To reduce convection loss related to different temperature characteristics between a cold storage apparatus of a multi-stage pulse tube to be mounted in helium gas in a neck tube of an MRI cryostat and the pulse tube.

The convection loss related to the different temperature characteristics between the cooling storage apparatus of the multi-stage pulse tube to be mounted in helium gas in the neck tube of the MRI cryostat and the pulse tube is reduced, by disposing one or more heat bridges, a thermal insulation sleeve, and/or one or more pulse tubes between one or more pulse tubes and the cooling storage apparatus and disposing a spacer and spacer tube in the cooling storage apparatus.