Radio-frequency powered glow discharge device and method with high voltage interface
First Claim
1. An apparatus for using radio frequency electromagnetic energy to form a glow discharge from a solid sample for use in a mass spectrometer, whether the sample is electrically conducting or nonconducting, and whether the sample is machineable or nonmachineable, the apparatus comprising:
- (a) an enclosure,i) said enclosure defining a vacuum chamber,ii) said enclosure defining an electrically conducting counterelectrode having a surface exposed to the interior of said vacuum chamber;
(b) means for disposing the sample relative to said counterelectrode such that application of a predetermined radio frequency electrical potential between the sample and said counterelectrode in the presence of an inert gas inside said vacuum chamber forms a sustainable glow discharge;
(c) means for generating a radio frequency electromagnetic potential;
(d) means for electrically connecting to the sample the radio frequency electromagnetic potential generated by said generating means;
(e) means for applying a preselected high direct current voltage to said counterelectrode to aid in providing ions from the glow discharge for subsequent analysis;
(f) means for matching the impedance of said generating means and a combination of said connecting means, said counterelectrode, the sample disposed by said disposing means, said disposing means, and the glow discharge, said impedance matching means being electrically connected in series between said electrically connecting means and said generating means; and
(g) means for blocking direct current flow between said electrically connecting means and said impedance matching means due to said preselected high direct current voltage.
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Accused Products
Abstract
A high voltage accelerating potential, which is supplied by a high voltage direct current power supply, is applied to the electrically conducting interior wall of an RF powered glow discharge cell. The RF power supply desirably is electrically grounded, and the conductor carrying the RF power to the sample held by the probe is desirably shielded completely excepting only the conductor'"'"'s terminal point of contact with the sample. The high voltage DC accelerating potential is not supplied to the sample. A high voltage capacitance is electrically connected in series between the sample on the one hand and the RF power supply and an impedance matching network on the other hand. The high voltage capacitance isolates the high DC voltage from the RF electronics, while the RF potential is passed across the high voltage capacitance to the plasma. An inductor protects at least the RF power supply, and desirably the impedance matching network as well, from a short that might occur across the high voltage capacitance. The discharge cell and the probe which holds the sample are configured and disposed to prevent the probe'"'"'s components, which are maintained at ground potential, from bridging between the relatively low vacuum region in communication with the glow discharge maintained within the cell on the one hand, and the relatively high vacuum region surrounding the probe and cell on the other hand. The probe and cell also are configured and disposed to prevent the probe'"'"'s components from electrically shorting the cell'"'"'s components.
55 Citations
19 Claims
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1. An apparatus for using radio frequency electromagnetic energy to form a glow discharge from a solid sample for use in a mass spectrometer, whether the sample is electrically conducting or nonconducting, and whether the sample is machineable or nonmachineable, the apparatus comprising:
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(a) an enclosure, i) said enclosure defining a vacuum chamber, ii) said enclosure defining an electrically conducting counterelectrode having a surface exposed to the interior of said vacuum chamber; (b) means for disposing the sample relative to said counterelectrode such that application of a predetermined radio frequency electrical potential between the sample and said counterelectrode in the presence of an inert gas inside said vacuum chamber forms a sustainable glow discharge; (c) means for generating a radio frequency electromagnetic potential; (d) means for electrically connecting to the sample the radio frequency electromagnetic potential generated by said generating means; (e) means for applying a preselected high direct current voltage to said counterelectrode to aid in providing ions from the glow discharge for subsequent analysis; (f) means for matching the impedance of said generating means and a combination of said connecting means, said counterelectrode, the sample disposed by said disposing means, said disposing means, and the glow discharge, said impedance matching means being electrically connected in series between said electrically connecting means and said generating means; and (g) means for blocking direct current flow between said electrically connecting means and said impedance matching means due to said preselected high direct current voltage. - View Dependent Claims (2, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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3. An apparatus for using radio frequency electromagnetic energy to form a glow discharge from a solid sample for use in a mass spectrometer, whether the sample is electrically conducting or nonconducting, and whether the sample is machineable or nonmachineable, the apparatus comprising:
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(a) an enclosure, i) said enclosure defining a vacuum chamber, ii) said enclosure defining an electrically conducting counterelectrode having a surface exposed to the interior of said vacuum chamber; (b) means for disposing the sample relative to said counterelectrode such that application of a predetermined radio frequency electrical potential between the sample and said counterelectrode in the presence of an inert gas inside said vacuum chamber forms a sustainable glow discharge; (c) means for generating a radio frequency electromagnetic potential; (d) means for electrically connecting to the sample the radio frequency electromagnetic potential generated by said generating means; (e) means for applying a preselected high direct current voltage to said counterelectrode to aid in providing ions from the glow discharge for subsequent analysis; (f) means for matching the impedance of said generating means and said combination of said connecting means, said counterelectrode, the sample disposed by said disposing means, said disposing means, and the glow discharge, said impedance matching means being electrically connected in series between said electrically connecting means and said generating means; and (g) mean for blocking direct current flow between said electrically connecting means and said impedance matching means, wherein said connecting means comprises; i) a first coaxial connector configured to be electrically connected to one end of a radio frequency coaxial cable, ii) an elongated conductor having a first end and a second end disposed opposite said first end, said first end of said conductor being electrically connected to said first coaxial connector, iii) an electrically conducting sample holder member having one end configured to receive a sample therein and having an opposite end electrically connected to said second end of said conductor, iv) an annular insulator member configured and disposed to surround a predetermined length of said conductor extending from said sample holder member toward said first end of said conductor, v) an adapter member configured and disposed to form a vacuum-tight seal with the exterior surface of an intermediate circumferential portion of said insulator member, vi) an electrically conducing probe body configured and disposed to surround said conductor and extending between and electrically connecting said first coaxial connector and said adapter member, vii) an electrically insulating sleeve configured and disposed to surround said conductor and said insulator member and extending between said first coaxial connecter and said adapter member and disposed between said probe body and said annular insulator member, and viii) an annular cap member configured and disposed with one end forming a vacuum-tight seal with the end of said insulator member disposed farther away from said sample holder member, said annular cap member having a second end configured and disposed to form a vacuum-tight seal with said conductor. - View Dependent Claims (4)
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17. A method for using radio frequency electromagnetic energy to transform a solid sample, whether the sample is electrically conducting or nonconducting, into a glow discharge source and analyzing the sample with a mass spectrometer, the method comprising the steps of:
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(a) enclosing an inert gas within a vacuum chamber defining a counterelectrode having a surface exposed to the interior of said vacuum chamber; (b) disposing the sample relative to said counterelectrode such that application of a predetermined radio frequency electrical potential between said sample and said counterelectrode in the presence of said inert gas inside said vacuum chamber forms a sustainable glow discharge; (c) electrically connecting the sample in series to an isolating high voltage capacitance; (d) electrically connecting in series said isolating high voltage capacitance to a capacitive impedance matching network; (e) electrically connecting in series to said capacitive impedance matching network, means for generating a radio frequency electromagnetic potential; (f) applying a radio frequency electromagnetic potential between said counterelectrode and said sample via said isolating high voltage capacitance; and (g) applying a preselected high direct current voltage to said counterelectrode to accelerate ions from said vacuum chamber to a mass spectrometer for analysis. - View Dependent Claims (18, 19)
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Specification