Showing papers by "Varian Associates published in 1996"

Unconventional electronic structure evolution with hole doping in Bi2Sr2CaCu2O8+ delta : Angle-resolved photoemission results.

Abstract: We report angle-resolved photoemission results on ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{Ca}}_{1\ensuremath{-}x}{\mathrm{Dy}}_{x}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ and oxygen depleted ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ investigating the electronic structure changes above ${T}_{c}$ in materials with hole doping levels ranging from insulating to slightly overdoped. Near optimal hole doping, the Fermi surface is large and consistent with band calculations. In underdoped samples with ${T}_{c}$ of 60--70 K, portions of this Fermi surface are not seen. This change is related to the opening of an energy gap near $(\ensuremath{\pi},0)$ above ${T}_{c}$.

Apparatus for obtaining dose uniformity in plasma doping (PLAD) ion implantation processing

Abstract: An apparatus for improving dose uniformity in the PLAsma Doping (PLAD) ion implantation of a target material is described. By providing means for simultaneously biasing both the electrode, upon which the target is disposed, and a separately biasable concentric structure introduced about the electrode and sufficiently close to the target, together with means for adjustable bias variation between the electrode and the structure one can sufficiently adjust the shape of the implantation plasma, e.g. induced electric field and plasma sheath thickness, in order to effectively provide a uniform dose distribution during PLAD ion implantation processes.

Long-pulse and CW tests of a 110-GHz gyrotron with an internal, quasi-optical converter

Abstract: A high-power gyrotron, employing an internal converter that produces a Gaussian-like output mode, has been designed and tested. The tube employed a TE/sub 22.6.1/-mode interaction cavity that was designed for operation at a frequency of 110 GHz. An internal converter, consisting of an advanced launcher design and four mirrors, produced a Gaussian mode that had a relatively uniform profile at the tube output window to minimize the peak power density. Tests on the tube resulted in output power levels of 680, 530, and 350 kW for pulse durations of 0.5, 2.0, and 10.0 s, respectively. Measurements of the temperature of the output window were made during the long-pulse tests. Output power levels of 1 MW were achieved under short-pulse (1 ms) operation and the tube was operated at CW power levels in excess of 100 kW.

Pressing plate for linearized pulses from a peristaltic pump

Abstract: A peristaltic pump comprises a rotatable drum 2 having rollers 5 or cams 5' for squashing a flexible tube 9 against a profiled surface 10 of a presser plate 7. Tube 9 is mounted between supports 14 and 15 on presser plate 7 and is automatically movable between an inoperative and operative (pumping) position by pivotal movement of plate 7 about axis 8 produced by an electro mechanical actuator. A flexible membrane 33 is sandwiched between rollers 5 or cams 5' for eliminating shear forces on the tube 9. The construction of the pump and shape of profile 10 are such as to mimimise pulsations in the output flow. Systems for supplying a sample for analysis to spectroscopic apparatus using the peristaltic pump are also described.

Fluid thermal mass flow sensor

Abstract: A fluid thermal mass flow meter including a composite flow tube having four tubular segments of high thermal conductivity formed in a length of tube made of a material having a relatively low thermal conductivity, a thin film element formed on the surface of and extending around each of the four tubular segments, circuitry for incorporating the elements into a bridge circuit, and a housing for containing the flow tube, elements, and circuitry.

Positioning system for a patient support apparatus

Abstract: An accessory has a fixed member and a rotatably supported and eccentrically mounted disk which are each inserted into a corresponding one of a pair of crescent-shaped indentations formed on a panel of a couch top. As the disk is rotated, its center moves towards the fixed member, causing the disk to press against the inner wall of the indentation and locking the accessory to the panel securely and repeatably.

Zero deflection magnetically-suppressed Faraday for ion implanters

Abstract: A magnetically suppressed Faraday system for use in an ion beam treatment system, such as an ion implanter, includes a Faraday cage defining a chamber having an entrance, and a magnetic suppression assembly positioned at the entrance of the chamber. The downstream end of the Faraday cage is positioned adjacent to a workpiece such as a semiconductor wafer. The magnetic suppression assembly includes a suppression magnet structure for producing suppression magnetic fields of sufficient strength to inhibit escape of electrons from the chamber, a field cancellation magnet structure for producing cancellation magnetic fields for substantially canceling magnetic fields, produced by other magnets in the magnetic suppression assembly, near the downstream end of the chamber, and an angle correction magnet structure for producing angle correction magnetic fields selected such that the ion beam is subjected to zero or nearly zero net angular deflection as it passes through the Faraday system.

