Pulsed ultraviolet ion source
View Patent ↗A system and method for providing a pulsed atmospheric source of ions for chemical analysis includes a chamber containing a pair of electrodes and a second chamber with the sample gas. A narrow pulse of high voltage is applied between the electrodes to form an arc which emits ultraviolet light directly into the sample gas chamber through an aperture connecting the chambers. The ultraviolet photons ionize the sample gas and the resultant sample gas ions are then swept into a chemical detector by an electric field.
1. A method for providing a pulsed atmospheric source of ions for chemical analysis, comprising:
providing a first chamber for generating a pulsed source of ultraviolet radiation;
providing first and second electrically-conducting electrodes in the first chamber;
providing a gap to electrically separate the first and second electrically-conducting electrodes;
triggering a pulse of high voltage electricity across the gap to form a pulsed arc within the first chamber;
providing a second chamber containing a sample gas in optical communication with the pulsed arc through an open aperture to the first chamber;
ionizing the sample gas in the second chamber using the ultraviolet radiation produced by the pulsed arc in the first chamber; and
providing an electric field to sweep the resultant sample gas ions from the second chamber.
2. The method according to claim 1 , wherein the material of at least one of the first and second electrically-conducting electrodes is selected from a group consisting of: a noble metal, a refractory metal, and metal alloys containing substantially these metals.
3. The method according to claim 1 , wherein the material for at least one of the first and second electrically-conducting electrodes is selected from a group consisting of: platinum, tungsten, iridium, lanthanum, rhenium, thorium, and zirconium.
4. The method according to claim 1 , wherein at least one of the first and second electrically-conducting electrodes is coated at least in part with a coating metal that facilitates making an electrical connection.
5. The method according to claim 4 , wherein the coating metal is selected from a group consisting of: copper, nickel, gold, platinum, chromium, silver, and alloys thereof.
6. The method according to claim 1 , wherein the gap has a length less than 5 millimeters but greater than 1 millimeter.
7. The method according to claim 6 , wherein the triggered pulse of voltage is greater than: 1500 Volts plus the length of the gap in millimeters times 1000 Volts per millimeter.
8. The method according to claim 1 , wherein triggering is caused by operating an electronic switch for a high voltage pulse forming circuit.
9. The method according to claim 1 , wherein the pulse of high voltage electricity is less than 1 millisecond in duration.
10. The method according to claim 1 , wherein the current of the pulse of high voltage electricity is limited by a resistor in series with an output of a high voltage transformer.
11. The method according to claim 1 , further comprising:
a plurality of pairs of first and second electrically-conducting electrodes in the first chamber.
12. The method according to claim 1 , further comprising:
a plurality of open apertures between the first and second chambers that provides the optical communication.
13. An atmospheric ion source, comprising:
a first chamber;
first and second electrically-conducting electrodes disposed in the first chamber and electrically separated by a gap;
a high voltage pulse forming circuit that provides a pulse of high voltage electricity across the gap to form a pulsed arc within the first chamber;
a second chamber that contains a sample gas in optical communication with the pulsed arc through an open aperture to the first chamber, wherein the pulsed arc ionizes the sample gas in the second chamber with ultraviolet radiation produced by the pulsed arc in the first chamber; and
an electric field generator that provides an electric field to sweep resultant sample gas ions from the second chamber.
14. The ion source according to claim 13 , wherein the pulse of high voltage electricity is greater than: 1500 Volts plus the length of the gap in millimeters times 1000 Volts per millimeter.
15. The ion source according to claim 13 , wherein the pulse of high voltage electricity is less than 1 millisecond in duration.
16. The ion source according to claim 13 , further comprising:
an electronic switch that triggers the high voltage pulse forming circuit.
17. The ion source according to claim 13 , wherein the current of the pulse of high voltage electricity is limited by a resistor in series with an output of a high voltage transformer in the high voltage pulse forming circuit.
18. The ion source according to claim 13 , further comprising:
a plate disposed between the first chamber and the second chamber, the plate including a plurality of open apertures that provides the optical communication between the first chamber and the second chamber.
19. The ion source according to claim 13 , further comprising:
a plurality of pairs of first and second electrically-conducting electrodes in the first chamber.
20. A chemical detection system, comprising:
a chemical analysis device;
an atmospheric ion source coupled to the chemical analysis device, the ion source including:
first and second electrically-conducting electrodes disposed in the first chamber and electrically separated by a gap;
a high voltage pulse forming circuit that provides a pulse of high voltage electricity across the gap to form a pulsed arc within the first chamber;
a second chamber that contains a sample gas in optical communication with the pulsed arc through an open aperture to the first chamber, wherein the pulsed arc ionizes the sample gas in the second chamber with ultraviolet radiation produced by the pulsed arc in the first chamber; and
an electric field generator that provides an electric field to sweep resultant sample gas ions from the second chamber to the chemical analysis device.
21. The chemical detection system according to claim 20 , wherein the pulse of high voltage electricity is greater than: 1500 Volts plus the length of the gap in millimeters times 1000 Volts per millimeter.
22. The chemical detection system according to claim 20 , wherein the pulse of high voltage electricity is less than 1 millisecond in duration.
23. The chemical detection system according to claim 20 , further comprising:
an electronic switch that triggers the high voltage pulse forming circuit.
24. The chemical detection system according to claim 20 , wherein the current of the pulse of high voltage electricity is limited by a resistor in series with an output of a high voltage transformer in the high voltage pulse forming circuit.
25. The chemical detection system according to claim 20 , further comprising:
a plate disposed between the first chamber and the second chamber, the plate including a plurality of open apertures that provides the optical communication between the first chamber and the second chamber.
26. The chemical detection system according to claim 20 , further comprising:
a plurality of pairs of first and second electrically-conducting electrodes in the first chamber.