Miniaturized cooling systems for HTS antennas

Two types of miniaturized cooling systems for High-Temperature Superconducting (HTS) antennas were designed and built. In this paper, details of these systems, measured and simulated properties of patch antennas installed in these systems, and results of a seal-off trial for 1 month are reported. Both the systems had portable size and weight and could cool the HTS devices. When a patch antenna with resonant frequency of 4.9 GHz was installed in the 1st cooling system, the radiation pattern of the antenna was strongly focused in the forward direction. This is because the vacuum chamber in which the antenna was packaged influenced the microwaves radiated from the antenna. Due to this effect, the directive gain of the antenna was enhanced by 11.2 dB. In the 2nd system, a seal-off trial was carried out to investigate the airtight property that is necessary for thermal isolation. The temperature of the sample stage could be kept under the critical temperature of YBCO for 1 month without continuous vacuum pumping. The cooling systems developed in this work are expected to promote the practical use of HTS antennas.