Low vacuum mode can also be known as variable pressure, whereby gas is introduced into the chamber to create a low vacuum and varying pressures can be set. This is similar to the charge compensation mode used in the Crossbeam 550, but on a much larger scale.
The gas in the chamber increases the mean free path of the incoming electrons.
The gaseous atoms will become ionised to form cations, which neutralises the negatively charged sample surface.
The gas can also 'absorb' some of the emitted electrons to reduce charging.
This mode is especially effective with biological samples that would otherwise need to be dried and coated.
The microscope can be placed into LV mode straight away. This will help preserve the sample and reduce damage from a high vacuum. The vacuum can then be slowly increased to the desired point (or even high vacuum mode), whilst keeping the sample intact.
At the PEMC, the low vacuum mode in the JEOL 6610 is combined with the backscattered electron detector.
