Search

We have developed a new type of photon detector for an experiment aimed at searching for the lepton flavor violating decay μ+ → e+γ. In this experiment, a total of 900 L of liquid xenon is used in order for the scintillation detector to detect γ-rays with an extremely high sensitivity, where the liquid xenon is viewed by an array of 846 photomultipliers from all sides. The entire amount of xenon should be stored in certain storage systems before the start of the experiment, during detector maintenance in the period of accelerator shutdown, etc. We have developed a new liquid xenon storage system by employing the zero boil-off condition by using a pulse tube cryocooler. The details of system and its performance results are described in this article.

Hydrodynamics, sediment suspension, and morphological response on an estuarine intertidal sand flat in Tokyo Bay, Japan, are examined through a field experiment performed for 16 days in winter 2000 and using a bathymetry data set based on a 6-year series of surveys. Topography of the sandy flat was found to fluctuate by approximately 8 cm during the deployment, while the long-term accumulation rate is estimated with the surveyed bathymetries to be only 3.8 cm/y. Cross-spectral analysis of the measured data indicates that on the sandy tidal flat, semidiurnal or shorter-period fluctuations in current velocity are mostly attributed to semidiurnal tides and waves, whereas wind above the sea generally drives diurnal or longer-period fluctuations. The field data also confirm that suspended sediment concentrations were highly correlated with bed shear stress, which is generated by combination of tidal current, wind-induced current, and wind waves. Episodic erosion is observed on the sandy flat with high...

The development of a Timing Counter detector with a resolution in the range of ≈ 30 ps will be presented. The detector was designed for the upgrade of the MEG II experiment looking for the μ+ → e+γ decay with an improved sensitivity of one order of magnitude with respect to the previous MEG setup. In this paper the design of the TC single pixel is explained together with the results obtained in beam tests.

A coupled wave and circulation model that includes tide, wind, buoyancy, and wave processes is necessary to investigate tracer exchange in the shelf region. Here, a coupled Regional Ocean Model System (ROMS)–Simulating Waves Nearshore (SWAN) model, resolving midshelf to the surfzone region of the San Pedro Bay, California, is compared to observations from the 2006 Huntington Beach experiment. Waves are well modeled, and surfzone cross- and alongshore velocities are reasonably well modeled. Modeled and observed rotary velocity spectra compare well in subtidal and tidal bands, and temperature spectra compare well in the subtidal band. Observed and modeled mid- and inner-shelf subtidal velocity ellipses and temperature variability determined from the first vertical complex EOF (cEOF) mode have similar vertical structure. Although the modeled subtidal velocity vertical shear and stratification are weaker than observed, the ratio of stratification to shear is similar, suggesting model vertical mixing is consistent with observations. On fortnightly and longer time scales, the surface heat flux and advective heat flux divergence largely balance on the inner shelf and surfzone. The surfzone and inner-shelf alongshore currents separated by 220 m are unrelated. Both modeled and observed subtidal alongshelf current and temperature are cross-shelf coherent seaward of the surfzone. Wind forcing explains 50% of the observed and modeled inner-shelf alongshore current variability. The observed and modeled inner-shelf alongshelf nonuniformities in depth-averaged alongshore velocities are similar. Inferred, inner-shelf, wave-induced, cross-shore exchange is more important than on the U.S. East Coast. Overall, the coupled ROMS–SWAN model represents well the waves and subtidal circulation dynamics from the midshelf to the surfzone.

A new timing detector measuring ~50 MeV/c positrons is under development for the MEG II experiment, aiming at a time resolution $\sigma_t \sim 30~\mathrm{ps}$. The resolution is expected to be achieved by measuring each positron time with multiple counters made of plastic scintillator readout by silicon photomultipliers (SiPMs). The purpose of this work is to demonstrate the time resolution for ~50 MeV/c positrons using prototype counters. Counters with dimensions of $90\times 40\times 5~\mathrm{mm}^3$ readout by six SiPMs (three on each $40\times 5~\mathrm{mm}^2$ plane) were built with SiPMs from Hamamatsu Photonics and AdvanSiD and tested in a positron beam at the DA$\Phi$NE Beam Test Facility. The time resolution was found to improve nearly as the square root of the number of counter hits. A time resolution $\sigma_t=26.2\pm1.3~\mathrm{ps}$ was obtained with eight counters with Hamamatsu SiPMs. These results suggest that the design resolution is achievable in the MEG II experiment., Comment: 12 pages, 18 figures. Published in NIM A

