Which group of people most often use Kelvin scale?

Yes, the Kelvin scale is very widely used in the sciences because it provides an absolute temperature scale as opposed to the relative scales like Celsius and Fahrenheit. In the world of cryogenics, particularly that of the really low temperatures, those nearer absolute zero, we see the Kelvin scale used frequently. To cite a single example, it is easier to talk about the boiling point of helium being 4.22 K rather than −268.93 °C, or −452.07 °F.