arXiv subjects

Kentaro Miuchi

Publications and source records attributed to Kentaro Miuchi.

At least 37 records · Page 2Linked to original sources

arXiv2020

Probing GHz Gravitational Waves with Graviton-magnon Resonance

A novel method for extending frequency frontier in gravitational wave observations is proposed. It is shown that gravitational waves can excite a magnon. Thus, gravitational waves can be probed by a graviton-magnon detector which measures resonance fluorescence of magnons. Searching for gravitational waves with a wave length $λ$ by using a ferromagnetic sample with a dimension $l$, the sensitivity of the graviton-magnon detector reaches spectral densities, around $5.4 \times 10^{-22} \times (\frac{l}{λ/2π})^{-2} \ [{\rm Hz}^{-1/2}]$ at 14 GHz and $8.6 \times 10^{-21} \times (\frac{l}{λ/2π})^{-2} \ [{\rm Hz}^{-1/2}]$ at 8.2 GHz, respectively.

gr-qc↗

arXiv2019

Measurement of ambient neutrons in an underground laboratory at Kamioka Observatory and future plan

Ambient neutrons are one of the most serious backgrounds for underground experiments in search of rare events. The ambient neutron flux in an underground laboratory of Kamioka Observatory was measured using a $\mathrm{^3He}$ proportional counter with various moderator setups. Since the detector response largely depends on the spectral shape, the energy spectra of the neutrons transported from the rock to the laboratory were estimated by Monte-Carlo simulations. The ratio of the thermal neutron flux to the total neutron flux was found to depend on the thermalizing efficiency of the rock. Thus, the ratio of the count rate without a moderator to that with a moderator was used to determine this parameter. Consequently, the most-likely neutron spectrum predicted by the simulations for the parameters determined by the experimental results was obtained. The result suggests an interesting spectral shape, which has not been indicated in previous studies. The total ambient neutron flux is $(23.5 \pm 0.7 \ \mathrm{_{stat.}} ^{+1.9}_{-2.1} \ \mathrm{_{sys.}}) \times 10^{-6}$ cm$^{-2}$ s$^{-1}$. In this paper, we explain our method of the result and discuss our future plan.

physics.ins-det↗

arXiv2019

MPGD simulation in negative-ion gas for direction-sensitive dark matter searches

Negative-ion time projection chambers (NITPCs) provide the absolute z-position from the arrival-times' difference of several species of negative-ions. This is a strong background reduction method for rare event searches, such as direct dark mater searches. The characteristics of micro pattern gaseous detectors (MPGDs) in negative-ion gas were studied by both experiments and simulations to develop an NITPC for dark matter search experiments. An MPGD simulation method for the negative-ion gas with Garfield++, which has not yet been established, was developed. We present herein the MPGD simulation results in negative-ion gas, $\mathrm{SF_{6}}$ gas, together with the experimental results, such as gain, energy resolution, and signal creation from the MPGD for future NITPC optimization.

physics.ins-det↗

arXiv2019

Development of a time projection chamber with a sheet-resistor field cage

A new-concept time projection chamber (TPC) using a commercial resistive sheet, sheet-resistor micro-TPC SR-microPIC, was developed and its performance was measured. SR-microTPC has the potential to create a more uniform electric field than conventional TPCs with resistor-chains owing to its continuous sheet resistivity, and its production would be easier than that of conventional TPCs. The material used in this study, Achilles-Vynilas, was found to be thin, transparent, and low-radioactive. The performance test with cosmic muons showed very promising results, including the demonstration of a good tracking-performance. This type of TPC field cage can offer an alternative for the widely used conventional field cages

physics.ins-det↗

arXiv2019

Prototype Analog Front-end for Negative-ion Gas and Dual-phase Liquid-Ar TPCs

We report on the recent development of a versatile analog front-end compatible with a negative-ion $μ$-TPC for a directional dark matter search as well as a dual-phase, next-generation $\mathcal{O}$(10~kt) liquid argon TPC to study neutrino oscillations, nucleon decay, and astrophysical neutrinos. Although the operating conditions for negative-ion and liquid argon TPCs are quite different (room temperature \textit{vs.} $\sim$88~K operation, respectively), the readout electronics requirements are similar. Both require a wide-dynamic range up to 1600 fC, and less than 2000--5000 e$^-$ noise for a typical signal of 80 fC with a detector capacitance of $C_{\rm det} \approx 300$~pF. In order to fulfill such challenging requirements, a prototype ASIC was newly designed using 180-nm CMOS technology. Here, we report on the performance of this ASIC, including measurements of shaping time, dynamic range, and equivalent noise charge (ENC). We also demonstrate the first operation of this ASIC on a low-pressure negative-ion $μ$-TPC.

