関本 裕太郎

We report on a design of broadband circular waveguide coupled planar ortho-mode transducer (OMT) with Microwave Kinetic Inductance Detector (MKID) for LiteBIRD mission, a small-size satellite for cosmic microwave background (CMB) polarization signal full-sky mapping at large angular scale by JAXA. In our 4-pixel prototype design, each single pixel is sensitive to two frequency bands (90 GHz and 150 GHz) corresponding to atmospheric window for testing at Nobeyama 45-m telescope. Silicon on insulator (SOI) has been selected for OMT structure and a broadband coplanar waveguide (CPW) 180- degree hybrid is designed to cancel higher modes of a circular waveguide and add two signals from the fundamental mode together. After a distributed microstrip bandpass diplexer, a microstrip line to coplanar waveguide transition structure couples signal to MKID and MKIDs are read out with frequency domain multiplexing. MKIDs are designed with Nb ground plane and Al/Ti bilayer central strip to achieve low frequency response, high sensitivity and also adjustable transition temperature. A 4-pixel module is under test and we plan to deploy these multi-chroic polarimeters on Nobeyama 45-m telescope.

© 2016 IEEE. Broadband parametric amplifiers (PAs), which utilize the nonlinear kinetic inductance of superconducting transmission lines, provide new access to ultimate sensing capability for radio astronomical observation and microwave quantum electronics. In this paper, the parametric amplification is investigated with a time-domain numerical method. The results present direct images of the traveling waves, which clarify the distinctively different features of the parametric gain in uniform and impedance-perturbed nonlinear transmission lines. The results indicate that the traveling-wave PAs (TWPAs) are susceptible to impedance mismatching because of the lack of isolation between the input and the output ports. In the experimental part of this paper, we tested, for the first time, microstrip TWPAs based on NbTiN. A parametric gain was observed at liquid helium temperature.

© 2015, Springer Science+Business Media New York. Cosmic microwave background (CMB) is an important source of information about the origin of our universe. In particular, odd-parity large angular scale patterns in the CMB polarization, the primordial B-modes, are strong evidence for an inflationary universe, related to the accelerating expansion of the metric. We are developing a unique telescope, GroundBIRD, to take CMB polarization measurements. The telescope combines novel techniques: high-speed rotation scanning, cold optics, and microwave kinetic inductance detectors (MKIDs). We evaluated the response of MKIDs on the rotation stage. Method of shielding from the geo-magnetic field is established. We have also developed a receiver cryostat. We are able to maintain a sufficient cold status for observations on the optical configuration. We plan to start commissioning the system by observing CMB in Japan in 2015–2016. We will then deploy GroundBIRD in the Canary Islands for further scientific observations.

© 2016, Springer Science+Business Media New York. Microwave kinetic inductance detector (MKID) is one of the candidates of focal plane detector for future satellite missions such as LiteBIRD. For the space use of MKIDs, the radiation tolerance is one of the challenges to be characterized prior to the launch. Aluminum (Al) MKIDs with 50 nm thickness on silicon substrate and on sapphire substrate were irradiated with a proton beam of 160 MeV at the heavy ion medical accelerator in Chiba. The total water-equivalent absorbed dose was ∼ 10 krad which should simulate the worst radiation absorption of 5 years observation at the Lagrange point L2. We measured characteristics of these MKIDs before and after the irradiation. We found no significant changes on resonator quality factor, responsivity, and recombination time of quasi-particles. The change on electrical noise equivalent power was also evaluated, and no significant increase was found at the noise level of O(10 - 18) W/Hz.

© 2016, Springer Science+Business Media New York. LiteBIRD is a proposed CMB polarization satellite project to probe the inflationary B-mode signal. The satellite is designed to measure the tensor-to-scalar ratio with a 68 % confidence level uncertainty of σr< 10 - 3, including statistical, instrumental systematic, and foreground uncertainties. LiteBIRD will observe the full sky from the second Lagrange point for 3 years. We have a focal plane layout for observing frequency coverage that spans 40–402 GHz to characterize the galactic foregrounds. We have two detector candidates, transition-edge sensor bolometers and microwave kinetic inductance detectors. In both cases, a telecentric focal plane consists of approximately 2 × 10 3 superconducting detectors. We will present the mission overview of LiteBIRD, the project status, and the TES focal plane layout.

© 2002-2011 IEEE. The Mattis-Bardeen theory is extended by introducing the complex number of the superconducting gap energy, by which BCS density of states is broadened and the small density of quasiparticle states that appears in the energy gap is well predicted. Using the extended Mattis-Bardeen theory, the surface resistance of superconductors and quality factors of superconducting resonators are calculated. It is shown that simulated temperature dependence of quality factors of superconducting resonators agree very well with the measured ones. It is also demonstrated that the calculated residual quasiparticle number of a superconducting resonator using the density of states consisting of the gap-broadened and localized quasiparticle states agrees quantitatively with the measured one.

