An electrostatic linear ion trap has first and second axially aligned ion mirrors separated by a charge detection cylinder axially aligned with each ion mirror. Electric fields are selectively established within the first and second ion mirrors in a manner which causes an ion in the trap to oscillate back and forth through the charge detection cylinder between the first and second ion mirrors with a duty cycle, corresponding to a ratio of time spent by the ion passing through the charge detection cylinder and total time spent traversing a combination of the first and second ion mirrors and the charge detection cylinder during one complete oscillation cycle, of approximately 50%.

A system for trapping ions for measurement thereof may include an electrostatic linear ion trap (ELIT), a source of ions to supply ions to the ELIT, a processor operatively coupled to ELIT, and a memory having instructions stored therein executable by the processor to produce at least one control signal to open the ELIT to allow ions supplied by the source of ions to enter the ELIT, determine an ion inlet frequency corresponding to a frequency of ions flowing from the source of ions into the open ELIT, generate or receive a target ion charge value, determine an optimum threshold value as a function of the target ion charge value and the determined ion inlet frequency, and produce at least one control signal to close the ELIT when a charge of an ion within the ELIT exceeds the optimum threshold value to thereby trap the ion in the ELIT.

An electrostatic linear ion trap (ELIT) array includes multiple elongated charge detection cylinders arranged end-to-end and each defining an axial passageway extending centrally therethrough, a plurality of ion mirror structures each defining a pair of axially aligned cavities and an axial passageway extending centrally therethrough, wherein a different ion mirror structure is disposed between opposing ends of each cylinder, and front and rear ion mirrors each defining at least one cavity and an axial passageway extending centrally therethrough, the front ion mirror positioned at one end of the arrangement of charge detection cylinders and the rear ion mirror positioned at an opposite end of the arrangement of charge detection cylinders, wherein the axial passageways of the charge detection cylinders, the ion mirror structures, the front ion mirror and the rear ion mirror are coaxial to define a longitudinal axis passing centrally through the ELIT array. In a second aspect, an ELIT array comprises a plurality of non-coaxial ELIT regions, wherein ions are selectively guided into each of the ELIT regions.

A charge detection mass spectrometer may include an ion source, an electrostatic linear ion trap (ELIT) including a charge detection cylinder disposed between a pair of coaxially aligned ion mirrors, means for selectively establishing electric fields within the ion mirrors configured to cause the trapped ions in the ELIT to oscillate back and forth between the ion mirrors each time passing through the charge detection cylinder, and means for controlling a trajectory of the beam of ions entering the ELIT to cause the subsequently trapped ions to oscillate with different planar ion oscillation trajectories angularly offset from one another about the longitudinal axis with each extending along and crossing the longitudinal axis in each of the ion mirrors or with different cylindrical ion oscillation trajectories radially offset from one another about the longitudinal axis to form nested cylindrical trajectories each extending along the longitudinal axis.

An MCP detector (620) receives an ion packet along an ion path (601) of mass spectrometer through a hollow central cylindrical tube (621) of the MCP detector. The MCP detector includes coaxial rings (622) of MCPs surrounding the hollow central cylindrical tube. The MCP detector transmits the ion packet along the ion path to an ELIT (610) through holes in the center of a first set of reflectron plates (613) of the ELIT to oscillate the ion packet between the first set and a second set of reflectron plates (614) of the ELIT. The ELIT transmits the oscillated ion packet back to the MCP detector along the ion path through the holes of the first set. The MCP detector detects ions of the oscillated ion packet that are radially deflected from the ion path using the rings of MCPs. The MCP detector allows ions to be transmitted to or from either port of the ELIT.

A CDMS may include an ELIT having a charge detection cylinder (CD), a charge generator for generating a high frequency charge (HFC), a charge sensitive preamplifier (CP) having an input coupled to the CD and an output configured to produce a charge detection signal (CHD) in response to a charge induced on the CD, and a processor configured to (a) control the charge generator to induce an HFC on the CD, (b) control operation of the ELIT to cause a trapped ion to oscillate back and forth through the CD each time inducing a charge thereon, and (c) process CHD to (i) determine a gain factor as a function of the HFC induced on the CD, and (ii) modify a magnitude of the portion of CHD resulting from the charge induced on the CD by the trapped ion passing therethrough as a function of the gain factor.

Systems and multiplexing methods for measuring the mass of multiple large molecules simultaneously using multiple ion trapping with charge detection mass spectrometry (CDMS) are described. The methods trap ions with a broad range of energies that decouple ion frequency and m/z measurements allowing energy measurements of each ion throughout the acquisition. The ion energy may be obtained from the ratio of the intensity of the fundamental to the second harmonic frequencies of the periodic trapping oscillation making it possible to measure both the m/z and charge of each ion. Because ions with the exact same m/z but different energies appear at different frequencies, the probability of ion-ion interference is significantly reduced. By maximizing the decoupling of ion m/z from frequency, the rate of signal overlap is significantly reduced making it possible to trap more ions and substantially reduce analysis time.

A CDMS may include an ion source to generate ions from a sample, a mass spectrometer to separate the generated ions as a function of ion mass-to-charge ratio, an electrostatic linear ion trap (ELIT) having a charge detection cylinder disposed between first and second ion mirrors, wherein ions exiting the mass spectrometer are supplied to the ELIT, a charge generator for generating free charges, a field free region between the charge generator and the charge detection cylinder, and a processor configured to control the charge generator, with no ions in the charge detection cylinder, to generate a target number of free charges and cause the target number of free charges to travel across the field-free region and into contact with the charge detection cylinder to deposit the target number of free charges thereon and thereby calibrate or reset the charge detection cylinder to a corresponding target charge level.

A charge detection mass spectrometer may include an ion source to generate ions, a mass spectrometer to separate the generated ions as a function of ion mass-to-charge ratio to produce beam of separated ions, an electrostatic linear ion trap (ELIT) including a charge detection cylinder disposed between a pair of coaxially aligned ion mirrors, and means for controlling a trajectory of the beam of separated ions entering the ELIT to cause the ions subsequently trapped in the ELIT to oscillate therein with different planar ion oscillation trajectories angularly offset from one another about the longitudinal axis with each extending along and crossing the longitudinal axis in each of the ion mirrors or with different cylindrical ion oscillation trajectories radially offset from one another about the longitudinal axis to form nested cylindrical trajectories each extending along the longitudinal axis.

A charge detection mass spectrometer may include an ion source, an electrostatic linear ion trap (ELIT) including a charge detection cylinder disposed between a pair of coaxially aligned ion mirrors, means for selectively establishing electric fields within the ion mirrors configured to cause the trapped ions in the ELIT to oscillate back and forth between the ion mirrors each time passing through the charge detection cylinder, and means for controlling a trajectory of the beam of ions entering the ELIT to cause the subsequently trapped ions to oscillate with different planar ion oscillation trajectories angularly offset from one another about the longitudinal axis with each extending along and crossing the longitudinal axis in each of the ion mirrors or with different cylindrical ion oscillation trajectories radially offset from one another about the longitudinal axis to form nested cylindrical trajectories each extending along the longitudinal axis.