The Great East Japan Earthquake in March 2011 destroyed the Fukushima Dai-ichi Nuclear Power Plant (FNPP) and almost all residents in a 20 km radius from the plant eventually evacuated. FNPP reactors ...were stabilised in December 2011; some evacuees decided to return to their hometowns, and the other evacuees remained. Efforts were made to identify the determinants that affect the decision to return home in order to promote recovery of the surrounding area of FNPP. Seventy-one residents who had not returned to hometown and 56 residents who had returned were selected. Logistic regression analysis adjusted for confounding factors showed that being female odds ratio (OR): 2.43, p = 0.03, living in areas with relatively higher ambient doses (OR: 3.60, p=0.01) and expressing anxiety over radiation exposure (OR: 8.91, p < 0.01) were independently associated with decisions not to return. Results of this study suggest the importance of active participation by scientists and local authorities in communicating the risk to the general population involved in returning home.
CsI calorimeter for the J-PARC KOTO experiment Sato, K.; Lee, J.W.; Banno, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2020, Volume:
982, Issue:
C
Journal Article
Peer reviewed
Open access
An electromagnetic calorimeter made of undoped CsI crystals is used in the J-PARC KOTO experiment to search for new physics beyond the standard model with the KL→π0νν̄ decay. The calorimeter is ...designed to operate in vacuum of 0.1 Pa and in a high-rate environment where the counting rate due to KL decays is O(100) kHz. A special method to calibrate the calorimeter during the data taking without using a tracking system for charged particles is reported. The energy, position, and timing resolutions of the calorimeter were evaluated in several beam tests, and the resolutions satisfy the required performance. The energy resolution with the total energy E is 0.66⊕1.81∕EGeV% in the inner region of the calorimeter.
The JEOL Automated Data Acquisition System (JADAS) is a software system built for the latest generation of the JEOL Transmission Electron Microscopes. It is designed to partially or fully automate ...image acquisition for ice-embedded single particles under low dose conditions. Its built-in flexibility permits users to customize the order of various imaging operations. In this paper, we describe how JADAS is used to accurately locate and image suitable specimen areas on a grid of ice-embedded particles. We also demonstrate the utility of JADAS by imaging the epsilon 15 bacteriophage with the JEM3200FSC electron cryo-microscope, showing that sufficient images can be collected in a single 8
h session to yield a subnanometer resolution structure which agrees with the previously determined structure.
The Outer-Edge Veto (OEV) counter subsystem for extra-photon detection from the backgrounds for the KL0→π0νν¯ decay is located at the outer edge of the endcap CsI calorimeter of the KOTO experiment ...at J-PARC. The subsystem is composed of 44 counters with different cross-sectional shapes. All counters are made of lead and scintillator plates and read out through wavelength-shifting fibers. In this paper, we discuss the design and performances of the OEV counters under heavy load (~8tons/m2) in vacuum. For 1-MeV energy deposit, the average light yield and time resolution are 20.9 photo-electrons and 1.5ns, respectively. Although no pronounced peak by minimum-ionizing particles is observed in the energy distributions, an energy calibration method with cosmic rays works well in monitoring the gain stability with an accuracy of a few percent.
Erbium oxide (Er
2
O
3
) coating layer is one of the suitable coatings to realize an advanced breeding blanket system because it has high electrical resistivity and hydrogen permeation suppression ...effect. In order to enhance these properties of Er
2
O
3
coating, it is necessary to form a thick coating layer with high crystallinity. The formation of a double stacked coating layer on an austenitic stainless steel 316 substrate using an intermediate layer (buffer layer) was investigated for the thicker and high crystallinity of Er
2
O
3
coating formation. Yttrium oxide (Y
2
O
3
) and cerium oxide (CeO
2
) were selected as buffer layer between the Er
2
O
3
layer and austenitic stainless steel 316 substrate due to their similar lattice constant to that of Er
2
O
3
crystal. The texture and grain growth direction of Er
2
O
3
was controlled by the Y
2
O
3
and CeO
2
buffer layer. However, the suppression effect of hydrogen permeation by the double stacked coating was smaller than that of the single layer coating due to the thin Er
2
O
3
formation.
We searched for the CP-violating rare decay of the neutral kaon, KL→π0νν¯, in data from the first 100 hours of physics running in 2013 of the J-PARC KOTO experiment. One candidate event was observed ...while 0.34±0.16 background events were expected. We set an upper limit of 5.1×10−8 for the branching fraction at the 90% confidence level (C.L.). An upper limit of 3.7×10−8 at the 90% C.L. for the KL→π0X0 decay was also set for the first time, where X0 is an invisible particle with a mass of 135 MeV/c2.
The KOTO (
$K^0$
at Tokai) experiment aims to observe the CP-violating rare decay
$K_L \rightarrow \pi ^0 \nu \bar {\nu }$
by using a long-lived neutral-kaon beam produced by the 30 GeV proton beam ...at the Japan Proton Accelerator Research Complex. The
$K_L$
flux is an essential parameter for the measurement of the branching fraction. Three
$K_L$
neutral decay modes,
$K_L \rightarrow 3\pi ^0$
,
$K_L \rightarrow 2\pi ^0$
, and
$K_L \rightarrow 2\gamma $
, were used to measure the
$K_L$
flux in the beam line in the 2013 KOTO engineering run. A Monte Carlo simulation was used to estimate the detector acceptance for these decays. Agreement was found between the simulation model and the experimental data, and the remaining systematic uncertainty was estimated at the 1.4% level. The
$K_L$
flux was measured as
$(4.183 \pm 0.017_{{\rm stat.}} \pm 0.059_{{\rm sys.}}) \times 10^7$
$K_L$
per
$2\times 10^{14}$
protons on a 66-mm-long Au target.
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