© 2016 IEEE. Due to their multiplexing capability and their good sensitivity to radiation from submillimeter to X-ray wavelengths, microwave kinetic inductance detectors (MKIDs) are increasingly used in the field of astrophysics. The Advanced Technology Center of the National Astronomical Observatory of Japan is developing MKIDs for astronomical observations such as CMB B-mode search with LiteBIRD. MKIDs are made of superconductors whose energy gap determines the detector frequency range. The energy gap depends on Tc, the critical temperature of the superconductor. It is thus important to be able to adjust Tc in order to choose the suitable frequency range. When using a single-layer MKID, the Tc is fixed by the superconducting gap energy of the unique component and cannot be changed. One possibility is to make a bilayer MKID using the proximity effect to adjust its critical temperature. This paper presents our new study on MKIDs made of superconductor/metal bilayers. We investigated niobium and copper bilayers (Nb/Cu) and fabricated different bilayers in our clean room. The critical temperature of each of them has been measured. We show that the Tc depends on the ratio between Nb and Cu thicknesses and that we are able to control it. Then, we characterized one of these Nb/Cu bilayers (Nb = 8nm and Cu = 22 nm) once integrated in a MKID. We measured the temperature dependence of the resonant frequency, and we achieved quality factors as high as 2 × 104. The measurement of the noise spectrum provided a lower limit equal to-85 dBc/Hz, and the calculation of the noise equivalent power has shown that the sensitivity of the Nb/Cu bilayer MKID is not very far from that of an Al monolayer MKID.

© 2015, Springer Science+Business Media New York. We propose an entirely plane-structure camera for millimeter wave astronomy, in order to reduce production cost and time. The camera is composed of a silicon lens-let, antennas, feed lines, and detectors made from the same superconducting aluminum film on a silicon substrate. A couple of double-slot antennas are located the same focal plane of a small substrate lens to enhance the packing density of detectors and observation efficiency. To achieve high sensitivity, we adapted a microwave kinetic inductance detector as a photon sensor, which consists of a superconducting microresonator. We examined the optical performance of the camera attached to a silicon lens array at 220 GHz in a 0.3 K cryostat. The measured beams were in good agreement with the calculations within the dynamic range of the setup (20 dB). Polarization misalignments between the dual-double slot antenna were less than 2∘, and cross-polarization level was around −7 dB. The relatively high cross-polarization would be explained by an antenna crosstalk mediated by quasiparticle diffusion.

© 2016 SPIE. LiteBIRD aims to detect the footprint of the primordial gravitational wave on the Cosmic Microwave Background (CMB) in a form of polarization pattern called B mode. In order to separate CMB from the Galactic emission, our measurements cover 35 GHz to 450 GHz. The LiteBIRD optics consists of two telescopes: A crossed Dragone type for lower frequencies, which provides a compact configuration with a wide field of view, and a refractor type for higher frequencies. The whole optical system is cooled down to around 5 K to minimize the thermal emission. We use two kinds of approaches of designing calculations as well as the experimental confirmation particularly for the lower frequency telescope.

© 2002-2011 IEEE. We developed SIS mixers for Atacama large millimeter/submillimeter array (ALMA) Band 8 (385-500 GHz) receiver cartridges and evaluated their performance. DC IV curves of the SIS mixers showed small leakage current at the high current density. The current density and quality factor (R-{sg}/R-{n}) of the Band 8 SIS junction were 13 \hbox{kA/cm}{2} and approximately 20, respectively. Double-sideband noise temperature of the 266 SIS mixers was 92.8 K at 4.0 K bath temperature on the average from 385 to 500 GHz with a standard deviation of 7.0%. A couple of sideband-separating (2SB) mixers for dual polarizations were used in the Band 8 receiver cartridge. The 73 receivers have met ALMA specifications of the noise temperature. Single-sideband noise temperature and image rejection ratio of the receivers were 139.5 K and 20.5 dB on the average from 385 to 500 GHz, respectively. These test results of the receivers indicate high quality and uniformity of the 2SB mixers.

© 2011-2012 IEEE. We have been developing a superconductive detector array for terahertz astronomical observation using Microwave Kinetic Inductance Detector (MKID) technology. MKID is accomplished by making a strip of superconductor part of a microwave resonant circuit, and monitoring the phase and amplitude of a probe signal transmitted through the resonator. Frequency-domain multiplexing will allow up to thousands of resonators to be read out through a single line. We developed a 600-pixel 220 GHz detector array and a 102-pixel 440-GHz detector array. We have developed a new scheme readout system for the detector arrays, and which uses a frequency-sweeping probe signal instead of a fixed-frequency probe signal. This scheme enables us a direct measurement of the changed resonance frequency after optical loading.

© 2011-2012 IEEE. We have been developing a superconductive detector array for terahertz astronomical observation using Microwave Kinetic Inductance Detector (MKID) technology. MKID is accomplished by making a strip of superconductor part of a microwave resonant circuit, and monitoring the phase and amplitude of a probe signal transmitted through the resonator. Frequency-domain multiplexing will allow up to thousands of resonators to be read out through a single line. We developed a 600-pixel 220 GHz detector array and a 102-pixel 440-GHz detector array. We have developed a new scheme readout system for the detector arrays, and which uses a frequency-sweeping probe signal instead of a fixed-frequency probe signal. This scheme enables us a direct measurement of the changed resonance frequency after optical loading.

