Progress in low noise cooling performance of a pulse-tube cooler for HT-SQUID operation
Progress in low noise cooling performance of a pulse-tube cooler for HT-SQUID operation
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用于 HT-SQUID 操作的脉冲管冷却器的低噪声冷却性能的进展
DOI：
10.1109/77.919468
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发表时间：
2001
影响因子：
1.8
通讯作者：
C. Heiden
中科院分区：
文献类型：
--
作者：
C. Lienerth;G. Thummes;C. Heiden
此前的研究表明，焦耳-汤姆逊冷却器和脉冲管冷却器 (PTC) 是 HT-SQUID 低噪声冷却的有吸引力的候选者。对直接安装在这些冷却器冷端上的高灵敏度 HT-SQUID 进行的测试显示，通量噪声频谱中存在离散峰值，这是由压力波引起的冷却器振动造成的。通过使用 Ti-V-Al 管代替不锈钢作为再生器和脉冲管，首次实现了 PTC 的额外降噪。通过将传感器安装在一个单独的平台上，该平台通过使用柔性铜链路热连接到冷端，可以进一步减少压力。测得冷平台处的剩余轴向振动幅度约为 0.5 /spl mu/m，而没有振动补偿时则为 6.0 /spl mu/m。我们报告了 PTC 不同振动补偿方法的测试，使用带有共面谐振器的灵敏 rf HT-SQUID 磁力计，显示在 100 Hz 以上的频率下固有噪声为 45 fT//spl 基数/Hz，在 10 Hz 频率下为 110 fT//spl 基数/Hz。将介绍使用新型 PTC 冷头对 HT-SQUID 通量噪声频谱进行的测量。
Previously it was shown that Joule-Thomson- and pulse tube coolers (PTC) are attractive candidates for low noise cooling of HT-SQUIDs. Tests of a highly sensitive HT-SQUID that was mounted directly on the cold tips of these coolers revealed discrete peaks in the flux noise spectrum which were attributed to pressure wave-induced vibrations of the coolers. A first additional noise reduction for the PTC was achieved by using Ti-V-Al tubes instead of stainless steel for the regenerator and pulse tube. Further reduction was obtained by mounting the sensor on a separate platform that was thermally connected to the cold tip by use of a flexible copper link. The remaining amplitude of axial vibrations at the cold platform was measured to be about 0.5 /spl mu/m as compared to 6.0 /spl mu/m without vibration compensation. We report on the tests of different methods of vibration compensation for the PTC, using a sensitive rf HT-SQUID magnetometer with coplanar resonator showing an intrinsic noise of 45 fT//spl radic/Hz at frequencies above 100 Hz and 110 fT//spl radic/Hz at 10 Hz. Measurements of the flux noise spectrum of the HT-SQUID using the new PTC cold head will be presented.