Showing papers by "Kaori Hattori published in 2012"

The POLARBEAR Experiment

Abstract: We present the design and characterization of the POLARBEAR experiment. POLARBEAR will measure the polarization of the cosmic microwave background (CMB) on angular scales ranging from the experiment's 3.5 arcminute beam size to several degrees. The experiment utilizes a unique focal plane of 1,274 antenna-coupled, polarization sensitive TES bolometers cooled to 250 milliKelvin. Employing this focal plane along with stringent control over systematic errors, POLARBEAR has the sensitivity to detect the expected small scale B-mode signal due to gravitational lensing and search for the large scale B-mode signal from inflationary gravitational waves. POLARBEAR was assembled for an engineering run in the Inyo Mountains of California in 2010 and was deployed in late 2011 to the Atacama Desert in Chile. An overview of the instrument is presented along with characterization results from observations in Chile.

The POLARBEAR experiment

Abstract: We present the design and characterization of the POLARBEAR experiment. POLARBEAR will measure the polarization of the cosmic microwave background (CMB) on angular scales ranging from the experiment’s 3.5’ beam size to several degrees. The experiment utilizes a unique focal plane of 1,274 antenna-coupled, polarization sensitive TES bolometers cooled to 250 milliKelvin. Employing this focal plane along with stringent control over systematic errors, POLARBEAR has the sensitivity to detect the expected small scale B-mode signal due to gravitational lensing and search for the large scale B-mode signal from inflationary gravitational waves. POLARBEAR was assembled for an engineering run in the Inyo Mountains of California in 2010 and was deployed in late 2011 to the Atacama Desert in Chile. An overview of the instrument is presented along with characterization results from observations in Chile.

LiteBIRD: a small satellite for the study of B-mode polarization and inflation from cosmic background radiation detection

Abstract: 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 bolometric focal plane array of the Polarbear CMB experiment

Abstract: The POLARBEAR Cosmic Microwave Background (CMB) polarization experiment is currently observing from the Atacama Desert in Northern Chile. It will characterize the expected B-mode polarization due to gravitational lensing of the CMB, and search for the possible B-mode signature of inflationary gravitational waves. Its 250 mK focal plane detector array consists of 1,274 polarization-sensitive antenna-coupled bolometers, each with an associated lithographed band-defining filter. Each detector’s planar antenna structure is coupled to the telescope’s optical system through a contacting dielectric lenslet, an architecture unique in current CMB experiments. We present the initial characterization of this focal plane.

Development of the balloon-borne sub-MeV gamma-ray Compton camera using an electron-tracking gaseous TPC and a scintillation camera

Abstract: We have developed an Electron-Tracking Compton Camera (ETCC) for use onboard a balloon to observe sub-MeV/MeV gamma rays from celestial objects. The ETCC is constructed with a three dimensional gaseous tracker for recoil electrons from Compton scattering, and GSO:Ce pixel scintillator arrays as absorber of the Compton-scattered gamma-ray. By using the ETCC, we can reconstruct the energy and direction of individual gamma rays. We have developed a prototype ETCC with a (30 cm)3 TPC, and tested its performance in the range of 356 - 835 keV in the laboratory. As the result, we succeeded in taking images of gamma ray sources and determined a detection efficiency of 9.0 × 10−6 and an effective area of 8.0 × 10−3 cm2 at 662 keV for the prototype ETCC. Furthermore, we developed a new power saving readout circuit for the scintillators that achieves the electric power consumption of 0.41 W/channel, an energy dynamic range of 81 - 1333 keV, and an energy resolution of 10.3% at full width at half maximum at 662 keV.