A precise measurement of Cosmic Microwave Background (CMB) provides us rich information about the universe. In particular, its asymmetric polarization patterns, B-modes, are smoking gun signature of inflationary universe. Magnitude of the B-modes is order of 10 nK. Its measurement requires a high sensitive millimeter-wave telescope with a large number of superconducting detectors on its focal plane. Microwave Kinetic Inductance Detector (MKID) is appropriate detector for this purpose. MKID camera has been developed in cooperation of National Astronomical Observatory of Japan (NAOJ), Institute of Physical and Chemical Research (RIKEN), High Energy Accelerator Research Organization (KEK), and Okayama University. Our developments of MKID include: fabrication of high-quality superconducting film; optical components for a camera use; and readout electronics. For performance evaluation of total integrated system of our MKID camera, a calibration system was also developed. The system was incorporated in a 0.1 K dilution refrigerator with modulated polarization source. These developed technologies are applicable to other types of detectors.

Copyright © 2015 The Institute of Electronics, Information and Communication Engineers. A precise measurement of Cosmic Microwave Background (CMB) provides us rich information about the universe. In particular, its asymmetric polarization patterns, B-modes, are smoking gun signature of inflationary universe. Magnitude of the B-modes is order of 10nK. Its measurement requires a high sensitive millimeter-wave telescope with a large number of superconducting detectors on its focal plane. Microwave Kinetic Inductance Detector (MKID) is appropriate detector for this purpose. MKID camera has been developed in cooperation of National Astronomical Observatory of Japan (NAOJ), Institute of Physical and Chemical Research (RIKEN), High Energy Accelerator Research Organization (KEK), and Okayama University. Our developments of MKID include: fabrication of high-quality superconducting film; optical components for a camera use; and readout electronics. For performance evaluation of total integrated system of our MKID camera, a calibration system was also developed. The system was incorporated in a 0.1 K dilution refrigerator with modulated polarization source. These developed technologies are applicable to other types of detectors.

© 2014 IEEE. We have developed an optics for 220 GHz observations, which is a compact cold re-imaging one from a telescope focal plane, with F/# = 6 to a detector plane with F/# = 1 at 100 mK. It employs two high refractive lenses, high purity alumina (n=3.1) and silicon (n=3.4). To reduce the incident stray light into the detector, a cold nested baffle composed of four reflectors with the same spherical shape has been developed. The stray light power is simulated to be 0.2 μW which corresponds a quarter of that of a without-baffles case. The total transmittance of three kinds of IR blocking filters is 0.78 at the observation frequency, and less than 10-10 above 6 THz. Thermal flow power into the detector, including the stray light power, is about 0.7 μW. The cold optics with an 600 pixels MKID camera has been cooled down to 100 mK.

We have been developing a large-format millimeter-wave camera based on lens-antenna-coupled microwave kinetic inductance detectors (MKIDs) for a planned telescope at Dome Fuji (3810 m a.s.l.), Antarctica. Optical coupling to the MKID incorporates double-slot antennas and a silicon lens array. To realize a large-format camera (> 10,000 pixels), a highly integrated small-diameter lens array and fast optics are required. Lens diameters of 1.2, 2, and 3 times the target wavelength are investigated for the main beam symmetry, side-lobe level, cross-polarization level, and bandwidth, considering the effects of the surrounding lenses. In this study, we present the simulated beam pattern profiles of close-packed lens antenna and the effect of misalignment between the silicon lens and double-slot antenna. We also show the evaluations of the developed 721-pixel close-packed silicon lens array. © 2013 Springer Science+Business Media New York.

A dielectric lens with high refractive index is suitable for focusing cryogenic devices in millimeter-wave bands when an appropriate anti-reflection (AR) coating is applied. Two types of AR coatings for silicon and alumina were studied at the millimeter-wave (220 GHz) band: one is by direct machining of mixed epoxy for a silicon lens array, while the other is by laser machining of an antireflective subwavelength structure for a large alumina lens used in a re-imaging optics system. The millimeter-wave optical properties of silicon, alumina, aluminum nitride, and Stycast epoxies were measured with a Fourier Transform Spectrometer (FTS) at cryogenic temperatures. The measured refractive index of the AR coating with a mixture of Stycast 1266 (n = 1.68) and Stycast 2850FTJ (n = 2.2) for silicon at 30 K was 1.84. The thickness of the epoxy AR coating was precisely controlled with direct machining. Transmittance of the AR-coated silicon substrate, measured with FTS, was approximately 95 % at the center frequency of the 220 GHz band with a bandwidth of 25 % at 27 K. An antireflective subwavelength structure was designed for an alumina sample with periodic cylindrical holes. The measured 220-GHz-band transmittance was above 90 % with a bandwidth of 25 % at 25 K. © 2014 Springer Science+Business Media New York.

LiteBIRD is a next-generation satellite mission to measure the polarization of the cosmic microwave background (CMB) radiation. On large angular scales the B-mode polarization of the CMB carries the imprint of primordial gravitational waves, and its precise measurement would provide a powerful probe of the epoch of inflation. The goal of LiteBIRD is to achieve a measurement of the characterizing tensor to scalar ratio r to an uncertainty of δr = 0.001. In order to achieve this goal we will employ a kilo-pixel superconducting detector array on a cryogenically cooled sub-Kelvin focal plane with an optical system at a temperature of 4 K. We are currently considering two detector array options; transition edge sensor (TES) bolometers and microwave kinetic inductance detectors. In this paper we give an overview of LiteBIRD and describe a TES-based polarimeter designed to achieve the target sensitivity of 2 μK arcmin over the frequency range 50-320 GHz. © 2014 Springer Science+Business Media New York.