Method and apparatus for improved low pressure collimated magnetron sputter deposition of metal films

Abstract: A method and apparatus are provided which increase the collimation of sputter deposited films by increasing the mean free path (MFP) of sputtered atoms so as to reduce redirecting collisions with the buffer gas. This is accomplished by reducing buffer gas pressure while employing mechanisms to maintain or increase plasma electron density so as to sustain the plasma in the absence of normally required gas pressure. A first mechanism used to permit reduced gas pressure is to provide gas flow directly to the immediate region of the plasma discharge rather than to another remote area of the sputter deposition chamber. A second mechanism used to permit reduced gas pressure is to provide an electron emitting source near the plasma discharge to increase the plasma electron density without requiring further ionization of buffer gas atoms. These two mechanisms can be used either alone or together, as desired, in view of the circumstances presented.

pless vacuum heat transfer station

Abstract: A clampless heat exchange station for a semiconductor wafer for use in a vacuum chamber, at pressures from 2 Torr to 30 Torr using commercial grade inert gas. The heat exchange chuck has apertures therethrough in the region where the wafer is to be mounted to serve as a miniature plenum gas to provide equal pressure along the bottom and top sides of the wafer. This configuration avoids chipping and particle deposition and provides improved heat transfer rate and wafer temperature uniformity.

Broadband linearly polarized beat-wave TE/sub m1//TE/sub 11/ mode converters

Abstract: Broadband linearly polarized waveguide mode converters have been developed to transform the high-order cylindrical TE/sub m1/ output wave from harmonic gyrotron amplifiers into the more useful TE/sub 11/ fundamental waveguide mode. The converter's corrugation period is equal to the beat between the two waves and the bandwidth is predicted to be inversely proportional to the number of periods. Four-period TE/sub 31//TE/sub 11/ and TE/sub 41//TE/sub 11/ converters with an azimuthal perturbation of m/sub c/=4 and m/sub c/=5, respectively, have yielded a peak conversion efficiency of 98% with a bandwidth greater than 3% and a one-period beat-wave converter has been designed to yield 12% bandwidth. However, it has been observed in measurements that the strong coupling in a short converter can lead to a shift of the center-frequency with an accompanying reduction of the efficiency and bandwidth. A two-period TE/sub 41//TE/sub 11/ converter with 5% bandwidth displayed a 5% frequency shift and a conversion efficiency of only 86%.

Wafer orientation alignment system

Abstract: An apparatus and method for precisely calibrating the transfer arm of a multiple station wafer processing system without breaking vacuum and with a minimum of system downtime is provided. A system of determining and properly aligning the crystallographic orientation of the wafers before processing as well as monitoring the orientation of individual wafers during wafer transfer between processing stations is also provided.

Method for injection of externally produced ions into a quadrupole ion trap

Abstract: A method of ion collection over a wide mass-to-charge range from continuous ion source into a quadrupole ion trap filled with a buffer gas directing an ion beam, from an external ion source to a radio frequency ion trap through a gating device for a predetermined period of accumulation time to allow the beam to enter the trap, trapping ions over a range of masses by applying a radio frequency voltage to the trap and changing an amplitude of the radio frequency voltage adiabatically to achieve a uniform trapping efficiency for ions over a predetermined mass range. The predetermined period of accumulation time may be divided into a plurality of segments, and the amplitude of the radio-frequency voltage is changing adiabatically within each segment.

HTS coils for high resolution nuclear magnetic resonance spectroscopy

Abstract: Low noise detectors offer improved performance in low-signal-level nuclear-magnetic-resonance (NMR) spectroscopy and imaging (MRI) applications. High temperature superconducting coils, fabricated with YBa2Cu3O7-δ thin films, were developed for high resolution NMR spectroscopy. Quality factors exceeding 104 have been achieved in a 9.4 T magnet. Current handling and magnetization of the coils approach the desired requirements. High resolution NMR spectra have been successfully obtained with these coils. A signal-to-noise ratio improvement over conventional technology of more than a factor of 4 was realized.