POLARBEAR-2 optical and polarimeter designs

Abstract: POLARBEAR-2 is a ground based cosmic microwave background (CMB) radiation experiment observing from Atacama, Chile. The science goals of POLARBEAR-2 are to measure the CMB polarization signals originating from the inflationary gravity-wave background and weak gravitational lensing. In order to achieve these science goals, POLARBEAR-2 employs 7588 polarization sensitive transition edge sensor bolometers at observing fre­ quencies of 95 and 150 GHz with 5.5 and 3.5 arcmin beam width, respectively. The telescope is the off-axis Gregorian, Huan Tran Telescope, on which the POLARBEAR-1 receiver is currently mounted. The polarimetry is based on modulation of the polarized signal using a rotating half-wave plate and the rotation of the sky. We present the developments of the optical and polarimeter designs including the cryogenically cooled refractive optics that achieve the overall 4 degrees field-of-view, the thermal filter design, the broadband anti-reflection coating, and the rotating half-wave plate.

Radiation imaging device and nuclear medicine diagnostic device using same

Abstract: The radiation imaging device acquires incident position information of radiation for each detector by setting the size of a through-hole such that at least one pixel is arrayed in a plane view from a direction perpendicular to the detector plane; arranges a septa in displacing from a boundary line between a detector pair in a plane view from a direction perpendicular to the detector plane; further arranging the septa so as to be orthogonal to the boundary line between the detector pair in a plane view from a direction perpendicular to the detector plane; arranges the top of the through-hole in a plane view from a direction perpendicular to the detector plane, in displacing from the boundary line of the detector pair; and arranges the top of the detectors in a plane view from a direction perpendicular to the detector plane so as to be visible through the through-hole.

Novel Frequency-Domain Multiplexing MKID Readout for the LiteBIRD Satellite

Abstract: The satellite LiteBIRD (Light satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection) is being designed to detect the B-mode polarization of the cosmic microwave background radiation. LiteBIRD will carry about 2,000 detectors for measurements in five bands (60, 80, 100, 150, and 220 GHz). Microwave kinetic inductance detectors (MKIDs) that can be multiplexed in a single readout line are suitable for the large focal plane detector array. We develop an MKID readout system for LiteBIRD to monitor the amplitude, phase, and resonant frequency of each MKID resonator simultaneously and follow movements of the resonant frequency caused by changes in the input radiation intensity. This mechanism enables us to have a larger dynamic range for the MKIDs, compared with a system that monitors the amplitude and phase on the resonant frequency. We also propose an MKID having a half-wavelength resonator. This MKID transmits the resonant microwave signal from one feedline to another. It can offer clear microwaves passing through the resonators, even if the coupling and internal quality factors are mismatched. With this MKID, our readout system can track resonance frequency changes much more easily. We present the status of the readout system development and demonstrate the performance with the half-wavelength MKID.

Refinement of position resolution in two-dimensional X-ray detector based on μ-PIC gaseous detector

Abstract: We have successfully refined the position resolution of a two-dimensional X-ray photon-counting detector based on the micro-pixel gas chamber (μ-PIC) by measuring the charge distribution of an X-ray interaction without the use of analog-to-digital converters (ADCs). By updating the logic of the Field Programmable Gate Arrays (FPGAs) included in the data acquisition system, we were able to acquire the pulse widths, or time-above-threshold of the μ-PIC signals, by measuring both the leading and trailing edges of the digital signals. By using the measured widths to estimate the peak of the charge distribution, the position resolution of our detector was improved to σ=93.3±2.8μm from a value of σ=229.5±6.8μm found using the FPGA logic of the previous system. This represents an improvement of nearly 60%.

The bolometric focal plane array of the Polarbear CMB experiment

Abstract: The Polarbear Cosmic Microwave Background (CMB) polarization experiment is currently observing from the Atacama Desert in Northern Chile. It will characterize the expected B-mode polarization due to gravitational lensing of the CMB, and search for the possible B-mode signature of inflationary gravitational waves. Its 250 mK focal plane detector array consists of 1,274 polarization-sensitive antenna-coupled bolometers, each with an associated lithographed band-defining filter. Each detector's planar antenna structure is coupled to the telescope's optical system through a contacting dielectric lenslet, an architecture unique in current CMB experiments. We present the initial characterization of this focal plane.