Temperature sensing and control are essential in experiments running in cryocooled systems, as with the case of liquid helium-free superconducting devices. A Josephson junction as on-chip temperature sensor operated in ac provides the highest sensitivity and minimal power loading to the cryogenic environment, thanks to the noise rejection of lock-in detection. To demonstrate the advantages of on-chip sensing, we tested it with a Josephson voltage standard array in cryocooler and compared with the conventional case of a sensor on the cold surface of the refrigerator, showing that the power dissipated within the chip may further increment the device temperature up to some tenths of kelvin. An ac Josephson junction sensor is proven to be capable of directly stabilizing the temperature of the superconductive circuit from fluctuations of dissipated power during operation. Reliability issues related to flux trapping are discussed and solutions are proposed suited to different applications. Overall, on-chip control with ac Josephson temperature sensing has the advantage of avoiding the complexities in minimization of cryogenic thermal links, virtually reducing to zero the contact resistance and keeping the operating temperature of the superconductor constant, independently of instantaneous operating power.

与无液氦超导设备一样，在低温冷却系统中运行的实验中，温度感测和控制至关重要。约瑟夫森结作为片上温度传感器在交流电下工作，这归功于锁定检测的噪声抑制能力，从而为低温环境提供了最高的灵敏度和最小的功率负载。为了演示片上传感的优势，我们在低温冷却器中用约瑟夫森电压标准阵列对其进行了测试，并将其与冰箱冷表面上传感器的常规情况进行了比较，结果表明，芯片内耗散的功率可能会进一步增加传感器的功耗。设备温度高达开尔文的十分之一。事实证明，交流约瑟夫森结传感器能够直接稳定超导电路的温度，使其免受运行过程中功耗的波动的影响。讨论了与通量捕获有关的可靠性问题，并提出了适合于不同应用的解决方案。总的来说，采用交流约瑟夫森温度感测的片上控制的优势在于避免了将低温热链接最小化的复杂性，实际上将接触电阻减小至零，并使超导体的工作温度保持恒定，而与瞬时工作功率无关。