The Electrostatic Trap or Orbitrap

The electrostatic trap or orbitrap according to the description of Makarov in [27]. An outer electrode has the shape of a barrel cut into two parts separated by a small gap. Inside is a second spindle-shaped electrode. Only DC voltages (some kilovolts) are applied. The ions turn around the central electrode while oscillating back and forth along the z axis. The resulting movement is made of intricate spirals. 

The orbitrap is an electrostatic ion trap that uses the Fourier transform to obtain mass spectra. This analyser is based on a completely new concept, proposed by Makarov and described in patents in 1996 [26] and 2004 [27], and in Analytical Chemistry in 2000 [28], A third patent describes a complete instrument including an atmospheric pressure source [29], Another article was also published with Cooks in 2005 [30]. The first commercial instrument was introduced on the market by the Thermo Electron Corporation in June 2005. 

With this instrument, at injection the outer electrode is about at ground, while the inner electrode is set at about —3200 V for positive ions. To have a reasonably circular or oval trajectory around the centre electrode, the ions need to have a kinetic energy around 1600 eV. The ions start to rotate around the inner electrode and together oscillate along the z axis. 

In this equation, r and z are cylindrical coordinates (z = 0 being the axis of symmetry of the field), C is a constant, k is field curvature, and Rm is the characteristic radius. The 

An ion with mass m and total charge q = ze is accelerated along z, which results from the force induced by the electric field. The electric force -qkz is equal to the mass times the acceleration m(d2z/df2)  

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