Title:
AUTOMATIC GAIN CONTROL WITH DEFOCUSING LENS
Document Type and Number:
WIPO Patent Application WO/2014/164198
Kind Code:
A8
Abstract:
In mass spectrometry, the number of ionized sample molecules affects various performance specifications of the resulting spectrum, including resolution, sensitivity, dynamic range, and scan speed. A voltage-controlled lens is used to control the number of electrons emitted from an electron source that enter the ion trap and ionize the target sample molecules. By monitoring a feature of the resulting spectrum, such as the resolution, total ion current, or a combination of these features, the lens voltage may be adjusted to create the optimal number of ions in the trap for a particular sample spectrum scan. Generally, for low concentration samples, the number of electrons introduced to the trap is increased, hence creating more ions in the trap, which in turn increases the intensity of the output signal improving the probability of detecting a sufficient number of ions by raising the intensity well above the noise floor. For higher concentration samples, the number of electrons is reduced, thus reducing interactions in the trap which in turn reduces peak broadening and improves resolution, as well as avoids saturating the detector. Several methods for adjusting the lens voltage may be used. First, the lens voltage may be repeatedly adjusted until the resulting spectrum reaches a desired trade-off between resolution and sensitivity. The lens voltage may also be incrementally increased until the resulting spectrum begins to exhibit space charge effects. Finally, all lens voltages in a list of usable voltage settings may be applied, and all the resulting spectra are compared. The optimal voltage setting is selected and used for subsequent scans.
Inventors:
RAFFERTY DAVID (US)
SPENCER MICHAEL (US)
WYLDE JAMES (US)
GARDNER DAVID LORENZ (US)
MINO WARREN (US)
SPENCER MICHAEL (US)
WYLDE JAMES (US)
GARDNER DAVID LORENZ (US)
MINO WARREN (US)
Application Number:
PCT/US2014/021184
Publication Date:
December 31, 2014
Filing Date:
March 06, 2014
Export Citation:
Assignee:
1ST DETECT CORP (US)
International Classes:
H01J49/14; H01J49/06; H01J49/42
Attorney, Agent or Firm:
CHAPMAN, Ernest F. et al. (HENDERSON FARABOW, GARRETT,& DUNNER LLP,901 New York Avenue N, Washington DC, US)
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