Charged particle beam system having beam-defining slit formed by rotating cyclinders

Abstract: A slit assembly for use in a charged particle beam system wherein a charged particle beam is directed along a beam path. The slit assembly may be a mass resolving slit assembly for an ion implanter. The slit assembly includes first and second cylinders spaced apart from each other. Opposing surfaces of the first and second cylinders adjacent to the beam path define a slit for passing the charged particle beam. The first and second cylinders have first and second central axes, respectively. The slit assembly further includes a drive system for rotating the first cylinder about the first central axis and for rotating the second cylinder about the second central axis. The slit assembly provides low contamination and a long operating life. The slit assembly may include a system for adjusting the width of the slit. The slit assembly may further include a cooling system for controlling the temperatures of the first and second cylinders.

Method of operating an ion trap mass spectrometer

Abstract: A method of operating a quadrupole ion trap as a mass spectrometer, in which the ion mass to be detected is selected by adjusting the three dimensional quadrupole storage field to make the βz value of the selected mass equal to a fixed, predetermined βz value of a narrow range of frequencies excluded from a broadband supplemental RF electric field. The ions are detected to provide a signal corresponding to the amount of the selected ion mass.

Method of detecting selected ion species in a quadrupole ion trap

Abstract: A method of detecting ions of a single ion species that have been selectively stored in a quadrupole ion trap mass spectrometer is disclosed. After the selected ion species is isolated the trapping field in rapidly changed to cause ions to leave the ion trap in the axial direction where they are detected using a conventional detector. Preferably, a dipole pulse is applied to the ion trap simultaneously with the reduction of the trapping field, such that all of the ions are caused to leave the trap in a single direction, doubling the ion current over prior art methods. The method of the invention allows ejection of all of the ions in a time period which is nearly twenty times faster than the prior art resonance ejection scanning technique, and without the artifacts in the signal current caused by frequency beating.

Optical position calibration system

Abstract: An apparatus and method for precisely calibrating the transfer arm of a multiple station wafer processing system without breaking vacuum and with a minimum of system downtime is provided. A system of determining and properly aligning the crystallographic orientation of the wafers before processing as well as monitoring the orientation of individual wafers during wafer transfer between processing stations is also provided.

Optical detector for echelle spectrometers

Abstract: A solid-state detector for use in an atomic spectrometer comprises a plurality of arrays of sensing elements, or pixels, each of the arrays being positioned along and on the locations of spectral signals on a focal plane of an echelle grating spectrometer. The sensing elements are positioned along the many diffraction orders presented on a two-dimensional echelle grating focal plane so that at least one element is located at each and every resolution element regardless of global x-y coordinate positioning of the elements or with reference to each other. The result is a series of skewed lines of sensing elements, those lines being in the same shape as the series of diffraction order lines which comprise an echelle spectrum. The solid-state detector is particularly useful in an atomic spectrometer wherein an echelle grating is used to diffract incident radiation such that the various components of the radiation may be observed.

A rotor for turbomolecular pump

Abstract: The present invention relates to a rotor (1) of a vacuum pump comprising a rotatable shaft (5) and a plurality of spaced apart parallel rotor disks (2, 3) secured to said rotatable shaft (5), such rotor being provided with a corrosion-resistant protective coating formed by a layer of polymeric material.

Photoelectric X-ray tube with gain

Abstract: An X-ray tube has an anode and a photocathode inside a vacuum envelope and an electron multiplier is disposed between them. Such an electron multiplier may be a plurality of sequentially disposed dynodes or a microchannel plate. Because of the secondary electron emission from such an electron multiplier, a higher-power radiation is obtained without requiring a high optical power level to generate photoelectrons. The vacuum envelope may be of a rotary type with the anode and photocathode having annular regions.

Evaluation of an ultrasonic nebulizer-membrane separation interface (USN-MEMSEP) with ICP-AES for the determination of trace elements by solvent extraction

Abstract: The introduction of volatile organic solvents and metal organic complexes into an inductively coupled plasma (ICP) is problematic due to overloading and pyrolysis effects. These include carbon built up in the torch and spectral interferences. As a consequence, solvent extraction as a method for preconcentrating trace metals for the determination by ICP has been limited. In this report a commercial ultrasonic nebulizer-membrane separation interface (USN-MEMSEP) for the direct introduction and separation of organic solvents using ICP atomic emission spectrometry (AES) and a sequential spectrometer has been evaluated for solvent extraction of chelated trace metals. The ability of the MEMSEP to separate volatile organic flows from metal aerosols has been demonstrated by determining the recoveries of several transition metals in an oil-based methyl-isobutyl ketone (MIBK) standard relative to an aqueous solution. However, low recoveries of several metal chelates have been found evidently due to the volatilization of the organic metal species at the boiling point of MIBK (160° C). Moreover, the multielement capability and limits of detection have been limited due to sequential atomic emission detection. Advantages of the technique include enhanced limits of detection (LODs) and reduced plasma and spectral interferences.

