Abstract: A method of detecting specific gas species in an ion trap, the specific gas species initially being a trace component of a first low concentration in the volume of gas, includes ionizing the gas including the specific gas species, thereby creating specific ion species. The method further includes producing an electrostatic potential in which the specific ion species are confined in the ion trap to trajectories. The method also includes exciting confined specific ion species with an AC excitation source having an excitation frequency, scanning the excitation frequency of the AC excitation source to eject the specific ion species from the ion trap, and detecting the ejected specific ion species. The method further includes increasing the concentration of the specific ion species within the ion trap relative to the first low concentration prior to scanning the excitation frequency that ejects the ions of the specific gas species.

Abstract: A fast response output signal circuit (10) for a cold cathode gauge is provided to produce a fast response output signal (48) in addition to a voltage output signal (40) that is representative of the pressure in the cold cathode gauge. The fast response output signal (48) is either on or off, thus can be used to trigger a closing of an isolation valve or other responsive action upon a change in pressure that attains or exceeds a certain set point threshold. The fast response output signal is produced and processed with analog circuits, but the set point is produced with a microprocessor. The voltage output signal can be produced as a logarithmic function of the pressure.

Abstract: A smoke detection sensor ion chamber has a leakage current that is dependent upon the permittivity of the ionized gas (air) in the chamber. Smoke from typical fires is mainly composed of unburned carbon that has diffused in the surrounding air and rises with the heat of the fire. The permittivity of the carbon particles is about 10 to 15 times the permittivity of clean air. The addition of the carbon particles into the air in the ion chamber changes the permittivity thereof that is large enough to detect by measuring a change in the leakage current of the ion chamber.

Abstract: An ion chamber provides a current representative of its characteristics as affected by external conditions, e.g., clean air or smoke. A direct current (DC) voltage is applied to the ion chamber at a first polarity and the resulting current through the ion chamber and parasitic leakage current is measured at the first polarity, then the DC voltage is applied to the ion chamber at a second polarity opposite the first polarity, and the resulting current through the ion chamber and parasitic leakage current is measured at the second polarity. Since substantially no current flows through the ion chamber at the second polarity, the common mode parasitic leakage current contribution may be removed from the total current measurement by subtracting the current measured at the second polarity from the current measured at the first polarity, resulting in just the current through the ion chamber.

Abstract: An IMS system or the like has dopant contained in a way such that it is only released when needed. The dopant could be contained in a device (50) similar to an ink-jet printer and released as droplets (55) when required. Alternatively, the dopant could be trapped in material (156) of a molecular sieve (150) in such a way that it is not normally released into air flowing through the sieve but can be released by energising a heater (157) in the sieve.

Abstract: There is disclosed a method of measuring formation of a barrier to restrict or reduce movement of an electroactive species. The method comprises providing an electrochemical cell having a working electrode and a counter electrode spaced from the working electrode, providing a subject component, a testing component and at least one electroactive species within the cell, the subject and testing components being intended to cause the formation of a barrier to restrict or reduce movement of an electroactive species, applying a potential between the working electrode and the counter electrode sufficient to produce a current proportional to the concentration of the electroactive species being measured, and measuring the current at the working electrode to obtain a measure of the formation of the barrier to restrict or reduce movement of the electroactive species.

Abstract: A nondestructive testing method of condensed matter surfaces, and a sensing device for the measurement of the work function of the surface of a conducting or semiconducting sample. The sensing device includes an ionization chamber, a probe having a first surface, and a potential difference measurement circuit that is capable of measuring a difference in potential between the first surface of the probe and a surface made of another material to be tested. The ionization chamber produces ionized particles that travel out of an output of the ionization chamber and toward the probe. The probe is a non-vibrating probe having a first surface that is either a positively or negatively charged electrode. The measurement circuit of the present invention is capable of sensing the small amount of electrical current that the electrons and ions moving toward the first surface and the testing surface represent.

