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Gamma-ray transition edge sensors (TESs) are intensively studied not only to measure isotopic composition of nuclear materials but to monitor transuranic radionuclides inside the human body. We have recently proposed a thick-trilayer membrane as an alternative to silicon-nitride (Si x N y ) single-layer ones. It consists of silicon dioxide (SiO 2 ), Si x N y , and SiO 2 layers. Their total thickness is 6.9 μ m and exhibits almost the same thermal conductance as conventional Si x N y ones with 1- μ m thickness. The thick-trilayer membrane is expected to have better mechanical strength against implementing heavy-bulk absorbers. In this paper, the gamma-ray TES with the thick-trilayer membrane is used to carry out the spectroscopy for the nuclear radiation source. Neptunium-237 and its decay product Protactinium-233 emit 86.5 and 86.6-keV lines, respectively, and they are clearly resolved by four pixels with the full-width-half-maximum (FWHM) resolution of ( 43.7 ± 0.9 ) eV. Furthermore, their intensity ratio agrees with the radioactive equilibrium between the two nuclides. Our experimental results predict that a vast array of pixel formats will reduce the statistical uncertainty in less measuring time. [ABSTRACT FROM AUTHOR]

The performance of a traveling-wave type LiNbO3 optical modulator with superconducting electrode was evaluated. Calculated values of the attenuation constants of the device's superconducting and normal-conducting striplines show that the performance of this optical modulator may be superior than modulators using normal metals with respect to the figure of merit of bandwidth/driving-voltage.

Thick membranes of the gamma-ray transition-edge sensor (γ -TES) generally exhibit great mechanical strength and can support a bulk metal absorber typical for γ -TES. However, for conventional silicon-nitride (SixNy) membranes, thermal conductance (G) is proportional to the thickness, indicating that thicker membranes provide larger thermal-fluctuation noise in TESs. We propose a thick-trilayer membrane consisting of the silicon oxide (SiO2), SixNy, and SiO2 layers. The SixNy layer accounts for 5.8 μm of the total 6.9 μm, and thus, it is expected to be hard compared with conventional SixNy membranes with a typical thickness below 1 μm. G of the trilayer membrane is characterized as a function of heat-transport distance (L), and the G-L relation follows that of the intermediate model between ballistic and diffusive transports. Resulting G of the thick-trilayer membrane is 1.1–1.7 nW/K, which is not far from the one reported by conventional SixNy membranes. Gamma-ray spectroscopy around 93 keV is carried out based on series biased 5-pixels TES. The best full-width-half-maximum energy resolution among all pixels under characterization is 43.1 ± 1.6 eV for 93-keV, which is close to the median value of a state-of-the-art 236-pixels γ -TES in the literature. The measured low-frequency noise can be represented by theoretical phonon noise and its excess component with the same order as conventional ones. The thick-trilayer membrane is demonstrated to be able to work without any problems in a γ -TES regime. [ABSTRACT FROM AUTHOR]

Two, five and 10 stacked NbCN/MgO/NbCN Josephson junctions with thin intermediate electrodes were developed in a computerized sputtering system. Measured tunneling data revealed that the intermediate electrodes' energy gap reduced with the thickness linearly depending on 1/d, with d as the number of stacks and thickness of electrodes. Results also show that the junctions' quality parameter decreased with the rise of stack number and with the decrease of electrode thickness.

The modulation of quasiparticle injection-induced self-resonant modes in NbCN/MgO/NbCN Josephson junctions is studied in the submillimeter wave region. The voltage-current characteristics of the devices are measured at 4.2 degrees Kelvin and varying magnetic field levels. Results show that the Q factors due to electrode loss at the injected state decrease with the increase in the bias voltage of the injector.

The electrical characteristics of flux-flow-type Josephson oscillators (FFOs) with epitaxial NbCn/MgO/NbCn junctions were studied. The FFOS, which were fabricated by the radio frequency-magnetron sputtering of NbCn/MgO/NbCn layers on the MgO substrate, were tested for their magnetically-induced current-voltage behavior using a four-terminal method. Results show that the oscillators are capable of operating with high output power at very high frequencies.

The experimental and analytical current-voltage characteristics of four types of direct current superconducting quantum interference devices with different parameters of coupling section were studied. The mechanism and damping condition for resonant peak in the devices' were then evaluated based on the devices' current-voltage properties. A strong agreement is observed between the experimental and analytical results.

Submillimeter-wave surface resistances of epitaxial and polycrystalline NbCN thin films have been computed from current-voltage measurements of Josephson tunnel junctions operating in the Friske-resonant mode at 4.2 K. The obtained values revealed that the surface resistance of polycrystalline films are one order of magnitude higher than those of epitaxial films. The results also indicated that the surface resistance can be described as a function of frequency with the two-fluid model.

An experiment to study proximity-effect induced superconductivity was conducted on yttrium-barium-copper-oxide/gold (YBCO/Au) junctions with a-, c- and (103)-orientations. The investigation, which utilized low temperature scanning tunneling microscopy at 4.2 K, also examined niobium/nitrogen interfaces. It provided no evidence of proximity-effect induced superconductivity for the a- and c-oriented YBCO/Au junctions although gap structures were detected in the (103)-oriented structures.

Presents a study which investigated the effects of a damping resistance on noise characteristics of a direct current Superconducting Quantum Interference Device (SQUID). Equivalent circuit of the SQUID; Results and discussion; Conclusion.