An ELIT includes voltage sources (1101), switches (1102), a first set of electrode plates (1110) aligned along a central axis, and a second set of electrode plates (1120) aligned along the central axis with the first set. A first group of plates (310, 320; 810, 820) of the first set and the second set is positioned to trap ions within a first path length (340, 940). A second group of plates (410, 420) of the first set and the second set is positioned to trap ions within a shorter second path length (440, 1040). The switches select the first path length by applying voltages from the voltage sources to the first set and the second set that cause the first group of plates to trap ions within the first path length. Alternatively, the switches can select the second path length by applying voltages that cause the second group of plates to trap ions within the second path length.

A method for examining a gas by mass spectrometry includes: ionizing the gas for producing ions; and storing, exciting and detecting at least some of the produced ions in an FT ion trap. Producing and storing the ions in the FT ion trap and/or exciting the ions prior to the detection of the ions in the FT ion trap includes at least one selective IFT excitation, such as a SWIFT excitation, which is dependent on the mass-to-charge ratio of the ions. The disclosure further relates to a mass spectrometer. A mass spectrometer includes: an FT ion trap; and an excitation device for storing, exciting, and detecting ions in the FT ion trap.

A method of processing an image-charge/current signal representative of one or more ions undergoing oscillatory motion within an ion analyser apparatus. The method comprising obtaining a recording of the image-charge/current signal generated by the ion analyser apparatus in the time domain. By a signal processing unit, the method comprises determining a value for the period of a periodic signal component within the recorded signal. Then, the method includes truncating the recorded signal to provide a truncated signal having a duration substantially equal to an integer multiple of said period. A step of reconstructing a time-domain signal is done based on a selected one or more frequency-domain harmonic components of the truncated signal. Next, the method determines a magnitude of the reconstructed time-domain signal and therewith calculating a value representative of the charge of a said ion undergoing oscillatory motion within the ion analyser apparatus.

In one aspect, a method of operating a mass spectrometer is disclosed, which comprises ionizing a sample to generate a plurality of ions, and introducing at least a portion of the ions into an inlet orifice of the mass spectrometer. At least a portion of the ions and/or fragments thereof is detected by a downstream detector to generate a plurality of ion detection events, and the ion detection events are monitored to determine an ion count. The ion count is compared with a reference level to determine whether the detected level exceeds the reference level.

An electrostatic ion trap for mass analysis includes a first array of electrodes and a second array of electrodes, spaced from the first array of electrode. The first and second arrays of electrodes may be planar arrays formed by parallel strip electrodes or by concentric, circular or part-circular electrically conductive rings. The electrodes of the arrays are supplied with substantially the same pattern of voltage whereby the distribution of electrical potential in the space between the arrays is such as to reflect ions isochronously in a flight direction causing them to undergo periodic, oscillatory motion in the space, focused substantially mid-way between the arrays. Amplifier circuitry is used to detect image current having frequency components related to the mass-to-charge ratio of ions undergoing the periodic, oscillatory motion.

A method of processing data determined from an image-charge/current signal representative of ions of a given charge state (Q) undergoing oscillatory motion of a respective oscillation frequency (f) within an ion analyser apparatus. A data set comprises a measured signal frequency (f.sub.0) common to a plurality of a measured image-charge/current signals and a plurality of estimated ion charge values corresponding to respective amplitudes of each one of the plurality of measured image-charge/current signals. An integer charge value ([Q]) is generated corresponding to a said estimated ion charge value rounded to the nearest integer value. Using the integer charge value ([Q.sub.i]) a plurality of different candidate image-charge/current signal frequency values (f.sub.Cand.sup.i) are calculating according to said selected measured signal frequency (f.sub.0) and according to a corresponding one of one or more different candidate charge states of ion (e.g., protonation) and/or of ion isotope or isotopologue. The calculated plurality of different candidate image-charge/current signal frequency values (f.sub.Cand.sup.i) are compared to a plurality of different signal frequencies (f) of the measured image-charge/current signals and a score value is calculated representing a degree of similarity therebetween according to the comparison. The charge state (Q) of the ion undergoing oscillatory motion of said selected measured signal frequency (f.sub.0), is then determined to be equal to the integer charge value ([{circumflex over (Q)}.sub.l,]) if the score value matches or exceeds a threshold score value.

A process for charge detection mass spectrometry includes acquiring a time-varying signal representative of a current induced on a detector by oscillatory motion of an ion within a trapping region; processing the time-varying signal to derive a frequency of the oscillatory motion; generating, based on the amplitude of the time-varying signal and the derived frequency of the oscillatory motion, Selective Temporal Overview of Resonant Ion (STORI) data representing STORI.sub.real values versus time and STORI.sub.imag values versus time; regenerating the STORI data based on a variation of the frequency of the oscillatory motion over time; and determining a charge state of the ion based on the regenerated STORI data.

A method for examining a gas by mass spectrometry includes: ionizing the gas for producing ions; and storing, exciting and detecting at least some of the produced ions in an FT ion trap. Producing and storing the ions in the FT ion trap and/or exciting the ions prior to the detection of the ions in the FT ion trap includes at least one selective IFT excitation, such as a SWIFT excitation, which is dependent on the mass-to-charge ratio of the ions. The disclosure further relates to a mass spectrometer. A mass spectrometer includes: an FT ion trap; and an excitation device for storing, exciting, and detecting ions in the FT ion trap.

An apparatus, method, or computer program. spectrometer test data of a sample may be received for processing. The spectrometer test data may include time-of-flight data in units of time and intensity of ionized particles travelling through a flight tube. The spectrometer test data may be matched to a reference library to determine characteristic information of the sample. The reference library may include spectrometer sample data in units of time and intensity of ionized particles of pre-stored reference samples detected by spectrometers in the past. The spectrometer reference data has known characteristics that the matching associates with the received spectrometer test data.

The invention relates to the linear dynamic range of ion abundance measurement devices in mass spectrometers, such as time-of-flight mass spectrometers. The invention solves the problem of ion current peak saturation by producing a second ion measurement signal at an intermediate stage of amplification in a secondary electron multiplier, e.g. a signal generated between the two multichannel plates in chevron arrangement. Because saturation effects are observed only in later stages of amplification, the signal from the intermediate stage of amplification will remain linear even at high ion intensities and will remain outside saturation. In the case of a discrete dynode detector this could encompass, for example, placement of a detection grid between two dynodes near the middle of the amplification chain. The invention uses detection of the image current generated by the passing electrons.