US3950641A
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US
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Methods of mass spectrometry and mass spectrometers
Assignee: Associated Electrical Industries Ltd
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Filing: 1974-12-31
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Granted: 1976-04-13
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Expires: 1994-12-31
Abstract
Abstract Ions are formed from an unknown substance in a first ion source of a double beam mass spectrometer and accelerated therefrom at a low accelerating voltage, e.g. 1kV or 2kV. Ions are formed from a reference substance in the second ion source and accelerated therefrom at a relatively high accelerating voltage, e.g. 8kV. The ion beams so formed pass through a common magnetic analyser to produce respective mass spectra. With pefluorokerosene as a reference substance producing a reference mass scale up to about 1000a.m.u., the mass spectrum of the unknown substance can be accurately calibrated (mass marked) up to 8000a.m.u. or 4000a.m.u. (with the above exemplary low accelerating voltages). Thus the invention enables the inherently very accurate chemical mass marking ability of a double-beam mass spectrometer to be scaled up along the mass scale of the unknown substance.
Inventors
- 👤 Sydney Evans
- 👤 Thomas Oliver Merren
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 23:07
CPC Classifications
H; H01; H01J; H01J49/00; H01J49/26; H01J49/28; H01J49/32; H01J49/326
Claims Analysis
Total Claims: 45
Claim 1
Independent Claim
244 words
A method of mass spectrometry comprising the steps of forming ions from a substance to be analyzed in a first ion source and accelerating the ions therefrom at a first accelerating voltage to form a first ion beam, forming ions in a range of masses from a reference substance in a second ion source and accelerating the ions therefrom at a second accelerating voltage substantially different from the first accelerating voltage to form a second ion beam, directing the first and second ion beams into a magnetic analyzer having a varying magnetic field thereby to deflect the ions in both the beams according to their respective accelerating potentials and mass to charge ratios, making a scanning variation of said magnetic field, simultaneously collecting deflected ions from the respective beams which have passed through the analyzer, the ions collected at any time from both beams being ions having substantially like products of their respective accelerating voltages times their respective mass charge ratios and the ions collected at such time from one beam having substantially different masses than ions from the other beam, and producing a first mass spectrum of the substance to be analyzed and a second mass spectrum of the reference substance, the first and second mass spectra having substantially different mass scales which are correlated and in inverse relationship to the first and second accelerating voltages, whereby to provide accurate chemical mass marking of the first mass spectrum by the second mass spectrum.
Claim 2
Independent Claim
244 words
A method of mass spectrometry comprising the steps of forming ions from a substance to be analyzed in a first ion source and accelerating the ions therefrom at a first accelerating voltage to form a first ion beam, forming ions in a range of masses from a reference substance in a second ion source and accelerating the ions therefrom at a second accelerating voltage substantially different from the first accelerating voltage to form a second ion beam, directing the first and second ion beams into a magnetic analyzer having a varying magnetic field thereby to deflect the ions in both the beams according to their respective accelerating potentials and mass to charge ratios, making a scanning variation of said magnetic field, simultaneously collecting deflected ions from the respective beams which have passed through the analyzer, the ions collected at any time from both beams being ions having substantially like products of their respective accelerating voltages times their respective mass charge ratios and the ions collected at such time from one beam having substantially different masses than ions from the other beam, and producing a first mass spectrum of the substance to be analyzed and a second mass spectrum of the reference substance, the first and second mass spectra having substantially different mass scales which are correlated and in inverse relationship to the first and second accelerating voltages, whereby to provide accurate chemical mass marking of the first mass spectrum by the second mass spectrum.
Claim 3
Dependent Claim
48 words
The method of claim 1 including the further steps of collecting the ion beam or beams formed from the reference substance or substances at a low resolution and collecting the ion beam or ion beams formed from the substance or substances to be analyzed at a high resolution.
Claim 4
Dependent Claim
31 words
The method of claim 1 wherein at least one of the ion means is subjected to at least one electrostatic field arranged to cause double focusing of the respective ion beam.
Claim 5
Dependent Claim
19 words
The method of claim 1 wherein the ion beams are passed through the magnetic field along paths which intersect.
Claim 6
Dependent Claim
20 words
The method of claim 1 wherein the ion beams are passed through the magnetic field along paths which are parallel.
Claim 7
Dependent Claim
20 words
The method of claim 1 wherein the ion beams are passed along a common path at least immediately before deflection.
