US3430040A - Apparatus for recording mass spectra without ionizing a carrier gas - Google Patents

Apparatus for recording mass spectra without ionizing a carrier gas Download PDF

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Publication number
US3430040A
US3430040A US519875A US3430040DA US3430040A US 3430040 A US3430040 A US 3430040A US 519875 A US519875 A US 519875A US 3430040D A US3430040D A US 3430040DA US 3430040 A US3430040 A US 3430040A
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Prior art keywords
ionization chamber
carrier gas
recording
mass spectra
energy
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Expired - Lifetime
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US519875A
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English (en)
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Ragnar Erik Ryhage
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Pfizer Health AB
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LKB Produkter AB
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S4/00—Devices using stimulated emission of electromagnetic radiation in wave ranges other than those covered by groups H01S1/00, H01S3/00 or H01S5/00, e.g. phonon masers, X-ray lasers or gamma-ray lasers
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21G—CONVERSION OF CHEMICAL ELEMENTS; RADIOACTIVE SOURCES
    • G21G4/00—Radioactive sources
    • G21G4/04—Radioactive sources other than neutron sources
    • G21G4/06—Radioactive sources other than neutron sources characterised by constructional features
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H01J49/022—Circuit arrangements, e.g. for generating deviation currents or voltages ; Components associated with high voltage supply
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H01J49/10—Ion sources; Ion guns
    • H01J49/14—Ion sources; Ion guns using particle bombardment, e.g. ionisation chambers

