Radiant energy – Ionic separation or analysis – Ion beam pulsing means with detector synchronizing means
Reexamination Certificate
2002-09-06
2003-09-02
Lee, John R. (Department: 2881)
Radiant energy
Ionic separation or analysis
Ion beam pulsing means with detector synchronizing means
C250S282000, C250S283000, C250S3960ML, C250S397000, C250S287000
Reexamination Certificate
active
06614020
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a miniature time-of-flight mass spectrometer (TOF-MS). The inventive spectrometer includes (1) a gridless, focusing ionization extraction device allowing for the use of very high extraction energies in a maintenance-free design, and (2) a low-noise, center-hole microchannel plate detector assembly that significantly reduces the noise (or “ringing”) inherent in the coaxial design.
2. Description of the Related Art
Miniature time-of-flight mass spectrometers (TOF-MS) have the potential to be used in numerous field-portable and remote sampling applications due to their inherent simplicity and potential for ruggedization. Conventional wisdom, however, holds that a compact TOF-MS would not have sufficient drift length to achieve high performance, as measured by good resolving power or the capability to detect and identify product ions.
These capabilities, found only in laboratory grade instruments, would greatly enhance the utility of a field portable TOF-MS. Without the benefit of an extended drift region (and thereby long flight times), good resolution can only be achieved in a compact TOF-MS if the ion peaks are quite narrow. All aspects of the miniature analyzer and ionization processes that affect ion peak widths must therefore be optimized for minimum peak broadening to improve the overall performance of the field portable TOF-MS.
Commercially available short-pulse lasers and fast transient digitizers enable the creation and measurement of very narrow ion signals, but the ion source region, reflector performance, and detector response will each contribute to the final peak width as well. To this end, components need to be developed for the miniature TOF-MS that improve its overall performance.
Accordingly, a need exists to develop components for the miniature TOF-MS that improve its overall performance and are compatible with short-pulse lasers and fast transient digitizers. More specifically, a need exists for a focusing ionization extraction device and a low-noise channel-plate detector assembly which improve the overall performance of the miniature TOF-MS.
SUMMARY OF THE INVENTION
The present invention provides a miniature time-of-flight mass spectrometer (TOF-MS) having (1) a gridless, focusing ionization extraction device allowing for the use of very high extraction energies in a maintenance-free design, (2) a miniature flexible circuit-board reflector using rolled flexible circuit-board material, and (3) a low-noise, center-hole microchannel plate detector assembly that significantly reduces the noise (or “ringing”) inherent in the coaxial design. The components described herein improve the overall performance of the TOF-MS. These components have been developed with special attention paid to ruggedness and durability for operation of the TOF-MS under remote and harsh environmental conditions.
The present invention also provides a method for increasing the collection efficiency of laser-desorbed ions in the TOF-MS. The method includes the steps of A method for increasing the collection efficiency of laser-desorbed ions in a TOF-MS, said method comprising the steps of providing an ionization extraction device within the TOF-MS, where the ionization extraction device has an unobstructed central chamber having a first region and a second region; creating an ion acceleration/extraction field within the first region; accelerating ions within the first region; de-accelerating the ions in the second region; and drifting the ions in a drift region to cause ion dispersion.
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Cooch Francis A.
Hughes James P.
Lee John R.
The Johns Hopkins University
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