Claim 8
Dependent Claim
20 words
The method of claim 1 including the step of energy filtering the ions after analysis and prior to their collection.
Claim 9
Dependent Claim
57 words
The method of claim 7 wherein the analyzed ions are collected by a single ion collector which is capable of energy discrimination, and which is switched between levels of energy discrimination at a relatively high rate compared to the variation of the magnetic field whereby to produce an output distinguishing between collected ions from different ion beams.
Claim 10
Dependent Claim
19 words
The method of claim 1 wherein one of the accelerating voltages is at least twice the other accelerating voltage.
Claim 11
Dependent Claim
39 words
The method of claim 1 wherein the second accelerating voltage is substantially greater than the first accelerating voltage whereby the mass scale of the first mass spectrum is substantially greater than the mass scale of the second mass spectrum.
Claim 12
Dependent Claim
20 words
The method of claim 1 wherein only the first ion beam is electrostatically analyzed before passing through the magnetic field.
Claim 13
Dependent Claim
152 words
The method of claim 1 wherein the deflected ions are collected by a single ion collector means capable of producing an output representative of collected ions below a predetermind and controllably variable energy level, and switching the collector means between a first level above the energy level of ions accelerated by the higher of the accelerating voltages and a second level below the energy level of ions accelerated by the higher of the accelerating voltages but above the energy level of ions accelerated by the lower of the accelerating voltages, the switching being performed at a substantially greater rate than the rate of variation of the magnetic field, whereby the output of the collector means at the first level is representative of the first and second mass spectra superimposed, and the output at the second level is representative of the mass spectrum of ions accelerated by the lower of the accelerating voltages.
Claim 14
Dependent Claim
37 words
The method of claim 12 wherein the output at the second level is subtracted from the output at the first level to provide the mass spectrum of the ions accelerated by the higher of the accelerating voltages.
Claim 15
Dependent Claim
28 words
The method of claim 12 wherein the difference between the first and second levels corresponds to not substantially more than 0.7% of the higher of the accelerating voltages.
Claim 16
Dependent Claim
130 words
A mass spectrometer comprising means to create a variable magnetic field in a given direction, source means to establish at least two ion beams each containing ions in a range of masses and to accelerate the respective beams with different potentials thereby to pass said beams through said field for deflection along different curved paths which are substantially in a common plane, and means for collecting from each of the deflected ion beams, the ions collected from one beam at any given time being of masses different than ions collected from the other beam but the ions collected at such given time being of substantially only a single product of the respective accelerating voltages times the respective mass to charge ratios to produce respective mass spectra as the field varies.
Claim 17
Dependent Claim
130 words
A mass spectrometer comprising means to create a variable magnetic field in a given direction, source means to establish at least two ion beams each containing ions in a range of masses and to accelerate the respective beams with different potentials thereby to pass said beams through said field for deflection along different curved paths which are substantially in a common plane, and means for collecting from each of the deflected ion beams, the ions collected from one beam at any given time being of masses different than ions collected from the other beam but the ions collected at such given time being of substantially only a single product of the respective accelerating voltages times the respective mass to charge ratios to produce respective mass spectra as the field varies.
Claim 18
Dependent Claim
20 words
The mass spectrometer of claim 15 further comprising a plurality of independently operable ion sources, one for each ion beam.
Claim 19
Dependent Claim
29 words
The mass spectrometer of claim 15 wherein the means for separately collecting the ion beams is capable of collecting different ones of the ion beams at substantially differing resolutions.
Claim 20
Dependent Claim
50 words
The mass spectrometer of claim 15 including means to give the ions of different beams substantially differing energies, and energy filtering means arranged immediately preceding the means for collecting the deflected ion beams, whereby each means for collecting a given ion beam substantially excludes ions from each other ion beam.
Claim 21
Dependent Claim
32 words
The mass spectrometer of claim 15 wherein at least one electrostatic analyzer is individually associated with one of the ion beams, such that the one ion beam is double focused in use.
Claim 22
Dependent Claim
26 words
The mass spectrometer of claim 15 wherein the means to pass the ion beams through the magnetic field causes the beams to intersect in the field.
Claim 23
Dependent Claim
28 words
The mass spectrometer of claim 15 wherein the means to pass the ion beams through the magnetic field causes the beams to follow non-intersecting paths in the field.
