US3016459A - Mass spectrometry - Google Patents
Mass spectrometry Download PDFInfo
- Publication number
- US3016459A US3016459A US860051A US86005159A US3016459A US 3016459 A US3016459 A US 3016459A US 860051 A US860051 A US 860051A US 86005159 A US86005159 A US 86005159A US 3016459 A US3016459 A US 3016459A
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- US
- United States
- Prior art keywords
- resolution
- spectrometer
- mass
- film
- beta
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000004949 mass spectrometry Methods 0.000 title description 2
- 239000000463 material Substances 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 7
- 238000012360 testing method Methods 0.000 claims description 6
- 230000002411 adverse Effects 0.000 claims description 4
- 230000003068 static effect Effects 0.000 claims description 4
- 238000009825 accumulation Methods 0.000 claims description 3
- 238000007599 discharging Methods 0.000 claims description 3
- 230000002285 radioactive effect Effects 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 6
- 239000007789 gas Substances 0.000 description 5
- 238000004140 cleaning Methods 0.000 description 4
- 150000002500 ions Chemical class 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- OKTJSMMVPCPJKN-NJFSPNSNSA-N Carbon-14 Chemical compound [14C] OKTJSMMVPCPJKN-NJFSPNSNSA-N 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 2
- 238000001819 mass spectrum Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- BDOSMKKIYDKNTQ-OIOBTWANSA-N cadmium-109 Chemical compound [109Cd] BDOSMKKIYDKNTQ-OIOBTWANSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000005520 electrodynamics Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000005253 gamme decay Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000010884 ion-beam technique Methods 0.000 description 1
- 230000005865 ionizing radiation Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 230000002688 persistence Effects 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- BQCADISMDOOEFD-NJFSPNSNSA-N silver-110 Chemical compound [110Ag] BQCADISMDOOEFD-NJFSPNSNSA-N 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/26—Mass spectrometers or separator tubes
Definitions
- the present invention relates to improvements in mass spectrometers, and more particularly, to a method for improving the resolution qualities of mass spectrometers.
- Mass spectrometers are utilized to obtain relative mass measurements of ions which are made to pass through the deflecting influences of an electrostatic and magnetic field.
- electrostatic and magnetic field With a deflection type of instrument, employing a combination of electrostatic and magnetic sector fields, ions of different mass in the incident ion beam will focus at different spatial positions on the instruments focal plane, producing the mass spectrum.
- the electrostatic and magnetic fields are combined to produce double focusing; that is, all ions of the same imass entering the instrument within a small divergence angle and which have an energy different from the mean energy by a.
- the degree of resolution obtainable in any given machine of this type decreases with use. All available evidence appears to indicate that the trouble is caused by the deposition on the interior walls and parts of the vacuum chamber of the spectrometer of a film of non-conducting material and the subsequent building up of a charge on the film.
- the nonconducting material is assumed to be primarily hydrocarbons or organic compounds obtained either by back diffusion of vapors from the oil diffusion pumps or from samples investigated in the mass spectrometer. Such a charge alters the path of the particles under study and thus affects the results of the work.
- the spectrometer is disassembled and thoroughly cleaned on its inner surfaces.
- the films are removed by heating the vacuum chamber without disassembling it and evaporating the films.
- this is not wholly effective and cannot be used on all spectrometers.
- Both of the above mentioned cleaning methods require that the spectrometer be taken out of service, at least for a short time; and neither of them prevents a drop in resolution with use.
- it involves the establishment of conducting paths on the surface of the insulating film building up as noted above so that any charge thereon may be dissipated.
- a radioactive gas such as hydrogen tritide (HT) or carbon-l4 methane (C I-l is supplied to the spectrometer along with the sample to be investigated.
- This gas continually emits beta particles and associated ionizing radiation which establishes leakage paths on the surface of the noncond-ucting film and thereby provides the means for the rapid dissipation of the charges thereon.
- Tests of this method show that the time between physical cleanings can be extended by a factor of from two to four, and that the rate of deterioration of the resolution of the machine is greatly reduced.
