STUDY ON AN INNOVATIVE VIBRATION-CANCELLATION METHOD FOR A PULSE TUBE CRYOCOOLER

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An innovative method for canceling the vibration at the cold stage of a pulse tube cryocooler has been investigated. A thin stainless tube of 20 mm in diameter and 200 mm in length was used to fabricate a model pulse tube cryocooler. The vibration of the cold stage of model cryocooler was measured for proving a method of this innovative vibration cancellation. A model cryocooler consists of multi-pairs of pipes on the same cold stage. When a presented working gas is supplied with a proper phase shift to those pairs, the vibration of the cold stage can be cancelled. We made models of the pulse tube cryocooler with a single pipe, two pairs of pipes and three pairs of pipes. Compared with the single-pipe model, the six-pipe model shows about a 98% reduction of vibration without any additional structure for vibration isolation.Then, we also made the regenerators with 500 sheets of stainless mesh # 100, and set up those components inside of the thin tube to realize the pulse tube cryocooler. The self-vibration canceling pulse tube cryocooler with two set of tube and regenerator was operated to verify cooling power. The cold stage was cooled down to 168 K as the lowest temperature by using a GM type helium compressor, digital circuits for anti-phase signal generation and the solenoid valves for pressure swing. In this condition, the model showed about a 70 % reduction of vibration. As the symmetry of two sets of pulse tube cryocooler is essential in this method, any asymmetric configuration could affect on effective vibration reduction.