PROBLEM TO BE SOLVED: To provide a mixing promotion structure capable of sufficiently mixing gas, such as helium gas having high viscosity and promoting the mixing to uniformize a temperature even though the temperatures of gases to be mixed are different.
SOLUTION: A mixing promotion structure 100 consists of a joining part double pipe 140 for joining a first double pipe 10 consisting of a first inner pipe and a first outer pipe arranged on the outer periphery of the first inner pipe and a second double pipe 20 consisting of a second inner pipe and a second outer pipe arranged on the outer periphery of the second inner pipe; a mixing promotion part double pipe 150 extended from the joining part double pipe 140; and a main double pipe 30 extended from the mixing promotion part double pipe 150. A baffle plate 160 is arranged in the mixing promotion part double pipe 150.