High temporal-resolution fluctuations in oxygen concentration and vertical velocity were measured over an intertidal sandflat (water depth 5 Hz) observed in the vertical velocity and oxygen concentration data made little contribution to the total oxygen flux (0 to 7%). However, trends (steady change over a longer time scale) caused significant artifacts in the estimated fluxes for several cases. Thus, removal of trends from raw time-series data is recommended. The co-spectrum of the fluctuating components of vertical velocity and oxygen con- centration revealed that the oxygen flux at a frequency band between 0.3 and 1.4 Hz (at a period from 0.7 to 3.3 s) was a major contributor to the total oxygen flux. This frequency was consistent with the dominant frequency of vertical velocity, indicating that transport and exchange of porewater and overlying water by wind-induced waves may be crucial processes to dissolved oxygen flux between permeable sandy sediments and shallow waters.

We are developing a new type of photon detector for an experiment to search for muons decaying into a positron and a gamma ray. In this experiment, the photon detector will utilize liquid xenon (Xe) as the scintillation material. Good transparency of the liquid Xe is required in order to gain the highest performance out of the detector. Impurities like water and oxygen must be removed efficiently for this purpose. We have developed a new purification system, dedicated to removing water from liquid Xe, by employing a cryogenic centrifugal pump and molecular sieves. The performance of the system is described in this article.

導流堤を有する感潮湖湖口周辺海岸の地形変化を検討するために, 静岡県浜名湖今切口において導流堤の建設中および建設後の30年間に取得された25枚の深浅データを経験的複素固有関数法などによって解析した. その結果, 引き潮によって生じた深みが解析期間中深くなっていること, 解析期間前半では湖口両側に形成された浅瀬は岸向きに移動していたけれども解析期間後半には漂砂上手側の浅瀬の移動方向が沖向きに変化したことを明らかにした. さらに, 湖口の漂砂上手側における堆積量は時間とともに減少するにもかかわらず下手の海岸に供給される土砂量は増加していないこと, これは導流堤を通過した土砂が引き潮デルタに捕捉されたためであること, デルタに捕捉された土砂の量は1992年にほぼ平衡状態に達していたことなどを示した.

A grid-based pollutant load runoff model was developed and applied to the basin of Turumigawa river. This model based on physical based hydrological cycle analysis model, and as a result reproducibility of calculations about water quantity is reasonably good. In this model, pollutant load source account for point source and non-point source. Calculated river water quality, using this model, have been verified for sunny and rainy condition. These calculations are consistent with the observations. This model is useful for basin water management because of it is used to assess water quality influence of land use change and effect of tactics.

Although it is important to measure and record radiation dose to a patient's skin, no standardized measuring method is available to compare the performance of digital subtraction angiography (DSA) systems with those of other institutions. We developed a new bidirectional information exchange system using a web page and, E-mail. Measurements are obtained using an original head phantom with skin dose monitors. This system was sent to institutions ordering it from the web page. The data obtained with this system by each institution were evaluated and displayed anonymously on a graph on the web page for comparison. This method for measuring radiation dose allows the comparison of DSA systems under identical conditions. This system can alert the user that the radiation dose delivered using ordinary parameters differs from that of other institutions or DSA systems. To promote the use of this system, we developed a web page with information about radiation dose measuring and initiated an online lending operation. This head phantom and standardized measuring method allows the accurate comparison of skin radiation dose and DSA performance under the same conditions.

The MEG detector is designed to test Lepton Flavor Violation in the $\mu^+\rightarrow e^+\gamma$ decay down to a Branching Ratio of a few $10^{-13}$. The decay topology consists in the coincident emission of a monochromatic photon in direction opposite to a monochromatic positron. A precise measurement of the relative time $t_{e^+\gamma}$ is crucial to suppress the background. The Timing Counter (TC) is designed to precisely measure the time of arrival of the $e^+$ and to provide information to the trigger system. It consists of two sectors up and down stream the decay target, each consisting of two layers. The outer one made of scintillating bars and the inner one of scintillating fibers. Their design criteria and performances are described., Comment: Presented at the 12th Topical Seminar on Innovative Particle and Radiation Detectors (IPRD10) 7 - 10 June 2010, Siena. Accepted by Nuclear Physics B (Proceedings Supplements) (2011)taly

A 50-year-old man presented with a 2-month history of dysarthria caused by a partially thrombosed vertebral artery (VA) aneurysm. Magnetic resonance imaging showed enhancement of the thickened wall and angiography detected staining. Stent-assisted coil embolization with protection of the parent artery patency was performed. The patient's clinical course was unremarkable and shrinking of the aneurysm was obtained. The stent-assisted coil embolization promoted intra-aneurysm flow disruption and stabilized the wall environment, suggesting another strategy for the treatment of partially thrombosed VA aneurysm.

