A tensioning apparatus for supporting a low-temperature apparatus in a vacuum vessel of a superconducting magnet of a magnetic resonance imaging apparatus, has a main body that has a fixed end for fixing the main body, and a free end, a locating piece, situated between the fixed end and the free end; and an adjusting piece having a supporting part, supported between the free end and the locating piece, and an operating part, connected to the supporting part, and operable for adjusting the length of the supporting part in the direction of extension of the main body and thereby tensioning the main body.