Reflectron

[1] In 1973, the dual-stage reflectron utilizing an ion mirror with two regions of homogeneous field was built in a laboratory of Boris Aleksandrovich Mamyrin.

The grid position is then referred as the entrance (exit) to the ion mirror and is used to calculate the retarding electric field.

So, the electric field Em in the mirror of a single-stage reflector should be In case of a wider variation of dU, the relative width of the time-of-flight peaks dt/t in such a reflectron is determined by the uncompensated part of the flight time t(U) proportional to the second derivative where k is a constant depending on the parameters of the single-stage reflector.

That is why dual-stage reflectrons can compensate flight times over larger variations in ion kinetic energy compared to single-stage ones.

This type of reflectrons is typically employed in orthogonal acceleration (oa) TOF MS. "Classical" (i.e., Mamyrin's) design includes two highly transparent conductive grids separating regions with homogeneous fields.

The effect of ion scattering on mass resolution in single- and dual-stage reflectrons can be diminished by utilizing polarized grid geometry.

Time of flight compensation for ions with different kinetic energy can be obtained by adjusting voltage on the elements producing the electric field inside the mirror, which values follow the equation of an arc of a circle: R2 = V(x)2 + kx2, where k and R are some constants.

[15] Bergmann et al. implemented an original numerical approach to finding voltage distribution across the stack of the metal electrodes to create a nonlinear field in different regions of the reflectron to provide conditions for both geometrical focusing and compensation of flight times caused by the spread of kinetic energies of ions entering the reflectron at different angles.

[16] A post-source decay (PSD) is a process specific to the ion source utilizing matrix-assisted laser desorption/ionization and operating in vacuum.

Use of gridless curved-field mirror or that with time-dependent field also improves the mass resolution for fragment ions generated in the post-source decay.

An ion mirror (right) attached to a flight tube (left) of the reflectron. Voltages applied to a stack of metal plates create the electric field reflecting the ions back to the flight tube.
In the reflection, the higher energy ion (red) takes a longer path but arrives at the detector at the same time as the lower energy ion (blue) of the same mass.
Schematic drawing of a single-stage reflectron.
Schematic drawing of an ion mirror with high- and low-field regions (dual-stage reflectron).