In this paper various eccentric hole dynamics are presented in defect turbulence of the one-dimensional complex Ginzburg-Landau equation. Each hole shows coherent particlelike motion with nonconstant velocity. On the other hand, successive hole velocities without discriminating each hole exhibit anomalous intermittent motions being subject to multi-time-scale non-Gaussian statistics. An alternate non-Markov stochastic differential equation is proposed, by which all these observed statistical properties can be described successfully.

自然干潟における浮遊砂の生成, 砂面変動等に代表される漂砂の基本特性を把握することを目的として, 冬期の東京湾盤洲干潟において, 波, 流れ, 浮遊砂, 地形に関する短期の現地観測を行った. その結果, 下げ潮時に大きな波浪が来襲し, かつ風の吹送方向と潮汐流の方向が一致したときに大量の浮遊砂が生成されて侵食が進行するという, 有意な地形変化を捉えることに成功した. 盤洲干潟は長期的には3.8cm/yの速度で徐々に堆積しているものの, 本観測では, 高濃度の浮遊砂が断続的に発生するイベントによって, 16日間の観測期間中に最大8cm程度の侵食が生じていた. また, シールズ数を用いた検討の結果, 盤洲干潟の底質移動には浮遊砂が大きく寄与していること, 潮汐による水深変化に追従して変動する波浪が高濃度の浮遊砂の発生に対して重要な役割を果たしていることなどを明らかにした.

海岸帯水層中の地下水の挙動を数値モデルによって調べた. まず, 飽和-不飽和浸透流式と塩分の移流分散方程式を連立させ, 海面の時間変動を境界条件として取り込むことにより, 海岸帯水層特有の地下密度流場を解き, かつ帯水層中に形成される塩水楔の非定常過程を解析し得る数値モデルを示した. この数値モデルを用いて, 砂浜海岸における帯水層中の浸透流場を解析した結果, 前浜表層においてH. W. L. の汀線付近で下向き, L. W. L. の汀線付近で上向きの, 局所的な循環流が形成され, 海水が滞留する領域が出現することを明らかにした. さらに, その形成メカニズムに関する考察を行い, 循環流が潮汐の作用によって形成されたものであること, 帯水層中の密度構造と密接に関連していること, 陸域からの淡水フラックスの大小, 潮位振幅, 海浜勾配等によってもその形態が大きく変化することを見出した.

The design and tests of Timing Counter elements for the upgrade of the MEG experiment, MEG II,is presented. The detector is based on several small plates of scintillator with a Silicon PhotoMultipliers dual-side readout. The optimisation of the single counter elements (SiPMs, scintillators, geometry) is described. Moreover, the results obtained with a first prototype tested at the Beam Test Facility (BTF) of the INFN Laboratori Nazionali di Frascati (LNF) are presented., 10 pages, 7 figures. Presented at the 13th Topical Seminar on Innovative Particle and Radiation Detectors (IPRD13) 7-10 October 2013 Siena, Italy

典型的な閉鎖性水域である東京湾と開放性沿岸域である鹿島灘の年間表層水温変動過程の大局的な特徴を定量的に把握するために, 閉鎖性がより強くかつほぼ同様な気象条件下にある霞ヶ浦も含めた形での長期連続観測データに基づく比較解析を行った. その結果, 1) 鹿島灘海岸域では移流による熱輸送が年間を通して水温変動に寄与するのに対し, 霞ヶ浦では大気側との熱交換によって水温変動がほぼ規定されていること, 2) 夏季の東京湾湾奥部においては, 7日以上の時間スケールでは水表面を通した大気側からの熱輸送によって表層混合層内の水温変動が支配されており, 夏季の表層水温が霞ヶ浦のそれとほぼ同じになること, 3) 冬季では, 湾口を通した外洋からの熱輸送が湾内の水温変動に大きく寄与すること, などが明らかになった.