- a low voltage instrument is the cycloidal focusing mass spectrometer developed by Consolidated Electrodynamic Corporation, while a high voltage high resolution instrument is one commonly known as the mass synchrometer, both found to be suitable for the practice of this invention.
- a practically chemically inert beta-emitting isotope such as cadmium-109, or silver-110, is plated on the interior of the metal shell or charged chamber of the spectrometer, in a thin layer. Radiations from the plated isotope form leakage paths from the surface of the non-conducting film to the metal shell of the spectrometer either over the surface of the film as in the radioactive gas method described above, or through the film, so that the charges on the surface of the film are dissipated. The effect of the coating of course'would linger to an extent depending upon the half-life of the radioactive isotope, as is understood in the art.
- Beta rays are very suitable for use in this invention because of the great availability of materials with such decay in a range of masses wherefrom such materials must be selected. Also, because of the short range of travel of these rays there is no significant shielding problem.
- gamma decay materials are generally not suitable for several reasons. There is a reduction in effectiveness on a surface path because of the great penetration and, because of the energies involved, problems in shielding are presented. With regard to alpha radiation, presumably, materials undergoing such decay would be useful, except that under certain circumstances the penetrating power of the rays is so small that an adverse effect on resolution might be found. The unstable materials with such decay are mostly found in the heavy end of the periodic table to begin with so that there is only a very limited choice of materials available.
- a method for improving the resolution qualities of a mass spectrometer in which non-conducting films are built up on the walls thereof which comprises the step of adding a small amount of a beta emitting material to each sample being tested for discharging before said testing, and thereby creating a leakage path in said film so as to prevent the accumulation of, a static electric charge on the interior walls of said spectrometer which would adversely afiect the resolution characteristics thereof.
- a method for improving the resolution qualities of a mass spectrometer in which non-conducting films are built up on the walls thereof which comprises the step of adding a small amount of a beta emitting material selected from a group consisting of hydrogen tritide and carbon- 14 methane to each sample being tested for discharging before said testing, and thereby creating a leakage path in said film so as to prevent the accumulation of, a static electric charge on the interior walls of said spectrometer which would adversely affect the resolution characteristics thereof.
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- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
Description
United States atent fifice 3,016,459 Patented Jan. 9, 1962 3,016,459 MASS SPECTROMETRY Lewis Friedman, Patchogue, N.Y., assignor to the United States of America as represented by the United States Atomic Energy Commission No Drawing. Filed Dec. 16, 1959, Ser. No. 860,051
, 2 Clairns. (CL 250-413) The present invention relates to improvements in mass spectrometers, and more particularly, to a method for improving the resolution qualities of mass spectrometers. Mass spectrometers are utilized to obtain relative mass measurements of ions which are made to pass through the deflecting influences of an electrostatic and magnetic field. With a deflection type of instrument, employing a combination of electrostatic and magnetic sector fields, ions of different mass in the incident ion beam will focus at different spatial positions on the instruments focal plane, producing the mass spectrum. The electrostatic and magnetic fields are combined to produce double focusing; that is, all ions of the same imass entering the instrument within a small divergence angle and which have an energy different from the mean energy by a. small amount will focus. If a photographic plate is placed in the focal plane, a mass spectrum will appear, and distance along the plate may be correlated with mass. It is thus apparent that the degree of resolution and thereby degree of accuracy of measurement obtainable with such an instrument will depend upon how closely the electorstatic and magnetic resolving fields can be maintained, especially when measurements with an accuracy of a few parts per million are to be made or where low magnetic fields and low accelerating voltages are used.
It is generally understood that the degree of resolution obtainable in any given machine of this type decreases with use. All available evidence appears to indicate that the trouble is caused by the deposition on the interior walls and parts of the vacuum chamber of the spectrometer of a film of non-conducting material and the subsequent building up of a charge on the film. The nonconducting material is assumed to be primarily hydrocarbons or organic compounds obtained either by back diffusion of vapors from the oil diffusion pumps or from samples investigated in the mass spectrometer. Such a charge alters the path of the particles under study and thus affects the results of the work. Usually, after a period of time when the degree of resolution has dropped to a point below acceptable values, the spectrometer is disassembled and thoroughly cleaned on its inner surfaces. In some situations, the films are removed by heating the vacuum chamber without disassembling it and evaporating the films. However, this is not wholly effective and cannot be used on all spectrometers. Both of the above mentioned cleaning methods require that the spectrometer be taken out of service, at least for a short time; and neither of them prevents a drop in resolution with use.
