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Actinium-225 (225Ac) has attracted global attention due to its applications in cancer therapy. A new 225Ac production method is proposed by muon nuclear-capture reactions with negative muons (μ−) irradiating on a 226Ra target. The 225Fr is produced by 226Ra (μ−, nν) 225Fr reaction and decays to 225Ra. The 225Ra subsequently decays to 225Ac. The method produces no carrier-added 225Ac, and 213Bi from a 225Ac-213Bi generator. The production method by muon nuclear-capture reactions with the 226Ra target is described. The radioactivity of 225Ac and 213Bi are calculated assuming the reaction branching ratio of 226Ra (μ−, nν) 225Fr. [ABSTRACT FROM AUTHOR]

A new 99Mo production method is proposed through 99Tc (μ−, v) 99Mo muon nuclear-capture reaction with recycled 99Tc material. The 99Mo is a parent nucleus of 99mTc for imaging diagnostics. The 99Mo is produced in the 99Tc target, and the molybdate ion (MoO42−) is separated from the pertechnetate ion (99TcO4−). High 99Mo-specific activity is obtained, and no radioactive by-product is generated. The 99Tc material has an unlimited resource: it is a decay product of 99Mo and is contained in spent nuclear fuel. The 99Mo-specific activity and production activities of 99Mo and 99mTc are calculated assuming the reaction branching ratios. [ABSTRACT FROM AUTHOR]

Spallation reaction for the long-lived fission product 107Pd has been studied for the purpose of nuclear waste transmutation. The isotopic-distribution cross sections on both proton and deuteron were obtained at 118 MeV/nucleon in inverse kinematics at the RIKEN Radioactive Isotope Beam Factory. A large cross-section difference was found between the proton and deuteron results for the light-mass products. The data were compared with the SPACS semi-empirical parameterization and the PHITS calculations including both the intranuclear cascade and evaporation processes. In addition, the potential of spallation reaction for transmutation of 107Pd is discussed.

The performance of germanium detectors for high-energy γ-rays was evaluated using a 992-keV resonance in the 27Al(p , γ)28Si reaction. The measurement was conducted at the RIKEN tandem accelerator. The energy of the excited state from the resonance was evaluated as 12540.7(2) keV. Using newly evaluated excitation energy, an energy calibration function and a photo peak efficiency of Ge detectors up to 10.8-MeV photons were deduced. Energy accuracy is achieved at 0.3 keV for the overall energy region. This reaction provides reliable energy and efficiency standards for high-energy γ-rays. [ABSTRACT FROM AUTHOR]

Isotopic production cross sections were measured for proton- and deuteron-induced reactions on 93Nb by means of the inverse kinematics method at RIKEN Radioactive Isotope Beam Factory. The measured production cross sections of residual nuclei in the reaction 93Nb + p at 113 MeV/u were compared with previous data measured by the conventional activation method in the proton energy range between 46 and 249 MeV. The present inverse kinematics data of four reaction products (90Mo, 90Nb, 88Y, and 86Y) were in good agreement with the data of activation measurement. Also, the model calculations with PHITS describing the intra-nuclear cascade and evaporation processes generally well reproduced the measured isotopic production cross sections.

Spallation reactions for the long-lived fission products 137Cs, 90Sr and 107Pd have been studied for the purpose of nuclear waste transmutation. The cross sections on the proton- and deuteron-induced spallation were obtained in inverse kinematics at the RIKEN Radioactive Isotope Beam Factory. Both the target and energy dependences of cross sections have been investigated systematically. and the cross-section differences between the proton and deuteron are found to be larger for lighter fragments. The experimental data are compared with the SPACS semi-empirical parameterization and the PHITS calculations including both the intra-nuclear cascade and evaporation processes.

