The cosmic ray neutron method was developed for intermediate-scale soil moisture detection, but may potentially be used for other hydrological applications. The neutron signal of different hydrogen pools is poorly understood and separating them is difficult based on neutron measurements alone. Including neutron transport modeling may accommodate this shortcoming. However, measured and modeled neutrons are not directly comparable. Neither the scale nor energy ranges are equivalent, and the exact neutron energy sensitivity of the detectors is unknown. Here a methodology to enable comparability of the measured and modeled neutrons is presented. The usual cosmic ray soil moisture detector measures moderated neutrons by means of a proportional counter surrounded by plastic, making it sensitive to epithermal neutrons. However, that configuration allows for some thermal neutrons to be measured. The thermal contribution can be removed by surrounding the plastic with a layer of cadmium, which absorbs neutrons with energies below 0.5 eV. Likewise, cadmium shielding of a bare detector allows for estimating the epithermal contribution. First, the cadmium difference method is used to determine the fraction of thermal and epithermal neutrons measured by the bare and plastic-shielded detectors, respectively. The cadmium difference method results in linear correction models for measurements by the two detectors, and has the greatest impact on the neutron intensity measured by the moderated detector at the ground surface. Next, conversion factors are obtained relating measured and modeled neutron intensities. Finally, the methodology is tested by modeling the neutron profiles at an agricultural field site and satisfactory agreement to measurements is found.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第22995号 / 理博第4672号 / 新制||理||1670(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 鶴 剛, 准教授 窪 秀利, 教授 中家 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Les particules cosmiques sont émises par différentes sources galactiques et sont composées de protons et de noyaux d'hélium. Ces éléments interagissent avec les matériaux et y déposent leur énergie par interaction nucléaire. L'instrument Planck/HFI a observé le ciel depuis l'espace dans le but de cartographier le fond diffus cosmologique. Pour cela, HFI embarque un plan focal refroidit à 100 mK composé de 54 bolomètres. Le flux de particules cosmiques, interagissant avec les composants des détecteurs (thermomètre, grille, wafer), chauffe ponctuellement les capteurs (glitches) ce qui entraine une dégradation du signal scientifique. Leur étude a révélé un autre effet thermique caractérisé par un chauffage global du plan focal de l'ordre du microkelvin, les High Coincidence Events (HCE). Deux familles de HCE ont été isolées dans les données : les rapides, générés par des gerbes de particules secondaires formées dans les couches externes du satellite et interagissant avec l'ensemble de l'instrument HFI ; les lents, généré par la vaporisation d'hélium formant un lien thermique ponctuel entre le plan focal et l'étage à 1,6 K lui faisant face. L'exposition d'une matrice de bolomètres TES à une source de particules α a démontré une réponse similaire mais également des glitches simultanés entre les pixels.Ces recherches démontrent que les particules cosmiques et les gerbes de particules doivent être étudiées afin d'éviter des effets thermiques prédominant. Le développement des prochaines générations de détecteurs, devront ainsi prendre en compte ces interactions indissociables d'une mission spatiale et s'en prémunir. / Cosmic rays are emitted from different galactic sources and consist of protons and helium nuclei. These elements interact with matter and deposit part of their energy by nuclear interaction.The Planck/HFI instrument observed the sky from space to map the Cosmic Microwave Background. For this purpose, HFI has a focal plane cool down to 100 mK and composed of 54 bolometers. The interactions of the cosmic ray flux with the detectors' components (thermometer, grid and wafer) heat up regularly the sensor (glitches) which leads to a degradation of the scientific signal. Studying them revealed another thermal effect characterized by a thermal increase of the entire focal plane up to the microkelvin range, the High Coincidence Events (HCE).Two HCE famillies were separated: the fast ones, generated by cosmic ray showers developed in the external layers of the satellite and interacting with the entire HFI instrument and the slow ones, generated by the vaporisation of helium forming a ponctual thermal link between the focal plane and the 1.6 K stage facing it.Exposure of a TES bolometer matrix to an α particules source showed a similar response but also simultaneous glitches on several pixels. This work demonstrates that cosmic rays and particle showers on next low temperature experiments has to be studied to prevent predominating thermal effects from it. The developpement of futur space experiments will have to take these interactions into account to elimiate them from data.

