Because of their intrinsic low level of mechanical vibrations pulse tube coolers (PTC) are attractive candidates for low-noise HT-SQUID cooling. Previous tests of a highly sensitive HT-SQUID that was mounted on the cold platform of a PTC, revealed discrete peaks which could be traced back to pressure wave-induced elastic residual vibrations of the cooler. Here we present vibration measurements on a pulse tube cooler that was modified in order to gain a very low level of mechanical vibration. A reduction of vibration was possible by mounting the sensor on a separate platform that was thermally anchored to the cold head using flexible copper braids. The remaining amplitude of axial vibrations was about 0.6 μm as compared to 6.0 μm for the former PTC cold head, both measured with a peak to peak pressure variation of 7 bar.
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