PULSED DISCHARGE IONIZATION SOURCE FOR MINIATURE ION MOBILITY SPECTROMETERS
First Claim
1. A method of pulsed discharge for an analytical instrument, comprising:
- flowing a sample gas and a reactant gas past a corona discharge electrode of non-radioactive material situated at a first location in an ion drift chamber;
applying a pulsed voltage to the corona discharge electrode to cause a corona which in turn produces ions from the sample gas and the reactant gas;
applying a dc bias to the ion drift chamber to cause the ions to drift to a second location in the ion drift chamber through a medium provided by a drift gas;
detecting the ions at the second location in the drift chamber;
timing a period for the ions to drift from the corona discharge electrode to the second location in the drift chamber; and
using the timed period to determine an identity of the sample gas.
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Accused Products
Abstract
A method and apparatus is disclosed for flowing a sample gas and a reactant gas (38, 43) past a corona discharge electrode (26) situated at a first location in an ion drift chamber (24), applying a pulsed voltage waveform comprising a varying pulse component and a dc bias component to the corona discharge electrode (26) to cause a corona which in turn produces ions from the sample gas and the reactant gas, applying a dc bias to the ion drift chamber (24) to cause the ions to drift to a second location (25) in the ion drift chamber (24), detecting the ions at the second location (25) in the drift chamber (24), and timing the period for the ions to drift from the corona discharge electrode to the selected location in the drift chamber.
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Citations
16 Claims
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1. A method of pulsed discharge for an analytical instrument, comprising:
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flowing a sample gas and a reactant gas past a corona discharge electrode of non-radioactive material situated at a first location in an ion drift chamber;
applying a pulsed voltage to the corona discharge electrode to cause a corona which in turn produces ions from the sample gas and the reactant gas;
applying a dc bias to the ion drift chamber to cause the ions to drift to a second location in the ion drift chamber through a medium provided by a drift gas;
detecting the ions at the second location in the drift chamber;
timing a period for the ions to drift from the corona discharge electrode to the second location in the drift chamber; and
using the timed period to determine an identity of the sample gas. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An analytical instrument comprising:
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a body forming an elongated chamber for reaction of gases and for movement of gases, said chamber having a first entrance for receiving a sample gas and having a second entrance for receiving a reactant gas and a drift gas;
a corona discharge electrode of non-radioactive material and a counter electrode positioned in the body at a first location in the chamber in a path of flow for the sample gas;
an ion detector at a second location the chamber spaced from the corona discharge electrode;
wherein a pair of electrodes are provided for applying a dc bias voltage along a length of the chamber; and
an electronic control for controlling application of a voltage to the corona discharge electrode and for timing an interval beginning with the application of the corona discharge voltage and ending with detection of the ions at the ion detector. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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Specification