the switching unit by the driver unit via the control logic section by command of a computer. The control logic section controls the system so as to first apply short pulses of the RF signal to the probe coil for a predetermined excitation time period, gating-off the demodulation unit. After this excitation period, the transmitter circuit is disabled, the demodulation circuit is gated-on, and the switching unit restores the normal connection of the probe coil to the demodulation unit, allowing the free induction decay signals sensed by the probe coil to be demodulated and furnished in analog form to the computer, which converts these analog signals into representations of the intensities versus frequency shift of the respective metabolite components of the tissue. Means is provided for applying a predetermined simulated free induction decay signal to the demodulation circuit for testing the apparatus.

Target assemblies of special materials for use in sputter coating apparatus

Abstract: In high rate sputter coating sources, it is generally necessary to liquid cool the sputter targets. In one type of source, a cooled wall of a cathode assembly is closely adjacent a sidewall of the sputter target. During normal operation the sidewall of the target expands thermally into tight contact with the cooled wall, whereby cooling of the target is effected without the need for bonding the target to the cooled wall using a solder or other adhesive. Thus, replacement of worn conventional targets is a relatively simple procedure. When the targets are made of certain special materials, such as fragile materials or materials with low coefficients of thermal expansion, target warping, cracking or melting can occur. Such problems are overcome or alleviated by the novel design approach of the present invention, which employs a sputter target assembly in place of a conventional target. The novel sputter target assembly comprises a sputter target of the special material, a retaining member, and a bonding means between the special sputter target and the retaining member. When the special target is worn out, the sputter target assembly is replaced with the same simple procedure used for a conventional target.

Health and safety consequences of shift work in the food processing industry.

Abstract: Both a questionnaire survey and an evaluation of health and safety records were used to characterize the health and safety consequences of day versus afternoon, night and rotating shifts for approximately 1000 food processing workers Relative to the day workers, the results indicated that those on shift work, particularly rotating and night shifts, showed greater adverse effects These included poorer sleep, altered eating habits, greater alcohol consumption, greater incidence of sick absence and greater incidence of work-related injuries Shift work was not related to self-reported health complaints or self-reported chronic disease states The impact of shift work on sick absence and work-related injuries differed depending on worker sex, age and work tenure

Strong anion exchange composition and methods

Abstract: A strong anion exchange composition useful in monophosphate nucleotide isomer separations is comprised of an inert porous particle having a silyl alkyl ammonium compound fixedly attached by a covalent silicon-oxygen-silicon bond to the surface thereof. A process for synthesizing the strong anion exchange composition in an aqueous solvent is disclosed together with methods for separation of monophosphate nucleotide isomers, highly phophorylated nucleotides and aldopentose carbohydrates using a column packed with this strong anion exchange composition.

Measurement of velocity and tissue temperature by ultrasound

Abstract: Temperature inside a tissue volume is noninvasively determined on the basis of its known relationship with the velocity of ultrasound inside the volume. The velocity of ultrasound between two field points inside the volume of interest is calculated from measurements of differences in transit times of sound beams scattered in substantially opposite directions at these field points.

Apparatus for enhanced neutralization of positively charged ion beam

Abstract: An apparatus for the enhanced neutralization of a positively charged particle beam has a source of primary electrons which are directed at a dummy target positioned adjacent the ion beam. The secondary electrons have a low energy and are susceptible to being entrapped within the volume of the positively charged beam. The ion beam attracts these low energy electrons until effective beam neutralization is achieved. The ions in the beam are individually neutralized when the beam strikes the target.

Beam scanning method and apparatus for ion implantation

Abstract: Method of and apparatus for scanning a charged particle beam over a semiconductor wafer in a prescribed pattern. A triangular waveform, including alternating positive and negative ramp portions of constant slope and controllable time durations, is applied to a horizontal deflection system and produces horizontal scanning of the beam. The time durations of the ramp portions determine the length of the horizontal scan lines and are controlled according to a predetermined sequence so as to provide the prescribed pattern. The triangular waveform is provided by an integrator which receives a square wave from a frequency source of controllable frequency. The predetermined sequence is stored in a read only memory which controls the frequency of the frequency source. At the completion of each ramp portion, a voltage applied to a vertical deflection system is incremented so as to step the beam vertically up or down.

