Abstract: Methods and systems are provided for sensing particulate matter in an exhaust system of a vehicle. An example system comprises a particulate matter sensor inside a tube configured to receive a portion of exhaust gas in an exhaust passage.

Abstract: A fission chamber count rate measurement device and to the associated fission chamber calibration device; the count rate measurement device comprises: (1) a measurement cell, which contains the fission chamber (CH); (2) a neutron generator, which emits neutrons in the form of periodic pulses towards the fission chamber; (3) a neutron counter (K), which detects and counts the neutrons emitted by the neutron generator; and (4) a computing circuit, which delivers, over a predetermined time interval, a fission chamber count rate normalized with reference to the number of neutrons counted by the neutron counter (K).

Abstract: A method for measuring high-energy radiation includes applying a voltage pulse to electrodes in an ion chamber filled with a gas capable of forming charged ions by the high-energy radiation; measuring an ion current signal related to ion currents induced by the voltage pulse; and determining a magnitude of the high-energy radiation based on the ion current signal.

Abstract: A method for measuring high-energy radiation flux includes applying a positive voltage to electrodes in an ion chamber filled with a gas capable of forming charged ions by a high-energy radiation, measuring a positive ion current signal related to ion currents induced by the positive voltage, applying a negative voltage to the electrodes, measuring a negative signal related to ion currents induced by the negative voltage, and determining a magnitude of the high-energy radiation flux based on the ion current signal.

Abstract: A radiation detector, comprising a sensitive volume filled with a counter gas; an anode and a cathode each in communication with the counter gas; a voltage supply for maintaining a potential difference between the anode and the cathode, said potential difference being less than required to cause gas discharge in the counter gas. The radiation detector further comprises a photoemissive material in communication with the sensitive volume. The photoemissive material may be provided as a coating on the cathode. The radiation detector may further comprise a controllable light source for supplying photons of a known wavelength to the photoemissive material. Electrons may be emitted by the photoemissive material in response to the provision of said photons, said electrons causing avalanche breakdown of the counter gas, indicating satisfactory operation of the radiation detector.

Abstract: A beam modulation device gate is constructed from a silicon material, such as a silicon layer on an silicon on insulator wafer. The device further comprises a set of electrical contacts on the layer. The layer defines a set of electrically conducting silicon material fingers forming an array, wherein each of at least some of the fingers is connected electrically to one of the electrical contacts. The gate may be used in a mass or ion mobility spectrometer. Where the gate is constructed from a silicon on insulator wafer, an insulator layer supports the silicon layer and a handle layer supports the insulator layer. When predetermined electrical potentials are applied to the electrical contacts, at least some of the fingers will be substantially at said predetermined electrical potentials to modulate a beam of charged particles that passes through said array of fingers.

Abstract: Bradbury-Nielson gates for the modulation of beams of charged particles, particularly ion beams in mass spectrometry, have been produced with an adjustable wire spacing down to 0.075 mm or a smaller spacing. The gates are robust, they can be fabricated in less than 3 hours, and the method of production is reproducible. In time-of-flight mass spectrometers, fine wire spacing leads to improvements in mass resolution and modulation rates. Gates that were produced using this new method have been installed in a Hadamard transform time-of-flight mass spectrometer in order to demonstrate their utility.

Abstract: A method of measuring impedance is based on carrier function Laplace transform. The measurement includes detecting a response signal from a device under test, to which signal an excitation such as a pulse, interrupt or constant load is applied. Resulting data is fitted to a carrier function, selected so as to be capable of providing a good fit and for which an analytical Laplace transform is known, in order to obtain parameters of such function providing best fit. Obtained parameters are further substituted into the analytical expression of Laplace transform of carrier function which is used to calculate a frequency dependent impedance function in the Laplace domain. The resulting impedance function is used for calculating the impedance spectrum in a frequency domain and for calculating the measurement error of the frequency domain impedance spectrum using the standard deviations of the parameters, obtained during fitting of time-domain data.

Abstract: A detector for detection of ionizing radiation comprises a chamber (13) filled with an ionizable gas, and including a first (17, 19) and a second (21) electrode arrangement between which a first voltage (U1, U2) is applicable, a radiation entrance (33) arranged such that radiation (1) can enter the chamber between and substantially in parallel with the first and second electrode arrangements, for ionization of the ionizable gas, an electron avalanche amplification arrangement (15) including an avalanche cathode arrangement (25) and an avalanche anode arrangement (27), between which a second voltage (Ua) is applicable, and a read-out arrangement (29), wherein the first voltage is applicable for drifting electrons created during ionization towards the electron avalanche amplification arrangement, the second voltage is applicable for avalanche amplification of said electrons, and the read-out arrangement is arranged for detection of the electron avalanches and/or correspondingly produced ions.

