A sample tube holder for receiving and holding a sample tube having a cylindrical shape, a length symmetry axis and an outer diameter lying in a predetermined range. The sample tube holder comprises a solid body comprising at least one elongated chamber adapted for receiving a longitudinal portion of a sample tube, and an elastic element associated with and located outside of said chamber. When a sample tube is arranged in the chamber there is a gap between the sample tube and the side walls of the chamber, and the elastic element is in direct contact with at least three points of the outer surface of the sample tube, the elastic element thereby holds the sample tube and brings the length symmetry axis of the sample tube into coincidence with the length symmetry axis of the chamber.