Abstract: A sensor for detecting volatile organic compounds in ambient air by positioning a detection cell adjacent a gas discharge device to cause molecules of organic compounds to become ionized, and applying an electric field across the collection cell to attract ions and free electrons formed in the cell to develop a current, and amplifying the current magnitude so created.

Abstract: A device for measuring a total concentration of impurities in a sample gas is provided which includes a housing having an inlet to allow the sample gas to enter the housing, an emitter to generate ions from the sample gas, a field gradient to accelerate the ions toward a collector, the collector adapted to measure total ions, and an outlet to allow the sample gas to exit the housing, whereby a change in total ions received by the collector indicates a change in the total concentration of impurities in the sample gas.

Abstract: An ionization detector for detection of an analyte includes a source chamber having a source of ionizing particles and receiving a fluid stream of detector gas; an ionization chamber connected to the source chamber at an ionization chamber entrance therebetween so as to allow metastables and photons to be generated in the source chamber and to be transferred in the fluid stream to the ionization chamber; a signal electrode assembly located in the ionization chamber; and a signal measuring circuit for measuring ionized analyte molecules. The signal electrode assembly includes a spaced array of electrodes including a collector electrode, a first signal electrode, and a second signal electrode. The first signal electrode is situated immediately downstream from the ionization chamber entrance and substantially upstream of the collector electrode, so as to extend the detection zone to the vicinity of the ionization chamber entrance.

Abstract: An ionization detector having an upper ionization chamber, a lower ionization chamber, and a radioactive source located in the upper ionization chamber but shielded from the lower ionization chamber by a barrier. A substantially constant fluid stream of detector gas is supplied to the upper ionization chamber so as to fill the upper ionization. The radioactive particle emitter is disposed on the periphery of the interior of the upper ionization chamber so as to generate a constant supply of alpha particles into the internal volume defined by the upper ionization chamber. The interaction of the alpha particles and the detector gas generates metastables and photons as the alpha particles traverse a portion of the volume in the upper ionization chamber. The lower ionization chamber is coupled to the upper ionization chamber so as to receive the detector gas flow and the metastables.

Abstract: The objective of the invention is a method for detection of alien matter contents in gas, in which method the gas and the substances contained in it are ionized in an ionization room (1). By the present methods impurities in gases cannot be determined fast and in small concentrations. In the method of the invention the ions contained in the gas are separated in a separation section (2) into positive and negative ions, of which at least the ions of either sign are led into a narrow analyzer channel (4). There, due to the capillary force, they are forced to move in the middle section of the channel, from where they are deflected by electric fields of different strength caused by different voltages (U1-U10) into an electrode located at the edge of the channel, where they cause ion current (I1-I10).

Abstract: Apparatus for detecting an electronegative species comprises an analysis chamber, an inlet communicating with the analysis chamber for admitting a sample containing the electronegative species and an ionizable component, a radioactive source within the analysis chamber for emitting radioactive energy for ionizing a component of the sample, a proportional electron detector within the analysis chamber for detecting electrons emitted from the ionized component, and a circuit for measuring the electrons and determining the presence of the electronegative species by detecting a reduction in the number of available electrons due to capture of electrons by the electronegative species.

Abstract: A small, light and portable sensor for detecting and quantifying a harmful high molecular weight substance present in a sample gas in trace amounts is herein disclosed. In the sensor, light and heavy ions are formed by ionizing molecules of the sample gas components in an ionization region. The heavy ions are formed through an ion-molecule reaction. The passage of ions through an ion-passage control region is controlled by directly or indirectly controlling the electric field established between a central electrode and a counter electrode The ions which pass through the control region are collected on a collector electrode. The high molecular weight substance is detected and quantified on the basis of the output from the collector electrode.

Abstract: An ion drag air flow meter (10) including a gas ionizer (16), an ion collector (14) and apparatus (30) for converting the collected ions into a signal providing an indication of the flow of a gas (40).

