Abstract: A fast atomic line filter capable of operating at speeds and quantum efficiencies greatly in excess of prior art atomic line filters. Signal light excites to an intermediate energy level the atoms of a contained vapor. A pump beam further excited these atoms to a higher Rydberg level. Simultaneously the atoms are subjected to an electric field that Stark splits the Rydberg level and ionizes very quickly the doubly excited atoms. The resulting ions or electrons are then detected with near unity quantum efficiency by a detector sensitive to either ions or electrons. By directly detecting the resulting ions or electrons the fast atomic line filter has an inherently higher quantum efficiency and much greater speed than prior art ALF's which must use photosensitive detectors to detect fluorescence.

Abstract: Method and apparatus for detecting and differentiating organic compounds based on their electron affinity. An electron capture detector cell (ECD) is operated in a plurality of multiplexed electroncially programmable operating modes to alter the detector response during a single sampling cycle to acquire multiple simultaneous chromatograms corresponding to each of the different operating modes. The cell is held at a constant subatmospheric pressure while the electron collection bias voltage applied to the cell is modulated electronically to allow acquisition of multiple chromatograms for a single sample elution from a chromatograph representing three distinctly different response modes.

Abstract: It has been discovered that a glass envelope at elevated temperature containing a noble gas will result in electrons being evolved. The phenomenon has been employed to construct both argon and helium detectors for gas chromatography.

Abstract: A smoke detector is provided having an ionization chamber (1). For counterbalancing the removal of ions (5.sub.1), taken out of the chamber by the violent air currents (C) passing through this chamber, these air currents are previously enriched with ions (7.sub.

Abstract: Aerosol particles, resulting from the combustion of organic substances with insufficient oxygen supply, usually contain toxic, higher hydrocarbonic substances (e.g. tar) on their surface. These substances, e.g. tar, has the property to be photoelectrically more active than other substances contained in the atmosphere. In the method and apparatus according to the invention an aerosol, i.e. the carrier gas containing the particles to be characterized, is used which has been brought to at least one predetermined temperature sufficient for evaporation or decomposition or preventing condensation of molecules on particles of said aerosol that quench or enhance photoelectric activity. Such aerosol is exposed to electromagnetic radiation and, thereby, activated to electron emission. Thereafter the charge of the photoelectrically positively charged particles is determined by means of size selective filter means which are connected to current or charge measuring equipment.

Abstract: An ionization detector for gas chromatography employs as an electron source a film (66) of gold deposited on an ultra-violet lamp (64) within a cylindrical glass body (60) closed at the ends by PTFE plugs (62 and 68). A jet anode (72) receiving effluent from a chromatographic column has its nozzle (74) adjacent the lamp (64) with a triode collector ring (78) between them. A ground wire (80) is connected to the gold film (66). Ultra-violet radiation from the lamp (64) produces a cloud of gold electrons and the consequent ionization of sample molecules from the jet (72) with a corresponding current when voltage is applied.

Abstract: An improved photoionization detector has a sweep gas inlet which is used to introduce sweep gas near the window of the detector's ultraviolet lamp. The detector's chamber has a vent which allows selective removal of spurious analyte. The detector is adapted to have directly mounted on it, a second detector. Sweep gas used to keep analyte away from the window may be used as a reagent in the second detector. In addition, a means for regulating the ionization lamp voltage is disclosed which prolongs lamp life expectancy.

Abstract: A photoionization type detector utilizes a photoionization sensor to detect the concentration of contaminants in the air, a humidity sensor to detect the water vapor concentration in the air and a temperature sensor to detect the temperature of the air. A microcomputer first calculates the water vapor concentration present in the air from the humidity and temperature sensor readings. Then, the microcomputer applies a predetermined correction factor corresponding to the calculated absolute humidity to the response of the photoionization sensor. This correction factor compensates for the negative cross-sensitivity of the photoionization sensor the humidity in the art and produces an accurate contaminant concentration level which is then displayed.

Abstract: An apparatus for the detection of airborne, low volatility materials, comprising a mobile carrier, preferably made of silica, onto which material to be detected is caused to be deposited. The mobile carrier is arranged to carry the material to the first location where unwanted volatile materials are purged from the trap, then to a second location where the remaining material is caused to be ionized and then to a third location where the ionized material is caused to be lifted off the carrier into an ion collector.

Abstract: In order to provide an ionization-type smoke detector, wherein the radiation from a radioactive source mounted on the inner electrode disposed within the inner ionization chamber also reaches into the outer ionization chamber through a through-hole formed in the intermediate electrode, which is easy to assemble and which has a constitution to prevent scattering of the radioactive source even though inner and outer ionization chambers are provided with the insulation base board for supporting the inner and intermediate electrodes at a predetermined spacing is connected to the printed circuit board by a mounting rod, and the outer electrode surrounding the intermediate electrode and the insulation base board with smoke inlet openings is connected at its end periphery to the printed circuit board, the printed circuit board being connected to the base of the detector by connecting pins.