No description available.

<p>  Present WIMP Dark Matter search strategies are mainly focused on possible direct detection through elastic or inelastic scatterings on atomic nuclei, or with electrons. This approach<br> becomes insensitive to M(DM) < 10 GeV. Indirect DM detection refers to the search for DM-DM or DM-M annihilation, decay debris from DM particles, or other particle production,<br> resulting in detectable species. </p> <p><br>    New physics processes, initiated by cosmic ray or dark matter interactions may be observable in underground indirect search experiments by excess high multiplicity neutron<br> production in nuclear targets. Even for M(DM) < 10 GeV, DM-M interaction is capable of<br> producing large signals, >200 neutrons if the energy is deposited in a Pb target.</p> <p><br></p> <p>  The NMDS-II detector, located at an underground laboratory within the Pyhasälmi<br> complex metal mine in central Finland, collated data for 6504 ± 1 hours at 583 m.w.e.<br> and for 1440 ± 1 hours at 1166 m.w.e.. The detector system consists of a 30 cm cube<br> Pb-target surrounded by 60 He-3 proportional tubes and a two layer Geiger Counter muon<br> detection system. The lead target is used to interact with potential dark matter particles, and<br> neutron numbers are measured with He-3 tubes. The neutron event multiplicity production is<br> compared to Geant4 simulations, starting with the well measured absolute muon momentum<br> and angular distribution flux rate at sea level, then propagating the muon flux through rock<br> while preserving the momentum-angular correlation to a depth 4m above the the detector at<br> the two depth locations. The muon flux modeling is compared to the uncorrelated Miyake<br> model at each depth as verification of the muon propagation simulation. Finally, the Geant4<br> fully simulates the passage of the muon and its induced showers through a model universe<br> 10000 m^2 x 12 m depth, and the simulated response of the detector to the calculated muon<br> flux, is compared with the data. <br>  </p> <p>  The Geant4 prediction and the observed data neutron event multiplicity distributions<br> have matching power law shapes, k × n^(-p), and do not have exponential shapes. For the<br> data collected at 583 m.w.e., p=2.36±0.10 with χ2/DoF = 0.76 and for the simulation<br> p=2.34±0.01 with χ2/DoF = 1.05. At 1166 m.w.e., p=2.29±0.007 for the simulation with  χ2/DoF = 1.16. And for the data the collection with only 6 detected events above multiplicity 5, yields p=2.50 ± 0.35 predicted by the Maximum Likelihood Estimatation method. </p> <p><br></p> <p>  The DM acceptance as a function of mass is found using a proton-Pb spallation model.<br> The dark matter mass is assumed to be equal to the proton kinetic energy and to interact<br> uniformly over the volume of the lead target. The number of excess events is found to be<br> -6.1 ± 5.1, that is no excess events are observed. The upper limit with 90% confidence<br> level is then found assuming 2.3 events. The Poisson estimation then yielding search limits<br> 1.1×10^(-44) cm^(-2) for 10 GeV deposited energy, 1.9×10^(-45) cm^(-2) at 1 GeV and 3.0×10^(-45) cm^(-2) for 500 MeV deposited energy and no acceptance at 100 MeV.<br> </p> <p>    An indirect dark matter search was conducted based on DM-M interactions depositing<br> energy in a Pb-target allowing DM masses to be probed in a region 100 MeV < M(DM) <<br> 10 GeV not accessible to direct dark matter searches. Limits are placed on DM-M energy<br> deposition independent of the DM-M interaction. <br>  <br>  <br>  <br>  </p>

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24407号 / 理博第4906号 / 新制||理||1701(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 鶴 剛, 准教授 細川 隆史, 教授 永江 知文 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

No description available.

