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A new submicron scanning nuclear microprobe beam line was constructed in early 2016 at the accelerator facility of the University of Tsukuba, Japan. A microbeam scanning endstage (OM-2000, Oxford Microbeams, Oxford, UK) was installed at the end of this system. The distance from the object slit to the target position is 8730 mm and the working distance is 180 mm. This ion microbeam system will be used mainly for X-ray imaging of two-dimensional distributions of light elements in structural materials using particle-induced X-ray emission (PIXE). A silicon drift detector (SDD) with a thin window of Si 3 N 4 was installed to detect characteristic X-rays emitted from light elements such as B, C, and N, which are common additive elements in structural materials. In addition, a superconducting tunnel junction (STJ) array detector is going to be installed to perform PIXE measurements more efficiently. By combining a microbeam scanning technology with the X-ray detectors, we plan to obtain two-dimensional maps of additive light elements in structural materials. Experiments for obtaining proton microbeams are ongoing, and a 6 MeV proton beam with a diameter of between 12 and 20 μm has been obtained to date. [ABSTRACT FROM AUTHOR]

Abstract: In geological science, hydrogen analysis of melt inclusions can provide important insights into the dynamic mechanism of magmatic activities. Melt inclusions are specimens of the magma trapped within capsules in crystals in the magma chamber that are subsequently expelled from volcano and end up in volcanic rocks. Since the sizes of the melt inclusions are very small, ranging from tens to several hundred micrometers in diameter, hydrogen analysis by means of elastic recoil coincidence spectrometry (ERCS) has been developed at a proton microbeam facility. This method of hydrogen analysis is simple, non-destructive, and rapid, especially when using a newly developed calibration method that employs Mylar films as hydrogen standards. The depth profile of hydrogen can be derived from the measured sum-energy spectrum using our ERCS analysis method. [Copyright &y& Elsevier]

This study reports the present status of our work on the hydrogen analysis of mineral and rock samples. The preparation of a standard material by means of ion implantation, a method of its calibration and the application of the method are described. The number of hydrogen atoms per unit volume in the standard material can be determined from the simultaneous observation of α-particles, γ rays and α–γ coincidence events for the 1H(19F,αγ) reaction at the 16.44 MeV resonance energy. The hydrogen content in a natural obsidian determined with the method mentioned above is in agreement with that obtained by FTIR. A heavy-ion microbeam system under construction, which consists of a Russian-type quadrupole magnet for beam focusing, a beam defining slit system and a γ-ray detector, is also described. [Copyright &y& Elsevier]

We report on the preliminary studies for two-dimensional (2D) mapping of hydrogen and other elements in materials with transmission ERDA and PIXE using a microbeam of 8 MeV 4He. The extremely enhanced forward recoil cross section of hydrogen in the non-Rutherford scattering allows 2D mapping of hydrogen in the sample. The mapping by PIXE, which provides complementary information to the mapping by ERDA, was obtained simultaneously. The present work probably leads to 3D mapping of hydrogen in bulk materials, i.e., the present spatial 2D plus depth as an additional dimension, since the energy of the outgoing hydrogen corresponds to the depth where the hydrogen is originally located. [ABSTRACT FROM AUTHOR]

Particle induced X-ray emission with the use of focused ion beam (µ-PIXE) utilizing a superconducting tunnel junction (STJ) X-ray spectrometer has been developed to realize light element mapping in the soft X-ray region. A five hundred pixels array of STJ detector has been installed in the µ-PIXE beamline at the accelerator facility in the University of Tsukuba. Performance of a single-pixel STJ detector is tested. The K-lines of light elements C to Al have been separately detected in the pulse height spectra with a broad background, which is attributed substrate-hit events caused by scattered protons and high-energy characteristic X-ray lines. The background is rejected by using the anticoincidence technique or rise-time discrimination. [ABSTRACT FROM AUTHOR]

This paper describes an application of a proton–proton elastic recoil coincidence spectroscopy to hydrogen analysis using a proton microbeam at an energy of 20 MeV. This method provides depth profiles of hydrogen over a thickness of 200 μm of silicate samples in a short time. A typical beam size is as small as 27 × 32 μm. The depth resolution is about 10 μm. The present work proves that the proton–proton elastic recoil coincidence spectroscopy is a promising method for measurements of hydrogen in mineral and rock samples with thickness up to 200 μm. [Copyright &y& Elsevier]

