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.
In this paper, we introduce the receiver architecture for the Black Hole Explorer (BHEX) Mission, designed to reveal the photon ring of black holes. The primary instrument is a dual-polarization receiver operating over the 240-320 GHz frequency range, utilizing a Superconductor-Insulator-Superconductor (SIS) mixer. This Double-Side-Band (DSB) receiver has an intermediate frequency (IF) range of 4-12 GHz and operates at a bath temperature of 4.5 K, for optimal performance , which necessitates the integration of a cryocooler. Complementing the primary receiver is a secondary unit covering the 80-106 GHz spectrum, featuring a cryogenic low noise amplifier. This secondary receiver, affixed to the cryocooler’s 20 K stage, serves to augment the SIS receiver’s performance by employing the Frequency Phase Transfer technique to boost the signal-to-noise ratio at the correlator output. Together, this sophisticated receiver duo is engineered to achieve the quantum-limited sensitivity required to detect the photon ring of black holes, marking a breakthrough in astrophysical observation.
This paper introduces a potential low-power-consumption and low-noise microwave amplifier operated at cryogenic temperature, essential for large-scale multi-pixel heterodyne receivers and fault-tolerant quantum computers. The amplifier employs two millimeter-wave superconductor-insulator-superconductor (SIS) mixers as amplifying elements and a millimeter-wave Josephson array oscillator as the local oscillator source. A proof-of-concept experiment utilizing waveguide SIS mixer modules demonstrated an average gain of approximately 7.5 dB and a noise temperature of around 10 K at microwave frequencies. Additionally, a waveguide Josephson array oscillator module, developed to validate the design, exhibited an output power of roughly 52 nW, estimated from the response of a waveguide SIS detector connected to the oscillator module. These findings indicate the feasibility of realizing a monolithically integrated amplifier chip incorporating SIS mixers and a Josephson array oscillator.
KEYWORDS: Receivers, Optical amplifiers, Radio astronomy, Antennas, Astronomy, Observatories, Cryogenics, Simulation of CCA and DLA aggregates, Roads, Galactic astronomy
The Atacama large millimeter/submillimeter array (ALMA) band-1 receiver covers the frequency band between 35-50 GHz. An extension of up to 52 GHz is on a best-effort basis. Covering the longest wavelengths visible with ALMA, this receiver is enabling studies of dust grain evolution in proto-planetary systems probing dust grain sizes close to 1 cm, and with multiple red-shifted molecular lines it will open up a new window in the high-redshift universe. The band-1 project has recently achieved first light and with this passed a major project milestone. We present the challenges, from initial development to prototype, to establishing the infrastructure, integration, and evaluation of 73 production receiver units, and to the final tasks to complete the project. We conclude with the initial performance and characterization of the first band-1 receivers installed on ALMA.
We present the results of a digital calibration technique applied to an Atacama Large Millimeter/submillimeter Array sideband separating wideband astronomical receiver of 275 to 500 GHz radio frequency (RF) and 3 to 22 GHz intermediate frequency bandwidth. The calibration technique consists of computing the magnitude ratio and the phase difference of the receiver output, and then applying correction constants to the digitized signals. Two analog-digital converters are used to digitize the signals and an field-programmable gate array for the processing. No modification in the analog receiver is required to apply the calibration, as it works directly on upper sideband/lower sideband signals. The technique improved the receiver temperature compared with the double sideband case by increasing the sideband rejection ratio by around 30 dB on average. It is shown that even more rejection can be obtained with more careful control of the RF calibration input power.
The ALMA telescope has been producing ground-breaking science since 2011, but it is mostly based on technology from the 2000s. In order to keep ALMA competitive in the coming decade, timely updates are necessary in order to further improve the science output of the telescope in the coming decades. In this contribution, we will present the status of the different projects and studies which constitute the contribution of East Asia to the ALMA Development Program, such as the production of band 1 receivers, the development of band 2 receivers optics, and of the ACA spectrometer. We will also update on the different hardware and software studies towards the implementation of the ALMA Development Roadmap and additional opportunities.
In recent years, NAOJ has contributed designs and production of waveguide and optics components for ALMA bands 1 (35-50 GHz) and 2 (67-116 GHz) receivers. This includes several novel ideas in the design of corrugated horns and OMTs and the application of 3D printing for the fabrication of key components of radio receivers. These frequency bands coincide approximately with bands 5 and 6 of ngVLA, the most promising project in the 2020s to exploit synergies with ALMA with the goal of increasing the scientific output of both facilities. This paper reports on the recent ALMA development results and discusses their future application to ngVLA.