Claim 24
Dependent Claim
17 words
The mass spectrometer of claim 21 including an ion impermeable barrier between the non-intersecting ion beam paths.
Claim 25
Dependent Claim
50 words
The mass spectrometer of claim 15 including means to give the ions of different beams substantially differing energies, and energy filtering means forming part of the means for collecting the deflected ion beams, whereby each means for collecting a given ion beam substantially excludes ions from each other ion beam.
Claim 26
Dependent Claim
198 words
A mass spectrometer comprising a first ion source to form ions which have a range of masses from a substance to be analyzed, a second ion source to form ions which have a range of masses from a reference substance, means to accelerate ions from the first ion source at a first accelerating voltage to form a first ion beam, means to accelerate ions from the second ion source at a second accelerating voltage substantially different from the first accelerating voltage, to form a second ion beam, magnetic analyzer means to create a variable magnetic field, ion beam directing means to direct the first and second ion beams through said field to deflect ions in the beams according to their mass to charge ratios, and ion collector means arranged to collect ions from each beam which have passed through the magnetic analyzer, the ions collected from the first beam at any given time having substantially the same accelerating potential mass charge ratio product as ions collected from the second beam at such time and said ions from the first beam collected at said time having masses substantially different than those collected from the second beam at said time.
Claim 27
Dependent Claim
198 words
A mass spectrometer comprising a first ion source to form ions which have a range of masses from a substance to be analyzed, a second ion source to form ions which have a range of masses from a reference substance, means to accelerate ions from the first ion source at a first accelerating voltage to form a first ion beam, means to accelerate ions from the second ion source at a second accelerating voltage substantially different from the first accelerating voltage, to form a second ion beam, magnetic analyzer means to create a variable magnetic field, ion beam directing means to direct the first and second ion beams through said field to deflect ions in the beams according to their mass to charge ratios, and ion collector means arranged to collect ions from each beam which have passed through the magnetic analyzer, the ions collected from the first beam at any given time having substantially the same accelerating potential mass charge ratio product as ions collected from the second beam at such time and said ions from the first beam collected at said time having masses substantially different than those collected from the second beam at said time.
Claim 28
Dependent Claim
30 words
The mass spectrometer of claim 24 further comprising an electrostatic analyzer arranged to perform an electrostatic analysis of only the first ion beam before the beams enter the magnetic analyzer.
Claim 29
Dependent Claim
72 words
The mass spectrometer of claim 24 wherein the ion beams pass along a common path before entering the magnetic analyzer, the ion collector means comprises a single ion collector assembly capable of conrollable discrimination between collected ions of different energy levels, and further including control means to control the discrimination between levels at which respectively ions from one of the beams are collected, and ions from both of the beams are collected.
Claim 30
Dependent Claim
314 words
A double beam mass spectrometer comprising a first ion source to produce a first ion beam containing ions in a first range of masses, a second ion source to produce a second ion beam containing ions in a second range of masses, a first ion accelerating voltage supply to accelerate said first ion beam out of said first ion source along a first ion path, a second ion accelerating voltage supply to accelerate said second ion beam out of said second ion source along a second ion path, a common variable magnetic analyzer disposed about both said first and second ion paths to apply a variable magnetic field to both said first and second ion beams, said analyzer separating at any given time ions having like accelerating voltage times mass charge ratio products, the ions separated from the first beam at said time being of mass different than those separated from the second beam, a first ion collector means disposed on said first ion path to collect ions from said first ion beam after passing through said magnetic analyzer, a second ion collector means disposed on said second ion path to collect ions from said second ion beam after passing through said magnetic analyzer, a first ion energy discriminating means disposed about said first ion path between said first ion source and said magnetic analyzer to pass only monoenergetic ions from said first ion source to said magnetic analyzer, a second ion energy discriminating means disposed about said first ion path between said magnetic analyzer and said first ion collector means to pass only ions from said first ion source to said first ion collector means, and a third ion energy discriminating means disposed about said second ion path between said magnetic analyzer and said second ion collector means to pass only ions from said second ion source to said second ion collector means.
