arXiv subjects

Sho Masui

Publications and source records attributed to Sho Masui.

10 recordsLinked to original sources

arXiv2026

FINER: development of the wideband millimeter-wave receiver system and preparations for first light on the Large Millimeter Telescope

The recent discovery of an excess of luminous galaxies in the early Universe necessitates sensitive and wideband millimeter spectroscopy to understand their rapid growth. To address this, we present the development of the Far-Infrared Nebular Emission Receiver (FINER) for the Large Millimeter Telescope (LMT). The FINER frontend comprises two receivers covering 120-350 GHz (corresponding to ALMA Bands 4+5 and 6+7). The warm optics are designed to enable simultaneous two-band observations. Combined with the 10.24-GHz-wide digital spectrometer array, the system aims to deliver an instantaneous bandwidth approximately five times wider than current ALMA capabilities. We report that the 210-350 GHz receiver has already achieved commissioning-level performance, with sideband rejection further enhanced by the digital sideband separation technique. With installation expected in 2026, we discuss parallel preparations, including integrated testing and commissioning plans for first-look targets.

astro-ph.IM↗

arXiv2026

A Wideband Millimeter-wave Receiver at 210-350 GHz for LMT-FINER

The Far-Infrared Nebular Emission Receiver (FINER) project is developing two wideband dual-polarization sideband-separating receivers covering 120-210 GHz and 210-350 GHz to efficiently identify high-redshift galaxy candidates in the early universe. Based on high-critical-current-density superconductor-insulator-superconductor mixer technology originally developed for the ALMA wideband sensitivity upgrade, the FINER receivers are designed to provide an intermediate-frequency bandwidth of 3-21 GHz per sideband and per polarization, approximately five times wider than the current ALMA specifications. After installation on the Large Millimeter Telescope, these receivers are expected to offer highly efficient spectral-scanning capability among (sub)millimeterwave facilities in the northern-hemisphere. This paper reports the initial laboratory characterization of the 210-350 GHz receiver. The measured single sideband receiver noise temperature is approximately 100 K over most of the radio-frequency band. Digital sideband separation was also demonstrated using a wideband spectrometer array (DRS4), achieving an image rejection ratio of around 20 dB in the initial tests. These results represent an important step toward the realization of a wideband spectral-scanning receiver system for FINER.

astro-ph.IM↗

arXiv2026

Observations of DNC and DCO$^+$ toward the $\int$-shaped Filament and Starless Cores in the Orion Molecular Clouds

Although the deuterium fraction is known to be a powerful evolutionary tracer, its variation within individual molecular cloud cores is still poorly understood. The northern $\int$-shaped filament and 20 individual starless cores in the Orion A and B clouds were mapped in the deuterated molecules of DNC and DCO$^+$ with the Receiver 7BEE installed on the Nobeyama 45~m radio telescope. In a ~ 5' X 30' map of the northern $\int$-shaped filament in the Orion A cloud, the DNC emission is detected over the filament, whereas the DCO$^+$ emission is localized toward OMC-3, the northernmost region of the filament. The difference in distribution between DNC and DCO$^+$ can be attributed to that between N- and C-bearing molecules as previously suggested by Tatematsu et al. High DNC/HN$^{13}$C column density ratios were observed in OMC-2 and OMC-3, and low ratios in OMC-1. It seems that OMC-2 and OMC-3 still contain molecular gas close to the onset of star formation. In 3' X 3' maps of the individual starless cores in Orion, the column density ratios of DNC/HN$^{13}$C and DCO$^+$/H$^{13}$CO$^+$ are found to be rather constant locally within each core, although the core-to-core variation is not small. Similar timescales of deuterization, depletion, and dynamical evolution might explain the locally constant ratio.

astro-ph.GA↗

arXiv2025

Fabrication and characterization of Nb/Al-AlN /Nb superconducting tunnel junctions

We report a Nb/Al-AlN /Nb superconducting tunnel junction process in which the AlN barrier is formed by plasma nitridation using a compact microwave electron-cyclotron-resonance (ECR) nitrogen plasma source integrated into a standard sputter cluster. This enables growth of uniform tunnel barriers across a broad range of specific resistances, with $R_n A$ down to $\approx 3,\Omega,\mu\mathrm{m}^2$. Junctions maintain excellent quality, exhibiting $R_j/R_n \ge 25$ at the highest barrier transparencies. We characterize resistivity, specific capacitance, and the evolution of junction parameters under room-temperature aging and thermal annealing. A consistent calibration of the junction specific capacitance $C_s$ versus $R_n A$ is established and independently validated by the performance of demonstrator SIS mixers designed using the extracted $C_s$.

