Magnetic shielding of Josephson parametric amplifier for axion searching experiment with haloscope

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题名:	Magnetic shielding of Josephson parametric amplifier for axion searching experiment with haloscope
作者:	賴紹白;Lai, Shao-Bai
贡献者:	物理學系
关键词:	超導線圈;磁場屏蔽罩;Superconducting coil;magnetic shielding
日期:	2024-06-13
上传时间:	2024-10-09 15:45:13 (UTC+8)
出版者:	國立中央大學
摘要:	The Taiwan Axion Search Experiment with Haloscope (TASEH) 是一個利用微波共振腔搜索暗物質的團隊。在這個實驗中，外加9特斯拉的強磁場，讓我們想要尋找的粒子—軸子與磁場相互作用並轉化為可探測的光子。為探測微小的信號，需要一個具有高訊噪比的放大器。約瑟夫森參數放大器 (JPA) 是我們放大鏈中的第一階段放大器，該放大器具有量子極限的外加噪聲。然而，JPA 對磁場非常敏感，我們在實驗中施加9特斯拉的磁場，因此需要設計磁場屏蔽來保護 JPA。磁場屏蔽總共有五層，從外到內分別是：超導線圈、第一層mu-metal、鉛、第二層mu-metal和鈮。超導線圈作為磁屏蔽的原理是基於法拉第定律和邁斯納效應。mu-metal由於其高透磁率可以作為磁屏蔽。鉛和鈮是超導體；當溫度低於其臨界溫度時，它們可以由於邁斯納效應而作為磁屏蔽。我們準備了兩種不同製程的超導線圈焊接方式：一種是冷焊接法，另一種是使用鉛鉍合金作為焊料 (PbBi 方法)。通過控制焊點的溫度在其臨界溫度以及磁場的增減，可以量測焊點的電阻、線圈對磁場的承受能力和線圈的屏蔽效果。根據我們的發現，PbBi 樣本的電阻小於 $10^{-13} \Omega$，而冷焊樣本的電阻為 $10^{-11} \Omega$。PbBi 樣本展示出比冷焊樣本更大的磁場承受力。兩種樣本都可以屏蔽大約三分之一的外部磁場。我們使用PbBi方法製作了三個超導線圈，並將它們安裝在z=27公分、31公分和36公分的位置（z=0為磁鐵的中心）。實驗中，頂部和底部的線圈無法正常工作。中間的線圈可以屏蔽約$40\%$的外部磁場。未來，我們將修復這兩個品質較差的線圈，並在更高的磁場（超過4.2特斯拉）下進行測試。如果這些線圈能在高磁場下正常工作，我們將把它們與其他四層屏蔽層結合，然後在屏蔽層內安裝JPA裝置，測試JPA的運行情況。;The Taiwan Axion Search Experiment with Haloscope (TASEH) uses a microwave cavity in a 9 Tesla magnetic field to detect dark matter axions by converting them into photons. A Josephson Parametric Amplifier (JPA) with a high signal-to-noise ratio is used to detect the small signal. Since JPA is sensitive to magnetic fields, a five-layer magnetic shielding is designed: superconducting coils, the first mu-metal shield, lead (Pb) shield, the second mu-metal shield, and niobium (Nb) sheet. These layers use Meissner effect and high permeability to protect the JPA from the magnetic field. We prepare two kinds of joints for superconducting coils using different fabrication processes: the cold-welding method and the lead-bismuth alloy as solder (the PbBi method). By controlling the temperature of the joints higher and under their critical temperature and ramping the magnet, we can examine the joints′ resistance, capability of persistent current, and shielding effect. According to our findings, the resistance upper bound of the PbBi sample is $ R \ll \frac{L}{\tau} \sim \times 10^{-13} \ \Omega $, while the cold-welding sample is $R =\frac{L}{\tau} = \frac{90 nH}{21 hours} = 10^{-11} \Omega$. The PbBi sample exhibits a greater capability for induced persistent current than the cold-welding sample. Both samples can shield approximately one-third of the external field. We use the PbBi method to make three superconducting coils and install them at positions z= 27cm, 31 cm, and 36 cm (z=0 is at the magnet′s center). The top and the bottom coils can not work correctly in the experiment. The middle coil can shield about $40\%$ of the external field. In the future, we will repair two bad-quality coils and test them under a higher field (greater than 4.2 Tesla). If the coils can work properly in the higher field, we will combine them with the other four shielding layers and then install the JPA device inside the shielding to test the operation of JPA.
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