Astrophysical observations give convincing evidence for a vast non-baryonic component, the so-called dark matter, accounting for over 20% of the overall content of our Universe. Direct dark matter search experiments explore the possibility of interactions of these dark matter particles with ordinary baryonic matter via elastic scattering resulting in single nuclear recoils. The ZEPLIN-III detector operated on the basis of a dualphase (liquid/gas) xenon target, recording events in two separate response channels { scintillation and ionisation. These allow discrimination between electron recoils (from background radiation) and the signal expected from Weakly Interacting Massive Particle (WIMP) elastic scatters. Following a productive first exposure, the detector was upgraded with a new array of ultra-low background photomultiplier tubes, reducing the electron recoil background by over an order of magnitude. A second major upgrade to the detector was the incorporation of a tonne-scale active veto detector system, surrounding the WIMP target. Calibration and science data taken in coincidence with ZEPLIN-III showed rejection of up to 30% of the dominant electron recoil background and over 60% of neutron induced nuclear recoils. Data taking for the second science run finished in May 2011 with a total accrued raw fiducial exposure of 1,344 kg days. With this extensive data set, from over 300 days of run time, a limit on the spin-independent WIMP-nucleon cross-section of 4.8 10-8 pb near 50 GeV/c2 WIMP mass with 90% confidence was set. This result combined with the first science run of ZEPLIN-III excludes the scalar cross-section above 3.9 10-8 pb. Studying the background data taken by the veto detector allowed a calculation of the neutron yield induced by high energy cosmic-ray muons in lead of (5.8 0.2) 10-3 neutrons/muon/(g/cm2) for a mean muon energy of 260 GeV. Measurements of this kind are of great importance for large scale direct dark matter search experiments and future rare event searches in general. Finally, this work includes a comprehensive measurement of the energy dependent quenching factor for low energy nuclear recoils in a plastic scintillator, such as from the ZEPLIN-III veto detector, increasing accuracy for future simulation packages featuring large scale plastic scintillator detector systems.

]The scale difference between point in situ soil moisture measurements and low resolution satellite products limits the quality of any validation efforts in heterogeneous regions. Cosmic Ray Neutron Probes (CRNP) could be an option to fill the scale gap between both systems, as they provide area-average soil moisture within a 150-250 m radius footprint. In this study, we evaluate differences and similarities between CRNP observations, and surface soil moisture products from the Advanced Microwave Scanning Radiometer 2 (AMSR2), the METOP-A/B Advanced Scatterometer (ASCAT), the Soil Moisture Active and Passive (SMAP), the Soil Moisture and Ocean Salinity (SMOS), as well as simulations from the Global Land Data Assimilation System Version 2 (GLDAS2). Six CRNPs located on five continents have been selected as test sites: the Rur catchment in Germany, the COSMOS sites in Arizona and California (USA), and Kenya, one CosmOz site in New SouthWales (Australia), and a site in Karnataka (India). Standard validation scores as well as the Triple Collocation (TC) method identified SMAP to provide a high accuracy soil moisture product with low noise or uncertainties as compared to CRNPs. The potential of CRNPs for satellite soil moisture validation has been proven; however, biomass correction methods should be implemented to improve its application in regions with large vegetation dynamics.

Research of the highest energy cosmic ray particles is in the middle of the interest of theoretical and experimental physics. Their energies are several orders of magnitude higher than energies accessible at present accelerators. In this work, the reconstruction techniques of extensive air showers measured at the Pierre Auger Observatory are studied. For this purpose, extensive air showers are modelled in the simulation tool CORSIKA. Data collected at the Pierre Auger Observatory together with simulations are used to calculate resolutions of reconstruction methods. The Multiple--eye reconstruction is the main interest of this work. It can be used for independent verification of experimental results of the Observatory.