US 2003/0155496 A1Published application

Mass spectrometer including a quadrupole mass analyser arrangement

AssigneeVarian Australia PTY LTD

InventorIouri Kalinitchenko

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Abstract

A mass spectrometer (10) having an ion optics system (32, 34, 36, 40, 42) in a first vacuum chamber (28) which diverts ions travelling in a first direction from a source (12, 16, 24) through an angle such that neutral particles and photons from the source continue in the first direction and are removed. The diverted ion beam (38) is then directed into a quadrupole mass analyser arrangement (52) in a second vacuum chamber (48) which comprises a configured, for example curved, set of fringe electrodes (56) followed by a linear mass analyser (54) and then an ion detector (46). The configured fringe electrodes (56) again divert the ions prior to their passage into the linear quadrupole mass analyser (54) whereby additional neutral particles possibly created by passage of the ion beam through residual gas in the vacuum chambers (28, 48) are shielded from entering the linear mass analyser (54). The use of the configured set of fringe electrodes (56) in front of the linear mass analyser (54) has been found to substantially reduce background count rates, particularly for detection of isotypes of low atomic masses.

Claims14

Dependent claims

A mass spectrometer including,

a source for producing particles including ions representative of chemical elements in a sample together with neutral particles and photons,
an ion optics system contained in a first vacuum region for receiving particles from the source, the ion optics system including
at least one first electrode for establishing an electrostatic field for directing a beam of said ions in a first direction from the source and at least one second electrode for establishing an electrostatic field for diverting the beam of ions from the first direction through an angle whereby neutral particles and photons emanating from the source continue in the first direction and are separated from the beam of ions,
a quadrupole mass analyser arrangement contained in a second vacuum region and including
a set of quadrupole fringe electrodes for receiving the beam of ions, and
a linear quadrupole mass analyser for receiving ions directly from the set of quadrupole fringe electrodes, and
an ion detector also contained in the second vacuum region for receiving ions from the linear quadrupole mass analyser,
wherein the set of quadrupole fringe electrodes are configured to divert the ions prior to their passage into the linear quadrupole mass analyser and to shield the linear quadrupole mass analyser entrance.

5 more elements

Dependencies are inferred from the claim text.