Definitions

  • This invention is related to a method and means for recording mass spectra, involving a gas, the mass spectrum of which is to be determined, the said gas being introduced into an ionization chamber of a mass spectrometer to be ionized within this chamber by means of electrons of a certain energy.
  • a common value of the electron energy in the ionization chamber is 70 ev.
  • the electrons are emitted from a filament, accelerated to the desired energy and captured by an electrode after the passage through the ionization chamber.
  • the ions produced are extracted from the chamber, focused, accelerated and transmitted into a magnetic analyzer.
  • a collector is normally arranged at a certain distance from the exit slit of the ionization chamber but in front of the magnetic analyzer. This electrode will catch part of the ion beam current. The caught part of the ion current is led from the collector to an electrometer amplifier, the output of which is connected to a recording apparatus. The part of the ion current caught by the collector is proportional to the total ion current and by means of this device it is possible to record variations occurring in the ion current, when different quantities and kinds of atoms and molecules are ionized.
  • This method of measuring the total ion current has a certain drawback in cases when a small amount of the gas to be investigated, e.g., an organic compound, for example, is introduced. into the ionization chamber in a mixture of carrier gas, e.g., helium.
  • a normal electron energy Le. 70 ev.
  • the carrier gas will be ionized.
  • the part of the ion current which originates from the gas to be investigated will be small in comparison with the part of the ion current originating from the carrier gas, thus causing difiiculties in significantly indicating the ion current from the gas to be investigated.
  • the ionization potential e.g. of helium is 24.8 ev.
  • the ionization potential for organic compounds is lower and usually of the order of 8-15 ev.
  • the gas stream could be split into two parts being separately investigated in two ionization chambers.
  • One part of the gas stream will be introduced into a normal ionization chamber and the ion beam originating from this chamber will pass the analyzer tube where the ions are separated according to their mass/ charge ratio, upon which they are recorded in a form of a mass spectrum.
  • the electron energy in this first ionization chamber could be varied as desired but is normally set at 70 ev.
  • the other part of the gas stream is introduced into a second ionization chamber, and the ions produced within this chamber are attracted to an electrode which is connected to an instrument for recording the ion current.
  • the electron energy in the second ionization chamber say 24.8 ev.
  • An object of the present invention is to provide a novel method and means for making it possible, while using but a single ionization chamber, to obtain a normal mass spectrum based on a safe indication of the total ion current.
  • the method and means according to the invention is accomplished firstly by setting the electron energy in the ionization chamber to a first value before recording a mass spectrum which, at the beginning of the recording of the mass spectrum is changed to a second value which is maintained until the desired mass range has been recorded.
  • the first value of the electron energy is suitably set at substantially 20 ev., while the second value which is used when recording a mass spectrum suitably is approximately 70 ev. Thus a normal mass spectrum will be obtained.
  • the electron energy used when recording mass spectra could, however, also be set for some gases at other values between 10l00 ev.
  • FIG. 1 schematically shows the main parts of the mass spectrometer apparatus for recording mass spectra
  • FIG. 2 shows a circuit diagram of the novel apparatus of this invention for carrying out the method of recording mass spectrum according to the invention.
  • the ion source is designated in the figures as IS. It receives the necessary voltages from a high tension regulator HV and an emission regulator ER.
  • the gas, to be investigated, is introduced into the ion source through a tube GS.
  • the ions produced are directed by means of focusing and accelerating electrodes into the analyzer tube AT (FIG. 1).
  • a part of the ion current is captured by a collector CE before entering tube AT and is fed into an electrometer amplifier Al, the exit of which is connected to a recorder RECI for the recording of the total ion current.
  • the remainder of the ion current will pass through the analyzer tube AT and the magnetic analyzer DE.
  • the analyzer tube AT is connected to a high vacuum pump and cold traps by the tube VP.
  • a vacuum gauge VM is connected to the tube VP.
  • the ion beam will pass through a magnetic field, in which the ions are deflected to a varying extent according to the mass/ charge ratio.
  • the magnetic field in the analyzer DE is produced by an electromagnet which is fed with direct current from a magnet current regulator MC.
  • the magnet current is linearly varied versus time, causing the ion beams, originating from the magnetic analyzer DE, to sweep over the entrance of an electron multiplier EM.
  • the output current from the electron multiplier EM is amplified in two amplifiers A2 and A3, A3 being a wideband amplifier feeding a photographic recorder REC2, in which the mass spectra will be recorded on a paper chart RS.
  • the recorder REC2 is started by means of a switch S1.
  • the recorder can also be combined with a switch $22 for starting the sweep current from the magnet current regulator MC, causing this regulator to be started after the paper chart RS in the recorder has been fed a certain length.
  • the electron current ec in FIG. 2, as indicated by ammeter I, passing through the ionization chamber is emitted from a filament F and captured after the passage through the ionization chamber by an electrode P.
  • the energy of the electrons is prescribtd or determined by the voltage across the filament F and the ionization chamber IS as indicated by voltmeter V.
  • This voltage is taken from a potentiometer or voltage divider, including the resistor R2 and alternatively the resistors R1 and R3 or the resistors R4 and R5.
  • the end connections of the resistor R2 are connected to make-and-break contacts on two relays X1 and X2. When these relays are not energized, the resistors R1 and R3 are kept connected to the voltage divider as shown in FIG.
  • the resistors R4 and R5 are instead kept connected to the voltage divider.
  • a suitable voltage (D0,) is fed to the voltage divider from the voltage supply HV, which in FIG. 2 is marked with plus and minus signs.
  • the ionization chamber IS is directly connected to the positive end of the voltage divider, while the filament F is connected to the connection between resistor R2 and the make-and-break contact on relay X2 via the middle point of a resistor R8, which is connected between the filament current leads.
  • the resistors R1, R3, R4 and R5 are made in the form of rheostats, the sliding contacts of R1 and R3 being interconnected by movable arm A1 and the sliding contacts of R4 and R5 being interconnected by movable arm A2 as shown in FIG. 2.
  • the sliding contacts on R1, R3 and R4, R5, respectively, are connected with each other as by pivotal link L so that a decrease of resistance within one resistor R1 or R4 will cause a corresponding increase of the resistance in the other resistor R3 and R5, respectively.
  • the resistor R2 is made in the form of a potentiometer, and to the movable arm of this potentiometer is connected an electron aperture EB, which is placed between the filament F and the ionization chamber 18.
  • the coils of relays X1 and X2 are connectable in parallel with the output of a rectifier G1, which is fed from an A.C. supply via the switch S2 and the transformer T.
  • a rectifier G1 which is fed from an A.C. supply via the switch S2 and the transformer T.
  • another rectifier G2 intended for supplying operationg current to a third relay X3.
  • Relays X1, X2 and X3 can be connected to their rectifiers by means of the switch S1, which, as mentioned earlier, is
  • the switch S2 is closed.
  • the photographic recorder and the magnet sweep will be started as before, and the relays X1, X2 and X3 will also be energized.
  • the relays X1 and X2 will disconnect the resistors R1 and R3 from the voltage divider and instead connect in the resistors R4 and R5.
  • the electron energy in the ionization chamber will now be prescribed by the voltage across the resistor R4, this resistor is premised to be adjusted so that the voltage across the same is considerably higher than the voltage prescribed by R1.
  • the electron energy for the ionization will be increased.
  • a considerably increased ion current will be obtained resulting in an increase of the reading of the recorder RECl (FIG. 1), indicating the total ion current.
  • the input of the recorder is disconnected by means of the contact S3 on relay X3, when change over to higher electron energy is effected.
  • the relays X1, X2 and X6 are deenergized, causing the e ectron energy to return to its previous value and the recorder for total ion current is switched in again. It is desirable, however, that the switching in of the recorder is somewhat delayed.
  • the relay X8 is therefore, as appears in FIG. 2, combined with .a RC- circuit R6 and C6, having a suitable time constant for delaying the disengaging of relay X3.
  • the change-over from one electron energy level to another is carried out manually by operating the switch S1.
  • the device could also, if desired however, be arranged to automatically effect this change-over.
  • Apparatus for mass spectrum determination comprising a mass spectrometer having an ionization chamber, a magnetic analyser and an indicator for obtaining a mass spectrum of a gas, means for passing a gas to be investigated'i-nto said chamber together with a carrier gas, means for passing an electron beam through said chamber, and voltage divider means connectable to a voltage supply for setting the electron beam energy of said electron beam '(firstly) at a first relatively low value suit-able for ionizing the gas to be investigated but not the carrier gas, and at a second and higher value suitable for ionizing both gases, and for determining the mass spectrum, said voltage divider means comprising two sets of resistors, each set of resistors being adapted to be connected in series across said voltage supply, relays for selectively connecting said sets of resistors across said voltage sup ply, and means connecting said resistors to said electron beam passing means for determining the electron voltage applied to the beam, and an ion collector disposed before said analyser to permit the determination of the

