Categories of exhibits
Orbitrap
Exhibit no. 111
An orbitrap is an ion trap mass analyzer consisting of an outer barrel-like electrode and a coaxial inner spindle-like electrode that form an electrostatic field. The analyzed ions are trapped in an orbital motion around the spindle. The frequency of harmonic oscillations along the axis of the electrostatic field is inversely proportional to the square root of m/z. The image current from the trapped ions is detected and converted to a mass spectrum using the Fourier transform of the frequency signal.
There are two variants of Orbitrap, a standard one, and a newer high-field Orbitrap. The exhibit is the standard Orbitrap, which was introduced commercially in 2005. In this Orbitrap, the inner electrode is maintained at 3.5 kV and the outer electrode is at the ground. Both electrodes have to be machined with the highest accuracy possible to exactly define the electric field and thus maintain fine control of ion motion. Since collisions with background gas limit resolution and accuracy, very low pressures (<10-9 mbar) are required in Orbitrap.
