摘要:
A conductance limit plate 14 divides the vacuum chamber into two portions 30 and 31 which are separately evacuated by pumps 28 and 27, respectively, to maintain molecular flow conditions. Coil 25 generates axial magnetic field B while an ionising electron beam is directed from gun 32 to collector 38. Sample introduced into chamber 31 increases the pressure in this chamber and thus increases the ionization. Orifice 20 of plate 14 is small enough to maintain the pressure differential between the chambers but ions will equilibrate between the chambers, resulting in an increase in the transient decay time in chamber 30 to facilitate excitation and analysis. Trapping plates 10 and 11 trap the ions between the plates by reason of the potential applied to the plates.
摘要:
A remote ion source (14) within an ICR mass spectrometer which provides an enhanced trapping (within an analyzer cell (12)) of ions formed within that remote ion source (14). In a preferred embodiment, trapping enhancement is accomplished by means of magnetic perturbations of the magnetic field within the analyzer cell. The perturbations may be established by ferromagnetic means (30) or electromagnetic means (31) or by the use of permanent magnets to form a magnetic bottle. Ions formed within the remote ion source (14) are extracted from that source by an electrostatic lens (16) and directed toward the analyzer cell (12) along the Z axis of the spectrometer magnetic field. Deceleration lenses (37), external to the analyzer cell, may be employed to further enhance the trapping capability of the analyzer cell (12). In some modes of operation, a ramped deceleration potential may be applied to the declaration lens for "grouping" of ions of different masses for analysis. Provision for mass selection is also made within the spectrometer disclosed herein.
摘要:
On soumet le spectre de fréquence (181) haché en phase à une transformation inverse de Fourier (182) afin de produire la forme d'onde (183) du domaine de temps finale, utilisée pour générer le champ électrique (177) excitant les ions se trouvant dans une cellule de résonnance (101) d'un cyclotron d'ions. Selon le procédé itératif de l'invention, le spectre de fréquence voulu (181) est haché en phase de sorte qu'aucune fréquence n'est en phase à n'importe quel moment dans le temps, puis on procède à une transformation inverse de Fourier (182) sur le spectre de fréquence (181) haché en phase, et on multiplie le résultat par une fonction de fenêtrage (185). On soumet la forme d'onde du domaine de temps (183) à une transformation avant de Fourier (187) afin de produire un spectre de sortie que l'on compare à un spectre de référence (188), afin de produire des facteurs de correction utilisés pour prédéformer l'intensité du spectre de fréquence final (189), les étapes étant répétées jusqu'à ce que le spectre de fréquence de sortie (187) soit suffisamment proche du spectre de référence (188), après quoi la forme d'onde du domaine de temps (183) correspondant à ce spectre de fréquence de sortie (187) est appliquée en tant que signal d'excitation.
摘要:
The phase-scrambled frequency spectrum (181) is inverse Fourier transformed (182) to produce the final time domain waveform (183) which is used to generate the electric field (177) which excites the ions in an ion cyclotron resonance cell (101). In the iterative method of the invention, the desired frequency spectrum (181) is phase scrambled such that all frequencies are not in phase in any point in time, an inverse Fourier transform (182) is performed on the phase scrambled frequency spectrum (181) and the result multipled by a window function (185). The time domain waveform (183) is forward Fourier transformed (187) to produce an output spectrum which is compared to a reference spectrum (188) to provide correction factors which are used to predistort the magnitude of the final frequency spectrum (189) the steps are repeated until the output frequency spectrum (187) is sufficiently close to the reference spectrum (188) whereafter the time domain waveform (183) corresponding to that output frequency spectrum (187) is applied as the excitation signal.
摘要:
Gaseous ions trapped within an analyzer cell (10) of an ion cyclotron resonance mass spectrometer are excited into resonance by a swept radio-frequency electric field having an envelope of trapezoidal shape. The envelope includes an onset region which ramps linearly from a zero level to a non-zero constant-amplitude level, a constant-amplitude region having the non-zero constant-amplitude level, and a termination region which ramps linearly from the constant-amplitude level to the zero level. The field has a generally constant-amplitude power spectrum and imparts relatively uniform energy to ions having natural cyclotron frequencies of interest.