physics.ins-det↗

arXiv2018

Measurement of ambient neutrons in an underground laboratory at Kamioka Observatory

Ambient neutrons are one of the most serious backgrounds for underground experiments searching for rare events. The ambient neutron flux in an underground laboratory of Kamioka Observatory was measured using a $\mathrm{^3He}$ proportional counter with various moderator setups. Since the detector response largely depends on the spectral shape, the energy spectra of the neutrons transported from the rock to the laboratory are estimated by Monte-Carlo simulations. The ratio of the thermal neutron flux to the total neutron flux was found to depend on the thermalizing efficiency of the rock. Therefore, the ratio of the count rate without a moderator to that with a moderator was used to determine this parameter. Consequently, the most-likely neutron spectrum predicted by the simulations for the parameters determined by the experimental results was obtained. The result suggests an interesting spectral shape, which has not been indicated in previous studies. The total ambient neutron flux is $(23.52 \pm 0.68 \ \mathrm{_{stat.}} ^{+1.87}_{-2.13} \ \mathrm{_{sys.}}) \times 10^{-6}$ cm$^{-2}$ s$^{-1}$. This result, especially the energy spectrum information, could be a new and important input for estimating the background in current and future experiments in the underground laboratory at Kamioka Observatory.

physics.ins-det↗

arXiv2017

Study of Negative-Ion TPC Using μ-PIC for Directional Dark Matter Search

Negative-ion time projection chambers(TPCs) have been studied for low-rate and high-resolution applications such as dark matter search experiments. Recently, a full volume fiducialization in a self-triggering TPC was realized. This innovative technology demonstrated a significant reduction in the background with MWPC-TPCs. We studied negative-ion TPC using the μ-PIC+GEM system and obtained sufficient gas gain with CS$_{2}$gas and SF$_{6}$ gas at low pressures. We expect an improvement in detector sensitivity and angular resolution with better electronics.

astro-ph.IM↗

arXiv2017

Development of a low-alpha-emitting μ-PIC for NEWAGE direction-sensitive dark-matter search

NEWAGE is a direction-sensitive dark-matter-search experiment that uses a micro-patterned gaseous detector, or μ-PIC, as the readout. The main background sources are α-rays from radioactive contaminants in the μ-PIC. We have therefore developed a low-alpha-emitting μ-PICs and measured its performances. We measured the surface α-ray emission rate of the μ-PIC in the Kamioka mine using a surface α-ray counter based on a micro TPC.

physics.ins-det↗

arXiv2017

Imaging Polarimeter for a Sub-MeV Gamma-Ray All-Sky Survey using an Electron-Tracking Compton Camera

X-ray and gamma-ray polarimetry is a promising tool to study the geometry and the magnetic configuration of various celestial objects, such as binary black holes or gamma-ray bursts (GRBs). However, statistically significant polarizations have been detected in few of the brightest objects. Even though future polarimeters using X-ray telescopes are expected to observe weak persistent sources, there are no effective approaches to survey transient and serendipitous sources with a wide field of view (FoV). Here we present an electron-tracking Compton camera (ETCC) as a highly-sensitive gamma-ray imaging polarimeter. The ETCC provides powerful background rejection and a high modulation factor over a FoV of up to 2$π$ sr thanks to its excellent imaging based on a well-defined point spread function. Importantly, we demonstrated for the first time the stability of the modulation factor under realistic conditions of off-axis incidence and huge backgrounds using the SPring-8 polarized X-ray beam. The measured modulation factor of the ETCC was 0.65 $\pm$ 0.01 at 150 keV for an off-axis incidence with an oblique angle of 30$^\circ$ and was not degraded compared to the 0.58 $\pm$ 0.02 at 130 keV for on-axis incidence. These measured results are consistent with the simulation results. Consequently, we found that the satellite-ETCC proposed in Tanimori et al. (2015) would provide all-sky surveys of weak persistent sources of 13 mCrab with 10% polarization for a 10$^{7}$ s exposure and over 20 GRBs down to a $6\times10^{-6}$ erg cm$^{-2}$ fluence and 10% polarization during a one-year observation.

astro-ph.IM↗

arXiv2017

Establishment of Imaging Spectroscopy of Nuclear Gamma-Rays based on Geometrical Optics

