arXiv subjects

Hidetoshi Kubo

Publications and source records attributed to Hidetoshi Kubo.

31 records · Page 2Linked to original sources

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↗

arXiv2007

Detector performance of the NEWAGE experiment

NEWAGE(NEw generation WIMP search with an Advanced Gaseous tracking device Experiment) project is a direction-sensitive dark matter search experiment with a gaseous micro time-projection-chamber(micro-TPC). We report on the performance of the micro-TPC with a detection volume of 23x28x30 cm3 operated with a carbon-tetra uoride (CF4) of 0.2 bar.

physics.ins-det↗

arXiv2007

Performance of a Time-Projection-Chamber with a Large-Area Micro-Pixel-Chamber Readout

A micro time-projection-chamber (micro-TPC) with a detection volume of 23*28*31 cm^3 was developed, and its fundamental performance was examined. The micro-TPC consists of a micro pixel chamber with a detection area of 31*31 cm^2 as a two-dimensional imaging device and a gas electron multiplier with an effective area of 23*28 cm^2 as a pre-gas-multiplier. The micro-TPC was operated at a gas gain of 50,000, and energy resolutions and spatial resolutions were measured.

physics.ins-det↗

arXiv2005

Simulation study of electron drift and gas multiplication in Micro Pixel Chamber

The physical processes of charge collection and gas multiplication of a Micro Pixel Chamber (mu-PIC) were studied in detail using a three-dimensional simulation. The collection efficiencies of primary electrons and gas multiplication factors were calculated for several electrode structures. Based on those studies, we analyzed the optimization of the electrode structure of the mu-PIC, in order to obtain a high gas gain of more than 10^4 and a simultaneous suppression of discharges. Consequently, we found that these characteristics strongly depend on the substrate thickness and the anode diameter of the mu-PIC. In addition, a gas gain of 10^5 would be expected for a mu-PIC having a thick substrate of > 150um.

physics.ins-det↗

arXiv2004

MeV Gamma-Ray Imaging Detector with micro-TPC

We propose a new imaging gamma-ray detector in the MeV region. By measuring the directions and energies of not only a scattered gamma ray but also a recoil electron, the direction of an incident gamma ray would be essentially reconstructed event by event. Furthermore, one of two measured (zenith and azimuth) angles of a recoil electron gives us an additional redundancy which enables us to reject the background events by kinematic constraints. In order to measure the track of a recoil electron, the micro Time Projection Chamber($μ$-TPC) has been developed, which can measure the successive positions of the track of charged particles in a few hundred micron meter pitch. The $μ$-TPC consists of the new type of a gas proportional chamber: micro PIxel gas Chamber ($μ$-PIC) which is one of wireless gas chambers and expected to be robust and stable. Using this $μ$-TPC and the Anger camera for the detection of a scattered gamma ray, we have obtained the first gamma-ray image by the full reconstruction of the direction of gamma rays event by event.

astro-ph↗

arXiv2003

Detecting the WIMP-wind via spin-dependent interactions

Revealing the nature of dark matter is one of the most interesting tasks in astrophysics. Measuring the distribution of recoil angles is said to be one of the most reliable methods to detect a positive signature of dark matter. We focused on measurements via spin-dependent interactions, and studied the feasibility with carbon tetrafluoride($\rm CF_4$) gas, while taking into account the performance of an existing three-dimensional tracking detector. We consequently found that it is highly possible to detect a positive signature of dark matter via spin-dependent interactions.

astro-ph↗

arXiv2003

Performance of a micro-TPC for a time-resolved neutron PSD

We report on the performance of a micro-TPC with a micro pixel chamber($μ$-PIC) readout for a time-resolved neutron position-sensitive detector(PSD). Three-dimensional tracks and the Bragg curves of protons with energies of around 1 MeV were clearly detected by the micro-TPC. More than 95% of gamma-rays of 511 keV were found to be discriminated by simple analysis. Simulation studies showed that the total track length of proton and triton emitted from the $\rm {}^{3}He$(n,p(573 keV))$\rm {}^{3}H(191 keV)$ reaction is about 1.2 cm, and that both particles have large energy losses ($\rm > 200 keV/cm$) in 1 atm Ar+$\rm C_{2}H_{6}(10%)$+${}^{3}$He($< 1%$). These values suit the current performance of the micro-TPC, and we conclude that a time-resolved neutron PSD with spatial resolution of sub-millimeters shall be developed as an application of the micro-TPC.

physics.ins-det↗

arXiv2003

Performance of the TPC with Micro Pixel Chamber Readout: micro-TPC

Micro-TPC, a time projection chamber(TPC) with micro pixel chamber($μ$-PIC) readout was developed for the detection of the three-dimensional fine(sub-m illimeter) tracks of charged particles. We developed a two-dimensional position sensitive gaseous detector, or the $μ$-PIC, with the detection area of 10$\times$10 cm${}^{2}$ and 65536 anode electrodes of 400 $μ$m pitch. We achieved the gas gain of over 10000 without any other multipliers. With the pipe-line readout system specially developed for the $μ$-PIC, we detected X-rays at the rate as high as 7.7 Mcps. We attached a drift cage with an 8 cm drift length to the $μ$-PIC and developed a micro-TPC. We measured the basic performances of the micro-TPC and took three-dimensional tracks of electrons. We also developed a prototype of the MeV gamma-ray imaging detector which is a hybrid of the micro-TPC and NaI(Tl) scintillators and confirmed its concept by reconstructing the obtained data.

hep-ex↗

arXiv1999

Initial Performance of CANGAROO-II 7m telescope

CANGAROO group constructed an imaging air Cherenkov telescope (CANGAROO-II) in March 1999 atWoomera, South Australia to observe celestial gamma-rays in hundreds GeV region. It has a 7m parabolic mirror consisting of 60 small plastic spherical mirrors, and the prime focus is equipped with a multi-pixel camera of 512 PMTs covering the field of view of 3 degrees. We report initial performance of the telescope.

astro-ph↗

arXiv1999

X-ray Observations of TeV Blazars and Multi-Frequency Analysis

The non-thermal spectra of blazars, observed from radio to GeV/TeV gamma-rays, reveal two pronounced components, both produced by radiation by energetic particles. One peaks in the IR - to soft X-ray band, radiating via the synchrotron process; the other, peaking in the high-energy gamma-rays, is produced by the Compton process. These spectra -- and, in particular, the \asca data -- suggest that the origin of the seed photons for Comptonization is diverse. In the High-energy peaked BL Lac objects (HBLs), the dominant seed photons for Comptonization appear to be the synchrotron photons internal to the jet (SSC process). In the quasar-hosted blazars (QHBs), on the other hand, the X-ray band emission is still dominated by the SSC process, while the MeV to GeV range is produced by Comptonization of external photons such as the emission line light. In the context of this three-component model, we derive the magnetic field of 0.1 - 1 Gauss for all classes of blazars. Lorentz factors gamma_{peak} of electrons radiating at each peak of the nuFnu spectra are estimated to be ~10^{5}$ for HBLs; this is much higher than ~10^{3}$ for QHBs. This difference is consistent with the fact that the four sources that are known to emit TeV gamma-rays (TeV blazars) are all classified as HBLs. Among the TeV blazars, Mkn 421 is one of the brightest and most variable emitters from ultraviolet (eV) to hard gamma-ray (TeV) energies.The multi-frequency observations including TeV energy band provide the best opportunity to understand high-energy emission from blazar jets. In this paper, we discuss results of multi-frequency analysis and review the results of intensive campaigns for Mkn 421 from 1994 to 1998

astro-ph↗