Abstract: In a chromatographic column oven, a particular arrangement of a fan, heater and baffles provides low thermal gradients and rapid oven cool-down. Low thermal gradients are obtained by providing an air circulation pattern that promotes optimum mixing of the air within the oven enclosure. A fast cool-down time is obtained by providing a high-velocity air flow along the walls of the oven enclosure. A fan is mounted substantially at the geometric center of a first wall of the oven enclosure. A second wall of the enclosure, which faces the first wall, comprises a door for providing access to the oven enclosure. An elongate heating element is mounted on the first wall so as to substantially surround the periphery of the fan. A plurality of baffles are mounted symmetrically around the periphery of the fan on and extending perpendicularly from the first wall. A gap is provided between each particular baffle and the wall or walls intersecting the first wall nearest that particular baffle.

Abstract: An improvement is disclosed for use in a chromatographic system of the type including detector means providing a detector output signal indicative of the level of a component sought to be determined, detector output amplifier means for receiving the signal, an error signal balancing loop connected to the amplifier output to provide a balancing signal in feedback relationship to the amplifier, and means for adjusting the sensitivity range of the amplifier.

Abstract: A slit device for use in optical systems, and in particular for use in spectrophotometers. The device comprises an integral plate structure having two jaw assemblies, each of which includes two jaws arranged to define a slit between them, and flexible hinge means interconnecting the two jaws to permit relative movement such that the slit width can be varied. Each hinge means includes a part of the plate structure which has been turned on edge relative to the plate structure parts forming the associated jaws so as to have maximum flexibility in the general direction of relative movement of the jaws. Two bridging portions are also formed as integral parts of the plate structure, and each bridging portion connects one of the jaws of one jaw assembly with a jaw of the other assembly. Thus, movement of one jaw in one assembly is transmitted to a jaw of the other assembly through one of the bridging portions.

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.

Abstract: Method and apparatus for damping oscillatory behavior and reducing the effective time constant incident to reattainment of equilibrium pressure and flow following a change in fluid pressure or flow rate in a liquid chromatography system. The system may include a chromatographic column, a reservoir for a slightly compressible liquid mobile phase, and piston means cooperating with the reservoir and normally driven at a velocity which is constant over a given time interval, for enabling pumping of the mobile liquid phase through the chromatographic column. In accordance with the invention, a transient velocity component is superimposed upon the constant velocity component of the mobile liquid phase caused by the piston motion. The transient velocity component is proportional to the reservoir volume and to the time derivative of pressure in the reservoir. The additionally imparted motion damps the transient oscillations that arise from any pressure change imposed on the slightly compressible liquid phase.

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.

Abstract: In a double beam spectrophotometer employing a rotating optical chopper to direct a beam of electromagnetic radiation alternately through sample and reference channels to a photomultiplier tube, a beam interrupter is used in combination with a photodiode and a photocell to generate a square wave signal having a predetermined temporal relation to the rotation of the optical chopper. The square wave signal is integrated to provide a triangular waveform, whose maxima and minima correspond, respectively, to the passage of the beam through one or the other of the sample and reference channels, and whose cross-over points with respect to a zero reference level correspond to dark intervals during which the beam is blocked from entering either channel.

Abstract: A reproducible mounting for use in conjunction with prealigned optional assemblies. The mounting comprises a base member and a mating member attached thereto by fastening means cooperating with first, second and third noncollinerly disposed mounting holes whereby all six degrees of freedom between the base and the mating member are eliminating.

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.

Abstract: A metal foil or plate for use in the slit mechanism of optical systems and having two jaw sections between which the slit is defined. The jaw sections are interconnected through an integral hinge portion of the plate which is adaptable to flex so that the jaw sections can move towards and away from each other and thereby vary the slit width. When incorporated in actual slit mechanism, the plate, or at least a portion thereof, is interposed between two mounting surfaces so that the jaw sections are maintained coplanar, and an actuator for causing relative movement of the jaw sections is connected to another section of the plate which is integrally connected with each jaw section through a relatively narrow plate portion. The last mentioned section of the plate and the hinge means form the only connections between the jaw sections.

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.

Abstract: Single and dual beam flow cells for liquid chromatography that provide good detectability and linear response with small sample volumes. A cylindrical window surrounds the sample flow path to permit focusing convergent light rays through the center of the flow path and along optical paths of equal length through the cell. Optical stops limit the light passing through the cell to convergent rays incident to the window surface. A wide acceptance angle for the rays results in high light transmission and averages variations in light output along the light source. A dual beam flow cell utilizes a common exit for the sample and reference liquids. The flow cells are economically constructed for direct coupling to a chromatographic column by using a standard compression fitting union and can be used in a single wavelength or discrete wavelength detector, or in a spectrophotometer.

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.

Abstract: An injection apparatus and method for use in high pressure liquid chromatography. A cylindrical sample holding means containing several sample cells is maintained in a chamber whose pressure is approximately equal to that of the head of the chromatograph separation column. The sample cells are bores through the cylinder, parallel to its axis and spaced along a cylinder of revolution concentric to the axis. The cells are preloaded with samples to be analyzed. Stationary carrier fluid inlet and outlet conduits extend into the chamber above and below corresponding points on the cylinder defined by the sample cell placement. The inlet conduit is connected to a high pressure source of carrier fluid. As the sample holder is rotated, successive sample cells are aligned with the inlet and outlet conduits such that the sample is forced through the outlet conduit into the column.

Abstract: A leak detection system comprising a mass spectrometer tuned to detect the presence of helium in a gas sample, and a gas sample inlet member comprising a multichannel array of capillary passages. In an ideal embodiment, the gas sample inlet member comprises a segment of commercially obtainable multistrand electrical wire encased in an insulating plastic sheath. The spaces between the individual strands provide the capillary passages for the admission of the gas sample.

Abstract: A metallic foil coated with scandium tritide is treated so as to manifest a legally acceptable tritium emanation rate at temperatures above 225.degree. C, thereby becoming usable as a beta particle emitter is ionization detectors such as electron capture detectors or the like operated at high temperatures. The treatment includes heating the foil for a length of time sufficient to cause the foil's tritium emanation ratio to reach a value which corresponds to a legally acceptable emanation ratio for the foil at selected operating temperatures above 225.degree. C.

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 .times. 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.

Abstract: The tubular stainless steel structure of a nuclear reactor fuel rod thermal simulator is heated to nuclear fuel rod operating temperatures by means of a gaseous glow discharge established within the tubular structure. In a preferred embodiment a length of the simulated fuel rod is internally clad with tungsten, or Mo or alloys thereof, hermetically sealed at both ends and filled with a glow discharge sustaining gas such as hydrogen or helium. A center electrode structure, as of tungsten, or Mo or alloys, is centrally disposed within the gas filled tubular envelope. Power is applied between the center electrode and the outer tubular envelope for initiating and sustaining the glow discharge for heating the outer tubular envelope to nuclear fuel rod simulating temperature.

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.

Abstract: A liquid chromatography system, including a reservoir for a liquid mobile phase, a liquid chromatography column, reciprocating pumping means for pumping the mobile phase through the column, and motor means for driving the pumping means through successive reciprocation cycles. Means are provided for controlling the rotational speed of the motor throughout the reciprocation cycle of the pump, so as to provide preselected average rotational speeds over predetermined subintervals of each successive reciprocation cycle. Application of the control cycle is synchronized with the pump cycle so that the said speed control is properly applied over each successive reciprocation cycle.