Claim 31
Dependent Claim
314 words
A double beam mass spectrometer comprising a first ion source to produce a first ion beam containing ions in a first range of masses, a second ion source to produce a second ion beam containing ions in a second range of masses, a first ion accelerating voltage supply to accelerate said first ion beam out of said first ion source along a first ion path, a second ion accelerating voltage supply to accelerate said second ion beam out of said second ion source along a second ion path, a common variable magnetic analyzer disposed about both said first and second ion paths to apply a variable magnetic field to both said first and second ion beams, said analyzer separating at any given time ions having like accelerating voltage times mass charge ratio products, the ions separated from the first beam at said time being of mass different than those separated from the second beam, a first ion collector means disposed on said first ion path to collect ions from said first ion beam after passing through said magnetic analyzer, a second ion collector means disposed on said second ion path to collect ions from said second ion beam after passing through said magnetic analyzer, a first ion energy discriminating means disposed about said first ion path between said first ion source and said magnetic analyzer to pass only monoenergetic ions from said first ion source to said magnetic analyzer, a second ion energy discriminating means disposed about said first ion path between said magnetic analyzer and said first ion collector means to pass only ions from said first ion source to said first ion collector means, and a third ion energy discriminating means disposed about said second ion path between said magnetic analyzer and said second ion collector means to pass only ions from said second ion source to said second ion collector means.
Claim 32
Dependent Claim
19 words
The mass spectrometer of claim 27, wherein said first and third ion energy discriminating means are electrostatic energy analyzers.
Claim 33
Dependent Claim
19 words
The mass spectrometer of claim 27 wherein said second ion energy discriminating means is an ion retarding slit means.
Claim 34
Dependent Claim
326 words
A double beam mass spectrometer comprising a first ion source to produce a first ion beam containing ions in a first range of masses, a second ion source to produce a second ion beam containing ions in a second range of masses, a first ion accelerating voltage supply to accelerate said first ion beam out of said first ion source along a first ion path, a second ion and different accelerating voltage supply to accelerate said second ion beam out of said second ion source along a second ion path, a common variable magnetic analyzer disposed about both said first and second ion paths to apply a variable magnetic field to both said first and second ion beams, said analyzer separating at any given time ions having like accelerating voltage times mass charge ratio products, the ions separated from the first beam at said time being of mass different than those separated from the second beam, a first ion collector means disposed on said first ion path to collect ions from said first ion beam after passing through said magnetic analyzer, a second ion collector means disposed on said second ion path to collect ions from said second ion beam after passing through said magnetic analyzer, a common mounting means mounting both said second ion source and said second ion collector means, a first ion beam deflector disposed about said second ion path between said second ion source and said magnetic analyzer to deflect said second ion beam from said second ion source into said magnetic analyzer, a second ion beam deflector disposed about said second ion path between said magnetic analyzer and said second ion collector means to deflect said second ion beam from said magnetic analyzer onto said second ion collector means, and ion discrimination means to prevent ions from said first ion source reaching said second ion collector means and to prevent ions from said second source reaching said first ion collector means.
Claim 35
Dependent Claim
326 words
A double beam mass spectrometer comprising a first ion source to produce a first ion beam containing ions in a first range of masses, a second ion source to produce a second ion beam containing ions in a second range of masses, a first ion accelerating voltage supply to accelerate said first ion beam out of said first ion source along a first ion path, a second ion and different accelerating voltage supply to accelerate said second ion beam out of said second ion source along a second ion path, a common variable magnetic analyzer disposed about both said first and second ion paths to apply a variable magnetic field to both said first and second ion beams, said analyzer separating at any given time ions having like accelerating voltage times mass charge ratio products, the ions separated from the first beam at said time being of mass different than those separated from the second beam, a first ion collector means disposed on said first ion path to collect ions from said first ion beam after passing through said magnetic analyzer, a second ion collector means disposed on said second ion path to collect ions from said second ion beam after passing through said magnetic analyzer, a common mounting means mounting both said second ion source and said second ion collector means, a first ion beam deflector disposed about said second ion path between said second ion source and said magnetic analyzer to deflect said second ion beam from said second ion source into said magnetic analyzer, a second ion beam deflector disposed about said second ion path between said magnetic analyzer and said second ion collector means to deflect said second ion beam from said magnetic analyzer onto said second ion collector means, and ion discrimination means to prevent ions from said first ion source reaching said second ion collector means and to prevent ions from said second source reaching said first ion collector means.
Claim 36
Dependent Claim
26 words
The mass spectrometer of claim 30 wherein said ion discrimination means comprises an ion-impermeable barrier disposed between said first ion path and said second ion path.
