Electrostatic lens

An electrostatic lens is a device that assists in the transport of charged particles.

An electrostatic lens can also be used to focus an ion beam, for example to make a microbeam for irradiating individual cells.

This makes the focal length of a single lens a function of the second order of the speed of the charged particle.

But because there is some distance between the lenses, the electron makes three turns and hits the focusing lens at a position farther away from the axis and so travels through a field with greater strength.

It consists of three or more sets of cylindrical or rectangular tubes in series along an axis.

In spirit of a Wien filter, a combined magnetic, electric quadrupole is achromatic around a given velocity.

To generate the magnetic field, an electric current is passed through the coil.

As a consequence, the image formed by a magnetic lens is rotated relative to the object.

This makes it possible to design and build more compact magnetic lenses with well defined optical properties.

So for an electrostatic lens the focal length varies with the second power of the kinetic energy, while for a magnetostatic lens the focal length varies proportional to the kinetic energy.