This study demonstrates that phosphorus-related radiation-induced absorption (RIA) bands such as P-OHC and P1 in erbium/ytterbium-doped optical fibers (EYDFs) are effectively decreased by germanium ...(Ge) co-doping. The suppression of the generation of both P-OHC during X-ray irradiation of glass preforms and P1 during gamma-ray irradiation of optical fibers was measured for Ge concentrations between 0 wt% and 6.7 wt%. For the 10 krad X-ray irradiation of glass preforms, it was found that the RIA decreased from 5.6 dB/cm to 1.3 dB/cm when the Ge concentration was increased from 0.79 wt% to more than 4.4 wt%. Furthermore, in multimode optical fibers (MMFs) exposed to 100 krad of gamma-ray irradiation, the RIA decreased from 3.7 dB/m to 0.90 dB/m when the Ge concentration was increased from 0.0 wt% to 4.0 wt%, whereas it was 0.35 dB/m for a single-mode optical fiber (SMF) with a Ge concentration of 6.7 wt%. These results demonstrate that Ge concentrations up to 4.4 wt% are strongly correlated with improved radiation tolerance for both glass preforms and optical fibers. This effect was more prominent for SMFs than MMFs and became saturated with excess co-doping in both cases. Therefore, Ge co-doping may represent a good solution for reducing P-related RIA in EYDFs for space applications.
Abstract
Chemical extraction using a molecular recognition resin named “Empore Radium Rad Disk” was developed to improve sensitivity for the low concentration of radium (Ra). Compared with the ...previous method, the extraction process speed was improved by a factor of three and the recovery rate for $^{226}$Ra was also improved from $81\pm4\%$ to $>99.9\%$. The sensitivity on the $10^{-1}$ mBq level was achieved using a high-purity germanium detector. This improved method was applied to determine $^{226}$Ra in Gd$_2$(SO$_4$)$_3{\cdot}$8H$_2$O which will be used in the Super-Kamiokande Gadolinium project. The improvement and measurement results are reported in this paper.
AbstractBecause fatigue damage considerably reduces the service life of steel bridges, maintenance for fatigue damage should be performed properly. For the effective maintenance of fatigue damage, it ...is important to monitor traffic loads over long periods of time because fatigue damage is caused by repeated high stresses due to the weight of traveling vehicles. This study verified the long-term effectiveness of a portable weigh-in-motion (pBWIM) system through 1-year field measurements conducted on an actual in-service bridge. The pBWIM consists only of microelectromechanical systems (MEMS) accelerometers and MEMS inertial measurement units (IMUs), which are ideal for field measurements because they can be easily attached and detached using a magnetic jig. Furthermore, because MEMS accelerometers and MEMS IMUs are low-power-consumption devices, they are suitable for long-term field measurements. Field measurements were performed using a test truck in winter, summer, and autumn. The results indicate that regardless of the ambient temperature, the pBWIM system can estimate gross vehicle weights (GVWs) within an error of ±10.6% over a 1-year period compared with static weights measured using a truck weighing scale. Furthermore, it is found to be important to determine the dependence of the influence line on ambient temperature to estimate GVWs with high accuracy.
Abstract
A high-pressure xenon gas time projection chamber, with a unique cellular readout structure based on electroluminescence, has been developed for a large-scale neutrinoless double-beta decay ...search. In order to evaluate the detector performance and validate its design, a 180 L size prototype is being constructed and its commissioning with partial detector has been performed. The obtained energy resolution at 4.0 bar is 1.73 $\pm$ 0.07% (FWHM) at 511 keV. The energy resolution at the $^{136}$Xe neutrinoless double-beta decay $Q$-value is estimated to be between 0.79 and 1.52% (FWHM) by extrapolation. Reconstructed event topologies show patterns peculiar to the track endpoint that can be used to distinguish $0\nu\beta\beta$ signals from gamma-ray backgrounds.