Abstract: An ionization monitor measures extremely small currents using a resistor containing a beta emitter to generate ion-pairs which are collected as current when the device is used as a feedback resistor in an electrometer circuit. By varying the amount of beta emitter, the resistance of the resistor may be varied.

Abstract: A thermal electron source suitable for use in an electron capture detector comprises a source of stable ultra-violet light, an ultra-violet transparent support member (20,31) located in the path of the ultra-violet light (41) and a thin photo-emissive metallic layer (1A, 24, 33) coated over the surface of the support member remote from the source. In one form the source is a cylindrical mercury vapor lamp (1) with the photo-emissive layer coated directly on the lamp. The coated lamp may then be enclosed within a cylindrical anode (8) with a gas flow between them and the electrical current is measured between the anode and cathode. In an alternative arrangement a planar geometrical assembly is provided. Preferably the photo-emissive material is gold and the carrier gas is an argon-methane mixture.

Abstract: Method and apparatus for differentiating organic compounds based on their electron affinity. An electron capture detector cell (ECD) is operated at pressures ranging from atmospheric to less than 1 torr. Through variation of the pressure within the ECD cell, the organic compounds are induced to either capture or emit electrons. Differentiation of isomeric compounds can be obtianed when, at a given pressure, one isomer is in the emission mode and the other is in the capture mode. Output of the ECD is recorded by chromatogram. The invention also includes a method for obtaining the zero-crossing pressure of a compound, defined as the pressure at which the competing emission and capture reactions are balanced and which may be correlated to the electron affinity of a compound.

Abstract: When using an electron capture detector for the molecular identification of electrophilic compounds, the sensitivity of the detector is made reproducible by controlling the voltage or frequency of the pulses applied to it to maintain a reference current whose set value is produced automatically by the device after determination of the characteristics of the state of the detector, namely a so-called saturation current CM and a so-called spontaneous current CS, according to a law of proportionality between these two currents.In addition, knowledge of these state characteristics gives information on the physical and physicochemical anomalies of the analysis device having an effect on the sensitivity of the detector, and consequently enables them to be remedied.

Abstract: In a method and apparatus for determining the fuel of a fire, an ionization detector is positioned to detect the ionization level in the fire gases. The natural logarithm of the ratio of the ambient ionization current when there is no fire to the change in ionization current from the ambient level is multiplied times a second characteristic, which may be the optical density, the change in carbon monoxide concentration from ambient, or the change in carbon dioxide concentration from ambient. The resulting product of this multiplication will be a value indicating the fuel being consumed in the fire. A chart recorder is connected to record the product of the multiplication.

Abstract: The specification describes a case for use with a hand-portable chemical agent detector for continuously monitoring an atmosphere for the presence of predetermined chemical agents. The detector having means for ionizing air samples and providing at an output terminal electrical signals representative of the mobility spectrum of ionized chemical vapors produced by the ionizing means. The case comprises means defining a chamber in the case for supporting and removably enclosing the detector, means for communicating ambient atmosphere to the chamber, electrical circuit means in the case, the circuit means being adapted to be detachably connected to the detector output terminal when the detector is positioned in the chamber and being responsive to the electrical signals for producing an alarm signal when the signals detect a chemical agent concentration in the atmosphere exceeding a predetermined concentration level, and alarm means responsive to the alarm signal.

Abstract: In operating an ECD in constant current mode, two pulses are implemented either to the same electrode or to separate electrodes, thereby dispersing the space charge sheath near the collector electrode and thus enhancing electron extraction at high frequencies. This has the effect of extending both the dynamic range and the linear dynamic range.

Abstract: An ion mobility detector has dual drift regions respectively on either side of a centrally located reaction region and respectively separated therefrom by dual shutter grids. Each drift region terminates in a Faraday cup. An ion accelerating electrical field gradient is provided between the Faraday cups so that negative ions are drawn into one drift region and positively charged ions are drawn into the other drift region.

Abstract: An improved drift tube wherein the high voltage electric field is generated as a function of atmospheric pressure. Such variation of the electric field provides good compensation for the effects produced by changes in atmospheric pressure. As a result, the identification of a particular compound at different altitudes is greatly simplified.