Submarine groundwater discharge (SGWD) and associated nutrient fluxes at Hasaki Beach along the Kashima coast in Japan were investigated through field measurements and numerical simulations. The field data indicate that (1) groundwater has higher concentrations of land-derived nutrients than seawater and river water; (2) microbial activity near the shoreline is likely to induce mineralization, reduction, and oxidation of nitrogen and phosphorus; and (3) in the portion of the aquifer underlying coastal forest, nitrate is appreciably reduced. A numerical model incorporating effects of water table and tidal fluctuations was developed to evaluate SGWD. Assuming that the aquifer consists of homogeneous sandy soil, the simulation results show that the nutrient flux due to SGWD is less than that of Tone River discharge. The nutrient flux via groundwater seepage is considered to be a minor component of primary productivity in the surf zone.

成層期における海-陸境界部としての極浅海域特有の水環境特性を, 東京湾奥部人工海浜海域を対象とした現地観測と, 数値計算により検討した. 現場海域の水温構造は風速と日射量の変動特性にかなり依存しており, 微風時には潮位変動に伴う沖側底層水塊の貫入が発生し, 強い沖出し風が連吹すると沿岸湧昇により沖側底層水塊の湧昇が起こる. 境界部である海岸域では貧酸素水の湧昇の影響により強い青潮が生じるとともに, 青潮後のブルーミングにより赤潮状態へと移行する. また, 水深が浅いほど日射の影響を強く受け, その結果, 水温成層構造に明確な岸沖分布が形成されるとともに, 水温・溶存酸素量・植物プランクトン量等の日周変動レベルが極めて大きくなる. さらに, 極浅海域では沖側と比較して, 風によって引き起こされる湧昇や吹き寄せなどに伴う水平移流による熱フラックスが, 日周期および長周期の水温変動特性に大きく寄与していることなどを明らかにした.

We present a development of scintillation counter system for a precise time measurement in the MEG II experiment searching for the lepton-flavor-violating decay, μ+ → e+γ. It consists of several hundreds of plastic scintillation counters each of which is read out by several silicon-photomultipliers (SiPM). To pursue the ultimate resolution of a single counter, we have studied and optimized types of SiPM and the way of connection, resulting in a single counter resolution of 40 ps. As a whole system, we achieve 30 ps resolution by combining several counter measurements. The resolution was demonstrated in a beam test.

We have investigated statistical properties of the defect turbulence in 1D CGLE wherein many body interaction is involved between local depressing wave (LDW) and local standing wave (LSW). It is shown that the counting number fluctuation of LDW is subject to the sub-Poisson statistics (SUBP). The physical origin of the SUBP can be ascribed to pair extinction of LDWs based on the master equation approach. It is also shown that the probability density function (pdf) of inter-LDW distance can be identified by the hyper gamma distribution. Assuming a superstatistics of the exponential distribution (Poisson configuration), a plausible explanation is given. It is shown further that the pdf of amplitude of LDW has a fattail. The underlying mechanism of its fluctuation is examined by introducing a generalized fractional Poisson configuration., {"references":["I. S. Aranson and L. Kramer, Rev. Mod. Phys. 74, 99 (2002).","J. Lega, Physica D, 152-153, 269 (2001).","H. W. M¨uller, M. Tveitereid and S. Trainoff, Phys. Rev. E 48, 263 (1993).","M. van Hecke and W. van Saarloos, Phys. Rev. E 55, R1259 (1997).","Y. Liu and R. E. Ecke, Phys. Rev. E 59, 4091 (1999).","A. T. Winfree, Science 175, 634 (1972).","Y. Kuramoto, Chemical Oscillations, Waves and Turbulence, Springer Verlag, 1984.","A. S. Mikhailov and K. Showalter, Phys. Rep. 425, 79 (2006).","Y. Kodama and A. Hasegawa, Opt. Lett. 17, 31 (1992). [10] L. F. Mollenauer, J. P. Gordon and S. G. Evangelides, Opt. Lett. 17, 1575 (1992). [11] C. Pat´e, L. Gagnon and P. A. B´elanger, Opt. Commun. 74, 228 (1989). [12] J. D. Gibbon and M. J. Mcguiness, Proc. R. Soc. Lond. A, 377, 185 (1981). [13] N. Nozaki and N. Bekki, J. Phys. Soc. Jpn. 53, 1581 (1984). [14] H. Chat´e, Nonlinearity 7, 185 (1994). [15] M. van Hecke and M. Howard, Phys. Rev. Lett. 86, 2018 (2001). [16] M. Howard and M. van Hecke, Phys. Rev. E 68, 026213 (2003). [17] J. Sherratt and M. J. Smith, Physica D 241, 1671 (2012). [18] H. Sakaguchi, Phys. Rev. E 76, 017205 (2007). [19] Y. Uchiyama and H. Konno, Proceedings of the 20th Australian Institute of Physics Congress, New South Wales, Australia, 9-13 December 2012. [20] H. Haken, Light: Vol. 1: Waves, Photons, Atoms, North Holland, 1981. [21] H. Konno and P. S. Lomdahl, J. Phys. Soc. Jpn. 69, 1629 (2000). [22] D. T. Gillespie, J. Phys. Chem. 81, 2340 (1977), Y. Cao, D. T. Gillespie and L. R. Petzold, J. Phys. Chem. 122, 014116 (2005), D. T. Gillespie, Annu. Rev. Phys. Chem. 58, 35 (2007). [23] C. Gardiner, Stochastic Methods: A Handbook for the Natural and Social Sciences, Springer Verlag, 2009. [24] M. Abramowitz and I. A. Stegun, Handbook of Mathematical Functions: With Formulas, Graphs, and Mathematical Tables, Dover, 1972. [25] E. Suzuki, Met. and Geophys. 18, 103 (1967). [26] C. Beck, Physica A 306, 189 (2002). [27] E. Orsinger and F. Polito, Stat. and Prob. Lett. 82, 852 (2012)."]}