Echelle spectrometer with a shaped oriented slit

Abstract: An improved echelle spectrometer comprises a slit in light blocking plate, an echelle grating, and a detector array. The slit is shaped and oriented to align an image of a light beam projected through the slit, onto the echelle grating and onto the detector in a desired orientation and shape relative to the detector array. Precise adjustment of the shape and orientation of the slit is dependent on the orientation of the detector with respect to the dispersion direction of the echelle grating. The echelle spectrometer provides high detector resolution with reduced read-out time.

Thin film processes for high-temperature superconductors

Abstract: Thin film processes have opened up new directions for research in the field of high-temperature superconductors, including the study of their fundamental physical properties, their application in electronics, and the synthesis of new superconducting compounds. In the past few years great progress has been achieved. Uniform, double-sided wafers with large surface area are now being made for passive electronics components. Advances in atomic layer engineering of precise heterostructures and multilayers are bringing forth a new generation of active devices. In spite of this progress, many challenges still remain in improving the control of thin film growth and understanding film microstructure.

Time correction for digital filters in transient measurments

Abstract: Observation of transient phenomena in an oversampled regime is implemented with a time correction obtained by prepending one or more pseudo datums to the oversampled data to constitute an effective negative delay for the oversampled data set including the pseudo datums. For an oversampling factor N and oversampling rate ω s , a digital filter furnishes downsampled data uniformly spaced in time by N/ω s and positioned at n (N/ω s ) where n is the discrete downsampled time coordinate.

Time-dependent modeling of the MFA-MOPA

Abstract: Semiconductor lasers present enormous potential for free-space laser communications. Recently, a new class of devices based on a master oscillator power amplifier configuration has emerged as the leading contender. The paper illustrates the monolithically integrated flared amplifier (MFA-MOPA) device. It incorporates an index-guided, single-lateral-mode- distributed Bragg reflector (DBR) master oscillator section that diffracts a relatively low- power, narrow spectral bandwidth signal into a tapered amplifier section. The tapered amplifier section then amplifies the output to a one-watt or greater level while the divergence precludes the formation of filaments, maintaining good beam quality during the amplification process. The final output facet of the amplifier section is anti-reflection coated so that feedback into the DBR master oscillator is minimized, while outcoupling the amplified power.

Digital filter pre-charging

Abstract: A method for treating M-degree oversampled impulse response data in real time includes generating N initial pseudo-data points derived from an N tap digital filter, processing each datum therewith, down sampling by a factor of r and displacing the processed datum toward the time origin by an appropriate amount. After fourier transform of the data set, the spectral background information bears improved fidelity to the actual spectral noise.

Transmission electron study of heteroepitaxial growth in the BiSrCaCuO system

Abstract: Films of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} and Bi{sub 2}Sr{sub 2}CuO{sub 6} have been grown using Atomic-Layer-by-Layer Molecular Beam Epitaxy (ALL-MBE) on lattice-matched substrates. These materials have been combined with layers of closely related metastable compounds like Bi{sub 2}Sr{sub 2}Ca{sub 7}Cu{sub 8}O{sub 20} (2278) and rare-earth-doped compounds like Bi{sub 2}Sr{sub 2}Dy{sub {ital x}}Ca{sub 1{minus}{ital x}}Cu{sub 2}O{sub 8} (Dy:2212) to form heterostructures with unique superconducting properties, including superconductor/insulator multilayers and tunnel junctions. Transmission electron microscopy (TEM) has been used to study the morphology and microstructure of these heterostructures. These TEM studies shed light on the physical properties of the films, and give insight into the growth mode of highly anisotropic solids like Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}. {copyright} {ital 1996 Materials Research Society.}

A new golden age.

Abstract: And yet, if we step back and take a longer view, we see that industrial society has been here before. The global economy is poised to enter a new phase of robust, dependable growth. Technological and economic historian Carlota Perez calls it a “golden age.” Such ages occur roughly every 60 years, and they last for a decade or more, part of a long cycle of technological change and financial activity. (See Exhibit 1.)