Showing papers by "Varian Associates published in 1985"

Catheter for use with nmr imaging systems

Abstract: A magnetic resonance catheter system combines. with a magnetic resonance imaging device (10). A catheter (26) comprises means (28, 32, 32', 36) for exciting a weak magnetic field at the tip of the catheter. The location of the catheter tip is, thereby obtained in cooperation with the magnetic resonance imager (10).

X-ray and electron radiotherapy clinical treatment machine

Abstract: A radiotherapy machine includes a microwave powered accelerator to produce an energetic beam of charged particles, bending and focussing magnets to parallel scan the beam in a plane and collimators to make the resulting parallel scanned beam into paraxial rays of charged particles or X-rays. The beam is intensity modulated as it is scanned to control dosage spatial distribution. The subject is moved perpendicular to the scanning plane in order to treat a 3-dimensional shape.

Electron channeling radiation from diamond.

Abstract: A series of channeling-radiation experiments for incident electrons of 16.9, 30.5, and 54.5 MeV has been performed, using a type-IIa natural diamond 23 \ensuremath{\mu}m thick. Channeling-radiation transition energies calculated with the standard (Hartree-Fock) potential are in good agreement with the observed results for the (100) and (110) planes as well as for the 〈100〉 axis at all energies, but are in error for the (111) plane. Corrections to the (111) potential due to anisotropic electron distributions which are based upon x-ray-diffraction data result in calculated transition energies that are in better agreement with the observed data; an empirical (111) potential yields calculated transition energies which are in even better agreement with the data. Calculated linewidths are considerably narrower than the observed values; this disagreement probably results from incoherent scattering by crystal defects having an average spacing of approximately 1 \ensuremath{\mu}m. The transition energies are shown to scale as ${\ensuremath{\gamma}}^{5/3}$ for transitions involving states that are localized close to the atomic planes and as ${\ensuremath{\gamma}}^{2}$ for those localized close to the midplane regions. Free-state populations are shown to increase relative to bound-state populations with incident electron-beam energy. Channeling radiation has been shown to constitute a practical source of x-ray photons utilizable at many existing accelerators.

Chemical vapor deposition apparatus

Abstract: A chemical vapor deposition apparatus includes a gas mixing chamber and a water-cooled reaction chamber with adjustable water-cooled baffle between them. A wafer is clamped face down to a chuck and an inert gas such as helium is forced between the chuck and the wafer to insure proper heat conduction from chuck to wafer. The chuck can be radiantly heated from above and operated in a plasma-enhanced mode. A wafer loading apparatus driven by a computer is isolated by a loadlock during deposition to enhance cleanliness. The chamber can be plasma cleaned to reduce downtime.

Method and apparatus for controlling thermal transfer in a cyclic vacuum processing system

Abstract: Apparatus for providing thermal transfer between a semiconductor wafer and a heat sink or source in a vacuum processing chamber includes a platen against which the wafer is sealed to define a thermal transfer region therebetween. The platen includes a passage for gas flow between the chamber and the thermal transfer region. The apparatus further includes a valve for controllably opening and closing the passage and a controller for closing the valve when the pressure in the chamber reaches a predetermined value. Gas at the predetermined pressure, typically 0.5 to 100 Torr, is trapped in the thermal transfer region and conducts thermal energy between the workpiece and the platen. In a preferred embodiment, a plurality of platens are positioned on a rotating disc in an ion implantation system and a centrifugally operated valve is utilized to close the passage.

Nebulizer particularly adapted for analytical purposes

Abstract: A nebulizer for analytical purposes includes a needle through which flows a liquid to be nebulized. The liquid flows from the needle onto a diaphragm planar surface that is vibrated in successive pulses. A continuous bridge of the liquid subsists between the liquid and the planar surface when the diaphragm is in the non-vibrating state. The liquid is nebulized to an aerosol when the diaphragm is pulsed. The needle and diaphragm are always spaced from each other. A wick on the planar surface in contact with the film removes excess amounts of the liquid not involved in forming the aerosol. The diaphragm vibration is pulsed by a piezoelectric crystal that responds to an FM wave whose frequency is swept over a band spanning the resonant frequency of the crystal. The crystal is configured as a spherical segment to direct a focused pressure wave on the diaphragm via a liquid medium. The diaphragm has a thickness that is about one-half wave length of the pressure wave supplied to the liquid medium by the crystal, to provide destructive interference of waves reflected from opposite faces of the diaphragm. A carrier gas for the nebulized aerosol is supplied to the diaphragm planar face to form a curtain about the liquid flowing from the needle to the diaphragm. The liquid circulates between the diaphragm and crystal to cool them and enable gases in the liquid to be removed.

