Abstract: A method of static gas mass spectrometry is provided. The method includes the steps of: introducing a sample gas comprising two or more isotopes to be analyzed into a static vacuum mass spectrometer at a time, t0; operating an electron impact ionization source of the mass spectrometer with a first electron energy below the ionization potential of the sample gas for a first period of time that is following t0 until a time t1; and operating the electron impact ionization source with a second electron energy at least as high as the ionization potential of the sample gas for a second period of time that is after time t1. The first time period from t0 to t1 is a period corresponding to a period taken for the isotopes of the sample gas to equilibrate in the mass spectrometer. A constant ion source temperature is preferably maintained. Also provided is a static gas mass spectrometer.

Abstract: A method of static gas mass spectrometry is provided. The method includes the steps of: introducing a sample gas comprising two or more isotopes to be analyzed into a static vacuum mass spectrometer at a time, t0; operating an electron impact ionization source of the mass spectrometer with a first electron energy below the ionization potential of the sample gas for a first period of time that is following t0 until a time t1; and operating the electron impact ionization source with a second electron energy at least as high as the ionization potential of the sample gas for a second period of time that is after time t1. The first time period from t0 to t1 is a period corresponding to a period taken for the isotopes of the sample gas to equilibrate in the mass spectrometer. A constant ion source temperature is preferably maintained. Also provided is a static gas mass spectrometer.

Abstract: A mass spectrometer is disclosed having a mass analyzer with a mass-to-charge dispersive element for separating ions according to their mass-to-charge ratios along a dispersive plane and an ion deflector to deflect ions leaving the mass analyzer in the dispersive plane. A shielding arrangement, located between the dispersive element and the ion deflector is arranged to define the portion of the beam to be deflected by the ion deflector. The deflected beam is steered onto a beam defining aperture, located at the focal plane of the mass analyzer is detected by at least one ion detector, located downstream from the beam defining aperture.

Abstract: A mass spectrometer is disclosed having a mass analyser with a mass-to-charge dispersive element for separating ions according to their mass-to-charge ratios along a dispersive plane and an ion deflector to deflect ions leaving the mass analyser in the dispersive plane. A shielding arrangement, located between the dispersive element and the ion deflector is arranged to define the portion of the beam to be deflected by the ion deflector. The deflected beam is steered onto a beam defining aperture, located at the focal plane of the mass analyser is detected by at least one ion detector, located downstream from the beam defining aperture.