We report on the design and on-site performance of the recently upgraded FLASH+ instrument operated at the APEX telescope in the Chilean Atacama desert in 5100 m altitude. The dual-channel receiver allows parallel observations in the atmospheric submillimeter windows between 268 and 516 GHz. A signal of in total 16 GHz is processed simultaneously. Equipped with state-of-the-art sideband separating mixers (spin-off developments from the ALMA bands 7 and 8), its outstanding on-sky performance makes FLASH+ a most efficient spectral line mapping machine. Operation is fully automated and allows flexible remote observations from the APEX base in San Pedro de Atacama. © 2014 IEEE.

Microwave kinetic inductance detectors (MKIDs) are being developed at the National Astronomical Observatory of Japan to enable precise measurements of the cosmic microwave background. One of the features of MKIDs is scalability using a frequency-division multiplexing (FDMUX) readout scheme. A digital fast fourier transform spectrometer (FFTS) is a good way to read out a number of resonance frequencies simultaneously and fully utilize the advantage of FDMUX of MKIDs. We have developed FFTS readout electronics using an ADC/DAC with 1 Gsps (sample per second) sampling rate and 270 MHz bandwidth. We measured the noise characteristics of a single MKID in the frequency range of 60 Hz-30 kHz with this readout system, and found the noise was almost equivalent to the noise measured by ordinary analog IQ down-converter readout. This indicates our FFTS electronics do not add any additional noise to the MKID readout system over the frequency range. © 2014 Springer Science+Business Media New York.

国立天文台・先端技術センターでは,宇宙マイクロ波背景放射(Cosmic Microwave Background,以下CMB)の精密観測及び,原始重力波起源のBモード偏光の世界初検出を目標として,超伝導共振器(Microwave Kinetic Inductance Detector,以下MKID)を用いた電波(ミリ波)カメラの開発を行っている.Bモード偏光の観測のためには,1000素子規模の高品質,高感度なMKIDカメラが必要であり,我々は,高品質な超伝導薄膜の成膜プロセスの確立及び薄膜の性能評価,カメラ用光学素子の開発,多素子読み出し回路の開発など,高感度MKIDカメラに必要な技術の開発を進めている.本稿では,国立天文台におけるMKIDカメラの開発状況について報告する.

We have developed a transportable 30-cm submillimeter-wave telescope to operate at the Dome Fuji station in the Antarctic plateau. Transportability is an important requirement in the design; the telescope can be divided into several subsystems by hands. The maximum weight of the subsystems is restricted to be below 60 kg, so that the telescope can be assembled without a lifting machine. A small 4 K mechanical cryocooler is used for cooling down a SIS mixer. Total power consumption was designed to be less than 2.5 kW. The optical system was designed to satisfy the frequency independent matching condition at the subreflector and the feed horn of the SIS mixer, so we could accommodate a higher frequency receiver without changing mirrors. A quasi-optical filter was employed for the single sideband operation in observations of the CO (J = 4-3) line at 461.04 GHz and the [CI] (3P1-3P 0) line at 492.16 GHz. It was equipped with a 1 GHz width spectrometer that covers a velocity width of 600 km/s with a velocity resolution of 0.04 km/s at 461 GHz. We carried out test observations at a 4400-m altitude site in northern Chile during winters of 2010 and 2011. The typical system noise temperature, including atmospheric loss, was 3000 K (SSB) at 461 GHz, that is mainly limited by atmospheric opacity. The beam size of the 30-cm offset Cassegrain antenna at 0.65 mm of wavelength was measured to be 9′.4 ×0′.4 by cross scanning of the sun. This angular resolution of the 30-cm telescope is same as those of the Columbia-CfA-U. Chile CO (J = 1-0) surveys. We estimated the main beam efficiency to be 87 × 5% by observing the new moon. We succeeded in mapping Orion Molecular Cloud A and M17 SW in CO (J = 4-3) followed by test observations toward Orion KL in both CO (J = 4-3) and [CI] (3P1-3P0). © 2011-2012 IEEE.

We have developed 220 and 440-GHz cameras using microwave kinetic inductance detectors (MKIDs) for astronomical observations. The optical system of the MKID camera is based on double-slot antennas and extended hemispherical silicon lens arrays. The lens diameter is three times the target wavelength. The 220-GHz camera and the 440-GHz camera have 9 pixels and 102 pixels, respectively. The silicon lens array has been directly machined using a high-speed spindle on an ultra-precision machine. The shape fabrication error and the surface roughness of the top of the lens were typically less than 10 μm (peak-to-valley) and about 0.7 μm (rms), respectively. The beam patterns of the MKID camera were measured and are in good agreement with the calculations. © 2011-2012 IEEE.