Concurrent NMR analysis of multiple samples

Abstract: Multiple concurrent sample processing in a single spectrometer is accomplished for the respective situation of (a) samples of strongly dissimilar character and (b) samples of similar character. For the class (a) samples yielding non-superimposed line spectra are axially separated by susceptability matched delimiters in a sample tube and analyzed in a conventional spectrometer. For the class (b), resonance response from axially separated samples induce signals in respective observe coils similarly spaced along the axis of said sample tube. Plural samples disposed in non-colinear parallel alignment are also treated in this manner.

Standing wave linear accelerator having non-resonant side cavity

Abstract: A linear accelerator includes cascaded standing wave main cavities with approximately the same resonant frequency and plural side cavities. A charged particle beam travels longitudinally through the main cavities. An electromagnetic wave excites the cavities with a frequency that is approximately the same as the resonant frequency of the main cavities. There is normally a fixed electromagnetic energy phase shift in adjacent main cavities. The resonant frequency of at least one side cavity is adjusted so it differs from the electromagnetic wave frequency. The detuned side cavity resonant frequency causes: (a) a change in the normal fixed phase shift of the main cavities adjacent the one side cavity and (b) a decrease in electric field strength in cavities electromagnetically downstream of the one side cavity relative to the electric field strength in cavities electromagnetically upstream of the one side cavity. In different embodiments, the electromagnetic wave is injected into a cavity where the particle beam is upstream and downstream of the one side cavity, respectively.

High speed pattern generator for electron beam lithography

Abstract: A pattern generator for supplying beam deflection and blanking signals in an electron beam lithography system which writes polygon pattern features by sweeping a beam of rectangular cross-section over each polygon and simultaneously varying the length of the rectangular cross-section. The pattern generator converts polygon size and shape data to an upper shape signal and a lower shape signal. The shaping signals are subtracted to provide a beam length signal. The lower shape signal controls the beam position during writing of the polygon. The pattern generator further includes a ramp generator for sweeping the beam over the polygon. The ramp signal and shaping signals are synchronized by detecting the points in the sweep at which polygon turn points occur. The shape signal generators utilize interleaved operation for high speed. A blanking circuit provides uniform exposure of pattern features by controlling the width of the rectangular beam. The beam is ramped on and off at a rate which matches the rate of the sweep signal.

Magnetron sputter device having planar and concave targets

Abstract: A magnetron sputter device includes a first target having a planar emitter surface and a second target having a concave emitting target defined by a side wall of a frustum of cone. Separate plasma discharges for the targets are confined by separate electromagnet derived magnetic fields, coupled to the targets by pole pieces.

Method and apparatus for gross leak detection

Abstract: A helium mass spectrometer leak detector includes a spectrometer tube connected to the inlet of a high vacuum pump. Helium tracer gas passes in reverse direction through the high vacuum pump from the foreline to the spectrometer tube. Relatively high pressure gross leak tests are performed, while maintaining the foreline of the high vacuum pump at the required operating pressure of about 100 millitorr, by passing the tracer gas in reverse direction through one or two stages of a mechanical vacuum pump. Test port pressures up to about atmosphere can be accommodated, with only a single mechanical vacuum pump required. According to another feature, high test port pressures are accommodated using a variable flow restrictor and reverse-connected mechanical vacuum pump in combination.

Vacuum pick for semiconductor wafers

Abstract: A vacuum pick suitable for removing semiconductor wafers from and replacing wafers in a cassette holder. The vacuum pick includes a thin profile housing having a wafer support surface with a cavity therein, a resilient, flexible member covering a portion of the cavity to form an enclosure, and a rigid chuck mounted on the flexible member so as to permit movement of the chuck relative to the housing. The chuck includes a wafer-receiving surface connected through a passage to the enclosure. When a vacuum is applied to the enclosure, the wafer and the chuck are retracted against the housing and held firmly in place. The chuck tilts relative to the housing when it contacts a tilted wafer, thereby insuring reliable attachment to the wafer.