Claim 37
Dependent Claim
36 words
The mass spectrometer of claim 30 wherein said ion discrimination means comprises ion energy discrimination means disposed about said first and second ion paths between said magnetic analyzer and said first and second ion collector means.
Claim 38
Dependent Claim
182 words
A mass spectrometer comprising a first ion source to produce a first ion beam containing ions in a first range of masses from a first substance, a second ion source to produce a second ion beam containing ions in a second range of masses from a second substance, said first source providing a first ion accelerating voltage supply to accelerate said first ion beam out of said first ion source, said second source providing a second and different ion accelerating voltage supply to accelerate said second ion beam out of said second ion source, a common variable magnetic analyzer, said analyzer separating at any given time ions of like product of their respective accelerating potentials times their respective mass charge ratios but the ions separated from the first beam at said time being of mass different than those separated from the second beam, a single ion energy discriminating ion collector means, and ion beam deflector means to deflect said first and second ion beams along a common ion path through said common variable magnetic analyzer and onto said single ion collector means.
Claim 39
Dependent Claim
182 words
A mass spectrometer comprising a first ion source to produce a first ion beam containing ions in a first range of masses from a first substance, a second ion source to produce a second ion beam containing ions in a second range of masses from a second substance, said first source providing a first ion accelerating voltage supply to accelerate said first ion beam out of said first ion source, said second source providing a second and different ion accelerating voltage supply to accelerate said second ion beam out of said second ion source, a common variable magnetic analyzer, said analyzer separating at any given time ions of like product of their respective accelerating potentials times their respective mass charge ratios but the ions separated from the first beam at said time being of mass different than those separated from the second beam, a single ion energy discriminating ion collector means, and ion beam deflector means to deflect said first and second ion beams along a common ion path through said common variable magnetic analyzer and onto said single ion collector means.
Claim 40
Dependent Claim
176 words
A double-focusing mass spectrometer comprising: a. an analyzer region composed of an electrostatic and a magnetic analyzer; b. a first ion source positioned to emit ions to pass through both the electrostatic and the magnetic analyzer; c. a second ion source positioned to emit ions from a reference substance to pass through the magnetic analyzer; d. a collector means positioned to receive ions from both sources after they have passed through the magnetic analyzer; and, e. a potential conrol means connected to said sources to provide ion accelerating potentials to the two sources in a predetermined relationship with the potential of one of the sources being substantially greater than the potential of the other of the sources whereby peaks of certain masses from a reference substance will be focused on said collector means by the magnetic analyzer substantially concurrently with ion peaks from ions of different masses emitted from said first source and whereby said substantially concurrently focused peaks are formed from ions whose respective products of accelerating potential times mass charge ratio are substantially equal.
Claim 41
Dependent Claim
176 words
A double-focusing mass spectrometer comprising: a. an analyzer region composed of an electrostatic and a magnetic analyzer; b. a first ion source positioned to emit ions to pass through both the electrostatic and the magnetic analyzer; c. a second ion source positioned to emit ions from a reference substance to pass through the magnetic analyzer; d. a collector means positioned to receive ions from both sources after they have passed through the magnetic analyzer; and, e. a potential conrol means connected to said sources to provide ion accelerating potentials to the two sources in a predetermined relationship with the potential of one of the sources being substantially greater than the potential of the other of the sources whereby peaks of certain masses from a reference substance will be focused on said collector means by the magnetic analyzer substantially concurrently with ion peaks from ions of different masses emitted from said first source and whereby said substantially concurrently focused peaks are formed from ions whose respective products of accelerating potential times mass charge ratio are substantially equal.
Claim 42
Independent Claim
195 words
A method of mass spectrometry comprising the steps of forming ions from a substance to be analyzed in a first ion souce and accelerating the ions therefrom at a first accelerating voltage to form a first ion beam, forming ions in a range of masses from a reference substance in a second ion source and accelerating the ions therefrom at a second accelerating voltage substantially different from the first accelerating voltage to form a second ion beam, directing the ion beams through the analyzer of a mass spectrometer and scanning the mass spectrum of the ion beams to deflect the ions in both the beams, simultaneously collectng deflected ions from the respective beams which have passed through the analyzer, the ions collected at any given time from both beams bein ions of substantially like product of their respective accelerating potential times their respective mass charge ratios but the ions collected from said first ion beam at said time having masses substantially different than the masses of ions from the second beam at such time, and producing a first mass spectrum of the substance to be analyzed and a second mass spectrum of the reference substance.
