Lumped element kinetic inductance detectors (LEKIDs) are made from a single layer superconducting thin film. Because of their low noise and highly multiplexibility, LEKIDs provide a sensitive technology for the detection of millimeter and submillimeter waves. In this work, a 5-pixel 50-nm-thick MgB2 array is made. The microwave properties of the array are measured under dark conditions. We show that the loaded quality factor Q of the resonant circuit is 30 000 at 7.5 K, which is comparable to that of lower-operating-temperature (usually several hundred mK) LEKIDs made from superconductors such as Al and Nb. Moreover, the temperature dependence of resonance frequency gives the two-gap character of MgB2, Δπ (0) = 2.58 meV and Δσ (0) = 8.26 meV. The gap frequency (f = 2Δ/h) indicates that MgB2 LEKIDs have a promising application on terahertz detection.

Magnetic shielding has been a key factor in the measurement of ultra-weak magnetic fields, especially for shielding from low frequency electromagnetic noise. With the recent development of superconducting quantum interference devices, superconducting magnetic shielding has become an important area of research. MgB 2 has shown great potential in magnetic shielding for its remarkable superconducting properties, the feasibility of its use in this capacity having been demonstrated by MgB 2 bulk samples. However, the potential for application of such bulk samples is limited. In this work, we have investigated the possibility of the fabrication of MgB 2 films on three-dimensional (3D) structures using a hybrid physical−chemical vapor deposition system. MgB 2 films 10 μm thick have been fabricated on the outer surface of a polycrystalline Al 2 O 3 cylinder. The deposited film showed a transition temperature (T C ) of 39 K and J C of 5.1×10 5 A•cm −2 , which are comparable to those of planar MgB 2 films. This work shows the feasibility of depositing MgB 2 films onto a 3D structure, and sheds light on the potential use of MgB 2 films in superconducting magnetic shielding.

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