Collimation system for electron arc therapy

Abstract: An electron collimation system for electron arc therapy treatments consists of a slit collimation system which is movable with the electron beam applicator and is designed to allow for dose compensation in the sagittal direction and a hoop-and-clamp assembly for final field shaping. By correctly designing the shape of the slit in the former and properly adjusting the components of the latter, it is possible to accomplish quite uniform shielding without causing any weight of the shielding material to rest on the patient.

Wafer lifting and holding apparatus

Abstract: An automatic sputtering apparatus for coating semiconductor wafers uses shuttle wafer carriers and elevators to handle wafers within the apparatus. The wafer carrier has a hole in the center. One side of the wafer carrier is opened, thereby forming a throat in the shuttle wafer carrier in the form of the letter C. The elevator has a cantilevered shaft. The upper part of the shaft of the elevator is centered under the wafer while the lowest part of the cantilevered shaft is under a point outside the wafer carrier. The connecting portion of the shaft passes through the throat of the wafer carrier as the wafer is lifted. Since the lifting portion of the shaft is outside the wafer carrier, the shuttle can move with the elevator in the up position. The pedestal for holding the wafer on the elevator is equipped with arms which project upward at an angle to the horizontal, thereby confining the wafer to a pedestal.

Magnetron sputter device using the same pole piece for coupling separate confining magnetic field to separate targets subject to separate discharges

Abstract: A magnetron sputter device includes separate first and second targets over which first and second discharges are formed by separate ionizing electric fields and separate confining magnetic fields. The separate confining magneticfields include first and second magnetic circuits through the first and second targets, respectively. The first magnetic circuit includes first and second pole pieces for coupling magnetic flux from a first magnetic field source to the first target. The second magnetic circuit includes the second pole piece and a third pole piece for coupling magnetic flux from a second magnetic field source to the second target. The magnetic circuits and the magnetic field sources are arranged so that magnetic fluxes from the first and second magnetic field sources flow in opposite directions through the second pole piece.

A Small Diameter Standing Wave Linear Accelerator Structure

Abstract: A compact, small diameter, standing-wave linear accelerator structure suitable for industrial and medical applications is presented. The novel structure utilizes a new type of coaxial cavity as the coupling cavity for ?/2 mode, standing-wave operation. This structure offers a significant reduction in overall diameter over the side-coupled, annular ring, and existing coaxial coupled structures, while maintaining a high shunt impedance and large nearest neighbor coupling (high group velocity). A prototype 4 MeV, 36 cm long, S-band accelerator incorporating the new structure has been built and tested. Theoretical accelerator design parameters, as well as experimental results, are presented.

Magnetron sputter etching system

Abstract: A planar magnetron etching device having a movable magnetic source which is moved with respect to a substrate to cause lines magnetic flux parallel to the surface of the substrate to sweep above the surface of the substrate during the etching process.

Triple-pane waveguide window

Abstract: A waveguide window contains a central transverse pane of a material with high dielectric constant such as alumina ceramic. The central pane is an integral number of half-wavelengths thick. On each side of the central pane and immediately adjacent it is a side pane of material with relatively low dielectric constant such as fused quartz. The side panes are odd numbers of quarter-wavelengths thick. The dielectric constants of the side panes are preferably the square root of the dielectric constant of the central pane. The improved wave impedance matching provides a low wave reflection over a wide frequency band.

Workpiece lifting and holding apparatus

Abstract: An automatic sputtering apparatus for coating semiconductor wafers uses shuttle wafer carriers and elevators to handle wafers within the apparatus. The wafer carrier has a hole in the center. One side of the wafer carrier is opened, thereby forming a throat in the shuttle wafer carrier in the form of the letter C. The elevator has a cantilevered shaft. The upper part of the shaft of the elevator is centered under the wafer while the lowest part of the cantilevered shaft is under a point outside the wafer carrier. The connecting portion of the shaft passes through the throat of the wafer carrier as the wafer is lifted. Since the lifting portion of the shaft is outside the wafer carrier, the shuttle can move with the elevator in the up position. The pedestal for holding the wafer on the elevator is equipped with arms which project upward at an angle to the horizontal, thereby confining the wafer to a pedestal.