Abstract: A method and apparatus for monitoring alpha contamination are provided in which ions generated in the air surrounding the item, by the passage of alpha particles, are moved to a distant detector location. The parts of the item from which ions are withdrawn can be controlled by restricting the air flow over different portions of the apparatus. In this way, detection of internal and external surfaces separately, for instance, can be provided. The apparatus and method are particularly suited for use in undertaking alpha contamination measurements during the commissioning operations.

Abstract: An alternating electromagnetic field in the radiofrequency range is applied in a gaseous environment (4). Free electrons produced in the gas (4), by an ionising source of radiation (5) or by interaction of a charged particle beam with a specimen, are acted upon by the alternating electromagnetic field and undergo an oscillatory motion resulting in multiple collisions with the gas molecules or atoms. Amplified electron and photon signals are generated in a controlled discharge, proportional to the initial number of free electrons, and are collected by suitable means (6, 7, 8). The alternating field is generated either by electrodes (1, 2) biased with an alternating voltage, or by a coil driven by an AC current, and may be superposed with a static electric field. The detection device may be used with instruments such as electron microscopes, in ion beam technologies, and with instruments used for detection of ionising radiations such as proportional counters.

Abstract: Disclosed is a picture information memory device, including a picture information memory means for generating electric charges corresponding to the intensity of write-in light incident thereon, and for holding the generated electric charges as polarized charges, an exposing means for exposing the picture information memory means to light from an object, and an alternating-current bias voltage applying means for applying an alternating-current bias voltage having a desired frequency to the picture information memory means, whereby electric charges generated by the portion of the object light the intensity of which varies at the same frequency as that of the alternating-current bias voltage, are selectively accumulated from the entirety of electric charges generated by the object light incident on the picture information memory means, and held as the polarized charges in the picture information memory means.

Abstract: An ionization chamber can stably measure a weak ionizing radiation with high sensitivity. The ionization chamber comprises an electrically conductive charge collecting electrode having a magnetic substance or a permanent magnet; an electromagnet for positioning the charge collecting electrode in non-contact with the other part of the ionization chamber; a position sensor for detecting the position of the charge collecting electrode; a circuit for feedback-controlling the magnetic force of the electromagnet to maintain the charge collecting electrode at the substantially same position; and ionization current detecting circuit for detecting an ionization current collected at the charge collecting electrode by ionization due to radiation applied to the ionization chamber.

Abstract: An optical ionizing radiation detector system (10) for determining the three-dimensional spatial distribution of all of the secondary electrons produced by the passage of ionizing radiation through a selected gas is provided. The detector system (10) can be used over a wide range of particle energies and gas pressures. The ionizing radiation passing through the gas produces prompt fluorescence and secondary electrons. A coincidence detector (30) recognizes coincident events of prompt fluorescence in the gas contained within that chamber to initialize the system cycle. At that time, an AC electric field is generated by an R.F. pulse generator (40) to localize the secondary electrons proximate their respective positions of production. Cameras (42) and 42'), preferably of a digital type, produce an image of the localized electrons to determine their three-dimensional spatial positions.

Abstract: A dosimeter that includes tissue equivalent bubbles of plastic defining volumes of gas to be ionized by radiation. One or more integrated circuits (ICs) are disposed below the volumes of gas and a collecting electrode on the IC is in direct contact with the gas. Circuitry for generating an electric field within the volume of gas moves the ions therein to the collecting electrode. The collecting electrode is part of an amplifying circuit disposed within the IC. The output from the amplifier is representative of the collected ions and therefore representative of the radiation. The signal from the amplifier is sent to an interface which conditions, buffers and stores the signal. The radiation dose and dose rate are computed in the interface. A communications section transfers that data from the dosimeter upon receipt of an externally generated data transfer command. A separate calibration and display unit calibrates the dosimeter by controlling the conditioning of the signal.

Abstract: A power supply for a gamma radiation detector, or other detector device electrically detecting the aperiodic occurrence of a phenomenon, comprises a free-running oscillator periodically outputting, at a low repetition rate, pulses having short widths and long intervals between them; a capacitor chargeable to the detector operating voltage for operating the electrical detector device; a charging circuit coupling the oscillator to the capacitor for charging same by the pulses periodically outputted by the oscillator, the capacitor being partially discharged by the detector device upon a detection of the phenomenon; and an oscillator control effective, upon a detection of the phenomenon by the detector device, to trigger the oscillator to immediately output a pulse for recharging the capacitor.

Abstract: A helium ionization detection system is provided which produces stable operation of a conventional helium ionization detector while providing improved sensitivity and linearity. Stability is improved by applying pulsed dc supply voltage across the ionization detector, thereby modifying the sampling of the detectors output current. A unique pulse generator is used to supply pulsed dc to the detector which has variable width and interval adjust features that allows up to 500 V to be applied in pulse widths ranging from about 150 nsec to about dc conditions.