On-column capillary gas chromatographic injector

Abstract: Apparatus (10) and method for injection of samples directly onto a' column (21) in a gas chromatograph with injection occurring in a temperature controlled zone outside the oven. The apparatus (10) combines a guide means and valve assembly (5) in alignment with an injection and thermal transfer assembly (6). In the guide means and valve assembly (5) a radial seal (12) engages the injection means to seal the injection volume, thereby eliminating back flash. In the injection and thermal transfer assembly (6) the capillary column (21) is centered and held in fixed position within a duct means (20). Means (24,31,32,30) is provided to lower the temperature of the capillary column (21) to a temperature below the vaporization temperature of the liquid sample prior to injection. After injection means is further provided to raise the temperature of the capillary column to a temperature above the volatilization temperature of the liquid sample to vaporize it and pass it into the capillary column. The method of on-column injection of the present invention comprises inserting an injection means through a radial seal means (12) to a point just above a valve (15), opening the valve (15), further inserting the injection means through the valve and into the end of that portion of the capillary column within the thermal transfer assembly and outside the oven of the gas chromatograph, injecting a liquid sample into the end of the capillary column (21) while maintaining the column at temperature below the vaporization temperature of said liquid sample, withdrawing the injection means from the capillary column (21) and the valve means (15), closing the valve means (15), withdrawing the injection means through the injector duct (13) and the radial seal means (12), and heating said column (21) within said temperature controlled zone to volatilize said sample and pass it into said column (21).

Evaluation of New Microparticulate Packings for Aqueous Steric Exclusion Chromatography

Abstract: Two types of high performance aqueous size exclusion columns have recently been developed, one a rigid spherical silica-based packing containing a new hydrophilic bonded phase (MicroPak TSK Gel Type SW) and the other an organic-based, semi-rigid gel (MicroPak TSK Gel Type PW). Characteristics of MicroPak TSK SW and PW columns were compared to other commercially available aqueous SEC columns packed with similar supports. Chromatographic performance of prepacked columns containing microparticulate support materials were compared for exclusion separations of water-soluble organic polymers, biopolymers, and small water-soluble oligomers. Amino acid probes were used to investigate non-exclusion effects of MicroPak TSK SW and PW columns.

Feed forward AC voltage regulator employing step-up, step-down transformer and analog and digital control circuitry

Abstract: A feed forward AC voltage regulator utilizes a step-up, step-down transformer to apply adjustment voltages to an unregulated AC line. Analog circuitry periodically samples the unregulated AC line input and compares it with a scaled representation of the desired line voltage. Digital circuitry converts the information from the analog sampling and comparison to an instruction command which activates an appropriate solid state switch associated with a tap on a multitap transformer connected to the regulated AC output line. The taps are successively located on the multitap transformer to provide selectable adjustment voltages of various values. The switched-in adjustment voltage is provided the proper polarity and applied to the primary of the step-up, step-down transformer, thereby applying to the secondary the adjustment voltage needed to move the regulated AC output line to the desired level.

Gridded electron power tube

Abstract: An efficient relatively high-power inductive output linear electron beam tube with broad-band capabilities is disclosed which is density modulated with a grid applying to the beam an RF modulating signal. The grid has a large active area which may be of the order of ten square inches, is closely spaced one-twentieth the grid diameter or less to a thermionic cathode, and is comprised of a plurality of curved thin narrow elongated members. With the aid of an annular anode downstream of the grid, the beam is accelerated by DC potential of at least several kilovolts. A high-isolation input signal means includes adjacent but physically and electrically isolated wide-diameter, axially reduced annular cathode and grid lead means for leading both the DC beam-accelerating potential into the cathode, and the modulating RF signal into the grid with minimal impedance. A grid support means at one end of the grid peripherally engages the grid with a resilient deformable contact member to facilitate differential expansion without grid distortion while accurately maintaining the close grid to cathode spacing. The resulting density modulation forms the beam into correspondingly high-density moving bunches of electrons. An axial drift tube means encloses the beam, extends to a collector, and is interrupted by a gap. A coaxial resonant cavity about the drift tube, and into which the gap opens allows the bunches passing closely past the gap to induce efficiently in the cavity a VHF, UHF or microwave output signal corresponding to the modulating signal, but with an output power of at least a kilowatt.

Method for suppression of acoustic ringing in NMR measurements

Abstract: Compensation rather than direct suppression removes the effects of acoustic ringing as encountered in pulsed nuclear magnetic resonance experiments. Single and double spin-echo excitation, combined with several alternative schemes for phase cycling both transmitter and receiver, is one type of compensatory technique. Another technique consists of acquiring free induction decay signals in pairs, with the second preceded by an inversion pulse a short time prior to the normal excitation pulse, and with the second acquisition acquired subtractively, assuring phase coherence of the signals and phase opposition and hence cancellation of the acoustic ringing. Phase cycling of the inversion pulse may also be employed in the latter technique to suppress acoustic ringing stimulated by the inversion pulse.

High resolution position sensing apparatus with linear variable differential transformers having phase-shifted energizing signals

Abstract: Apparatus for high resolution sensing of the position of a rapidly moving member. The apparatus includes at least two linear variable differential transformers (LVDT's) each having a magnetic core coupled to the movable member. A signal source and a phase shifter provide energizing signals to the primary coil of each LVDT. The energizing signals have the same frequency but are phase shifted relative to each other. The induced secondary voltages of the LVDT's are sampled by synchronous detectors, the outputs of which are combined by an adder into a high resolution output signal. When two LVDT's are utilized, the energizing signals have a relative phase shift of 90° and the effective position sampling rate is doubled. The apparatus can be used to sense the operating frequency of a tunable magnetron.