cond-mat.supr-con↗

arXiv2024

The Japanese Vision for the Black Hole Explorer Mission

The Black Hole Explorer (BHEX) is a next-generation space very long baseline interferometry (VLBI) mission concept that will extend the ground-based millimeter/submillimeter arrays into space. The mission, closely aligned with the science priorities of the Japanese VLBI community, involves an active engagement of this community in the development of the mission, resulting in the formation of the Black Hole Explorer Japan Consortium. Here we present the current Japanese vision for the mission, ranging from scientific objectives to instrumentation. The Consortium anticipates a wide range of scientific investigations, from diverse black hole physics and astrophysics studied through the primary VLBI mode, to the molecular universe explored via a potential single-dish observation mode in the previously unexplored 50-70\,GHz band that would make BHEX the highest-sensitivity explorer ever of molecular oxygen. A potential major contribution for the onboard instrument involves supplying essential elements for its high-sensitivity dual-band receiving system, which includes a broadband 300\,GHz SIS mixer and a space-certified multi-stage 4.5K cryocooler akin to those used in the Hitomi and XRISM satellites by the Japan Aerospace Exploration Agency. Additionally, the Consortium explores enhancing and supporting BHEX operations through the use of millimeter/submillimeter facilities developed by the National Astronomical Observatory of Japan, coupled with a network of laser communication stations operated by the National Institute of Information and Communication Technology.

astro-ph.IM↗

arXiv2024

Development Status of Wideband Millimeter-Wave Receivers for LMT-FINER

Spectroscopic observations of the far-infrared [O III] and [C II] lines present a pathway to explore the mechanisms of the emergence of massive galaxies in the epoch of reionization and beyond, which is one of the most fundamental questions in astronomy. To address this question, the Far-Infrared Nebular Emission Receiver (FINER) project is developing two wideband dual-polarization sideband-separating heterodyne receivers at 120--210 GHz and 210--360 GHz for the Large Millimeter Telescope (LMT) in Mexico. Compared with Atacama Large Millimeter/submillimeter Array (ALMA), LMT provides 40% of ALMA's light-collecting area and a similar atmospheric transmittance, but FINER plans to have an instantaneous intermediate frequency (IF) of 3--21 GHz per sideband per polarization which is five times wider than current ALMA's bandwidth. Therefore, FINER is going to offer cutting-edge spectral scanning capability in the next several years. The project is currently in an active development phase. In this proceeding, the latest development status for FINER, including the optics, wideband waveguide components as well as low-noise superconductor-insulator-superconductor (SIS) mixers is reported.

astro-ph.IM↗

arXiv2021

Development of a new wideband heterodyne receiver system for the Osaka 1.85-m mm-submm telescope -- Corrugated horn & Optics covering 210-375 GHz band

The corrugated horn is a high performance feed often used in radio telescopes. There has been a growing demand for wideband optics and corrugated horns in millimeter and submillimeter-wave receivers. It improves the observation efficiency and allows us to observe important emission lines such as CO in multiple excited states simultaneously. However, in the millimeter/submillimeter band, it has been challenging to create a conical corrugated horn with a fractional bandwidth of ~60% because the wavelength is very short, making it difficult to make narrow corrugations. In this study, we designed a conical corrugated horn with good return loss, low cross-polarization, and symmetric beam pattern in the 210-375GHz band (56% fractional bandwidth) by optimizing the dimensions of the corrugations. The corrugated horn was installed on the Osaka 1.85-m mm-submm telescope with the matched frequency-independent optics, and simultaneous observations of 12CO, 13CO, and C18O (J = 2-1, 3-2) were successfully made. In this paper, we describe the new design of the corrugated horn and report the performance evaluation results including the optics.

astro-ph.IM↗

arXiv2021

Development of a new wideband heterodyne receiver system for the Osaka 1.85-m mm-submm telescope -- Receiver development & the first light of simultaneous observation in 230GHz and 345GHz bands with an SIS-mixer with 4-21GHz IF output