We are developing Pixelated Photon Detector (PPD) sensitive to deep UV scintillation photons of liquid xenon as a possible candidate for the photosensor upgrade of the MEG liquid xenon γ-ray detector. The prototypes of the PPD preliminarily optimized for the detection of deep UV photons were tested in LXe and their basic properties were measured. The measured performance of the prototypes is described.

The analysis of a combined data set, totaling $3.6\ifmmode\times\else\texttimes\fi{}{10}^{14}$ stopped muons on target, in the search for the lepton flavor violating decay ${\ensuremath{\mu}}^{+}\ensuremath{\rightarrow}{e}^{+}\ensuremath{\gamma}$ is presented. The data collected by the MEG experiment at the Paul Scherrer Institut show no excess of events compared to background expectations and yield a new upper limit on the branching ratio of this decay of $5.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$ (90% confidence level). This represents a four times more stringent limit than the previous world best limit set by MEG.

The MEG (Mu to Electron Gamma) experiment has been running at the Paul Scherrer Institut (PSI), Switzerland since 2008 to search for the decay μ +→e+ γ by using one of the most intense continuous μ + beams in the world. This paper presents the MEG components: the positron spectrometer, including a thin target, a superconducting magnet, a set of drift chambers for measuring the muon decay vertex and the positron momentum, a timing counter for measuring the positron time, and a liquid xenon detector for measuring the photon energy, position and time. The trigger system, the read-out electronics and the data acquisition system are also presented in detail. The paper is completed with a description of the equipment and techniques developed for the calibration in time and energy and the simulation of the whole apparatus., The European Physical Journal C, 73 (4), ISSN:1434-6044, ISSN:1434-6052

Atmospheric environment and related thermal comfort on beaches in summer are significant factors for coastal space design to provide desirable amenity environments. Through a micrometeorological field observation conducted in summer on Makuhaii Beach facing Tokyo Bay, we found that;(1) an internal boundary layer of see breeze was clearly formed on the beach, (2) the beach surface with dry sand has appreciable effects of heating and drying on the surrounding air body, and (3) three physical comfort indices DI, SET* and EHF calculated with the observed data show that the sandy beach and its surroundings provide a highly contrasted spatial structure in thermal comfort.

Atmospheric environment and related thermal comfort on beaches in summer are significant factors for coastal space design to provide desirable amenity environments. Through a micrometeorological field observation conducted in summer on Makuhari Beach facing Tokyo Bay, we found that;(1) an internal boundary layer of see breeze was clearly formed on the beach, (2) the beach surface with dry sand has appreciable effects of heating and drying on the surrounding air body, and (3) three physical comfort indices DI, SET* and HS calculated with the observed data show that the sandy beach and its surroundings provide a highly contrasted spatial structure in thermal comfort.

The final results of the search for the lepton flavour violating decay $$\mathrm {\mu }^+ \rightarrow \mathrm {e}^+ \mathrm {\gamma }$$ based on the full dataset collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013 and totalling $$7.5\times 10^{14}$$ stopped muons on target are presented. No significant excess of events is observed in the dataset with respect to the expected background and a new upper limit on the branching ratio of this decay of $$ \mathcal{B} (\mu ^+ \rightarrow \mathrm{e}^+ \gamma ) < 4.2 \times 10^{-13}$$ (90 % confidence level) is established, which represents the most stringent limit on the existence of this decay to date.