Abstract: A particle detector (10, 12, 70) employs an upconversion laser medium (22, 72) to produce emission radiation (32) at an emission wavelength (56) that is less than the wavelength of the pumping radiation (26). The shorter emission wavelength (56) provides a significant increase in the scattering intensity (I.sub.sc) detected by the particle detector (10, 12, 70), based on the equation I.sub.sc =I.sub.o k/.lambda..sup.4, where I.sub.o represents the intensity of emission radiation (32), .lambda. represents the wavelength (56) of the emission radiation (32), and k represents a coefficient related to particle size. In addition, the emission wavelength (56) of the upconversion laser medium (22, 72) can be frequency doubled to excite biological chromophores such as tryptophan, NADH, and flavin compounds that absorb in the UV spectral range and emit fluorescence at longer wavelengths that can be discretely detected to determine the presence of biological particles.

Abstract: A particle detector employs a resonant cavity having a chromium doped colquiriite crystal lasing medium, such as an Cr:LiSrAlF.sub.6 crystal, adjacent to an intra-cavity view volume. The resonant cavity is defined by two spaced apart mirrors, with the crystal positioned between them, defining a light path through the crystal, but most of the light does not escape past the mirrors. The view volume is positioned in the light path, between the first mirror and the laser medium, to introduce particles into the resonant cavity so that light impinging thereupon produces scattered light. A detector is disposed to sense light scattered from the view volume and produces signals proportional to the light sensed. Harmonic generators are used in alternate embodiments to produce sub-micron wavelengths. Optical coatings on mirrors forming cascaded cavities are used to isolate a harmonic wavelength in a cavity containing the view volume.

Abstract: A particle counter of the condensation nucleus type wherein a primary stream of fluent material containing particles enlarged by vapor condensate of a working fluid flow through a viewing volume. A secondary stream of fluent material, termed purge gas, surrounds the primary stream of fluent material as the primary stream traverses the view volume, thereby providing a boundary layer of fluent material, reducing turbulence of the primary stream. The two streams are merged after passing through the view volume and the merged stream is drawn into one or more coalescent filters for conversion of vapor to working fluid which is then recycled for reuse, thereby extending the life of the working fluid and preventing escape of vapor which might contaminate the ambient environment.

Abstract: A particle detector employs a laser having a solid-state lasing medium, such as an Nd:YAG crystal, disposed in a resonant cavity, and includes an intracavity view volume. The resonant cavity is defined by two spaced apart mirrors, with the laser medium positioned between them, defining a light path. A pump source is optically coupled to drive the laser medium to produce coherent light having a first wavelength. The view volume is positioned in the light path, between the first mirror and the laser medium, to introduce particles into the resonant cavity so that light impinging there-upon produces scattered light. A detector is disposed to sense light scattered from the view volume and produces signals proportional to the light sensed. A displaying device, such as a pulse height analyzer, is in electrical communication to receive the signals produced by the detector to quantitatively display the intensity of the light sensed.

Abstract: A particle counter including a modulator to allow electronically determining calibration. The modulator is connected to a driving circuit of a source of light to cause the light to emit a beam of a constant amplitude, representing at least one particle of predefined size. Light transmitted along an optical axis changes in intensity in response to a signal produced by the modulator. A detector is positioned to sense the change in intensity to produce signals proportional to the light sensed. A displaying device, such as a pulse height analyzer, is in electrical communication to receive the signals produced by the detector to quantitatively display the change in intensity of the light.

Abstract: A condensation nucleus counter features an entropy control mechanism to regulate the entropy of a vaporized fluid present in a saturator, thereby facilitating supersaturation of the same about particulates entrained in a sample gas stream before the same passes through a condenser. The condensation nucleus counter includes a supply of sample gas, conduits adapted to allow the sample gas stream to flow therethrough, a saturator, a condenser and an optical detector, all of which are in fluid communication with each other. The manifold is disposed between the conduit and the saturator, and also a temperature control device. The manifold comprises a feed chamber and a plurality of channels positioned so that the sample gas stream entering the feed chambers evenly divides into a plurality of flows, with each flow entering the saturator. The temperature control device regulates the temperature difference between the flows entering the saturator and the vaporized fluid contained so as to be within a specified range.