Abstract: A helium ionization detector for gas chromatography is operated in a constant current, pulse-modulated mode by configuring the detector, electrometer and a high voltage pulser in a closed-loop control system. The detector current is maintained at a fixed level by varying the frequency of fixed-width, high-voltage bias pulses applied to the detector. An output signal proportional to the pulse frequency is produced which is indicative of the charge collected for a detected species.

Abstract: An improved ion detector device of the ionization detection device chamber ype comprises an ionization chamber having a central electrode therein surrounded by a cylindrical electrode member within the chamber with a collar frictionally fitted around at least one of the electrodes. The collar has electrical contact means carried in an annular groove in an inner bore of the collar to contact the outer surface of the electrode to provide electrical contact between an external terminal and the electrode without the need to solder leads to the electrode.

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: The invention substantially eliminates measurement errors in radiation field strength due to circuit propagation time delays and slow drift conditions, Geiger-Mueller tube turn-on time and response curve variations, and the need to manually calibrate the measurement apparatus in high radiation fields to compensate for time errors. The exponential probability function has the property that the expected value for the arithmetic mean of any right hand segment of the curve is always the same provided that the axis is adjusted so that the starting point of the selected segment is zero. The curve is trimmed dynamically each time a new rate is calculated. An individual count of strike events is kept for N separate but consecutive time units, and the counts for the later occurring events are lumped together as the Main Event. After the data collection period ends, a total accumulated time and accumulated count are constructed. This construction begins by examining the Main Event data.

Abstract: This invention describes apparatus for and a method of measuring radiation field strength which uses a pulse enabled detector (e.g. G-M tube) and is based on the equation R=K/t, where R is the radiation field strength, t is the time till first strike, and K is a proportionality constant for the given apparatus. The G-M detector is enabled by pulsing the bias voltage across the detector up into its active region and then measuring the elapsed time interval to the incident of first strike. Since the reciprocal of this time is proportional to the radiation field strength, all information necessary to determine the field strength has been obtained. A constant wait time is employed after each strike to assure that the G-M tube full recovery time has expired, and the G-M tube is then enabled and the process repeated. Because of the random nature of radiation phenomena the confidence level that any given measurement is an accurate representation of the true average field strength is low.

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: A spark chamber frame 8 is manufactured using only inorganic materials. Spark chamber frame 8 includes a plurality of beams 10, 12, 14, and 16 formed from inorganic material, such as ceramic or glass, and are connected together at ends 9 with inorganic bonding material having substantially the same thermal expansion as the beam material. A plurality of wires 18 and 20 formed from an inorganic composition are positioned between opposed beams 10 and 14 and 12 and 16 so that wires 18 and 20 are uniformly spaced and form a grid. A plurality of hold-down straps 22, 23, 24, and 25 are formed of inorganic material such as ceramic or glass having substantially the same chemical and thermal properties as the beam material. Hold-down straps 22, 23, 24, and 25 overlie wires 18 and 20 extending over beams 10, 12, 14, and 16 and are bonded thereto with inorganic bonding material.

Abstract: A method and apparatus for automatically stabilizing drift in radiation measurements which employ a detector whose pulse amplitude corresponds to the energy absorbed by the detector, involves the use of a peak produced in the pulse amplitude spectrum by individual electrons. The peak is at the low energy end of the spectrum and is drift stable. It can be produced by for example a direct or indirect light source such as a light emitting diode, by the phosphorescence of e.g. a sodium iodide crystal used as a scintillation crystal in nuclear radiation measurement, or by spontaneous surface emission within the detector, which is suitably a photomultiplier. The apparatus includes a determination device to determine the position of the drift stable peak and a control device to control the detector in response to the output of the determination device.

Abstract: A circuit improvement is disclosed for use in an electron capture detector of the type including an electron capture cell, means for applying polarization pulses to the cell to derive a cell current, means for varying the pulse rate to maintain the cell current constant, and means for converting the pulse frequency to an analog signal indicative of the concentration of an electron-capturing component.

Abstract: A cold cathode ionization gauge controller utilizing a periodically varying potential across the gauge tube at higher pressure and substantially constant potential at low pressure provides a wide-range pressure measurement capability from about 10.sup.-.sup.1 to about 10.sup.-.sup.7 torr.

Abstract: Improved circuitry for increasing the sensitivity of an electron-capture ionization detector includes a closed-loop feedback circuit which varies the frequency of pulses which are applied to the detector. The circuit responds to greater concentrations of predetermined compounds such as gases by increasing the pulse repetition frequency and responds to lower concentrations by decreasing the pulse repetition frequency, always tending to keep the current flowing in the detector circuit near a constant preset value. The pulse frequency will then vary directly with the concentration of sampled compound in the detector, and simple frequency-to-voltage conversion devices can be used to signal such concentrations. .Iadd.