It is thus a first object of this invention to provide for the prevention or continual correction of the condition described above and to greatly extend the time during which a spectrometer may be operated before it must be disassembled for cleaning. As a further object it involves the establishment of conducting paths on the surface of the insulating film building up as noted above so that any charge thereon may be dissipated.
In a first preferred aspect of this invention a radioactive gas such as hydrogen tritide (HT) or carbon-l4 methane (C I-l is supplied to the spectrometer along with the sample to be investigated. This gas continually emits beta particles and associated ionizing radiation which establishes leakage paths on the surface of the noncond-ucting film and thereby provides the means for the rapid dissipation of the charges thereon. Tests of this method show that the time between physical cleanings can be extended by a factor of from two to four, and that the rate of deterioration of the resolution of the machine is greatly reduced.
For example, in one series of tests it was found that the addition of small amounts of radioactive carbon-14 methane (C H to water vapor being measured the resolution of the instrument was found to increase from one part in 27,400 to one part in 33,500.
The principle of this invention was shown in a series of tests in which a mass comparison of He and D showed a resolution of 19,500 followed by a comparison of HD and He in which a resolution of 21,700 was obtained. Then radioactive HT was compared with He and the resolution was increased to 25,900. The machine was then pumped out and left unused for two days and He and D; were compared with a resolution of 18,900 thereby indicating a lack of persistence in the effect of the radioactive gas, hence, that this effect was due solely to the presence of the radioactive gas and not due to any chemical reaction with the insulating film building up. This was confirmed by a comparison of HT and He at a resolution of 26,000.
As would be expected, this effect is evident only where a very high resolution instrument is being used, or where low accelerating voltages are present, so that the relatively low static charge built up, i.e., of the order of one volt or less, would have a significant effect on the results. A low voltage instrument is the cycloidal focusing mass spectrometer developed by Consolidated Electrodynamic Corporation, while a high voltage high resolution instrument is one commonly known as the mass synchrometer, both found to be suitable for the practice of this invention.
In utilizing this principle, it is thus seen that a small amount of radioactivity introduced with each sample or group of samples being measured will effectively increase the resolution sensitivity of the instrument and extend the period of use before dismantling and cleaning is required.
In a second preferred embodiment of this invention, a practically chemically inert beta-emitting isotope, such as cadmium-109, or silver-110, is plated on the interior of the metal shell or charged chamber of the spectrometer, in a thin layer. Radiations from the plated isotope form leakage paths from the surface of the non-conducting film to the metal shell of the spectrometer either over the surface of the film as in the radioactive gas method described above, or through the film, so that the charges on the surface of the film are dissipated. The effect of the coating of course'would linger to an extent depending upon the half-life of the radioactive isotope, as is understood in the art.
It will be noted that all of the examples given involve the use of beta emitters. Beta rays are very suitable for use in this invention because of the great availability of materials with such decay in a range of masses wherefrom such materials must be selected. Also, because of the short range of travel of these rays there is no significant shielding problem. On the other hand, gamma decay materials are generally not suitable for several reasons. There is a reduction in effectiveness on a surface path because of the great penetration and, because of the energies involved, problems in shielding are presented. With regard to alpha radiation, presumably, materials undergoing such decay would be useful, except that under certain circumstances the penetrating power of the rays is so small that an adverse effect on resolution might be found. The unstable materials with such decay are mostly found in the heavy end of the periodic table to begin with so that there is only a very limited choice of materials available.
It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.
