A thermal radiation shield for cryogenic devices, especially cryogenic pu (cryopumps) comprises a stack of spaced apart plates formed preferably with a V-section configuration and lugs or openings enabling the plates to be stacked with appropriate spacers upon tubes through which a coolant is passed. The plates have an annular configuration, i.e. the V-section is closed along an annulus. The plates are so stacked as to overlap in the stacking direction, i.e. the vertex of the V of one plate is coplanar with the rim of the next plate or the vertex lies within the V of the next plate.