We successfully developed a new photomultiplier tube (PMT) with a three-inch diameter, convex-shaped photocathode, R13111. Its prominent features include good performance and ultra-low radioactivity. ...The convex-shaped photocathode realized a large photon acceptance and good timing resolution. Low radioactivity was achieved by three factors: (1) the glass material was synthesized using low-radioactive-contamination material; (2) the photocathode was produced with 39K-enriched potassium; and (3) the purest grade of aluminum material was used for the vacuum seal. As a result each R13111 PMT contains only about 0.4 mBq of 226Ra, less than 2 mBq of 238U, 0.3 mBq of 228Ra, 2 mBq of 40K and 0.2 mBq of 60Co. We also examined and resolved the intrinsic leakage of Xe gas into PMTs that was observed in several older models. We thus succeeded in developing a PMT that has low background, large angular acceptance with high collection efficiency, good timing resolution, and long-term stable operation. These features are highly desirable for experiments searching for rare events beyond the standard model, such as dark matter particle interactions and neutrinoless double beta decay events.
A high performance distillation system to remove krypton from xenon was constructed, and a purity level of Kr/Xe
=
∼3
×
10
−12 was achieved. This development is crucial in facilitating ...high-sensitivity low-background experiments such as the search for dark matter in the universe.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The angular dependence of columnar recombination in xenon (Xe) gas, if observed for low energy nuclear tracks, can be used for a direction-sensitive dark matter search. We measured both scintillation ...and ionization yields to study columnar recombination for 5.4 MeV alpha particles in a high pressure gas detector filled with Xe gas at a pressure of 8 atm. Because the recombination photons are emitted several microseconds after de-excitation, the scintillation photons are separated into fast and slow components. While the fast component is not dependent on the track angle relative to the drift electric field, the slow component increases when the track is aligned with the electric field. This result indicates that the track angle relative to the electric field can be reconstructed from the scintillation time profile.
We report an in-situ measurement of the nuclear recoil (NR) scintillation decay time constant in liquid xenon (LXe) using the XMASS-I detector at the Kamioka underground laboratory in Japan. XMASS-I ...is a large single-phase LXe scintillation detector whose purpose is the direct detection of dark matter via NR which can be induced by collisions between Weakly Interacting Massive Particles (WIMPs) and a xenon nucleus. The inner detector volume contains 832 kg of LXe. 252Cf was used as an external neutron source for irradiating the detector. The scintillation decay time constant of the resulting neutron induced NR was evaluated by comparing the observed photon detection times with Monte Carlo simulations. Fits to the decay time prefer two decay time components, one for each of the Xe2* singlet and triplet states, with τS=4.3±0.6 ns taken from prior research, τT was measured to be 26.9+0.7−1.1 ns with a singlet state fraction FS of 0.252+0.027−0.019. We also evaluated the performance of pulse shape discrimination between NR and electron recoil (ER) with the aim of reducing the electromagnetic background in WIMP searches. For a 50% NR acceptance, the ER acceptance was 13.7±1.0% and 4.1±0.7% in the energy ranges of 5–10 keVee and 10–15 keVee, respectively.
For noble gas Time Projection Chambers (TPCs) in the field of rare event searches, operation of high voltage to generate an electric field is a key point. We designed a new structure of electrodes to ...shape a strong and uniform drift field without electric discharge, in which electrodes of two different radius are used. We also developed Cockcroft-Walton voltage multiplier as a high voltage generator inside a pressure vessel. We achieved −30.0 kV output and examined such kind of voltage generator is feasible as a high voltage supplier in a TPC.
Abstract
Demand to use gadolinium (Gd) in detectors is increasing in the field of elementary particle physics, especially in neutrino measurements and dark matter searches. Large amounts of Gd are ...used in these experiments. To assess the impact of Gd on the environment it is becoming important to measure the baseline concentrations of Gd. Such measurement, however, is not easy due to interference by other elements. In this paper a method for measuring the concentrations of rare earth elements, including Gd, is proposed. In the method, inductively coupled plasma-mass spectrometry is utilized after collecting the dissolved elements in chelating resin. Results of the ability to detect anomalous concentrations of rare earth elements in river water samples in the Kamioka and Toyama areas are also reported.
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