Abstract: Two stage cryogenic pump having axially spaced baffle members for shielding the second stage from external thermal radiation while permitting substantially unimpeded gas flow from the inlet opening to the second stage.

Abstract: A cryogenic apparatus comprises refrigeration means utilizing a two-stage expansion of compressed helium gas that circulates in a closed loop, whereby a first pumping stage can be maintained at a temperature in the range from 50.degree. K. to 80.degree. K. and a second pumping stage can be maintained at a colder temperature in the range from 10.degree. K. to 20.degree. K. The first pumping stage comprises an array of louvers of chevron configuration. These louvers enclose the second pumping stage, and serve as baffles to shield the pumping surfaces of the second stage from thermal radiation that would reduce the usable refrigeration capacity of the second stage for removing gases from a chamber to be evacuated. The chevroned baffles also protect a cryosorbent coating on the interior surfaces of the second stage from becoming iced or plugged by gas species that cryocondense at the higher temperature of the first stage.

Abstract: Two-stage cryogenic pumping apparatus having individual plate members with cryosorbent coatings secured by removable fasteners to permit easy assembly and replacement of the plate members. The plate members are spaced apart to provide relatively unrestricted access to the cryosorbent material for the gases to be adsorbed thereon.

Abstract: A metal alloy for a thin film deposition process, an article coated with a thin film of the metal alloy and the method of thin film deposition coating of an article with the metal alloy is provided. The metal alloy consists of 78-97.5% Cr, 2-20% of at least one element selected from the group consisting of Mo, Ni and Co, and 0.5-2% of scavenger element selected from the group consisting of Al, B, Be, Ce, Hf, La, Nb, Nd, Si, Ta, Th, Ti, U, Y and Zr, all by weight. Two or more elements selected from the group of Mo, Ni and Co may be included in the metal alloy in the total proportion of 2-20% by weight. The deposition coating method may be either evaporation or sputtering.

Abstract: A filter for megavolt X rays has an absorbing member shaped to provide greater thickness for rays in the direction of higher intensity, e.g., the axis of the electron beam. A second absorbing member of a material of different atomic number is shaped to provide greater thickness for rays in the direction of higher photon energy, e.g., said axis. By selecting the combined shapes, both the intensity and the effective photon energy can be equalized over the field of radiation. Thin removable shims may be added for further adjustment. A neutron filter may also be added.

Abstract: Variable energy selection is accomplished in a side cavity coupled standing wave linear accelerator by shifting the phase of the field in a selected side coupling cavity by .pi. radians where such side coupling cavity is disposed intermediate groups of accelerating cavities. For an average acceleration energy of E.sub.1 (MeV) per interaction cavity, and a total number of N interaction cavities, the total energy gain is E.sub.1 (N-2N.sub.1) where N.sub.1 is the number of interaction cavities traversed beyond the incidence of the phase shift. The phase shift is most simply accomplished by changing the selected side cavity configuration mechanically in repeatable manner so that its resonant excitation is switched from TM.sub.010 mode to either TM.sub.011 or TEM modes. Thus, the total energy gain can be varied without changing the RF input power. In addition, the beam energy spread is unaffected.

Abstract: In an apparatus for removing a selected first gas from a chamber at a controllably variable pumping speed while maintaining a substantially constant pumping speed for removing a second gas from the same chamber, a flow restricting device is disposed between the chamber and a device that pumps the first gas. The flow restricting device comprises a stationary member having an apertured portion through which the first gas can flow from the chamber to the pumping device. Restriction of the flow of the first gas to the pumping device is accomplished by covering the apertured portion of the stationary member with a movable member to the extent necessary to provide the desired pumping speed for the first gas. The stationary member is maintained at a cryogenic temperature higher than the condensation temperature of the first gas, but at a value at which the second gas condenses.

Abstract: An oil pool in a rotary vane, oil sealed mechanical vacuum pump casing is cooled by air drawn by a relatively low pressure and low speed laminar flow fan mounted on a motor shaft for the pump and positioned in a shroud between end plates for the motor and casing. The air pumped by the fan flows axially relative to the shaft through a horizotally extending slot at the bottom of the shroud and vertically extending slots on the sides of the shroud. The pumped air flows against vertically and horizontally extending fins respectively on the pump casing bottom and sides. The vertically extending fins at the bottom of the casing have bases slightly above the horizontal slot at the bottom of the housing so air flowing through that slot flows against the bases of the fins at a shallow angle. A vertical surface of the housing remote from the fan and the shroud has vertically extending fins that are aligned with the vertically extending fins on the bottom of the casing.

Abstract: In a high-power grid-controlled electron tube, a common anode receives electrons from a modular electron source having a common support structure to which are attached a plurality of modules. Each module has at least one cathode and grid mounted on a base which is individually attached to the support structure. The grids are approximately flat sheets of carbon with apertures to pass the electrons. Pyrolytic graphite is a preferred grid material.

Abstract: A mechanical rotary vane vacuum pump has high and low vacuum stages for a pumped gas. Each stage includes a rotor for vanes cyclically driven about a common axis that is eccentric to a cylinder of a stator; the stator of each stage includes an inlet and outlet for the pumped gas. An oil seal between inlets and outlets for each stage is in a narrow gap between the stator and rotor. An interstage structure includes a flow path between the stages for the pumped gases and a shaft drivingly connected the rotors of the stages. An oil flow path comprises a first passage through the interstage structure leading radially to the shaft. The shaft includes diametrically opposed oil metering flats or cavities longitudinally aligned with an outlet of the first passage. A second passage through the interstage structure is longitudinally aligned with the cavities and leads tangentially from the peripheries of the shaft and a bore for the shaft.