Method for doping semiconductor wafers by rapid thermal processing of solid planar diffusion sources

Abstract: Doping of a semiconductor wafer is accomplished by placing the wafer in close proximity to a solid planar dopant source and rapidly heating the combination to a high temperature for a short time in a rapid thermal processing apparatus.

Target assembly for sputtering magnetic material

Abstract: An optimized annular sputter target assembly for use in sputtering magnetic material, comprising a thin target piece of magnetic material mounted on a backing structure of nonmagnetic material. Said backing structure provides means for easy mounting and removal of the target assembly and for providing good thermal and electrical contact with the cooling wall of the sputter source. The target piece has a portion extending radially outwardly from said cooling wall thereby providing greater target surface area.

Tungsten-iridium impregnated cathode

Abstract: Porous agglomerates (14) are made from pure tungsten by sintering fine particles together and mechnically breaking down the mass to form some agglomerates (14) considerably larger than the particles. These agglomerates (14) are mixed with fine iridium powder (18) and sintered to form a porous mass. The mass is machined to the cathode shapes (10') and impregnated with an alkaline earth aluminate (18). The large agglomerates (14) alloy with the iridium only on their outer surface. Their pure tungsten interior provides the surfaces to reduce the alkaline earth oxide to the metal which activates the cathode.

In-line beam scanning system

Abstract: A system for scanning a beam of charged-particles across a target is described which compensates for energy dispersion in the beam. A time-varying magnet with circular pole pieces is used to sweep the beam left to right. Two wedge-shaped magnet dipoles, one on each side of the center line are used to bend the beam parallel to the center line and compensate for beam energy dispersion.

History of microwave electron linear accelerators for radiotherapy

Abstract: Some of the far reaching contributions of Henry S. Kaplan are described which helped launch the development, improvement, and widespread use of microwave electron linear accelerators in radiotherapy. These are presented in historical relationship to the fundamental inventions and developments upon which modern medical accelerator technology is based.

Open loop control for spectrophotometer atomizer furnace

Abstract: Heating apparatus particularly for flameless atomization in spectrophotometers includes a variable electrical power source and a resistive heating element A desired final temperature and the rate of change of the element temperature (ramp rate) is input to a control circuit A storage means is provided for storing data relating the heating element temperature to the energy input (voltage) to the heating element required to maintain the heating element at a constant temperature Processing means calculates from the various data the voltage required to be supplied to the element by the power source to change the temperature thereof at the selected ramp rate until it reaches the final temperature In spectrophotometers the apparatus accurately controls the carbon rod temperature through drying, ashing and atomizing stages

Electron—Atom Bremsstrahlung

Abstract: In this chapter we discuss electron bremsstrahlung, the radiation of a photon in the scattering of an electron from an atom or ion. We shall focus our attention on incident electrons with kinetic energiesT i in the 100-eV to 10-MeV range (and especially for 1 keV to 1 MeV) and radiated photons in the vacuum ultraviolet, X-ray, and soft γ-ray regimes. Electron bremsstrahlung is only one particular consequence of the general coupling of the electromagnetic field and matter fields. The process is closely related, as we shall see, both to elastic electron scattering and to direct radiative recombination, in which the incident electron does not scatter but is captured by the atom. It is also closely related to pair production. Other charged particles also radiate in scattering, as follows from Maxwell’s equations, and we shall discuss the most closely related case of positron bremsstrahlung. More generally, the electromagnetic coupling to matter fields is responsible for radiative versions of all nonradiative processes, including “inverse bremsstrahlung” processes in which electromagnetic radiation is absorbed rather than emitted.

Thermal barrier for variable temperature nmr

Abstract: An NMR system for obtaining high resolution spectroscopic measurements at a selected temperature includes gradient correcting means (40) disposed in proximity to an NMR probe (32), for imposing desired gradients on the volume occupied by the sample (35) within the probe (32). A heat exchange gas is impelled through a heat exchanger (33) and then surrounds the sample (35) to bring the sample (35) to the desired temperature. A thermal barrier (72), innocuous to RF excitation and of relatively low magnetic susceptibility protects the gradient correcting means (40) from drift due to heat exchange with the heat exchanging gas.