We have been developing a terahertz camera based on antenna-coupled superconducting resonators, the so-called microwave kinetic inductance detectors (MKIDs), and a silicon lens array. The MKID consists of a coplanar waveguide coupled to a double slot antenna and is patterned on a high-quality aluminum film grown by molecular beam epitaxy. The camera is sensitive at frequencies of 200-240 GHz. Its bandwidth is limited by the impedance properties of the double slot antenna. The design, fabrication, and optical evaluations of the planar antennas and silicon lens arrays are presented in this paper. The MKID camera has been evaluated both in dark conditions and under optical radiation in a 0.1-K dilution refrigerator. The electrical noise equivalent power was around 5×10-18 W/Hz in dark conditions and 4×10-16 W/Hz, which is much lower than the photon noise level, with the optical load. The optical efficiency of the camera was estimated by three independent methods, and the results were consistent with each other and equal to 20%-25% without an anti-reflection coating on the lens surface. © 2011-2012 IEEE.

We have been developing a terahertz camera based on antenna-coupled superconducting resonators, the so-called microwave kinetic inductance detectors (MKIDs), and a silicon lens array. The MKID consists of a coplanar waveguide coupled to a double slot antenna and is patterned on a high-quality aluminum film grown by molecular beam epitaxy. The camera is sensitive at frequencies of 200-240 GHz. Its bandwidth is limited by the impedance properties of the double slot antenna. The design, fabrication, and optical evaluations of the planar antennas and silicon lens arrays are presented in this paper. The MKID camera has been evaluated both in dark conditions and under optical radiation in a 0.1-K dilution refrigerator. The electrical noise equivalent power was around 5×10-18 W/Hz in dark conditions and 4×10-16 W/Hz, which is much lower than the photon noise level, with the optical load. The optical efficiency of the camera was estimated by three independent methods, and the results were consistent with each other and equal to 20%-25% without an anti-reflection coating on the lens surface. © 2011-2012 IEEE.

The surface impedance of a superconductor has been calculated using the extended Mattis-Bardeen theory, in which the complex gap energy are taken into account. It is found that the surface resistance of the superconductor increases with increasing magnitude of the imaginary part of the gap energy. It is also found that the surface resistance of an NbN film calculated by the extended Mattis-Bardeen equation quantitatively agrees well with the measured one. It is shown that temperature dependence of not only $Q$ values but also residual numbers of quasiparticles of superconducting resonators agree well with those calculated by the extended Mattis-Bardeen equation. It is also shown that phonon-assisted gradual relaxation of excess quasiparticles passing through the intragap states is dominant rather than the direct recombination into Cooper pairs. © 2002-2011 IEEE.

A submillimeter (385-500 GHz) low-noise sideband-separating balanced SIS (Superconductor Insulator Superconductor) mixer (Balanced 2SB mixer) with high IRR (Image Rejection Ratio) has been successfully developed, whose SSB (Single SideBand) noise temperature is ∼ 200 K (10hf/k) with an image rejection ratio of ≥∼10 dB. Balanced mixers have become a promising technology which would break through the limitation especially in terahertz receivers and heterodyne arrays. However, though there are examples in microwave with relatively worse noise performance, submillimeter and terahertz balanced mixers have rarely been developed in spite of their astronomical importance. The developed balanced 2SB mixer is not only the first one demonstrated at submillimeter frequency range, but also has very low noise, high IRR, wide detectable frequencies (385-500 GHz), and a flat IF output spectrum. The balanced 2SB mixer is composed of three RF hybrids, four DSB (Double SideBand) mixers, two 180° IF hybrids, and an IF quadrature hybrid. Several important performance indicators such as noise temperature, IRR, required LO (Local Oscillator) power, and IF spectra were measured. The measured LO power required for the balanced 2SB mixer was typically ∼ 14 dB less than that of the single-ended mixers. © Springer Science+Business Media, LLC 2012.

We report here the effect of film qualities in superconductors on the properties of Microwave Kinetic Inductance Detectors (MKIDs). The sensitivity of MKIDs between crystal aluminum films and amorphous aluminum films is compared. The good quality and crystallized aluminum films have been prepared by using molecular beam epitaxy.We have confirmed that epitaxial Al(111) films were grown on Si(111) substrates with X-ray diffraction and in-situ reflection high-energy electron diffraction measurements. The amorphous aluminum films on the Si(111) wafers have been deposited by electron beam evaporation. We have measured transmission losses of MKIDs, noise spectrum and relaxation time against optical pulses, changing MKIDs' bath temperature from 0.11 K to 0.55 K in a dilution refrigerator. Despite of the improvement in normal resistivity, the quasiparticle decay time of both films are equivalent and 450 s at 0.11 K. The electrical noise equivalent power of the both MKIDs are also comparable and around 10-17 W/Hz. Fabrication details and performance data of both films are presented. © Springer Science+Business Media, LLC 2012.

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 1.8-Karcmin 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. © 2012 SPIE.

The Mattis-Bardeen theory for the anomalous skin effect in the superconductors has been extended taking the complex gap energy into account and the surface impedance of superconductors has been calculated using the extended Mattis-Bardeen theory. It is found that the surface resistance of the superconductor increases with increasing magnitude of the imaginary part of the gap energy. It is demonstrated that the calculated surface resistance for a NbN film quantitatively agrees with the measured one. It is also found that temperature dependence of Q values of superconducting resonators is well described by those calculated by the extended Mattis-Bardeen equation. (C) 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of Guest Editors.

