Open trap mass spectrometer

A method of mass spectral analysis comprising the following steps:

• (a) forming ion packets of multiple species from an analyzed sample;
• (b) arranging an electrostatic field which provides spatial ion trapping in at least two directions and an isochronous ion motion along a central ion trajectory;
• (c) injecting said ion packets for ion passage through said electrostatic field wherein said ion packets are capable of forming multiple ion oscillations;
• (d) detecting ions and measuring ion packets flight times (multiplets) at a detector for an integer number N of ion oscillation cycles within a span ΔN;
• and
• (e) reconstructing mass spectra from said detected signals containing multiplets, wherein the reconstructed mass spectra are capable of being used for mass spectral analysis,
• wherein said detection step comprises a step of sampling a portion of ion packet per single oscillation for generating multiplet signals per every ion m/z specie, and wherein the value of said sampled ion portion is set to provide m/z independent intensity distribution within multiplets.

An algorithm of decoding multiplet containing spectra in open isochronous ion traps comprising the following steps:

• (a) calibrating the intensity distribution within multiplets I(N) in reference spectra;
• (b) detecting peaks in raw spectra and composing a peak list with data on their centroids TOF, intensities I, and peak widths dT;
• (c) constructing a matrix of candidate flight times per single reflection t=TOF/N, corresponding to raw peaks TOF values and to guessed numbers of reflections N;
• (d) selecting likely t values corresponding to multiple hits and gathering groups of corresponding TOF values;
• i.e. hypothetical multiplets;
• (e) verifying peaks validity within the group by analyzing distribution of TOF and intensities I(N) within hypothetical multiplets;
• (f) checking TOF overlaps between groups, and discarding overlapping peaks;
• (g) recovering correct hypotheses of T (normalized flight times) and intensity I(T) using valid peaks of the group;
• and
• (h) accounting for number of discarded positions to recover the expected intensities I(T).

An open electrostatic trap mass spectrometer (E-trap) comprising:

• (a) a pulsed ion source or a pulsed converter to form ion packets from said ions;
• (b) a set of electrostatic trap electrodes substantially extended in a Z-direction to form a substantially two-dimensional electrostatic field in the orthogonal X-Y plane;
• (c) the shape of said trap electrodes and their potentials are adjusted to provide cyclic ion oscillations and a spatial confinement of said ion packets in said X-Y plane, as well as an isochronous ion motion along a central ion trajectory;
• (d) said pulsed source or pulsed converter is arranged to inject ion packets at an inclination angle α to the X-axis for ion passage through said electrostatic field while forming multiple oscillations within said X-Y plane and an average shift Z1 in the Z-direction per single ion oscillation;
• (e) a detector located at X=XD plane for measuring ion packets flight times-after an integer number N of ion oscillations, varying within some span ΔN, and thus forming signal ‘multiplets’ for any m/z ion specie;
• (f) means for reconstructing mass spectra from the detector signal containing multiplets;
• and
• (g) an ion-to-electron converter sampling a portion of ion packets per single ion cycle, wherein secondary electrons are sampled from both sides of said ion converter, and wherein the converter comprises a decelerator for matching the time focal plane with the converter surface plane.