High spatial resolution neutron transmission imaging using a superconducting two-dimensional detector

Shishido, Hiroaki*; Nishimura, Kazuma*; Vu, TheDang*; Aizawa, Kazuya; Kojima, Kenji M*; Koyama, Tomio*; Oikawa, Kenichi; Harada, Masahide; Oku, Takayuki; Soyama, Kazuhiko; et al.

IEEE Transactions on Applied Superconductivity, 31(9), p.2400505_1 - 2400505_5, 2021/12

https://doi.org/10.1109/TASC.2021.3111396

In this study, we employed a superconducting detector, current-biased kinetic-inductance detector (CB-KID) for neutron imaging using a pulsed neutron source. We employed the delay-line method, and high spatial resolution imaging with only four reading channels was achieved. We also performed wavelength-resolved neutron imaging by the time-of-flight method. We obtained the neutron transmission images of a Gd-Al alloy sample, inside which single crystals of GdAl were grown, using the delay-line CB-KID. Single crystals were well imaged, in both shapes and distributions, throughout the Al-Gd alloy. We identified Gd nuclei via neutron transmissions that exhibited characteristic suppression above the neutron wavelength of 0.03 nm. In addition, the Gd resonance dip, a dip structure of the transmission caused by the nuclear reaction between an isotope and neutrons, was observed even when the number of events was summed over a limited area of 15 m 12 m. Gd selective imaging was performed using the resonance dip of Gd, and it showed clear Gd distribution even with a limited neutron wavelength range of 1 pm.

Homogeneity of neutron transmission imaging over a large sensitive area with a four-channel superconducting detector

Vu, TheDang; Shishido, Hiroaki*; Kojima, Kenji M*; Koyama, Tomio*; Oikawa, Kenichi; Harada, Masahide; Miyajima, Shigeyuki*; Oku, Takayuki; Soyama, Kazuhiko; Aizawa, Kazuya; et al.

Superconductor Science and Technology, 34(1), p.015010_1 - 015010_10, 2021/01

https://doi.org/10.1088/1361-6668/abc2af

Energy-resolved neutron imaging with high spatial resolution using a superconducting delay-line kinetic inductance detector

Iizawa, Yuki*; Shishido, Hiroaki*; Nishimura, Kazuma*; Vu, TheDang*; Kojima, Kenji M*; Koyama, Tomio*; Oikawa, Kenichi; Harada, Masahide; Miyajima, Shigeyuki*; Hidaka, Mutsuo*; et al.

Superconductor Science and Technology, 32(12), p.125009_1 - 125009_8, 2019/12

https://doi.org/10.1088/1361-6668/ab4e5c

Quantum phases in intrinsic Josephson junctions; Quantum magnetism analogy

Machida, Masahiko; Kobayashi, Keita; Koyama, Tomio*

Physica C, 491, p.44 - 46, 2013/08

https://doi.org/10.1016/j.physc.2013.02.004

no abstracts in English

Numerical study for electromagnetic wave emission from intrinsic Josephson junction stacks with a dielectric cover

Koyama, Tomio*; Matsumoto, Hideki*; Ota, Yukihiro*; Machida, Masahiko

Physica C, 491, p.20 - 23, 2013/08

https://doi.org/10.1016/j.physc.2013.01.001

no abstracts in English

Electromagnetic wave emission from intrinsic Josephson junction stacks; A Review of theory and simulation

Machida, Masahiko; Ota, Yukihiro*; Koyama, Tomio*; Matsumoto, Hideki*

Journal of Physics; Conference Series, 393, p.012013_1 - 012013_8, 2012/09

https://doi.org/10.1088/1742-6596/393/1/012013

Since the discovery of intrinsic Josephson effects in High-Tc cuprate superconductors, a tremendous number of theoretical and experimental studies have been made to clarify the coupling nature between stacked junctions. The reason comes from an expectation that Josephson junctions stacked in atomic-scale synchronize and high-power electromagnetic wave radiates. Consequently, two types of couplings, called "inductive and capacitive couplings" have been so far established. On the basis of the inductive coupling, several papers suggested that THz high-power emission is possible by using Josephson vortex flow states in the presence of layer parallel magnetic field and c-axis transport current. However, there has been no clear evidence of the emission in vortex flow states, although a few works found out only the sign. Afterwards, Ozyuzer et al., reported that they successfully observe a clear emission from intrinsic Josephson junctions. The situation was rather an unexpected one, since the magnetic field is not applied and the employed size is much larger than the experimental trends at that time. In this presentation, we review a history of the quest of the high power electromagnetic wave emission from intrinsic Josephson stacks before and after the Ozyuzer's work from a theoretical and numerical view. Especially, we would like to emphasize that direct numerical simulation techniques on multi-scale dynamical problems between inside and outside the junction have fully developed by authors.

Theory of phase dynamics in intrinsic Josephson junctions with multigap superconducting layers

Ota, Yukihiro; Machida, Masahiko; Koyama, Tomio*

Physica C, 471(21-22), p.760 - 762, 2011/11

https://doi.org/10.1016/j.physc.2011.05.047

We construct a theory of dynamical behavior in intrinsic Josephson junction stacks (IJJ's) with multi-gap superconducting layers, motivated by recent discovery rush of highly-anisotropic iron-based superconductors with a thick perovskite block layers. The theory predicts the existence of two kinds of phase modes, one of which is the Josephson plasma mode and other of which is the Leggett's mode. The IJJ's with multiple tunneling channels have a novel energy scale, inter-band Josephson coupling on each superconducting layer which generates a mass of the Leggett's mode. We discuss a cooperative phenomena induced by such a coupling in addition to capacitive and inductive couplings between the superconducting layers.

Collective modes and Josephson vortices in a heterotic Josephson junction between single- and two-gap superconductors

Ota, Yukihiro; Machida, Masahiko; Koyama, Tomio*; Matsumoto, Hideki*

Physica C, 470(Suppl.1), p.S882 - S883, 2010/12

https://doi.org/10.1016/j.physc.2009.10.023

We construct a theory of a heterotic Josephson junction between single- and two-gap superconductors. The theory predicts the presence of in-phase and out-of-phase collective modes of superconducting phases. The former is the Josephson plasma mode, and the latter is a counterpart of Leggett's mode in Josephson junctions. A signature for -wave superconductivity is a drastic reduction of the frequency of the Josephson plasma mode. We also show that the magnetic field distribution of the Josephson vortex for -wave superconductivity is more enlarged than that for s-wave without sign change between the order parameters.

Theory and simulation of electromagnetic wave emission from intrinsic Josephson junctions

Machida, Masahiko; Ota, Yukihiro; Sasa, Narimasa; Koyama, Tomio*; Matsumoto, Hideki*

Journal of Physics; Conference Series, 248, p.012037_1 - 012037_8, 2010/11

https://doi.org/10.1088/1742-6596/248/1/012037

no abstracts in English

First-principles calculations for anisotropy of iron-based superconductors

Nakamura, Hiroki; Machida, Masahiko; Koyama, Tomio*; Hamada, Noriaki*

Physica C, 470(20), p.1066 - 1069, 2010/11

https://doi.org/10.1016/j.physc.2010.05.037