We present design and evaluations of a submillimeter double-ridged waveguide ortho-mode transducer (OMT) for ALMA Band 8 (385-500 GHz) cartridge receiver. The measured transmission loss of the OMTat 4 K was 0.4-0.5 dB according to noise measurements with an SIS mixer. The polarization isolation was measured to be larger than 29 dB from quasioptical measurements. The OMTconsists of a Bφifot junction and a double-ridged guide. A robust design with allowable mechanical errors of 20 μm has been demonstrated. © Springer Science+Business Media, LLC 2010.

We present design and evaluations of a submillimeter double-ridged waveguide ortho-mode transducer (OMT) for ALMA Band 8 (385-500 GHz) cartridge receiver. The measured transmission loss of the OMTat 4 K was 0.4-0.5 dB according to noise measurements with an SIS mixer. The polarization isolation was measured to be larger than 29 dB from quasioptical measurements. The OMTconsists of a Bφifot junction and a double-ridged guide. A robust design with allowable mechanical errors of 20 μm has been demonstrated. © Springer Science+Business Media, LLC 2010.

We have demonstrated an approach to predict the overall efficiency and system noise regarding optical systems in radio telescopes, based on a systematic evaluation of both the optical propagation efficiency through all optical components, from the receiver horn to the main reflector, and of their noise contributions. The analysis employs several conventional techniques, including the principle of multimode Gaussian optics and calculations of losses associated with optical components. A detailed analysis was performed for cases of ALMA band 4 (125-163 GHz) and 8 (385-500 GHz). The analysis predicts a reasonable efficiency of 0.75-0.76 (0.57-0.62) and a system noise of similar to 70 K (300-400 K) for band 4 (band 8). The calculated efficiency of the band 4 optics was found to be consistent with the efficiency measured by astronomical observations with the ALMA/ACA 12-m antenna. In addition to a confirmation that the bands 4 and 8 optics were designed to maximize the overall efficiency, the analysis for the bands 4 and 8 frequency ranges also confirmed that there is no difference in the optimum edge levels at the subreflector between the two different ways of maximization, i.e., toward the overall efficiency or the sensitivity, which is defined by the ratio of the overall efficiency over the sum of noises generated from all possible sources. We also applied a sensitivity analysis to the band 1 frequency case, and revealed a slight, but clear, difference in the optimum edge levels between the sensitivity and the efficiency (difference is 1-2 dB). This corresponds to a sensitivity loss of 1% if we optimize the optics to maximize the efficiency.

A beam waveguide system for connecting the ALMA front-end, which has been designed for the Cassegrain focus of the ALMA 12-m antenna, with the ALMA/ACA 7-m antenna was designed. The beam waveguide system, covering 30-950GHz, consists of flat mirrors or prisms to modify the boresight tilt angle from the front-end, and recovers more than the half of the sensitivity loss caused by a misalignment between the front-end optics and the 7-m antenna. No mechanical alignment procedure is needed for installation of the beam waveguide system, and thus it does not impact on the maintenance/operation scheme of the front-end system. Beam-pattern measurements in the frequency ranges of ALMA bands 4 (144 GHz), 6 (252 GHz), and 8 (385 GHz) have confirmed that directions of the radiation patterns transmitted to the subreflector are successfully shifted by the beam waveguide system without any serious deformation of the beam. The aperture efficiencies calculated from the measured radiation patterns were determined to be 84.6% at 144 GHz, 86.1% at 252 GHz, and 84.8% at 385 GHz, which are consistent with those of a simulated radiation pattern.

We have developed a near-field vector beam measurement system covering the range of frequencies from 385 to 500 GHz. The measurement set-up is capable of measurements with dynamic range exceeding 50 dB and amplitude and phase stability respectively of 0.1 dB/h and 1 degree/5 min at room temperature. Beam patterns of the ALMA band 8 corrugated horns and receiver optics block were measured at room temperature and lately compared with physical optics calculations obtained in the far-field. Both co-polar and cross-polar beam patterns of a qualification model of the ALMA band 8 cartridge cooled in a cartridge-test-cryostat have also been measured in the near-field as a detector of a submillimeter vector network analyzer. The measurements presented in this work refer to the lowest, middle and upper frequencies of band 8. The comparisons between software model and experimental measurements at these frequencies show good agreement down to -30 dB for the main polarization component. The cross-polarization level of the beam propagating through the receiver optics block was also characterized. We found that a cross-polarization level better than -28 dB can be achieved at all measured frequencies. The measured beam pattern of this receiver corresponds to efficiency of greater than 92% at the sub reflector (diameter of 750 mm) of the ALMA 12 m optics.

