T. Nakamori

Direct creation of three-dimensional photonic crystals by a top-down approach

Three-dimensional (3D) photonic crystals can block photons in any direction and are expected to make possible their ultimate control. However, creating 3D crystals without any unintentional defects over large areas at optical wavelengths has been challenging. For example, opal-based crystals inevitably contain unintentional defects, it is difficult to increase the sizes of micro-manipulated crystals over approximately 6 microm and producing stacked 3D crystals with thin 2D layers requires complicated and time-consuming processes. So far, these difficulties have hindered 3D photonic-crystal research. Here, we demonstrate a novel top-down approach to creating 3D crystals that overcomes these difficulties and significantly simplifies the process. We have developed a double-angled deep-etching method, which enables the direct creation of 3D woodpile crystals in single-crystalline silicon. A strong photonic bandgap effect with >20 dB attenuation in all directions has been achieved. Furthermore, bonding a light emitter onto or between 3D crystals created in this way has been shown to enhance or suppress spontaneous emission.

Broad-line Radio Galaxies Observed with Fermi-LAT: The Origin of the GeV γ-Ray Emission

We report on a detailed investigation of the γ-ray emission from 18 broad line radio galaxies (BLRGs) base d on two years ofFermi Large Area Telescope (LAT) data. We confirm the previously re po ted detections of 3C 120 and 3C 111 in the GeV photon energy range; a detailed loo k at the temporal characteristics of the observedγ-ray emission reveals in addition possible flux variability in both sources. No statistically significant γ-ray detection of the other BLRGs was however found in the con sidered dataset. Though the sample size studied is small, what appears to differentiate 3C 111 and 3C 120 from the BLRGs not yet detected in γrays is the particularly strong nuclear radio flux. This findi g, together with the indications of the γ-ray flux variability and a number of other arguments presented, indi cate that the GeV emission of BLRGs is most likely dominated by the beamed radiation of relativistic jets obse rved at intermediate viewing angles. In this paper we also analyzed a comparison sample of high accretion-rate Se yfert 1 galaxies, which can be considered radioquiet counterparts of BLRGs, and found none were detected in γ-rays. A simple phenomenological hybrid model applied for the broad-band emission of the discussed r adio-loud and radio-quiet type 1 active galaxies suggests that the relative contribution of the nuclear jets to he accreting matter is ≥ 1% on average for BLRGs, whilst ≤ 0.1% for Seyfert 1 galaxies. Subject headings: radiation mechanisms: non-thermal — galaxies: active — gal axies: individual (3C 111, 3C 120) — galaxies: jets — gamma rays: galaxies — X-rays: gala xiesWe report on a detailed investigation of the γ-ray emission from 18 broad-line radio galaxies (BLRGs) based on two years of Fermi Large Area Telescope data. We confirm the previously reported detections of 3C 120 and 3C 111 in the GeV photon energy range; a detailed look at the temporal characteristics of the observed γ-ray emission reveals in addition possible flux variability in both sources. No statistically significant γ-ray detection of the other BLRGs was found, however, in the considered data set. Though the sample size studied is small, what appears to differentiate 3C 111 and 3C 120 from the BLRGs not yet detected in γ-rays is the particularly strong nuclear radio flux. This finding, together with the indications of the γ-ray flux variability and a number of other arguments presented, indicates that the GeV emission of BLRGs is most likely dominated by the beamed radiation of relativistic jets observed at intermediate viewing angles. In this paper we also analyzed a comparison sample of high-accretion-rate Seyfert 1 galaxies, which can be considered radio-quiet counterparts of BLRGs, and found that none were detected in γ-rays. A simple phenomenological hybrid model applied for the broadband emission of the discussed radio-loud and radio-quiet type 1 active galaxies suggests that the relative contribution of the nuclear jets to the accreting matter is ≥1% on average for BLRGs, whereas it is ≤0.1% for Seyfert 1 galaxies.