Since the discovery of nuclear gamma-rays, its imaging has been limited to pseudo imaging, such as Compton Camera (CC) and coded mask. Pseudo imaging does not keep physical information (intensity, or brightness in Optics) along a ray, and thus is capable of no more than qualitative imaging of bright objects. To attain quantitative imaging, cameras that realize geometrical optics is essential, which would be, for nuclear MeV gammas, only possible via complete reconstruction of the Compton process. Recently we have revealed that "Electron Tracking Compton Camera" (ETCC) provides a well-defined Point Spread Function (PSF). The information of an incoming gamma is kept along a ray with the PSF and that is equivalent to geometrical optics. Here we present an imaging-spectroscopic measurement with the ETCC. Our results highlight the intrinsic difficulty with CCs in performing accurate imaging, and show that the ETCC surmounts this problem. The imaging capability also helps the ETCC suppress the noise level dramatically by ~3 orders of magnitude without a shielding structure. Furthermore, full reconstruction of Compton process with the ETCC provides spectra free of Compton edges. These results mark the first proper imaging of nuclear gammas based on the genuine geometrical optics.

physics.ins-det↗

arXiv2015

New readout and data-acquisition system in an electron-tracking Compton camera for MeV gamma-ray astronomy (SMILE-II)

For MeV gamma-ray astronomy, we have developed an electron-tracking Compton camera (ETCC) as a MeV gamma-ray telescope capable of rejecting the radiation background and attaining the high sensitivity of near 1 mCrab in space. Our ETCC comprises a gaseous time-projection chamber (TPC) with a micro pattern gas detector for tracking recoil electrons and a position-sensitive scintillation camera for detecting scattered gamma rays. After the success of a first balloon experiment in 2006 with a small ETCC (using a 10$\times$10$\times$15 cm$^3$ TPC) for measuring diffuse cosmic and atmospheric sub-MeV gamma rays (Sub-MeV gamma-ray Imaging Loaded-on-balloon Experiment I; SMILE-I), a (30 cm)$^{3}$ medium-sized ETCC was developed to measure MeV gamma-ray spectra from celestial sources, such as the Crab Nebula, with single-day balloon flights (SMILE-II). To achieve this goal, a 100-times-larger detection area compared with that of SMILE-I is required without changing the weight or power consumption of the detector system. In addition, the event rate is also expected to dramatically increase during observation. Here, we describe both the concept and the performance of the new data-acquisition system with this (30 cm)$^{3}$ ETCC to manage 100 times more data while satisfying the severe restrictions regarding the weight and power consumption imposed by a balloon-borne observation. In particular, to improve the detection efficiency of the fine tracks in the TPC from $\sim$10\% to $\sim$100\%, we introduce a new data-handling algorithm in the TPC. Therefore, for efficient management of such large amounts of data, we developed a data-acquisition system with parallel data flow.

astro-ph.IM↗

arXiv2015

Light Dark Matter Search with SOIPIX

We propose a light dark matter search experiment using an SOI pixel detector (SOIPIX). The event-driven SOIPIX can be a powerful tool for detecting light WIMPs because of its low energy threshold (< 1 keV) and high timing resolution (few μs). In this study, we evaluate the performance of an SOIPIX prototype detector and we examine the required specifications of SOIPIX for our target sensitivity.

physics.ins-det↗

arXiv2013

Development of a Time-resolved Neutron Imaging Detector Based on the μPIC Micro-Pixel Chamber

We have developed a prototype time-resolved neutron imaging detector employing a micro-pattern gaseous detector known as the micro-pixel chamber (μPIC) coupled with a field-programmable-gate-array-based data acquisition system. Our detector system combines 100μm-level spatial and sub-μs time resolutions with a low gamma sensitivity of less than 10^-12 and high data rates, making it well suited for applications in neutron radiography at high-intensity, pulsed neutron sources. In the present paper, we introduce the detector system and present several test measurements performed at NOBORU (BL10), J-PARC to demonstrate the capabilities of our prototype. We also discuss future improvements to the spatial resolution and rate performance.

physics.ins-det↗

arXiv2013

Spatial resolution of a μPIC-based neutron imaging detector

We present a detailed study of the spatial resolution of our time-resolved neutron imaging detector utilizing a new neutron position reconstruction method that improves both spatial resolution and event reconstruction efficiency. Our prototype detector system, employing a micro-pattern gaseous detector known as the micro-pixel chamber (μPIC) coupled with a field-programmable-gate-array-based data acquisition system, combines 100μm-level spatial and sub-μs time resolutions with excellent gamma rejection and high data rates, making it well suited for applications in neutron radiography at high-intensity, pulsed neutron sources. From data taken at the Materials and Life Science Experimental Facility within the Japan Proton Accelerator Research Complex (J-PARC), the spatial resolution was found to be approximately Gaussian with a sigma of 103.48 +/- 0.77 μm (after correcting for beam divergence). This is a significant improvement over that achievable with our previous reconstruction method (334 +/- 13 μm), and compares well with conventional neutron imaging detectors and with other high-rate detectors currently under development. Further, a detector simulation indicates that a spatial resolution of less than 60 μm may be possible with optimization of the gas characteristics and μPIC structure. We also present an example of imaging combined with neutron resonance absorption spectroscopy.