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  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Electromagnetism (AREA)
  • General Chemical & Material Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Optics & Photonics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Plasma & Fusion (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
  • Electron Tubes For Measurement (AREA)
US519875A 1965-01-18 1966-01-11 Apparatus for recording mass spectra without ionizing a carrier gas Expired - Lifetime US3430040A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE00638/65A SE334040B (Direct) 1965-01-18 1965-01-18

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GB (1) GB1117801A (Direct)
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2470745A (en) * 1945-05-15 1949-05-17 Socony Vacuum Oil Co Inc Mass spectrometer
US2761975A (en) * 1951-12-12 1956-09-04 Socony Mobil Oil Co Inc Method and apparatus for detecting hydrocarbons
US3157784A (en) * 1961-12-07 1964-11-17 Crosby Teletronics Corp Ion source for a mass spectrometer

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2470745A (en) * 1945-05-15 1949-05-17 Socony Vacuum Oil Co Inc Mass spectrometer
US2761975A (en) * 1951-12-12 1956-09-04 Socony Mobil Oil Co Inc Method and apparatus for detecting hydrocarbons
US3157784A (en) * 1961-12-07 1964-11-17 Crosby Teletronics Corp Ion source for a mass spectrometer

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Publication number Publication date
SE334040B (Direct) 1971-04-05
GB1117801A (en) 1968-06-26
DE1598708B2 (de) 1972-06-15
DE1598708A1 (de) 1971-01-07

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