Abstract: An air bearing sample spinner for use in an NMR probe has a first air bearing established between frusto-conical mating surfaces of rotor and stator to provide levitation and rotation. A cylindrical portion projects from the rotor into a similar coaxial cylindrical portion of the stator where a journal bearing is provided for centering of the rotor in the stator housing.

Abstract: A gas ballast device for an oil sealed mechanical rotary vane vacuum pump prevents vapor condensation in the outlet port region of the low vacuum stage of the pump as a vane cyclically approaches the outlet port, whereby molecules of condensed vapor in the oil do not flow back to the inlet port of the low vacuum stage through the oil seal between the inlet and outlet ports. A flow path for atmospheric air leading to the outlet port region includes a tortuous, constricted fluid passageway. An outlet passage connecting the tortuous, constricted fluid passageway to the outlet port region is positioned so that an orifice thereof into the outlet port region is filled with and sealed by oil except during a small portion of each vane cycle immediately after the vane passes the orifice, whereby no movement of mechanical parts is employed to control air flow in response to the cyclical movement of the vanes past the orifice.

Abstract: A diffusion pump includes a flat metal boiler plate having an upper face defining a floor for a pool of a vaporizable diffusion pump fluid or oil and a lower face against which the metallic sheath of a tubular electric heater is pressed by a coextensive massive clamping plate. The heater has a tendency to be overheated if only air is its thermal load. To prevent overheating of the heater because of variations in the geometry of the heater sheath which tend to cause air spaces between the sheath and the face of the boiler plate, a thin flexible metal crush plate is disposed between the clamping plate and the heater. The crush plate has a plurality of spaced, raised dimples adapted to contact many portions of the heater sheath throughout the length of the sheath. As the clamping plate, the flexible plate and the heater are urged toward the boiler plate by nut and bolt assemblies securing the clamping plate to the boiler plate, the dimples are deformed whenever they are in contact with the heater sheath.

Abstract: A translation mechanism for linearly moving a beam stopper in radiation therapy apparatus includes first and second arms pivotally mounted to a support and third and fourth arms pivotally mounted to the first and second arms. The third and fourth arms are attached to the beam stopper and can comprise part of the beam stopper. In one embodiment, the third and fourth arms include disc shaped portions stacked in axial alignment with a drive motor attached to one disc portion ahd having a drive shaft axially aligned with and coupled to the other portion whereby relative rotation of the disc portions effects linear translation of the beam stopper.

Abstract: A mounting fixture provides rotational freedom in each of two orthogonal planes for motion of an X-ray source and diametrically opposed image intensifier. The relative positions of the X-ray source and image intensifier can be inverted by a simple 180.degree. rotation about a third axis orthogonal to at least one of the two axes defined by the two rotational degrees of freedom.

Abstract: Scanning apparatus is disclosed for use in computerized axial tomography systems. The apparatus includes an assembly rotatable about an axis extending along a central opening defined therein, and means for positioning the body portion to be examined within the central opening. A source of penetrating radiation is mounted on the assembly toward one side thereof and provides radiation in the form of a fan beam. Signal processing and conditioning means mounted on the assembly and movable therewith, receive the output signals from the detector means and amplify and convert same to digital form. Slip ring interconnection means, rotatable with the assembly, receive the outputs from the signal processors and conditioners and interfeed these signals to a computerized image reconstruction station. Slip rings rotatable with the assembly also provide interconnection enabling power and control inputs to the radiation source and to other portions of the apparatus.

Abstract: The temperature of a substrate being coated by molecular beam epitaxial techniques is monitored during the deposition process. The substrate is mounted on a holder that is brought by a carriage to a treating station where the deposition occurs. At the station, a pair of metal contact pins selectively contact a surface of the holder. One of the contact pins and the surface, when contacting, form a first thermocouple junction; a second thermocouple junction is formed by the second contact pin and surface. The thermocouple junctions have dissimilar properties so that a voltage indicative of the temperature of the object is derived between them while the pins and surface contact each other. The holder is transferred between the treating station and carriage by translational and rotational motion of the holder and the carriage. While the translational and rotational motions occur, contact between the surface of the holder and the pins is prevented.

Abstract: A predetermined pressure ratio is maintained between a foreline and a load port of a vacuum diffusion pump including a bath of oil that is vaporized by a heater. A property of the pump is sensed to derive a signal indicative of the pressure ratio. The signal is compared with a set point value to derive an error signal that controls the amount of power continuously supplied by the heater to the oil bath. The sensed property can be the RMS power supplied by the heater, the heat supplied to the bath, or the density of vaporized fluid in the pump.

Abstract: Scanning apparatus is disclosed for use in computerized axial tomography systems. The apparatus includes an assembly rotatable about an axis extending along a central opening defined therein, and means for positioning the body portion to be examined within the central opening so that the axis of assembly rotation is perpendicular to a plane passing through the bodily structures to be examined. A source of penetrating radiation is mounted on the assembly toward one side thereof and provides radiation in the form of a fan beam. Detector means for the radiation are positioned on the assembly opposite the source, enabling detection of radiation which traverses laterally and is not absorbed in the thin body section in which the aforementioned plane resides. Means are provided for rotating the assembly so that the fan beam impinges upon said body portion at a plurality of incident directions.

Abstract: System and method are set forth enabling reconstruction of images of desired "frozen action" cross-sections of the heart or of other bodily organs or similar objects undergoing cyclic displacements. Utilizing a computed tomography scanning apparatus data is acquired during one or more full rotational cycles and suitably stored. The said data corresponding to various angular projections can then be correlated with the desired portion of the object's cyclical motion by means of a reference signal associated with the motion, such as that derived through an electrocardiogram--where a heart is the object of interest. Data taking can also be limited to only the times when the desired portion of the cyclical motion is occurring. A sequential presentation of a plurality of said frozen action cross-sections provides a motion picture of the moving object.