MoSi 2 formation by rapid isothermal annealing

Abstract: Formation of MoSi 2 by rapid isothermal annealing has been investigated using black-body radiation from a graphite heater. Although elemental Mo layers deposited on 3 in diameter silicon wafers failed to form silicides after annealing, excellent results were obtained using co-sputtered Mo and Si on similar substrates. It was found that regrowth began within the first few seconds at 900-1000°C, and a 20 sec anneal time at 1000°C reduces sheet resistivity by one order of magnitude from as-deposited values. This method of annealing might thus offer a practical solution to low-resistivity silicide formation in very large-scale integrated-circuit devices, without the significant dopant redistribution observed in furnace annealing.

A diagnostic technique for evaluation of cathode emission performance and defects in vehicle assembly

Abstract: A method for presenting cathode emission data has been developed which yields cathode performance curves in a convenient form for the cathode engineer, design engineer, and end user. The curves provide important diagnostic information not previously available which characterizes cathode emission performance over the entire range of operation and indicates defects in device fabrication. Direct comparisons of measurements on cathodes of various size and vehicle configuration are possible due to the normalized form of the performance curves. Construction of the curves and their interpretation are discussed.

Method for reflow of phosphosilicate glass

Abstract: In a method for reflow of a phosphosilicate glass (PSG) layer applied to a semiconductor wafer, the wafer is placed in a processing chamber in parallel alignment with a planar blackbody source. The chamber is evacuated, and the source rapidly and uniformly heats the PSG layer to a temperature at which plastic flow occurs. The blackbody source provides significant radiation in the 7-10 micron portion of the infrared spectrum. The thermal treatment is typically completed in 8-15 seconds, thereby avoiding impurity redistribution in the semiconductor device.

OM-VPE growth of Mg-doped GaAs

Abstract: The epitaxial growth of Mg-doped GaAs by the organometallic vapour phase epitaxial process (OM-VPE) has been achieved for the first time. The doping is controllable over a wide range of input fluxes of bis (cyclopentadienyl) magnesium, (C5H5)2Mg, the organometallic precursor to Mg.

Charged particle beam exposure system utilizing variable line scan

Abstract: A charged particle beam exposure system for selectively irradiating the surface of a workpiece to be patterned. The beam has a cross-section at the surface of the workpiece comprising a projected line on variable length, of controlled width and one of two orthogonal orientations. An image of an L-shaped aperture is focussed on a shaping aperture with two adjacent orthogonal edges and is deflected relative to the shaping aperture to provide an intermediate line of desired length, width and orientation. The intermediate line is defined by the portion of the image of the L-shaped aperture which is superimposed on the shaping aperture. An image of the intermediate line is projected onto the workpiece to form the projected line which is scanned over the surface of the workpiece. Radial beam spreading is reduced and pattern line resolution is improved in the disclosed system.

Method for superconducting magnet shimming

Abstract: Component coils for providing a desired magnetic field distribution, which coils are subject to interaction via mutual inductance thereof, are connected each to respective current regulated power supplies whereby the interaction is compensated. Circuits are provided to control selected pluralities of interacting coils via persistence switches with minimum number of control leads in order to reduce the thermal communication to the interior of a cryostat housing the magnet and persistence switches.

Method of making a transparent and electrically conductive bond

Abstract: Solar cells with different bandgaps are stacked to form a multijunction photovoltaic converter with a high conversion efficiency. By stacking the cells mechanically rather than by growing them all at one time, the most convenient combination of materials may be selected for the cells. The stacking is completed by means of a glass sealing layer with moats containing inter-cell contacts which are bonded to the cells.

Design and operation of magnetron injection guns for a 140 GHz gyrotron

Abstract: Two magnetron injection electron guns with different electrode geometries have been designed and constructed for use on a 140 GHz gyrotron oscillator. Computer simulations have been performed, detailing the behavior of both designs with variations of all relevant parameters. The first of the two designs has been incorporated into the gyrotron and has been operated up to a beam voltage of 80 kv and a beam current of 7.5 a. With this beam power, the gyrotron has emitted a peak power of 100 kw at 140 GHz, for 1.0 - 1.5 µs pulses. This represents the highest frequency at which a power level of 100 kw has ever been achieved on a gyrotron. In addition to the successful rf results, the gun operates into the highest magnetic mirror ratio (25:1), and the highest cavity and cathode magnetic fields (54 kG and 2.2 kG, respectively) of any magnetron injection guns.