京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22255号 / 理博第4569号 / 新制||理||1656(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)准教授 前田 啓一, 講師 LEE Shiu Hang, 教授 長田 哲也 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Die Reichweiteverifikation von Protonen ist ein wichtiger Schritt zur Erhöhung der Präzision der Protonentherapie. Eine neue Methode ist das Prompt -Ray Timing, bei dem Reichweiteinformation aus der Zeitverteilung detektierter Gammaquanten gewonnen wird. Für eine genaue Reichweitebestimmung wird jedoch eine präzise und konstante Zeitreferenz benötigt. Um entdeckte Phasenverschiebungen zwischen Protonbunch und der als Zeitreferenz genutzten Hochfrequenz des Zyklotrons korrigieren zu können, werden Proton- Bunch-Monitore eingesetzt. Diese Arbeit soll abschätzen, ob und wo Proton-Bunch-Monitore im Protonenstrahl eingesetzt werden können. Nach ersten Abschätzungen mit dem Lynx von IBA Dosimetry wurden zwei Monitore auf Basis einer szintillierenden Faser und dem U100-Spektrometer von Target in die äußeren lateralen Bereiche von Protonenstrahlen verschiedener Energien bei niedrigen Strahlströmen (0,01 nA bis 0,1 nA) gebracht. Es zeigt sich eine systematische Abhängigkeit der Relativzeit und der horizontalen Position im Strahl, welche auf die Strahlumlenkung zurückzuführen ist. Diese resultiert in einer systematischen Abhängigkeit der mittleren Reichweite und der horizontalen Position. Durch Abschätzung der Protonenrate für einen klinischen Strom von 2 nA konnten potentielle Einsatzorte im Strahl-Halo identifiziert werden. Weitere Untersuchungen sind jedoch notwendig, um die Einsetzbarkeit zur Korrektur von Phasenverschiebungen unter klinischen Bedingungen zu erproben. / The range verification of protons is an important step towards increasing the precision of proton therapy. A new method is the prompt -ray timing, where range information is obtained from the time distribution of detected gamma quanta. However, the method requires a precise and constant time reference for accurate range determination. proton bunch monitors can be used to correct detected phase shifts between proton bunch and the cyclotron radio frequency used as a time reference. This work should estimate if and where proton bunch monitors can be used in the proton beam. According to initial estimates with the Lynx from IBA Dosimetry, two monitors based on scintillating fiber and Target’s U100 spectrometer were used in the outer lateral regions of proton beams of different energies at low beam currents (0.01 nA to 0.1 nA). It shows a systematic dependence of the relative time and the horizontal position in the beam, which is due to the beam deflection. This results in a systematic dependence of the mean range and the horizontal position. By estimating the proton rate for a clinical current of 2 nA, potential positions of application in the beam halo were identified. However, further investigations are needed to test the applicability for the correction of phase shifts under clinical conditions.

Im Rahmen eines vom Bundesministerium für Bildung und Forschung geförderten Projektes (Förderkennzeichen 02NUK010A) wurden an einem senkrechten, mit Flüssigkeit umströmten und beheizten Stabbündel gammadensitometrische Gasgehaltsmessungen durchgeführt. Es wurden zwei Messpositionen, zwei Volumenstromraten des umströmenden Fluides, zwei Unterkühlungswerte und elf Wärmestromdichten zur Messung gewählt. Der Bericht umfasst die Beschreibung des Versuchsstandes, die Messmethodik, Ergebnisse und deren Interpretation. Im Detail wird ebenfalls die Messunsicherheit bewertet.

Galaxies are astronomically large systems that consist of vast amounts of stars, and in between there exists the interstellar medium. This medium consists of clouds of gas which play an important role in a galaxy’s history and formation. With the right conditions a region can experience a period of star formation which we measure with a Star Formation Rate (SFR). The lifecycle of stars can create outbursts of hot gas which collapse back into the galaxy over time to contribute more to the interstellar medium. The gas is hot enough to release X-rays which we can detect with orbiting space observatories such as NASA’s Chandra Telescope. By studying these hot, high energy regions we can relate them to other known properties of galaxies to give us insight on the processes of merging systems. Using archival data from Chandra we measured the spatial extent of the soft diffuse X-ray-emitting hot interstellar gas in a sample of 49 local merging galaxies. The galaxies or galaxy pairs are classified by merger stage based on their morphology. The stages range from post-merger remnants to premerger pairs in which two separate regions could be identified. After processing the data, we made initial estimates of the regions based on their optical extent. X-ray counts were extracted and background counts from the nearby sky were subtracted for calibration. An iterative procedure was used to produce and modify elliptical radial profiles by size and position angle until a good fit was found. The best fit radius was defined as the point where the background subtracted counts decreased to less than twice the uncertainty. With an accurate estimate of the region sizes, we infer a third dimension to find the volumes of the regions. The inferred volumes were used to calculate electron densities and total masses of the hot interstellar gas. Relationships among hot, molecular, and atomic gas were investigated and plotted to determine any trends. Our results show a strong correlation between the volume of hot gas and SFR. Another strong trend was between volume and X-ray luminosity. The SFR is correlated with the ratio of hot to cold gas. Galaxies with higher SFRs have proportionally more hot gas relative to the cold gas. These relationships show that major mergers have regions of starbursts which expel hot gas, and the more numerous the young stars, the larger the volume of hot gas. Future research in this area can reveal more about the process of merging and the evolution of galaxies.