Abstract: Provided is a gravity feed flow controller in which fluid communication with a particle sensor allows gas bubbles, present in a liquid flowing therethrough, to escape, under influence of a buoyant force associated therewith, before entering the sensor.

Abstract: A particle detector employs a laser having a solid-state lasing medium, such as an Nd:YAG crystal, disposed in a resonant cavity, and includes an intracavity view volume. The resonant cavity is defined by two spaced apart mirrors, with the laser medium positioned between them, defining a light path. A pump source is optically coupled to drive the laser medium to produce coherent light having a first wavelength. The view volume is positioned in the light path, between the first mirror and the laser medium, to introduce particles into the resonant cavity so that light impinging thereupon produces scattered light. A detector is disposed to sense light scattered from the view volume and produces signals proportional to the light sensed. A displaying device, such as a pulse height analyzer, is in electrical communication to receive the signals produced by the detector to quantitatively display the intensity of the light sensed.

Abstract: Small, mobile particles in a fluid are optically detected by an apparatus having spaced apart reflectors bordering and defining an optical cavity into which a light beam is introduced. The reflectors are arranged along axes which are slightly misaligned such that the light beam is introduced at a low angle, barely over the edge of one of the reflectors, and is repeatedly reflected between the two reflectors, overlapping itself many times in a view volume located within the optical cavity, thereby increasing the intensity of detected particles. A fluid flow is introduced into the view volume and the light scattered by particles as they pass through the intensely illuminated view volume is received by a detector which observes the view volume. The detector produces a signal which is indicative of characteristics such as the number or size of particles.

Abstract: Apparatus for monitoring fluid contaminant level that includes a light source positioned on one side of a fluid sample path for directing light energy into fluid flowing in the sample path, a photosensor positioned on the same side of the sample path, and a reflector positioned on an opposing side of the sample path for receiving light from the source transmitted through the sample fluid and reflecting such light back through the fluid to the photosensor. The photosensor provides an electrical signal as a function of intensity of light incident thereon from the light source after having twice passed through the fluid, and the concentration or level of contaminants in the fluid is indicated as a function of such electrical signal. Thus, the concentration of contaminants that extinguish light energy transmitted through the fluid is indicated as an inverse function of light intensity at the photosensor, and may be compared to a preset target threshold level for indicating an undesirably high contamination level.

Abstract: An apparatus for detecting and counting particles in a gas stream flowing at a preselected rate, wherein the apparatus includes a multi-tier inlet manifold and a plurality of sensors. The inlet manifold divides an aggregate sample flow into a plurality of substantially identical partial sample flows. Each partial sample flow enters one of the functionally duplicative sensors and is intersected by an incident beam to define a view volume. Particles contained within the partial sample flows scatter light as the particles pass through the view volume. The scattered light is directed to a photodetector which provides a signal having characteristics corresponding to the sensed light. Particle detection in each view volume is operationally independent of the others, but the information is combined to provide a total particle count of the aggregate sample flow.

Abstract: An apparatus and method for particle detection which includes a plurality of sample regions. A sensor body has internal walls which define spaced apart sample regions, with each sample region having an inlet port and an exhaust port. An aggregate sample flow is divided into partial flows which are directed from the inlet port to the exhaust port of an associated sample region. A light source, typically a laser, is positioned to project an incident beam along a light path which intersects each of the partial sample flows through the sample regions. Particles contained within the partial sample flows scatter light as the particles pass through the incident beam. The light from a sample region is directed to a photodetector which provides a signal corresponding to the sensed light. Particle detection in each sample region is operationally independent of the others, but the information is combined to provide a total particle count of the aggregate sample flow.