We have developed a cartridge-type receiver covering the frequency band of 385-500GHz as a qualification model of Atacama Large Millimeter/submillimeter Array (ALMA) band 8. It receives two orthogonal polarizations and down-converts the sideband-separated signals to intermediate frequencies (IF) of between 4 and 8GHz. The cartridge-type receiver consists of cold optics, two feed horns, a wire grid, mirrors, two sideband-separating SIS mixers, cryogenic multipliers of a local oscillator (LO), cryogenic and warm IF amplifiers, a cartridge body, and sensors/wirings. These components were individually tested, and then the cartridge was integrated and tested as a complete assembly. We have also developed equipment for efficiency tests of both the components and the integrated receiver. The single sideband (SSB) noise temperature of this receiver is 100K at the band center and 300K at the band edges. The beam pattern and cross-polarization pattern are consistent with a physical optical calculation. The amplitude stability is around 3 x 10(-4) in 1 s. The phase stability is less than 2.degrees 0 on a time scale of 0.1 s to 10 min. These results are promising for a receiver in the ALMA.

We have developed a 400-500 GHz low-noise balanced SIS (Superconductor Insulator Superconductor) mixer, which is based on a waveguide RF quadrature hybrid coupler. The RF quadrature hybrid was designed and fabricated as a broadband hybrid with good performance at 4 K. The fabricated RF quadrature hybrid was measured at room temperature with a submillimeter vector network analyzer to check amplitude and phase imbalance between two output ports. Then the balanced mixer was assembled with the RF hybrid, two DSB mixers, and a 180 IF hybrid. Several important parameters such as noise temperature, LO power reduction, and IF spectra were measured. The LO power reduction is defined as how much LO power the balanced mixer saves compared with a typical single-ended mixer. The measured noise temperature of the balanced mixer was similar to 55 K at the band center which corresponds to similar to 3 times the quantum noise limit (hf/k) in DSB, and similar to 120 K at the band edges. The noise performance over LO frequency was almost the same as that of the worse DSB mixer used in the balanced mixer. In addition the LO power required for the balanced mixer is similar to 11 dB less than that of the single-ended mixers.

The "integral-shaped filament" of the Orion A giant molecular cloud was mapped in N2H+, and its nor-them end, the OMC-2/3 region, was also observed in HC3N and CCS. The results were compared with maps of other molecular lines and the dust continuum emission. The N2H+ distribution is similar to the dust continuum distribution, except for the central part of the Orion Nebula. The distribution of (HCO+)-C-13 holds a resemblance to that of the dust continuum, but the N2H+ distribution looks more similar to the dust continuum distribution. The N-bearing molecules, N2H+ and NH3, seem to be more intense in OMC-2, compared with the, (HCO+)-C-13 and CS distribution. This suggests that OMC-2 has a higher abundance of N-bearing molecules, or a higher filling factor of the quiescent gas. We identified 34 cloud cores from N2H+ data. Over the Orion Nebula region, the N2H+ linewidth is large (1.1-2.1 km s(-1)). In the OMC-2/3 region, it becomes moderate (0.5-1.3 km s(-1)), and it is smaller (0.3-1.1 km s(-1)) in the south of the Orion Nebula. On the other hand, the gas kinetic temperature of the quiescent cores observed in N2H+ is rather constant (similar to 20 K) over the integral-shaped filament. We detected no CCS emission in the OMC-2/3 region. In general, the N2H+ and HC3N distribution is quite similar in the OMC-2/3 region, but we observed a displacement between N2H+ and HC3N over a 2' scale in OMC-3, which has a chain of Class 0-I protostars (candidates).

We have investigated the effect of a moderately. strong magnetic field (up to 1200 Gauss, 13 quantum fluxes within a single junction) on the heterodyne mixing performance of a 385-500 GHz superconductor-insulator-superconductor mixer. Both experimental and numerical results indicate that the mixer conversion gain can be significantly reduced by a magnetic field. Surprisingly, the mixer noise shows very weak dependence. The overall receiver noise increase is merely caused by the intermediate frequency noise contribution amplified by a factor of gain reduction. At the expense of little system noise degradation, a relatively strong magnet field can make the mixer more stable at the bias point corresponding to its noise minimum.

We analyzed deep 75 ks Chandra ACIS-I data of NGC 2024 with the aim of searching for diffuse X-ray emission in this most nearby (415 pc) of massive star-forming regions. After removing point sources, extended emission was detected in the central circular region with a radius of 0.5 pc, and it is spatially associated with this young massive stellar cluster. Its X-ray spectrum exhibits a very hard continuum (kT &gt; 8 keV) and shows signs of having a He-like Fe K alpha line with a 0.5-7 keV absorption-corrected luminosity of 2 x 10(31) ergs s(-1). Undetected faint point sources, estimated from the luminosity function of the detected sources, contribute less than 10% to this emission. Hence, the emission is truly diffuse in nature. Because of the proximity of NGC 2024 and the long exposure, this discovery is one of the strongest pieces of evidence in support of the existence of diffuse X-ray emission in massive star-forming regions.

We analyzed deep 75 ks Chandra ACIS-I data of NGC 2024 with the aim of searching for diffuse X-ray emission in this most nearby (415 pc) of massive star-forming regions. After removing point sources, extended emission was detected in the central circular region with a radius of 0.5 pc, and it is spatially associated with this young massive stellar cluster. Its X-ray spectrum exhibits a very hard continuum (kT > 8 keV) and shows signs of having a He-like Fe Kα line with a 0.5-7 keV absorption-corrected luminosity of 2 × 1031 ergs s-1. Undetected faint point sources, estimated from the luminosity function of the detected sources, contribute less than 10% to this emission. Hence, the emission is truly diffuse in nature. Because of the proximity of NGC 2024 and the long exposure, this discovery is one of the strongest pieces of evidence in support of the existence of diffuse X-ray emission in massive star-forming regions. © 2006. The American Astronomical Society. All right reserved.