Prospects for GRB Science with the Fermi Large Area Telescope

The Large Area Telescope (LAT) instrument on the Fermi mission will reveal the rich spectral and temporal gamma-ray burst (GRB) phenomena in the >100 MeV band. The synergy with Fermis Gamma-ray Burst Monitor detectors will link these observations to those in the well explored 10-1000 keV range; the addition of the >100 MeV band observations will resolve theoretical uncertainties about burst emission in both the prompt and afterglow phases. Trigger algorithms will be applied to the LAT data both onboard the spacecraft and on the ground. The sensitivity of these triggers will differ because of the available computing resources onboard and on the ground. Here we present the LATs burst detection methodologies and the instruments GRB capabilities.

Detection of gamma rays around 1 TeV from RX J0852.0-4622 by CANGAROO-II

We have detected gamma-ray emission at the 6 σ level at energies greater than 500 GeV from the supernova remnant RX J0852.0-4622 (G266.2-1.2) using the CANGAROO-II imaging atmospheric Cerenkov telescope. The flux was 0.12 times that of Crab at 1 TeV. The signal centroid is consistent with the peak of the X-ray emission in the northwest rim of the remnant.

SUZAKU OBSERVATIONS OF THE DIFFUSE X-RAY EMISSION ACROSS THE FERMI BUBBLES' EDGES

We present SuzakuX-ray observations along two edge regions of the Fermi Bubbl es, with eight≃ 20 ksec pointings across the northern part of the North Polar Spur (N PS) surrounding the north bubble and six across the southernmost edge of the south bubble. After removing co mpact X-ray features, diffuse X-ray emission is clearly detected and is well reproduced by a three-componen t sp ctral model consisting of unabsorbed thermal emission (temperature kT ≃ 0.1 keV) from the Local Bubble (LB), absorbed kT ≃ 0.3 keV thermal emission related to the NPS and/or Galactic Halo (GH), and a power-law component at a level consistent with the cosmic X-ray background. The emission measure (EM) of the 0. 3 keV plasma decreases by ≃ 50% toward the inner regions of the north-east bubble, with no accompan ying temperature change. However, such a jump in the EM is not clearly seen in the south bubble data. While it is unclear if the NPS originates from a nearby supernova remnant or is related to previous activity wi hin/around the Galactic Center, our Suzaku observations provide evidence suggestive of the latter sce nario. In the latter framework, the presence of a large amount of neutral matter absorbing the X-ray emission as wel l as the existence of the kT ≃ 0.3 keV gas can be naturally interpreted as a weak shock driven by the bubble s’ expansion in the surrounding medium, with velocityvexp ∼ 300 km s (corresponding to shock Mach number M ≃ 1.5), compressing the GH gas to form the NPS feature. We also derived an upper limit for any non-th ermal X-ray emission component associated with the bubbles and demonstrate, that in agreement with the findings above, the non-thermal pressure and energy estimated from a one-zone leptonic model of its broad -band spectrum, are in rough equilibrium with that of the surrounding thermal plasma. Subject headings: acceleration of particles — cosmic rays — Galaxy: center — Ga laxy: halo — X-rays: ISM

Development of a Dual-Sided Readout DOI-PET Module Using Large-Area Monolithic MPPC-Arrays

We are proposing a novel design for a module with depth of interaction (DOI) capability for gamma rays by measuring the pulse-height ratio of double-sided Multi-Pixel Photon Counters (MPPCs) coupled at both ends of a scintillation crystal block. Thanks to newly developed monolithic MPPC arrays consisting of 4 × 4 channels with a three-side buttable package, the module is very thin and compact, thereby enabling less dead space between each module when arranged into a fully designed gantry. To demonstrate our concept of a DOI measuring technique, we first made a 1-D crystal array consisting of five Ce-doped Gd₃Al₂Ga₃O₁₂ (Ce:GAGG) cubic crystals measuring 3×3×3 mm³ in size, separated by a layer of air approximately 10 μm-thick. When the light signals output from both ends are read with the 3×3 mm² MPPCs, the position of each crystal is clearly distinguished. The same measurements were also made using Ce-doped (Lu,Y)₂(SiO₄)O (Ce:LYSO), achieving a similarly good separation. We then fabricated thin Ce:GAGG 2-D crystal arrays consisting of two types: [A] 4 × 4 matrix of 3×3×3 mm³ pixels, and [B] 10 × 10 matrix of 0.8×0.8×5 mm³ pixels, with each pixel divided by a BaSO₄ reflector 0.2 mm-thick. Then four arrays are laid on top of each other facing the DOI direction through a layer of air 10 μm-thick. We demonstrated that the 3-D position of each Ce:GAGG pixel is clearly distinguished in both the 2-D and DOI directions for type A and B when illuminated by 662 keV gamma rays. Average energy resolutions of 9.8 ± 0.8% and 11.8 ± 1.3% were obtained for types A and B, respectively. These results suggest that our proposed method is simple and offers promise in achieving both excellent spatial and energy resolutions for future medical imaging, particularly in positron emission tomography (PET).

