Orbitrap for single particle mass spectrometry

An orbitrap, comprising:

• an elongated inner electrode defining a longitudinal axis centrally therethrough and a transverse plane centrally therethrough normal to the longitudinal axis,
• an elongated outer electrode defining a curved inner surface having a maximum radius R2, about the longitudinal axis, through which the transverse plane passes, wherein a cavity is defined between an outer surface of the inner electrode and the inner surface of the outer electrode,
• means for establishing an electric field configured to trap an ion in the cavity and to cause the trapped ion to rotate about, and oscillate axially along, the inner electrode, wherein the rotating and oscillating ion induces a charge on at least one of the inner and outer electrode, and
• a characteristic radius Rm, about the longitudinal axis, corresponding to a radial distance from the longitudinal axis at which the established electric field no longer attracts ions toward the longitudinal axis,
• wherein values of Rm and R2 are selected to maximize a percentage of the induced charge as a function of (Rm/R2).

An orbitrap, comprising:

• an elongated inner electrode defining a longitudinal axis centrally therethrough and a transverse plane centrally therethrough normal to the longitudinal axis, the inner electrode defining two axially spaced apart inner electrode halves with the transverse plane passing therebetween,
• an elongated outer electrode defining two axially spaced apart outer electrode halves with the transverse plane passing therebetween,
• a cavity defined radially about the longitudinal axis and axially along the inner and outer electrodes between an outer surface of the inner electrode and an inner surface of the outer electrode,
• means for establishing an electric field configured to trap an ion in the cavity and to cause the trapped ion to rotate about, and oscillate axially along, the inner electrode, wherein the rotating and oscillating ion induces charges on the inner and outer electrode halves, and
• charge detection circuitry configured to detect charges induced by the rotating and oscillating ion on the inner electrode halves and on the outer electrode halves, and to combine the detected charges for each oscillation to produce a measured ion charge signal.