Einzel lens

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The Einzel lens is used in ion optics to focus ions in flight and is accomplished through manipulation of the electric field in the path of the ions. It consists of three or more sets of cylindrical or rectangular prisms in series along an axis. As the prisms consist of four sides, each pair of facing plates manipulate the electric field to deflect ions as they pass through.

The plates are symmetric so the ions will regain their initial speed on exiting the lens although the velocity of the outer particles will be altered such that they converge on to the axis. This causes the outer particles to arrive at the focus intersection slightly later than the ones that travel along a straight path as they have to travel an extra distance.

See also

• Time of flight
• Mass spectrometry