Abstract: A time of flight mass spectrometer includes means for gating the flow of ions from the source to the detector with a modulation function, the frequency of which is swept. The detected ion current is obtained as a function of the ion current modulation frequency to derive an ion mass interferogram output in the frequency domain. The interferogram output is Fourier transformed from the frequency domain to the time domain to obtain a time of flight mass spectrum output in the time domain. The Fourier transform time of flight mass spectrometer provides increased duty cycle and signal-to-noise ratio for a given scan time.

Abstract: A magnetic rotator lens for rotating the momenta of particles transverse to the direction of the beam is disclosed. The rotator lens includes a solenoid axially aligned with the beam and employs a magnetic permeable flux return structure surrounding the solenoid. The flux return structure includes beam entrance and exit plates with magnetic permeable and charged particle permeable portions forming the beam entrance and exit ports of the magnetic lens. In a typical example, the beam entrance magnetic permeable and beam permeable portion of the pole piece structure is formed by a grid of magnetic permeable members. The magnetic permeable and beam permeable portions of the pole structures terminate the axial magnetic field without introducing any substantial transverse components to the magnetic field which would otherwise produce undesired rotation of the beam shape.