Mine Safety Appliances Company

Viktor Kouznetsov

Charles W Pipich

Alexander Semenovich Tarassov

Byron Lee Carnahan

Robert Eric Uber

John Michael Pertinarides

Generally, the present invention provides a high voltage waveform generator for use in an ion mobility spectrometer (IMS) that detects trace concentration level ionic species present in a sample gas stream. The present invention consists of a first electromagnetic transformer having a pair of oscillating circuits that are simultaneously excited by a transformer input winding controlled by a controller such as a power semiconductor device. Each oscillating circuit in the pair includes inductive and capacitive components that generate discrete frequency waveforms corresponding to the fundamental and second Fourier harmonic frequencies of an electric signal that approximates an ideal square wave used in creating a transverse electrical field for transport of ion species through an ion mobility spectrometer. The oscillating circuits are electromagnetically coupled to each other. The extent of this electromagnetic coupling can be varied by an inductance juxtapositioned to the first transformer so as to vary the magnetic field coupling the oscillating circuits. The amount of electromagnetic coupling is adjusted by a phase correction circuit to eliminate phase differences between the fundamental and second Fourier harmonic frequencies to ensure that the electrical signal generated by the present invention is as close an approximation of the ideal square voltage waveform as possible. The amplitudes of the fundamental and second Fourier harmonic frequency components of the output waveform are also adjusted by an amplitude correction circuit in such a way as to maintain a constant ratio between them to ensure that the output waveform is correctly shaped for use in the ion mobility spectrometer.

High voltage waveform generator

Generally, the present invention provides a device for heating the sample stream inlet of an ion mobility spectrometry (IMS) sensor. The heating device increases the temperature of the sample stream inlet surface to reduce the amount of time between adsorption and desorption taking place on the surface. This greatly improves the ability of the IMS sensor to follow rapidly changing analyte concentration levels. An alternate preferred embodiment of the present invention provides a flow smoothing device for decreasing the turbulence present in the fluid flow entering the IMS sensor's carrier stream inlet. This flow smoothing insert permits increasing the fluid flow rate entering the IMS sensor's carrier stream inlet to levels which maximize the IMS sensor's measurement sensitivity without causing mixing of the sample and carrier fluid stream flows.

Inlet heating device for ion mobility spectrometer

Generally, the present invention provides a recirculating filtration system for use with a transportable ion mobility spectrometer in gas chromatography applications. The transportable recirculating filtration system comprises a pump and a set of filters and flow sensors connected to an ion mobility spectrometry sensor having a gas chromatograph column at its inlet. The IMS sensor's outlet flow is cleaned by the filters and recirculated by the pump back into the IMS sensor as the carrier fluid stream flow. A portion of the IMS sensor's outlet flow equal to the amount of flow introduced into the sensor as the sample is exhausted from the filtration system to maintain a constant total flow volume through the system as the sample is being analyzed. Preferably, the multicapillary column is sealed to a heated transfer line leading to the sample stream inlet of the IMS sensor. The transfer line is preferably maintained at a temperature 10.degree. C.-40.degree. C. above that of the multicapillary column in order to ensure that analyte species will not adsorb on the walls of the transfer line instead of entering the sample stream inlet of the IMS sensor. The transfer line can be optionally configured with a flow smoothing insert to produce a laminar flow profile throughout the volume between the transfer line outlet end and the IMS sensor housing upon exit of the carrier flow stream from the flow smoothing insert.

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Mars, PA, United States of America

Viktor Kouznetsov