GM cryocooler and method of operating GM cryocooler

A GM cryocooler comprising:

• a first cold head including:
• a first displacer that is reciprocable in an axial direction,
• a first cylinder that houses the first displacer,
• a first drive piston that drives the first displacer in the axial direction, and
• a first drive chamber that houses the first drive piston;
• a second cold head including:
• a second displacer that is reciprocable in the axial direction,
• a second cylinder that houses the second displacer,
• a second drive piston that drives the second displacer in the axial direction, and
• a second drive chamber that houses the second drive piston;
• a first intake valve that is connected to both the first drive chamber and the second cylinder so as to supply a working gas in parallel to the first drive chamber and the second cylinder;
• a first exhaust valve that is connected to both the first drive chamber and the second cylinder so as to collect the working gas in parallel from the first drive chamber and the second cylinder;
• a second intake valve that is connected to both the second drive chamber and the first cylinder so as to supply the working gas in parallel to the second drive chamber and the first cylinder;
• and
• a second exhaust valve that is connected to both the second drive chamber and the first cylinder so as to collect the working gas in parallel from the second drive chamber and the first cylinder.