We are investigating a possible microwave amplifier with low noise and low power consumption at cryogenic temperature for large scale multi-pixel heterodyne superconductor-insulator-superconductor (SIS) receivers at millimeter and submillimeter wavelengths. We propose the use of SIS junctions as amplifier elements based on quasi-particle mixing. By connecting an SIS up-converter and an SIS down-converter in series with gain in both converters, a lownoise and low-power-consumption high-frequency amplifier can be obtained in principle. A proof-of-concept study has been made by configuring an amplifier with two Nb/Al-AlOx/Nb mixers in the 150-GHz band in a standard noise and gain measurement setup at 4 K with a microwave noise source as an input signal. We observed a maximum gain of more than 10 dB and a minimum noise temperature of less than 10 K, which suggests that our proposed SIS amplifier is capable for multi-pixel SIS receivers. On the other hand, we also observed a periodical behavior in frequency dependence of the measured noise temperature and gain due to a standing-wave effect between the two SIS mixers, which is a problem to be solved.
A compact 780–950 GHz sideband separating (2SB) superconductor-insulator-superconductor (SIS) mixer measuring 22 mm × 27 mm × 11 mm is designed in this study. In this mixer block, all components such as a radio frequency (RF) 90° hybrid coupler, a local oscillator (LO) power splitter, two LO couplers, two identical SIS chips, and an intermediate frequency (IF) 90° hybrid coupler are integrated. To minimize the waveguide length for the RF signal path, we separate the placement of the waveguide components into two layers in parallel. One layer contains the RF hybrid and LO couplers, and another layer contains the LO power splitter located above the RF hybrid coupler. They are connected by waveguides fabricated via wire electric discharge machining. We performed three-dimensional electromagnetic simulations and confirmed the results. Furthermore, a 4-12-GHz IF 90° hybrid coupler to combine the IF signals from each SIS chip is designed with an alumina substrate having a relatively high dielectric constant to be integrated in the mixer block. The preliminary test result of single sideband noise temperatures of the fabricated 2SB SIS mixer partly complied with the current Atacama Large Millimeter/submillimeter Array (ALMA) specifications without any loss correction in front of the receiver. Because the RF and LO interfaces of the mixer block are the same as that of the current ALMA band 10 mixer block, band 10 cartridges are expected to be upgraded to 2SB configurations without significant changes in optics.
NAOJ have studied wideband receiver technologies at submillimeter wavelengths toward implementation as future upgrades into the Atacama Large Millimeter/submillimeter Array telescope. We have developed critical components and devices such as waveguide components and superconductor-insulator-superconductor (SIS) mixers targeting radio frequencies (RF) in the 275-500 GHz range and an intermediate frequency (IF) bandwidth of 3-22 GHz. Based on the developed components, quantum-limited low-noise performance has been demonstrated by using a double-sideband receiver frontend in combination with a high-speed digitizer. In addition, a preliminary demonstration of a wideband RF/IF sideband-separating SIS mixer was performed. This paper describes the status of our efforts to develop technology toward wideband receivers for ALMA.
LiteBIRD is a next generation satellite aiming for the detection of the Cosmic Microwave Background (CMB) B-mode polarization imprinted by the primordial gravitational waves generated in the era of the inflationary universe. The science goal of LiteBIRD is to measure the tensor-to-scaler ratio r with a precision of δr < 10-3♦, offering us a crucial test of the major large-single-field slow-roll inflation models. LiteBIRD is planned to conduct an all sky survey at the sun-earth second Lagrange point (L2) with an angular resolution of about 0.5 degrees to cover the multipole moment range of 2 ≤ ℓ ≤ 200. We use focal plane detector arrays consisting of 2276 superconducting detectors to measure the frequency range from 40 to 400 GHz with the sensitivity of
3.2 μK·arcmin. including the ongoing studies.
Satellite missions for measuring winds in the troposphere and thermosphere will be launched in a near future. There is no plan to observe winds in the altitude range between 30-90 km, though middle atmospheric winds are recognized as an essential parameter in various atmospheric research areas. Sub-millimetre limb sounders have the capability to fill this altitude gap. In this paper, we summarize the wind retrievals obtained from the Japanese Superconducting Submillimeter Wave Limb Emission Sounder (SMILES) which operated from the International Space Station between September 2009 and April 2010. The results illustrate the potential of such instruments to measure winds. They also show the need of improving the wind representation in the models in the Tropics, and globally in the mesosphere. A wind measurement sensitivity study has been conducted for its successor, SMILES-2, which is being studied in Japan. If it is realized, sub-millimeter and terahertz molecular lines suitable to determine line-of-sight winds will be measured. It is shown that with the current instrument definition, line-of-sight winds can be observed from 20 km up to more than 160 km. Winds can be retrieved with a precision better than 5 ms-1 and a vertical resolution of 2-3 km between 35-90 km. Above 90 km, the precision is better than 10 ms-1 with a vertical resolution of 3-5 km. Measurements can be performed day and night with a similar sensitivity. Requirements on observation parameters such as the antenna size, the satellite altitude are discussed. An alternative setting for the spectral bands is examined. The new setting is compatible with the general scientific objectives of the mission and the instrument design. It allows to improve the wind measurement sensitivity between 35 to 90 km by a factor 2. It is also shown that retrievals can be performed with a vertical resolution of 1 km and a precision of 5-10 ms-1 between 50 and 90 km.