Cangaroo III observations of the supernova remnant RX J0852.0-4622

Sub-TeV gamma-ray emission from the northwest rim of the supernova remnant RX J0852.0-4622 was detected with the CANGAROO II telescope and recently confirmed by the HESS group. In addition, the HESS data revealed a very wide (up to 2° in diameter), shell-like profile of the gamma-ray emission. We carried out CANGAROO III observations in 2005 January and February with three telescopes and show here the results of threefold coincidence data. We confirm the HESS results about the morphology and the energy spectrum and find that the energy spectrum in the NW rim is consistent with that of the whole remnant.

Hard x-ray imager (HXI) for the ASTRO-H Mission

The Hard X-ray Imager (HXI) is one of four detectors on board the ASTRO-H mission (6th Japanese X-ray satellite), which is scheduled to be launched in 2014. Using the hybrid structure composed of double-sided silicon strip detectors and a cadmium telluride double-sided strip detector, the instrument fully covers the energy range of photons collected with the hard X-ray telescope up to 80 keV with a high quantum efficiency. High spatial resolution of 250 μm and an energy resolution of 1-2 keV (FWHM) are both achieved with low noise front-end ASICs. In addition, the thick BGO active shields surrounding the main detector package is a heritage of the successful performance of the Hard X-ray Detector on board the Suzaku satellite. This feature enables the instrument to achieve an extremely high background reduction caused by cosmic-ray particles, cosmic X-ray background, and in-orbit radiation activation. In this paper, we present the detector concept, design, latest results of the detector development, and the current status of the hardware.

A Search for Sub-TeV Gamma Rays from the Vela Pulsar Region with CANGAROO-III

We made stereoscopic observations of the Vela pulsar region with two of the 10 m diameter CANGAROO-III imaging atmospheric Cerenkov telescopes in 2004 January and February in a search for sub-TeV gamma rays from the pulsar and surrounding regions. We describe the observations, provide a detailed account of the calibration methods, and introduce the improved and bias-free analysis techniques employed for CANGAROO-III data. No evidence of gamma-ray emission is found from either the pulsar position or the previously reported position offset by 013, and the resulting upper limits are a factor of 5 less than the previously reported flux from observations with the CANGAROO-I 3.8 m telescope. Following the recent report by the H.E.S.S. group of TeV gamma-ray emission from the pulsar wind nebula, which is ~05 south of the pulsar position, we examined this region and found supporting evidence for emission extended over ~06.We made stereoscopic observations of the Vela Pulsar region with two of the 10 m diameter CANGAROO-III imaging atmospheric Cherenkov telescopes in January and February, 2004, in a search for sub-TeV gamma-rays from the pulsar and surrounding regions. We describe the observations, provide a detailed account of the calibration methods, and introduce the improved and bias-free analysis techniques employed for CANGAROO-III data. No evidence of gamma-ray emission is found from either the pulsar position or the previously reported position offset by 0.13 degree, and the resulting upper limits are a factor of five less than the previously reported flux from observations with the CANGAROO-I 3.8 m telescope. Following the recent report by the H.E.S.S. group of TeV gamma-ray emission from the Pulsar Wind Nebula, which is

CANGAROO III Search for Gamma Rays from Centaurus A and the ω Centauri Region

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