Innovative Demodulation Scheme for Coherent Detectors in CMB Experiments

We propose an innovative demodulation scheme for coherent detectors used in cosmic microwave background polarization experiments. Removal of non-white noise, e.g., narrow-band noise, in detectors is one of the key requirements for the experiments. A combination of modulation and demodulation is used to extract polarization signals as well as to suppress such noise. Traditional demodulation, which is based on the two- point numerical differentiation, works as a first-order high pass filter for the noise. The proposed demodulation is based on the three-point numerical differentiation. It works as a second-order high pass filter. By using a real detector, we confirmed significant improvements of suppression power for the narrow-band noise. We also found improvement of the noise floor.Comment: 3 pages, 4 figure

Calibration System with Cryogenically-Cooled Loads for CMB Polarization Detectors

We present a novel system to calibrate millimeter-wave polarimeters for CMB polarization measurements. This technique is an extension of the conventional metal mirror rotation approach, however it employs cryogenically-cooled blackbody absorbers. The primary advantage of this system is that it can generate a slightly polarized signal ($\sim100$ mK) in the laboratory; this is at a similar level to that measured by ground-based CMB polarization experiments observing a $\sim$ 10 K sky. It is important to reproduce the observing condition in the laboratry for reliable characterization of polarimeters before deployment. In this paper, we present the design and principle of the system, and demonstrate its use with a coherent-type polarimeter used for an actual CMB polarization experiment. This technique can also be applied to incoherent-type polarimeters and it is very promising for the next-generation CMB polarization experiments.Comment: 7 pages, 9 figures Submitted to RS

Mitigating Cosmic Microwave Background Shadow Degradation of Tensor-to-scalar Ratio Measurements through Map-based Studies

It has been pointed out that the spurious Cosmic Microwave Background (CMB) B-mode polarization signals caused by the absorption of the CMB monopole component due to the Galactic interstellar matter, called the CMB shadow, degrade the accuracy of detecting the CMB B-mode polarization signals imprinted by primordial gravitational waves. We have made a realistic estimation using simulated sky maps of how the CMB shadow affects forthcoming high-precision CMB B-mode experiments for the first time. The Delta-map method, an internal template method taking into account the first-order spatial variation of foregrounds' spectral parameters, is applied as a foreground removal method. We show that if the CMB shadow effects are not taken into account in the foreground removal process, future observations would lead to the false detection of the CMB B-mode polarization signals originating from primordial gravitational waves. We also show that the effect of the CMB shadow can be mitigated by our revised Delta-map method to target the CMB B-mode polarization signals at the level of tensor-to-scalar ratio r=0.001.Comment: 9 pages, 2 figure

Far-infrared all sky diffuse mapping with AKARI

We discuss the capability of AKARI in recovering diffuse far-infrared emission, and examine the achieved reliability. Critical issues in making images of diffuse emission are the transient response and long-term stability of the far-infrared detectors. Quantitative evaluation of these characteristics are the key to achieving sensitivity comparable to or better than that for point sources (< 20 -- 95 MJy sr-1). We describe current activity and progress toward the production of high quality images of the diffuse far-infrared emission using the AKARI all-sky survey data.Comment: 4 pages, 8 figures, to appear in the Proceedings of the Conference "AKARI, a light to illuminate the misty Universe", Fukutake Hall, The University of Tokyo, Japan, 16-19 February 200

Dentro/fuera: cartografías artísticas durante el confinamiento. : Una relación estética entre espacio interior [casa] y espacio exterior [ciudad].

This article presents the results of an educational research that relates two concepts formulated as duality during the period of confinement: the home and the city, through the interpretation of the routes in both spaces. The aim is to reveal, through artistic cartography, what happened on a spatial level inside our homes and in the urban setting. During the months of March-April 2020, an artistic education project based on cartographic drawing was carried out. The students of the Social Education Degree of the Faculty of Education Sciences expressed the enclosure and their need for urbanity, through artistic actions based on visual and spatial experimentation. These compositions guided them towards the construction of an aesthetic discourse on the lived experience and allowed them to connect both the inhabited space and the deprivation of the city from the sensitive point of view. The results were analysed using Arts-Based Research tools to generate a visual and meaningful interpretation of the data set, constructing an artistic cartography of the students' interior/exterior journeys, thus recovering individual experiences and creating unpublished images of what was experienced at the group level.Este artículo presenta los resultados de una investigación educativa que pone en relación dos conceptos formulados como dualidad durante el periodo de confinamiento: el hogar y la ciudad, a través de la interpretación de los recorridos en ambos espacios. El objetivo es revelar mediante la cartografía artística, lo ocurrido a nivel espacial en el interior de nuestras viviendas y en el escenario urbano. Durante los meses de marzo-abril 2020, se llevó a cabo un proyecto de educación artística basado en el dibujo cartográfico. Los alumnos de Grado de Educación Social de la Facultad de Ciencias de la Educación expresaron su encerramiento y su necesidad de urbanidad, a partir de acciones artísticas basadas en la experimentación visual y espacial. Estas composiciones les guiaban hacia la construcción de un discurso estético sobre lo vivido y les permitían conectar, desde lo sensible, tanto el espacio habitado, como la privación de ciudad. Los resultados fueron analizados mediante instrumentos de Investigación Basada en Artes para generar una interpretación visual y significativa del conjunto de datos, construyendo una cartografía artística de los recorridos interiores/exteriores de los estudiantes, recuperando así las experiencias individuales y creando imágenes inéditas de lo vivido a nivel grupal

AKARI Far-Infrared All Sky Survey

We demonstrate the capability of AKARI for mapping diffuse far-infrared emission and achieved reliability of all-sky diffuse map. We have conducted an all-sky survey for more than 94 % of the whole sky during cold phase of AKARI observation in 2006 Feb. -- 2007 Aug. The survey in far-infrared waveband covers 50 um -- 180 um with four bands centered at 65 um, 90 um, 140 um, and 160 um and spatial resolution of 3000 -- 4000 (FWHM).This survey has allowed us to make a revolutionary improvement compared to the IRAS survey that was conducted in 1983 in both spatial resolution and sensitivity after more than a quarter of a century. Additionally, it will provide us the first all-sky survey data with high-spatial resolution beyond 100 um. Considering its extreme importance of the AKARI far-infrared diffuse emission map, we are now investigating carefully the quality of the data for possible release of the archival data. Critical subjects in making image of diffuse emission from detected signal are the transient response and long-term stability of the far-infrared detectors. Quantitative evaluation of these characteristics is the key to achieve sensitivity comparable to or better than that for point sources (< 20 -- 95 [MJy/sr]). We describe current activities and progress that are focused on making high quality all-sky survey images of the diffuse far-infrared emission.Comment: To appear in Proc. Workshop "The Space Infrared Telescope for Cosmology & Astrophysics: Revealing the Origins of Planets and Galaxies". Eds. A.M. Heras, B. Swinyard, K. Isaak, and J.R. Goicoeche

Beat length measurement in directional couplers by thermo-optic modulation

In integrated optical directional couplers formed by two parallel waveguides, we measure the difference Δβ = βeven - βodd between the propagation constants of the 'supermodes'. They are coupled locally by heating a fine spot on one of the guides. When the spot is scanned along the coupler the output power from one of the guides is found to vary periodically. The period of variation is the modal beat length λ = 2π/Δβ. We demonstrate this technique with directional couplers fabricated by K+-exchange in glass. Beat lengths in the range of 0.6 ... 2.2 mm are measured with an accuracy of ±0.3%.<br/