Chandra ACIS-I data of the molecular cloud and H n region complex NGC 6334 were analyzed. The hard X-ray clumps detected with ASCA (Sekimoto and coworkers) were resolved into 792 point sources. After removing the point sources, an extended X-ray emission component was detected over a 5 × 9 pc2 region, with the 0.5-8 keV absorption-corrected luminosity of 2 × 10 33 ergs s-1. The contribution from faint point sources to this extended emission was estimated as at most ∼20%, suggesting that most of the emission is diffuse in nature. The X-ray spectrum of the diffuse emission was observed to vary from place to place. In tenuous molecular cloud regions with hydrogen column density of (0.5-1) × 1022 cm-2, the spectrum can be represented by a thermal plasma model with temperatures of several keV. The spectrum in dense cloud cores exhibits harder continuum, together with higher absorption of more than ∼3 × 1022 cm-2. In some of such highly obscured regions, the spectra show extremely hard continua equivalent to a photon index of ∼1, and favor a nonthermal interpretation. These results are discussed in the context of thermal and nonthermal emission, both powered by fast stellar winds from embedded young early-type stars through shock transitions. © 2006. The American Astronomical Society. All rights reserved.

We have developed a 385 - 500 GHz sideband-separating (20) mixer, which is based on a waveguide split-block coupler at the edge of the H-plane of the 508 mu m x 254 mu m (WR 2.0) waveguide, for the Atacama Large Millimeter/submillimeter Array (ALMA). An RF/LO coupler, which contains an RF quadrature hybrid, two LO couplers, and an in-phase power divider, was designed with the issue of mechanical tolerance taken into account. The RF/LO coupler was measured optically with a microscope and electrically with a submillimeter vector network analyzer. The image rejection ratio (IRR) and the single-sideband (SSB) noise temperature of the receiver using the RF/LO coupler have also been measured. The IRR was found to be larger than 8 dB and typically similar to 12 dB in the 385 - 500 GHz band. The SSB noise temperature of this receiver is 80 K at the band center, which corresponds to 4 times the quantum noise limit (hf/k) in SSB, and 250 K at the band edges.

We report on the design and experimental results of a fix-tuned Superconductor-Insulator-Superconductor (SIS) mixer for Atacama Large Millimeter/submillimeter Array (ALMA) band 8 (385-500 GHz) receivers. Nb-based SIS junctions of a current density of 10 kA/cm2 and one micrometer size (fabricated with a two-step lift-off process) are employed to accomplish the ALMA receiver specification, which requires wide frequency coverage as well as low noise temperature. A parallel-connected twin-junction (PCTJ) is designed to resonate at the band center to tune out the junction geometric capacitance. A waveguide-microstrip probe is optimized to have nearly frequency-independent impedance at the probe's feed point, thereby making it easy to match the low-impedance PCTJ over a wide frequency band. The RF embedding impedance is retrieved by fitting the measured pumped I-V curves to confirm good matching between PCTJ and signal source. We demonstrate here a minimum double-sideband receiver noise temperature of 3 times of quantum limits for an intermediate-frequency range of 4-8 GHz. The mixers were measured in band 8 cartridge with a sideband separation scheme. Single-sideband receiver noise below ALMA specification was achieved over the whole band. Copyright © 2006 The Institute of Electronics, Information and Communication Engineers.

The Atacama Submillimeter Telescope Experiment (ASTE) is a joint project between Japan and Chile to install and operate a 10 m high precision telescope for exploration of the Southern sky at submillimeter wavelengths. Due to the excellent atmospheric conditions at the site, Pampa la Bola (4800 m) in the Atacama desert in northern Chile, ASTE offers an unique opportunity to make extensive submillimeter observations. We successfully started scientific observations in August 2003 at 800, 500, and 350 GHz bands.

We have developed a cartridge-type 800 GHz receiver for the ASTE telescope in Atacama, Chile. The receiver has been assembled with a cooled receiver optics, a Nb-based SIS mixer, a local oscillator (LO) optics, and IF components in a 170 mm diameter column-type cartridge. The cooled optics is composed of a single ellipsoidal mirror to couple between the feed horn and the subreflector of the antenna, and an LO coupler with 10% efficiency. Owing to its cartridge and cryostat structure, the mechanical vibrations of the GM cryocooler are significantly reduced, and therefore the receiver is highly stable on the telescope. The receiver noise temperature, using a Nb-based SIS mixer and a 4-8 GHz HEMT amplifier, was attained to 1300 K in DSB at an LO frequency of 815 GHz. The system noise temperature, Tsys, was typically 4000-8000 K in DSB at an LO frequency of 812 GHz during operations, which depended on the atmospheric opacity. The typical zenith opacity at an LO frequency of 812 GHz was ∼ 1. The half-power beam width (HPBW) of the main beam was measured by total power scanning across the Moon, and was consistent with the diffraction limit. A spectrum of the CO J = 7-6 line (806.6518 GHz) toward Orion KL was successfully detected.