Using 8 micron infrared images from the Spitzer telescope we determine the half-light radius (the radius that contains half of the total light) for a sample of 49 nearby merging and merged pairs of galaxies. We compared this with other properties of the galaxies including a) the mass of X-ray emitting hot gas Mx(gas), b) the star formation rate (SFR), c) the large scale environment the galaxies reside in, and d) the chemical composition of the galaxies. Our goal is to better understand the processes that produce hot gas in galaxies

Philosophiae Doctor - PhD / Thoron Rn-220 is a radioactive gas with a half-life of 55.6 s. It has been identified as a possible health concern in specific places such as monazite processing plants and (rare-earth) mines. The short half-life of Rn-220 makes Rn-220 calibration sources and chambers less common than for the isotope Rn-222. There are many Rn-220 standard sources and chambers that are widely described in the literature and used for different applications and calibration. However, some of these chambers and sources are not easy to set up in typical nuclear environmental laboratories. In this project, we developed a Rn-220 standard source using a thorium nitrate solution (Th(NO3)4.6H2O). The solution was split into a large volume which was used in a Marinelli beaker to characterize its strength using a Hyper Pure Germanium (HPGe) detector, and a smaller volume of around 30 ml which was poured into a small bottle. The Rn-220 is extracted by bubbling air through the solution in the small bottle using an aerator. Gamma rays from the solution were measured simultaneously using a 76.2 mm × 76.2 mm NaI(Tl) detector. The gamma rays were measured for 66 hours. The accumulated spectra were thereafter analysed using an Excel spreadsheet where the counts in the Tl-208(2614 keV) peak were extracted and used to obtain the percentage of Rn-220 pumped out of the solution in the small bottle.

Philosophiae Doctor - PhD / Low- and medium-spin bands of 187Os have been studied using the AFRODITE array, following the 186W(4He,3n)187Os reaction at a beam energy of 37 MeV. The measurements of γ − γ coincidences, angular distribution ratios (RAD), polarization and γ-intensities were performed using eleven High Purity Germanium (HPGe) clover detectors. In the current work, all the previously known bands have been significantly extended and five new bands have been added to the level scheme. The observed bands are interpreted within the cranked shell model (CSM), cranked Nilsson-StrutinskyBogoliubov (CNSB) formalism and Quasiparticle-plus-Triaxial-Rotor (QTR) model. Systematic comparison of bands with the neighbouring isotopes has also been made. Comparison of the models with experimental data shows good agreement. The configurations of some of the previously observed bands have been modified. Most importantly, the coupling of 2+ γ band to the 11/2+[615] neutron configuration is observed for the first time.

This thesis treats the findings and current theories of the active galactic nuclei 3454.3. It mainly aims to describe the behavior of the specific source in the gamma-ray energy band as recorded by the Fermi-LAT satellite. Using NASA’s computational tools and all recorded data the variability of the source was assessed. As the received flux from the source varies substantially over time several periods of time for which the flux differs considerably were analysed. Spectral analysis for the various time-frames was performed in order to determine how we best can describe the results from each period. The Fermi-LAT results were then examined in the wider context of multi-wavelength astronomy. Finally, data retrieved at all wavelengths were modeled and compared in accordance with currently held theories.

abstract: Several key, open questions in astrophysics can be tackled by searching for and mining large datasets for transient phenomena. The evolution of massive stars and compact objects can be studied over cosmic time by identifying supernovae (SNe) and gamma-ray bursts (GRBs) in other galaxies and determining their redshifts. Modeling GRBs and their afterglows to probe the jets of GRBs can shed light on the emission mechanism, rate, and energetics of these events. In Chapter 1, I discuss the current state of astronomical transient study, including sources of interest, instrumentation, and data reduction techniques, with a focus on work in the infrared. In Chapter 2, I present original work published in the Proceedings of the Astronomical Society of the Pacific, testing InGaAs infrared detectors for astronomical use (Strausbaugh, Jackson, and Butler 2018); highlights of this work include observing the exoplanet transit of HD189773B, and detecting the nearby supernova SN2016adj with an InGaAs detector mounted on a small telescope at ASU. In Chapter 3, I discuss my work on GRB jets published in the Astrophysical Journal Letters, highlighting the interesting case of GRB 160625B (Strausbaugh et al. 2019), where I interpret a late-time bump in the GRB afterglow lightcurve as evidence for a bright-edged jet. In Chapter 4, I present a look back at previous years of RATIR (Re-ionization And Transient Infra-Red Camera) data, with an emphasis on the efficiency of following up GRBs detected by the Fermi Space Telescope, before some final remarks and brief discussion of future work in Chapter 5. / Dissertation/Thesis / Doctoral Dissertation Physics 2019

The directional correlation of the 346-136 Kev gamma-gamma cascade in Ta¹⁸¹ was measured using the delayed coincidence method with a source of Hf¹⁸¹ in 27 N HF. The contributions to the composite delayed coincidence spectrum of the interfering 133-482 Kev and 133 - 346 Kev cascades were removed by the subtraction from this spectrum of appropriate 133-482 Kev pure delayed coincidence data. The extracted 346 -136 Kev coincidence data then yielded the correlation coefficients A₂₂ = o.190 土0.011 and A₄₄. = -0.025 土O. 024 that are consistent with the established spin sequence 5/ 2(E2)9 / 2(Ml +E2)7 / 2 and with an admixture of 16.20/0土1. 2% E2 radiation in the 136 Kev mixed transition. The results of the experiment are in excellent agreement with those obtained from conversion electron measurements and resolve the discrepancy apparent in earlier work on the 346-136 Kev cascade