Abstract: As oxygen is an electron absorber it is desirable, when monitoring an atmospheric flow for the presence of tracer materials capable of detection in an electron capture detector, to remove the oxygen from the flow to the detector. The invention introduces a hydrogen supply directly into the atmospheric flow to allow the hydrogen to combine catalytically with the oxygen content of the flow to form water or water vapor. The thus formed water or water vapor is extracted from the flow proceeding to the detector. The reaction can occur within a palladium or palladium alloy conduit forming a part of the flow path to the detector.

Abstract: An electron capture detector in which a thermionic source such as a filament provides electrons for the reaction in a source chamber having a port that connects to a detection chamber having a collector. Guard gas is introduced into the source chamber and sample gas into the detection chamber, and an exhaust port is provided in the detection chamber.

Abstract: An electron capture detector in which electrons for the reaction are supplied by a filament in a cylinder through which guard gas is passed. Apertures in the cylinder permit electrons from the filament to pass into an annular space surrounding the cylinder and between it and a collector. Sample gas is passed between the aperture and the collector, the pressures being such as to be capable of minimizing the diffusion of sample gas to the filament.

Abstract: A corona discharge device capable of use as an ionization detector or as a solute switch. Corona discharge pulses of short duration, preferably not exceeding one microsecond, can ionize a gas flow through the device. In the detector mode, electrons produced by the corona discharge can react with a compound to be detected in the gas flow. In the switching mode, the device converts a compound in the gas flow into a reaction product, and fluctuations in output signal of a detector connected to receive flow from the device correspond to the switching frequency of the device and are indicative of the compound in the gas flow.

Abstract: Method and apparatus for detecting the presence of very small concentrations of certain vapors and gases in air or other gaseous backgrounds. A gas sample is ionized by a source of ionizing radiation. The ionized gas is then directed through a first drift region where the ions are subjected to a drift potential. Electrical biased grid means are provided to allow only heavier ions of lower mobility to pass through the first drift region into a second drift region, where electrical shutter means are provided to allow discrete packets of ions to pass and to drift at speeds depending upon their mobilities and be detected. In an alternate embodiment, the first draft region is positioned downstream from the second drift region.

Abstract: A location- or positionally-sensitive proportional counter tube of high resolution having a trough-shaped cathode in a counting chamber. A resiliently elastic wire forming the anode extends longitudinally through the counting chamber. Suitable fastening arrangements engage the ends of the wire so as to mount the wire equidistantly from the side walls of the cathode trough and in electrical communication with the input resistor of a preamplifier. The counting chamber is an openable high-pressure chamber with inlet and outlet apertures for a pressurized counter tube gas.

Abstract: Method and apparatus for the detection of electronegative chemical species in gas flows, such as exist from gas chromatographs, by sampling the detector volume via an aperture connecting to a lower pressure region containing apparatus to collect and measure the negative ion current. Because of the free diffusion of electrons in the region of the aperture, as opposed to ambipolar diffusion in a conventional electron capture detector volume, the electrons are largely removed from the negatively charged components in the gas stream there. Similarly, positive ion current may be measured, thus extending the analytical capability of the invention to classes of chemical species normally not yielding a response in electron capture detectors.

Abstract: Method and apparatus for detecting the presence of very small concentrations of certain vapors and gases in air or other gaseous backgrounds. A gas sample is ionized by a source of ionizing radiation. The sample of ionized gas is then directed through a recombination region where ions are selectively recombined. The ionized gas is further directed through a drift region where the ions are subjected to a drift potential and separated into different groups, depending upon their mobilities. In an alternate embodiment, the ionized gas is first directed through a drift region, followed by a recombination region.

Abstract: In a hydrogen cooled dynamoelectric machine, an ion chamber detector monitors thermally produced particulates. Specificity and sensitivity of the ion chamber detector are improved by applying an electrical potential of a limited predetermined range to the electrodes of the detector and operation of the detector occurs within a well defined subsaturation range.

Abstract: An instrument to detect submicron particles by charge-transfer attachment. The instrument is made up of a charging chamber with two concentric cylindrical electrodes, a remote third collector electrode, and a pump to force ambient air through the charging chamber and into the collection electrode. The innermost electrode of the charging chamber is supplied with a radioactive material having a gold foil covering. This material can create a small bipolar region symmetrical to the inner electrode where primary ionization takes place. Positive ions created in this region move to the larger outside unipolar region to attach themselves to submicron particles. These charged particles are then forced from the charged chamber at which time they may either impinge on the collection electrode to create a measurable axial current or the particles may enter a size discrimination chamber.

Abstract: Ion chambers adapted for use with radiant energy in the vacuum ultraviolet and X-ray spectral regions are provided wherein the ion repeller and collector electrodes are configured to provide an electric field therebetween which has a non-uniform potential gradient allowing a photon beam to be passed through a region of low field strength. A further aspect of the configuration of the ion repeller and collector electrodes is the elimination of the need for guard rings.