We have developed a wideband receiver system for simultaneous observations in CO lines of J = 2-1 and J = 3-2 transitions using the Osaka 1.85-m mm-submm telescope. As a frequency separation system, we developed multiplexers that connect three types of diplexers, each consisting of branch-line couplers and high-pass filters. The radio frequency (RF) signal is eventually distributed into four frequency bands, each of which is fed to a superconductor-insulator-superconductor (SIS) mixer. The RF signal from the horn is divided into two frequency bands by a wideband diplexer with a fractional bandwidth of 56%, and then each frequency band is further divided into two bands by each diplexer. The developed multiplexers were designed, fabricated, and characterized using a vector network analyzer. The measurement results showed good agreement with the simulation. The receiver noise temperature was measured by connecting the SIS-mixers, one of which has a wideband 4-21GHz intermediate frequency (IF) output. The receiver noise temperatures were measured to be ~70K in the 220GHz band, ~100K in the 230GHz band, 110-175K in the 330GHz band, and 150-250K in the 345GHz band. This receiver system has been installed on the 1.85-m telescope at the Nobeyama Radio Observatory. We succeeded in the simultaneous observations of six CO isotopologue lines with the transitions of J = 2-1 and J = 3-2 toward the Orion KL as well as the on-the-fly (OTF) mappings toward the Orion KL and W 51.

astro-ph.IM↗

arXiv2020

Current status and future plan of Osaka Prefecture University 1.85-m mm-submm telescope project

We report the current status of the 1.85-m mm-submm telescope installed at the Nobeyama Radio Observatory (altitude 1400 m) and the future plan. The scientific goal is to reveal the physical/chemical properties of molecular clouds in the Galaxy by obtaining large-scale distributions of molecular gas with an angular resolution of several arcminutes. A semi-automatic observation system created mainly in Python on Linux-PCs enables effective operations. A large-scale CO $J=$2--1 survey of the molecular clouds (e.g., Orion-A/B, Cygnus-X/OB7, Taurus-California-Perseus complex, and Galactic Plane), and a pilot survey of emission lines from minor molecular species toward Orion clouds have been conducted so far. The telescope also is providing the opportunities for technical demonstrations of new devices and ideas. For example, the practical realizations of PLM (Path Length Modulator) and waveguide-based sideband separating filter, installation of the newly designed waveguide-based circular polarizer and OMT (Orthomode Transducer), and so on. As the next step, we are now planning to relocate the telescope to San Pedro de Atacama in Chile (altitude 2500 m), and are developing very wideband receiver covering 210--375 GHz (corresponding to Bands 6--7 of ALMA) and full-automatic observation system. The new telescope system will provide large-scale data in the spatial and frequency domain of molecular clouds of Galactic plane and Large/Small Magellanic Clouds at the southern hemisphere. The data will be precious for the comparison with those of extra-galactic ones that will be obtained with ALMA as the Bands 6/7 are the most efficient frequency bands for the surveys in extra-galaxies for ALMA.

astro-ph.IM↗

arXiv2020

Development of the new multi-beam receiver and telescope control system for NASCO

We report the current status of the NASCO (NAnten2 Super CO survey as legacy) project which aims to provide all-sky CO data cube of southern hemisphere using the NANTEN2 4-m submillimeter telescope installed at the Atacama Desert through developing a new multi-beam receiver and a new telescope control system. The receiver consists of 5 beams. The four beams, located at the four corners of a square with the beam separation of 720$''$, are installed with a 100 GHz band SIS receiver having 2-polarization sideband-separation filter. The other beam, located at the optical axis, is installed with a 200 GHz band SIS receiver having 2-polarization sideband-separation filter. The cooled component is modularized for each beam, and cooled mirrors are used. The IF bandwidths are 8 and 4 GHz for 100 and 200 GHz bands, respectively. Using XFFTS spectrometers with a bandwidth of 2 GHz, the lines of $^{12}$CO, $^{13}$CO, and C$^{18}$O of $J$=1$-$0 or $J$=2$-$1 can be observed simultaneously for each beam. The control system is reconstructed on the ROS architecture, which is an open source framework for robot control, to enable a flexible observation mode and to handle a large amount of data. The framework is commonly used and maintained in a robotic field, and thereby reliability, flexibility, expandability, and efficiency in development are improved as compared with the system previously used. The receiver and control system are installed on the NANTEN2 telescope in December 2019, and its commissioning and science verification are on-going. We are planning to start science operation in early 2021.

astro-ph.IM↗