Plasma generator assembly for mass spectroscopy
First Claim
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1. A plasma unit for mass spectroscopy machines of a type providing a sampler cone having an aperture for receiving ionized sample material along an introduction axis therethrough, the plasma unit comprisinga dielectric annular ring having an axis aligned with the introduction axis;
- a conductive shell defining a microwave cavity about the dielectric annular ring comprised of electrically joined cavity walls including sidewalls passing around the axis, a rear end wall joining a first edge of the sidewalls and a front end wall joining an opposite end of the sidewalls and completed by the sampler cone when the plasma unit is installed on the mass spectroscopy machine;
a microwave generator communicating with the microwave cavity through a first aperture in a side wall to excite the dielectric annular ring into resonance to produce an axially extending plasma; and
a sample introduction assembly passing through a second aperture in the rear end wall to inject the ionized sample material axially into the dielectric annular ring for ionization;
further including a support plate adapted to attach to the mass spectroscopy machine around the sampler cone, the support plate supporting the dielectric annular ring, conductive shell, microwave generator and sample introduction assembly.
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Abstract
A plasma unit for a mass spectroscopy machine generates plasma using a microwave coupled dielectric ring held within a microwave cavity employing part of the mass spectrometer structure to define the microwave cavity, thereby permitting improved proximity of the plasma and plasma ionized sample material to the mass spectrometer aperture.
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Citations
11 Claims
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1. A plasma unit for mass spectroscopy machines of a type providing a sampler cone having an aperture for receiving ionized sample material along an introduction axis therethrough, the plasma unit comprising
a dielectric annular ring having an axis aligned with the introduction axis; -
a conductive shell defining a microwave cavity about the dielectric annular ring comprised of electrically joined cavity walls including sidewalls passing around the axis, a rear end wall joining a first edge of the sidewalls and a front end wall joining an opposite end of the sidewalls and completed by the sampler cone when the plasma unit is installed on the mass spectroscopy machine; a microwave generator communicating with the microwave cavity through a first aperture in a side wall to excite the dielectric annular ring into resonance to produce an axially extending plasma; and a sample introduction assembly passing through a second aperture in the rear end wall to inject the ionized sample material axially into the dielectric annular ring for ionization; further including a support plate adapted to attach to the mass spectroscopy machine around the sampler cone, the support plate supporting the dielectric annular ring, conductive shell, microwave generator and sample introduction assembly. - View Dependent Claims (2, 3)
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4. A plasma unit for mass spectroscopy machines of a type providing a sampler cone having an aperture for receiving ionized sample material along an introduction axis therethrough, the plasma unit comprising
a dielectric annular ring having an axis aligned with the introduction axis; -
a conductive shell defining a microwave cavity about the dielectric annular ring comprised of electrically joined cavity walls including sidewalls passing around the axis, a rear end wall joining a first edge of the sidewalls and a front end wall joining an opposite end of the sidewalls and completed by the sample cone when the plasma unit is installed on the mass spectroscopy machine; a microwave generator communicating with the microwave cavity through a first aperture in a side wall to excite the dielectric annular ring into resonance to produce an axially extending plasma; and a sample introduction assembly passing through a second aperture in the rear end wall to inject the ionized sample material axially into the dielectric annular ring for ionization; further including electrically neutral divider plate spaced from the sampler cone within the microwave cavity providing a thermal barrier thermally containing heat from the plasma generated in the region between the neutral divider plate and the sampler cone. - View Dependent Claims (5, 6, 7, 8, 9)
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10. A plasma unit for mass spectroscopy machines of a type providing a sampler cone having an aperture for receiving ionized sample material along an introduction axis therethrough, the plasma unit comprising a dielectric annular ring having an axis aligned with the introduction axis;
- a conductive shell defining a microwave cavity about the dielectric annular ring comprised of electrically joined cavity walls including sidewalls and a front end wall joining an opposite end of the sidewalls and completed by the sampler cone when the plasma unit is installed on the mass spectrometry machine;
a microwave generator communicating with the microwave cavity through a first aperture in a side wall to excite the dielectric annular ring into resonance to produce an axially extending plasma; and
a sample introduction assembly passing through a second aperture in the rear end wall to inject the ionized sample material axially into the dielectric annular ring for ionization;
wherein the microwave generator communicates with the microwave cavity through a waveguide directed at an angle away from a perpendicular to the introduction axis;
wherein the waveguide is directed at at least 45 degrees with respect to the introduction axis.
- a conductive shell defining a microwave cavity about the dielectric annular ring comprised of electrically joined cavity walls including sidewalls and a front end wall joining an opposite end of the sidewalls and completed by the sampler cone when the plasma unit is installed on the mass spectrometry machine;
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11. A plasma unit for mass spectroscopy machines of a type providing a sampler cone having an aperture for receiving ionized sample material along an introduction axis therethrough, the plasma unit comprising a dielectric annular ring having a n axis aligned with the introduction axis;
- a conductive shell defining a microwave cavity about the dielectric annular ring comprised of electrically joined cavity walls including sidewalls and a front end wall joining an opposite end of the sidewalls and completed by the sampler cone when the plasma unit is installed on the mass spectrometry machine;
a microwave generator communicating with the microwave cavity through a first aperture in a side wall to excite the dielectric annular ring into resonance to produce an axially extending plasma; and
a sample introduction assembly passing through a second aperture in the rear end wall to inject the ionized sample material axially into the dielectric annular ring for ionization;
wherein the dielectric annular ring is suspended within the cavity on an electrical insulator;
wherein the electrical insulator is a dielectric material having a lower dielectric constant than material of the dielectric annular ring.
- a conductive shell defining a microwave cavity about the dielectric annular ring comprised of electrically joined cavity walls including sidewalls and a front end wall joining an opposite end of the sidewalls and completed by the sampler cone when the plasma unit is installed on the mass spectrometry machine;
Specification