We present the mission design of LiteBIRD, a next generation satellite for the study of B-mode polarization and inflation from cosmic microwave background radiation (CMB) detection. The science goal of LiteBIRD is to measure the CMB polarization with the sensitivity of δr = 0:001, and this allows testing the major single-field slow-roll inflation models experimentally. The LiteBIRD instrumental design is purely driven to achieve this goal. At the earlier stage of the mission design, several key instrumental specifications, e.g. observing band, optical system, scan strategy, and orbit, need to be defined in order to process the rest of the detailed design. We have gone through the feasibility studies for these items in order to understand the tradeoffs between the requirements from the science goal and the compatibilities with a satellite bus system. We describe the overview of LiteBIRD and discuss the tradeoffs among the choices of scientific instrumental specifications and strategies. The first round of feasibility studies will be completed by the end of year 2014 to be ready for the mission definition review and the target launch date is in early 2020s.
This paper summarizes the performance of all the 73 ALMA band 10 cartridges in terms of noise performance and/or optical efficiencies compared to the required ALMA specifications. In particular, the measured optical performance is compared with the results of novel statistical Monte Carlo analyses carried out before receiver production. Some of the technical difficulties encountered during production are briefly described. Finally, some of the first light results of the first receivers used in Chile are presented.
A precise measurement of the Cosmic Microwave Background (CMB) provides us a wealth of information about early universe. LiteBIRD is a future satellite mission lead by High Energy Accelerator Research Organization (KEK) and its scientific target is detection of the B-mode polarization of the CMB, which is a footprint of primordial gravitational waves generated during inflation era, but has not been successfully observed so far due to lack of sensitivity. Microwave Kinetic Inductance Detector (MKID) is one candidate of sensitive millimeterwave camera which will be able to detect the B-mode polarization. We have been developing MKID at National Astronomical Observatory of Japan (NAOJ) in cooperation with KEK and RIKEN for the focal plane detector of the LiteBIRD. The developed technologies are: fabrication process of MKIDs with epitaxially-formed aluminum (Al) on silicon (Si) wafer; optical system of the camera consisting of double-slot antenna with Si lens array; and readout circuit utilizing Fast Fourier Transform Spectrometer (FFTS). With these technologies, we designed a prototype MKIDs camera for the LiteBIRD.
LiteBIRD [Lite (Light) satellite for the studies of B-mode polarization and Inflation from cosmic background
Radiation Detection] is a small satellite to map the polarization of the cosmic microwave background (CMB)
radiation over the full sky at large angular scales with unprecedented precision. Cosmological inflation, which
is the leading hypothesis to resolve the problems in the Big Bang theory, predicts that primordial gravitational
waves were created during the inflationary era. Measurements of polarization of the CMB radiation are known as
the best probe to detect the primordial gravitational waves. The LiteBIRD working group is authorized by the
Japanese Steering Committee for Space Science (SCSS) and is supported by JAXA. It has more than 50 members
from Japan, USA and Canada. The scientific objective of LiteBIRD is to test all the representative inflation models that satisfy single-field slow-roll conditions and lie in the large-field regime. To this end, the requirement
on the precision of the tensor-to-scalar ratio, r, at LiteBIRD is equal to or less than 0.001. Our baseline design
adopts an array of multi-chroic superconducting polarimeters that are read out with high multiplexing factors in
the frequency domain for a compact focal plane. The required sensitivity of 1.8μKarcmin is achieved with 2000
TES bolometers at 100mK. The cryogenic system is based on the Stirling/JT technology developed for SPICA,
and the continuous ADR system shares the design with future X-ray satellites.
The temperature dependence of the absorption of the thick niobium films was measured using an AC far-infrared laser calorimeter. Moreover the temperature and frequency dependences of the absolute transmission and reflection of same thin niobium nitride films were measured from 5 to 20 K and from 10 to 200 cm-1 using a fourier transform infrared spectrometer. The temperature dependencies of the skin depth and the absorptance determined independently by both methods are compared. However the skin depths and the absorptances agree well each other near and above Tc, they begin to deviate from each other with decreasing temperature below Tc.
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