Isotopic production cross sections in the proton- and deuteron-induced spallation reactions on 93Zr at an energy of 105 MeV/u were measured in inverse kinematics conditions for the development of realistic nuclear transmutation processes for long-lived fission products (LLFPs) with neutron and light-ion beams. The experimental results were compared to the PHITS calculations describing the intra-nuclear cascade and evaporation processes. Although an overall agreement was obtained, a large overestimation of the production cross sections for the removal of a few nucleons was seen. A clear shell effect associated with the neutron magic number N = 50 was observed in the measured isotopic production yields of Zr and Y isotopes, which can be reproduced reasonably by the PHITS calculation.

Muon spin relaxation has the unique ability to detect very low concentrations of vacancies and vacancy–solute complexes in solids. In this work, we investigate quaternary Al-Mg-Si-Cu alloys and show that after quenching to room temperature from 848 K (575 °C), vacancies gradually become incorporated into clusters in the Al matrix. The total amount of vacancies in the material increases as small vacancy-rich clusters are formed, which is the opposite of the behavior in Cu-free Al-Mg-Si alloys. [ABSTRACT FROM AUTHOR]

The precipitate microstructure and vacancy distribution in Al-Mg-Si alloys with different amounts of solute and different heat treatments were investigated by transmission electron microscopy and muon spin relaxation measurements. A high amount of vacancies is normally present in Al-Mg-Si alloys as these bind to atomic clusters. We observe these vacancies to leave the material not before over-aging at very high temperatures such as 623 K (350 °C), meaning that vacancies do not bind to incoherent over-aged precipitates. For samples only stored at room temperature after solution heat treatment, a reduction of muon trapping was found at a temperature of 140 K (−133 °C) when reducing the amount of solute in the alloy. This might be connected to a lower number density of Cluster (1), which contrary to Cluster (2) do not nucleate precipitates upon further aging of the material. [ABSTRACT FROM AUTHOR]

Magnetic properties of TlBa2Y1-xCaxCu2Oy which is one of the hole doped high TC superconducting (SC) oxides were investigated by zero field μ+SR. Two precession frequencies of the muon spin were observed for x=0, indicating the existence of a coherent long range antiferromagnetic ordered state of Cu spins. The saturated internal fields at the muon sites, Hint, was 170 Oe and 23 Oe, respectively and magnetic transition temperature, TN, was about 400 K. Both Hint and TN show no x dependence up to x=0.5. No sign of the magnetic ordered state was observed in the SC state for x=1.0 down to 1.8 K. [ABSTRACT FROM AUTHOR]

Hydrogen in the Earth's deep interior has been thought to exist as a hydroxyl group in high-pressure minerals. We present Muon Spin Rotation experiments on SiO2 stishovite, which is an archetypal high-pressure mineral. Positive muon (which can be considered as a light isotope of proton) implanted in stishovite was found to capture electron to form muonium (corresponding to neutral hydrogen). The hyperfine-coupling parameter and the relaxation rate of spin polarization of muonium in stishovite were measured to be very large, suggesting that muonium is squeezed in small and anisotropic interstitial voids without binding to silicon or oxygen. These results imply that hydrogen may also exist in the form of neutral atomic hydrogen in the deep mantle. [ABSTRACT FROM AUTHOR]

Muon spin methods are very sensitive to nanoscale defects such as trace elements and vacancies in metals. This sensitivity is required when investigating Al-Mg-Si alloys, a complicated system in which diffusion-controlled phase transformations are responsible for the most important hardening mechanisms. We present muon spin relaxation experiments conducted on Al-Mg-Si alloys at measurement temperatures in the range 20-300 K. Varying the alloy composition and heat treatment, we find differences in muon depolarization in several temperature regimes. This reflects differences in concentration of several types of muon-trapping defects. We identify free solute atom and vacancy regimes, and confirm that the concentration of these defects decreases when an alloy is annealed at low temperature. We further attribute one regime to Mg-Si vacancy clustering, a mechanism required for precipitation hardening during aging. After storage at room temperature, muon trapping in this regime is more pronounced for a Mg-rich alloy than a Mg-Si-balanced alloy. [ABSTRACT FROM AUTHOR]