We measured the yield of Auger electrons emitted through Coster–Kronig transitions from Rydberg states 1 s 2 p ( 3 P) nl (n = 7 , 8) and 1 s 2 2 p ( 2 P) nl (n = 5 , 6 , 7) of emergent atomic ions C q + under irradiation of 3.5-MeV/atom C+ and C 2 + ions on thin C foil targets. The Auger electron yields are suppressed for C 2 + irradiation compared with C+ irradiation and the relative yield becomes larger as n increases. Thus, amount of scattered electrons having lower relative energy in the projectile rest frame becomes larger. The results obtained in this study support the influence of projectile velocity on the cluster effect of secondary electron yields. [ABSTRACT FROM AUTHOR]

Abstract: The thermal neutron fluence that poured into the shielding concrete of proton accelerator facilities was estimated from the in situ production of 36Cl. The thermal neutron fluences at concrete surfaces during 10–30 years of operation were in the range of 1012–1014 n/cm2. The maxima in thermal neutron fluences were observed at ≈5–15cm in the depths analyzed for 36Cl/35Cl by AMS. These characteristics imply that thermalization of neutrons occurred inside the concrete. Compared to the several tens of MeV cyclotrons, secondary neutrons penetrate deeper into the concrete at the high-energy accelerators possessing acceleration energies of 400MeV and 12GeV. The attenuation length of neutrons reflects the energy spectra of secondary neutrons emitted by the nuclear reaction at the beam-loss points. Increasing the energy of secondary neutrons shifts the maximum in the thermal neutron fluences to deeper positions. The data obtained in this study will be useful for the radioactive waste management at accelerator facilities. [Copyright &y& Elsevier]

Abstract: We have measured the 36Cl/Cl ratio of uncultivated surface soil samples collected from 11 areas distributed throughout Japan to determine the undisturbed value of the ratio. The ratio was found to be on the order of 10−13 except for the Tokai-mura area, where four research reactors, two commercial nuclear power plants and a nuclear fuel reprocessing plant have been operated. The observed ratio in the Tokai-mura area was higher than 10−12. Notably, soil samples collected from a site of commercial BWR nuclear power plants in Fukushima prefecture showed no significant increase in 36Cl/Cl ratio. The 36Cl/Cl ratio depth profiles of soil samples collected at both of Makabe-town and Tokai-mura were also measured. Since Makabe-town is located about 50km apart from Tokai-mura, we do not expect it to be affected by the nuclear facilities. No large variations were observed in the Makabe depth profile; the measured ratios ranged from ∼3 to ∼5×10−13. The result obtained for Tokai-mura is significantly different in that from the surface to about 80cm depth, the measured ratios, ∼10−12, are much higher than any at Makabe. At depth below 80cm, the Tokai-mura ratios are lower and become indistinguishable from those at Makabe. The 36Cl/Cl ratio in unaffected areas of Japan is estimated to be 3–4×10−13. [Copyright &y& Elsevier]

Abstract: The mystery of 26Al origin has made the nuclide important in the astrophysics. It was proposed that the reaction, 14N(16O,α)26Al, may be one of the origin of the source of 26Al in the cosmic. In his work, the 26Al was measured with AMS by using full-stripping method, and the cross-sections of these reactions for around sub-barrier energies were deduced. The experiment details are described and the results represented. [Copyright &y& Elsevier]

36Cl is a long-lived radioisotope, which, because it is created mainly through a thermal neutron capture process by 35Cl, may be used to estimate the strength of thermal neutron flux from A-bombs or nuclear fuel facilities. The 36Cl contents in granite samples from the Hiroshima A-bomb site have been measured by the Cl-36 accelerator mass spectrometry (AMS) system at the University of Tsukuba. The 36Cl/Cl ratios deduced from the 36Cl measurements are compared with independent evaluations based upon the Dosimetry System 2002 (DS02) of the radiation doses received by the survivors of the Hiroshima A-bomb. The measurements corresponded well up to a ground distance of 1100 m, which proved the effectiveness of the DS02. Measurements of the 36Cl/Cl ratio of unexposed granite samples were 1.92 × 10-13 on average, and because the measured ratio for samples at a ground distance of 1163 m was 2.50 × 10-13, the assessment of the neutron flux by the 36Cl measurements of samples beyond about 1100 m is not practical. This limitation arises from the inability to distinguish bomb-induced Cl-36 from activation due to ambient sources. [Copyright &y& Elsevier]