I claim:
1. A method for improving the resolution qualities of a mass spectrometer in which non-conducting films are built up on the walls thereof which comprises the step of adding a small amount of a beta emitting material to each sample being tested for discharging before said testing, and thereby creating a leakage path in said film so as to prevent the accumulation of, a static electric charge on the interior walls of said spectrometer which would adversely afiect the resolution characteristics thereof.
2. A method for improving the resolution qualities of a mass spectrometer in which non-conducting films are built up on the walls thereof which comprises the step of adding a small amount of a beta emitting material selected from a group consisting of hydrogen tritide and carbon- 14 methane to each sample being tested for discharging before said testing, and thereby creating a leakage path in said film so as to prevent the accumulation of, a static electric charge on the interior walls of said spectrometer which would adversely affect the resolution characteristics thereof.
References Cited in the file of this patent UNITED STATES PATENTS 2,048,490 Bilstein July 21, 1936 2,264,683 Smith Dec. 2, 1941 2,378,936 Langmuir June 26, 1945 2,599,166 Dempster June 3, 1952 2,806,143 Carter Sept. 10, 1957 2,848,620 Backus Aug. 19, 1958
Claims (1)
1. A METHOD FOR IMPROVING THE RESOLUTION QUALITIES OF A MASS SPECTROMETER IN WHICH NON-CONDUCTING FILMS ARE BUILT UP ON THE WALLS THEREOF WHICH COMPRISES THE STEP OF ADDING A SMALL AMOUT OF A BETA EMMITTING MATERIAL TO EACH SAMPLE BEING TESTED FOR DISCHARGING BEFORE SAID TESTING, AND THEREBY CREATING A LEAKAGE PATH IN SAID FILM SO AS TO PREVENT THE ACCUMULATION OF, A STATIC ELECTRIC CHARGE ON THE INTERIOR WALL OF SAID SPECTROMETER WHICH WOULD ADVERSELY AFFECT THE RESOLUTION CHARACTERISTICS THEREOF.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US860051A US3016459A (en) | 1959-12-16 | 1959-12-16 | Mass spectrometry |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US860051A US3016459A (en) | 1959-12-16 | 1959-12-16 | Mass spectrometry |
Publications (1)
Publication Number | Publication Date |
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US3016459A true US3016459A (en) | 1962-01-09 |
Family
ID=25332393
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US860051A Expired - Lifetime US3016459A (en) | 1959-12-16 | 1959-12-16 | Mass spectrometry |
Country Status (1)
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Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2048490A (en) * | 1934-08-16 | 1936-07-21 | Radium Luminous Corp | Static neutralization |
US2264683A (en) * | 1939-04-27 | 1941-12-02 | Western Union Telegraph Co | Method of and means for neutralizing electrostatic charges on moving tapes and the like |
US2378936A (en) * | 1943-07-15 | 1945-06-26 | Cons Eng Corp | Mass spectrometry |
US2599166A (en) * | 1945-08-17 | 1952-06-03 | Atomic Energy Commission | Method of identifying radioactive compounds |
US2806143A (en) * | 1946-10-31 | 1957-09-10 | Rolla N Carter | Isotope separating apparatus |
US2848620A (en) * | 1945-08-11 | 1958-08-19 | John G Backus | Ion producing mechanism |
-
1959
- 1959-12-16 US US860051A patent/US3016459A/en not_active Expired - Lifetime
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2048490A (en) * | 1934-08-16 | 1936-07-21 | Radium Luminous Corp | Static neutralization |
US2264683A (en) * | 1939-04-27 | 1941-12-02 | Western Union Telegraph Co | Method of and means for neutralizing electrostatic charges on moving tapes and the like |
US2378936A (en) * | 1943-07-15 | 1945-06-26 | Cons Eng Corp | Mass spectrometry |
US2848620A (en) * | 1945-08-11 | 1958-08-19 | John G Backus | Ion producing mechanism |
US2599166A (en) * | 1945-08-17 | 1952-06-03 | Atomic Energy Commission | Method of identifying radioactive compounds |
US2806143A (en) * | 1946-10-31 | 1957-09-10 | Rolla N Carter | Isotope separating apparatus |
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