Claim 43
Independent Claim
195 words
A method of mass spectrometry comprising the steps of forming ions from a substance to be analyzed in a first ion souce and accelerating the ions therefrom at a first accelerating voltage to form a first ion beam, forming ions in a range of masses from a reference substance in a second ion source and accelerating the ions therefrom at a second accelerating voltage substantially different from the first accelerating voltage to form a second ion beam, directing the ion beams through the analyzer of a mass spectrometer and scanning the mass spectrum of the ion beams to deflect the ions in both the beams, simultaneously collectng deflected ions from the respective beams which have passed through the analyzer, the ions collected at any given time from both beams bein ions of substantially like product of their respective accelerating potential times their respective mass charge ratios but the ions collected from said first ion beam at said time having masses substantially different than the masses of ions from the second beam at such time, and producing a first mass spectrum of the substance to be analyzed and a second mass spectrum of the reference substance.
Claim 44
Independent Claim
342 words
A method of mass spectrometry comprising the steps of: a. forming ions from a substance to be analyzed in a first ion source and accelerating the ions therefrom at a first accelerating voltage to form a first ion beam; b. forming ions in a range of masses from a reference substance in a second ion source and accelerating the ions therefrom at a second accelerating voltage which is different from the first accelerating voltage by not substantially more than 0.7% of the first accelerating voltage; c. directing the ion beams into a magnetic analyzer having a varying magnetic field thereby to deflect the ions in both beams according to their respective accelerating potentials and mass to charge ratios; d. making a scanning variation of said magnetic field as the beams are passing through the analyzer; e. collecting deflected ions from both the first and second ion beams which have passed through the analyzer by a single ion collector means capable of producing an output representative of collected ions below a predetermined, controllable and selectable energy level; f. the ions collected at any time from both beams being ions having substantially like products of their respective accelerating voltages times their respective mass to charge ratios and the ions collected at such time from one beam having different masses than ions from the other beam; and, g. switching the collector means between a first level above the energy level of ions accelerated by the higher of the accelerating voltages and a second level below the energy level of ions accelerated by the higher of the accelerating voltages but above the energy level of ions accelerated by the lower of the accelerating voltages, the switching being performed at a substantially greater rate than the rate of variation of the magnetic field, whereby the output of the collector means at the first level is representative of the first and second mass spectra superimposed, and the output at the second level is representative of the mass spectrum of ions accelerated by the lower of the accelerating voltages.
Claim 45
Independent Claim
342 words
A method of mass spectrometry comprising the steps of: a. forming ions from a substance to be analyzed in a first ion source and accelerating the ions therefrom at a first accelerating voltage to form a first ion beam; b. forming ions in a range of masses from a reference substance in a second ion source and accelerating the ions therefrom at a second accelerating voltage which is different from the first accelerating voltage by not substantially more than 0.7% of the first accelerating voltage; c. directing the ion beams into a magnetic analyzer having a varying magnetic field thereby to deflect the ions in both beams according to their respective accelerating potentials and mass to charge ratios; d. making a scanning variation of said magnetic field as the beams are passing through the analyzer; e. collecting deflected ions from both the first and second ion beams which have passed through the analyzer by a single ion collector means capable of producing an output representative of collected ions below a predetermined, controllable and selectable energy level; f. the ions collected at any time from both beams being ions having substantially like products of their respective accelerating voltages times their respective mass to charge ratios and the ions collected at such time from one beam having different masses than ions from the other beam; and, g. switching the collector means between a first level above the energy level of ions accelerated by the higher of the accelerating voltages and a second level below the energy level of ions accelerated by the higher of the accelerating voltages but above the energy level of ions accelerated by the lower of the accelerating voltages, the switching being performed at a substantially greater rate than the rate of variation of the magnetic field, whereby the output of the collector means at the first level is representative of the first and second mass spectra superimposed, and the output at the second level is representative of the mass spectrum of ions accelerated by the lower of the accelerating voltages.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-04-13 | 1979-10-13 | 1980-04-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-04-13 | 1983-10-13 | 1984-04-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-04-13 | 1987-10-13 | 1988-04-13 | $7700.00 | Window Closed / Lapsed |