Abstract: Means and methods of detecting particular particles in an air stream at very low concentration levels and identifying the particles and magnitude of concentration are afforded. Thus, a particle detector cell has a source of ionizing radiation of constant magnitude, an anode and cathode for moving ions through a radiation activity region and a detector electrode for capturing and measuring free electrons as a dynamic signal indication of the presence of particular particles in the activity region. Particular gas molecules are identified by their fingerprint, namely a spectral response to resonating frequency of electrons orbiting in their molecular structure. The magnitude of free electrons detected determine the concentration of the particles present in air. The output may be recorded on a strip chart for identification and quantification or may be logged in a digital computer.

Abstract: The gas detection apparatus for detecting chemical agents in an air stream includes a radioactive source to ionize the air stream and an electrostatic field to increase the efficiency of the apparatus by neutralizing undesired ions, which allows a radioactive source with a lower radiation level to be used than would be required without such neutralization. A diffusion chamber including a baffle device is then used for an ion selection processes. Additional undesired ions are diffused into the walls of the diffusion chamber while the remaining ions, which are the ones sought to be detected, pass from the diffusion chamber into a collection chamber. Detection of the chemical agent ions is achieved when the remaining ions collide with the walls of a collection chamber, transferring their charge to thereby generate a current.

Abstract: A portable electronic instrument for detecting radon gas is provided by this invention. The presence of radon gas may be reliably and quantitatively measured with simple and inexpensive immediately operable in-situ detection means. Two detectors comparatively operated with respective filtered and thus uncontaminated air and inside dwelling air to be tested provide a monitoring process that can respond immediately to radon gas.

Abstract: A gas sensor and a method for detecting a small amount of a gas such as CO contained in air entering a space between electrodes ionized by a radiation source. At least one radiation source is provided for ionizing at least a part of the space between the electrodes disposed so as to oppose each other and a radio d/x of a distance d cm between the electrodes to a field strength x V/cm of the ionized space is set to be 0.4 or more so as to obtain a change in the ionic current sufficient to realize gas sensing based on the formation of cluster ions within the ionized space.

Abstract: A small volume electron capture detector has a cylindrical cell 120 inside which there is provided a generally funnel-shaped insert structure 130 having a cup-shaped section and a cylindrical section. The rims of the cup-shaped section nearly touch the inner walls of the cell 120 so as to separate the active volume from the areas at the top corners of the cell 120 which are not actively swept by the carrier gas, thus reducing the tailing of chromatographic peaks.

Abstract: An electron capture detector for use with a capillary column is provided with a sample inlet comprising a tubular anode through which sample molecules and a make-up gas are introduced into the detector cell. The tubular anode has side ports for producing a plug-like flow inside the cell. The inner surface of the anode is protected by an insulating tube so that the capillary column can be extended to a point beyond the side ports without the fear of its electrical contact with the anode. This allows the sample molecules to flow nearly entirely in the center section of the cell. The peripheral regions of the cell where a radioactive foil is disposed is swept nearly entirely by the make-up gas entering the cell through the side ports. This has the effects of reducing sample dilution by the make-up gas and sample loss due to contact with the detector walls.

Abstract: The invention concerns a method and apparatus for electrically charging particles of liquid or solid matter suspended in gases, especially in air. The particle carrying gas is irradiated with ultraviolet light having an energy below the threshold for ionization of the gas, but above the photoelectric threshold of the particles. The actual charging occurs by photoemission of electrons from the particles. The photoelectrons or negative small ions are removed from the neighborhood of the positively charged particles by diffusion to a charge absorbing surface. The photoelectric charging method and apparatus of the present invention are highly effective, particularly for very small particles and yields chemical information on the particles and their surface.

Abstract: The present invention is directed to an ionization cell for detecting the presence of very minute concentrations of certain chemical agents. The effective sensitivity of conventional chemical agent detectors is restricted in the presence of certain interferants such as jet fuel, gasoline, smoke, turpentine and the like. Herein a "chemical bias," that is a background concentration of a simulant is provided at the inlet of an ionization detector, which chemical bias is effective by charge exchange to prevent the interferants from dominating the signal.