physics.ins-det↗

arXiv2011

NEWAGE

NEWAGE is a direction-sensitive dark matter search experiment with a gaseous time-projection chamber. We improved the direction-sensitive dark matter limits by our underground measurement. After the first underground run, we replaced the detector components with radio-pure materials. We also studied the possibilities of head-tail recognition of nuclear tracks in the surface laboratory. For the future large volume detector, we are developing a pixel ASIC named QPIX. In this paper, these recent R&D activities are described.

astro-ph.IM↗

arXiv2011

Observation of Diffuse Cosmic and Atmospheric Gamma Rays at Balloon Altitudes with an Electron-tracking Compton Camera

We observed diffuse cosmic and atmospheric gamma rays at balloon altitudes with the Sub-MeV gamma-ray Imaging Loaded-on-balloon Experiment I (SMILE-I) as the first step toward a future all-sky survey with a high sensitivity. SMILE-I employed an electron-tracking Compton camera comprised of a gaseous electron tracker as a Compton-scattering target and a scintillation camera as an absorber. The balloon carrying the SMILE-I detector was launched from the Sanriku Balloon Center of the Institute of Space and Astronomical Science/Japan Space Exploration Agency on September 1, 2006, and the flight lasted for 6.8 hr, including level flight for 4.1 hr at an altitude of 32-35 km. During the level flight, we successfully detected 420 downward gamma rays between 100 keV and 1 MeV at zenith angles below 60 degrees. To obtain the flux of diffuse cosmic gamma rays, we first simulated their scattering in the atmosphere using Geant4, and for gamma rays detected at an atmospheric depth of 7.0 g cm-2, we found that 50% and 21% of the gamma rays at energies of 150 keV and 1 MeV, respectively, were scattered in the atmosphere prior to reaching the detector. Moreover, by using Geant4 simulations and the QinetiQ atmospheric radiation model, we estimated that the detected events consisted of diffuse cosmic and atmospheric gamma rays (79%), secondary photons produced in the instrument through the interaction between cosmic rays and materials surrounding the detector (19%), and other particles (2%). The obtained growth curve was comparable to Ling's model, and the fluxes of diffuse cosmic and atmospheric gamma rays were consistent with the results of previous experiments. The expected detection sensitivity of a future SMILE experiment measuring gamma rays between 150 keV and 20 MeV was estimated from our SMILE-I results and was found to be ten times better than that of other experiments at around 1 MeV.

astro-ph.IM↗

arXiv2010

First underground results with NEWAGE-0.3a direction-sensitive dark matter detector

A direction-sensitive dark matter search experiment at Kamioka underground laboratory with the NEWAGE-0.3a detector was performed. The NEWAGE- 0.3a detector is a gaseous micro-time-projection chamber filled with CF4 gas at 152 Torr. The fiducial volume and target mass are 20*25*31 cm3 and 0.0115 kg, respectively. With an exposure of 0.524 kgdays, improved spin-dependent weakly interacting massive particle (WIMP)-proton cross section limits by a direction-sensitive method were achieved including a new record of 5400 pb for 150 GeV/c2 WIMPs. We studied the remaining background and found that ambient gamma-rays contributed about one-fifth of the remaining background and radioactive contaminants inside the gas chamber contributed the rest.

astro-ph.CO↗

arXiv2007

Direction-sensitive dark matter search results in a surface laboratory

We developed a three-dimensional gaseous tracking device and performed a direction-sensitive dark matter search in a surface laboratory. By using 150 Torr carbon-tetrafluoride (CF_4 gas), we obtained a sky map drawn with the recoil directions of the carbon and fluorine nuclei, and set the first limit on the spin-dependent WIMP (Weakly Interacting Massive Particles)-proton cross section by a direction-sensitive method. Thus, we showed that a WIMP-search experiment with a gaseous tracking device can actually set limits. Furthermore, we demonstrated that this method will potentially play a certain role in revealing the nature of dark matter when a low-background large-volume detector is developed.

astro-ph↗