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1. (WO1993018540) SPECTROMETRE DE MASSE
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Claims :

1. A mass spectrometer comprising a quadrupole mass analyzer (12) having an entrance aperture, an ion source (1) disposed on the axis of said analyzer, particle intercepting means (8) blocking the line-of-sight path between said ion source and said entrance aperture, and field generating means (2-11) for
directing ions from said source into said entrance aperture, said field generating means comprising first field generating means (2-5) for deflecting ions from said source away from said axis to avoid said particle intercepting means and second field generating means (6-11) for directing into said entrance ions so deflected by said first means.
2. A mass spectrometer as claimed in claim 1 wherein said second field generating means comprises means (6-11) "for directing ions into said entrance aperture on trajectories aligned with our substantially parallel to said axis.
3. A mass spectrometer as claimed in either of claims 1 and 2 wherein said first and second field generating means comprise a plurality of conducting plates (2-11) which define apertures through which said ions may pass, and said particle intercepting means (8) is provided by at least one of said plurality of conducting plates extending into said line-of-sight path.
4. A mass spectrometer as claimed in claim 3 wherein one of said conducting plates (5) of said first field generating means tapers in thickness towards the path of said ions creating an electrostatic field which deflects said ions away from said line of sight path.
5. A mass spectrometer as claimed in claim 4 wherein said conducting plate (3,5) which tapers comprises an aperture the centre whereof is displaced from said line-of-sight path and said particle intercepting means comprises at least one conducting plate (6,8) defining an aperture the centre whereof is displaced from said line-of-sight path such that said line-of-sight path does not pass therethrough.
6. A mass spectrometer as claimed in claim 3 wherein said first field generating means comprises an array of substantially parallel plates (35-41) disposed with edges successively further distanced from said line-of-sight path in the direction of said entrance aperture (21) .
7. A mass spectrometer as claimed in claim 6 wherein said array of plates (35-41) is conductively linked.
8. A mass spectrometer as claimed in either of claims 6 and 7 wherein said array of plates (3, 35-41) comprises an aperture the centre whereof is displaced from said line-of-sight path and said particle
intercepting means comprises at least one conducting plate (8) defining an aperture the centre whereof is displaced from said line-of-sight path such that said line-of-sight path does not pass therethrough.
9. A mass spectrometer as claimed in claim 1 wherein said first field generating means comprises a pair of conductive plates (42,43) disposed on either side of said axis and maintained at different potentials whereby to deflect said ions away from said axis.
10. A mass spectrometer as claimed in any one of claims 1 to 9 wherein said second field deflecting means comprises two conducting plates (7,9) displaced from one another along said axis and defining an aperture whose centre is displaced from said axis.
11. A mass spectrometer as claimed in any of the preceding claims wherein said ion source (1) comprises a solid surface bombarded by a beam of neutral particles or ions to release ions for analysis therefrom.
12. A mass spectrometer as claimed in claim 11 wherein a sample to be analyzed is deposited on said surface so that said ions for analysis are released by bombardment of said sample.
13. A method of enhancing the sensitivity of mass analysis of a sample comprising the steps of:
a) creating an ionised, vaporised sample in an ion source lying on the axis of a quadrupole mass analyzer,
b) deflecting ions from said ionized vaporized sample away from said axis to avoid a particle
intercepting means disposed on the line-of-sight path between said ion source and said analyzer,
c) subsequently deflecting ions into the entrance of said analyzer, and
d) submitting said ions to mass analysis.