US 4,931,640 A · Mass spectrometer with reduced static electric field

Abstract

An ion cyclotron resonance cell (20) in which samples are analyzed has plates (21, 22) serving as excitation electrodes, top and bottom plates (25, 26) serving as detector electrodes and end trapping plates (23, 24). The cell (20) is maintained in a magnetic field of flux density B oriented longitudinally between the end trapping plates (23, 24). An ion generating source (30) causes ionization of the sample molecules within the cell (20). An electrostatic trapping potential is applied to the end trapping plates (23, 24) to prevent ions from escaping in the direction of the magnetic field B. Grounded screens (40, 41) are positioned within the cell (20) just inside the end trapping plates (23, 24) to reduce an electrostatic electric field in the cell (20) resulting from the application of a potential to the end trapping plates (23, 24).

Claims37

Dependent claims

Mass spectrometry apparatus comprising:

(a) an ion cell into which an ion sample may be introduced, the cell including a plurality of electrode plates that define the cell boundary, the electrode plates including trapping plates that produce a trapping potential by the application of a static voltage to the trapping plates, the trapping potential constraining movement of ions in the direction of a magnetic field to be applied to the cell;
(b) an ion generating source that produces ions in the cell;
(c) magnetic field means for creating a unidirectional magnetic field, the magnetic field means mounted so that the unidirectional magnetic field passes through the cell in a predetermined location;
(d) at least one screen positioned within the cell proximate each of the trapping plates, the screen having a plurality of interstitial openings, and means for maintaining the screen at a selected potential to substantially shield the interior of the cell from the potential applied to the trapping plate;
and
(e) means for detecting motion of ions in the cell and providing an output signal indicative thereof.

3 more elements

Dependencies are inferred from the claim text.

Mass spectrometer with reduced static electric field

Life of this patent

Mass spectrometer with reduced static electric field

Life of this patent

Abstract

Claims37