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Ice originating near the inland ice divide of the ice sheet can reappear as marginal ice at the surface near the ice terminal in the ablation area. We have analyzed δ18O values and ion concentrations of the Skallen, Skarvsnes and Hamna terminal ice sections, located along the estuary line in the Sôya drainage basin, East Antarctica. The data suggest that the upper part of the Skallen terminal ice section could have originated from inland precipitation on the Shirase drainage basin during marine isotope stage (MIS) 5e, while the upper part of Skarvsnes and Hamna terminal ice sections could have originated from inland precipitation on the Sôya drainage basin. We calculate past elevation maps for the Antarctic ice sheet using the three-dimensional model, SICOPOLIS. This model suggests that the upstream portion of the Sôya drainage basin during the glacial period (MIS 2, 3 or 4) was located to the northeast of its present location. A flow history is proposed wherein ice from the inland Shirase drainage area flowed over the present ice-divide line from the Shirase to the Sôya drainage basin during the glacial period. The ice in the Sôya drainage basin then flowed to the marginal part of the sheet after the ice divide had assumed its present position.

Evaluation of radiation exposure from diet is necessary under the assumption of a virtual accident as a part of emergency preparedness. Here, we developed a model with complete consideration of the regional food trade using deposition data simulated by a transport model, and estimated the dietary intake of radionuclides and the effectiveness of regulation (e.g., restrictions on the distribution of foods) after the Fukushima accident and in virtual accident scenarios. We also evaluated the dilution factors (i.e., ratios of contaminated foods to consumed foods) and cost-effectiveness of regulation as basic information for setting regulatory values. The doses estimated under actual emission conditions were generally consistent with those observed in food-duplicate and market-basket surveys within a factor of three. Regulation of restricted food distribution resulted in reductions in the doses of 54&ndash, 65% in the nearest large city to the nuclear power plant. The dilution factors under actual emission conditions were 4.4% for radioiodine and 2.7% for radiocesium, which are ~20 times lower than those used in the Japanese provisional regulation values after the Fukushima accident. Strict regulation worsened the cost-effectiveness for both radionuclides. This study highlights the significance and utility of the developed model for a risk analysis of emergency preparedness and regulation.

To investigate the contribution of ions to gas nucleation, we have performed experiments on the formation of water droplets in H 2 O/N 2 and H 2 O/Ar gas mixtures by irradiation with a 20 MeV proton beam and by positive corona discharge. The size of the formed nanoparticles was measured using a differential mobility analyzer equipped with a Faraday cup electrometer. Using the proton beam, droplets around 10 nm in diameter were observed for both positively and negatively charged particles, but none were found when the corona discharge was used. This implies the importance of the presence of both positive and negative ions for the formation of nanosize droplets, which attract each other by Coulomb interactions, enhancing the collision frequency and leading to the formation of the 10 nm droplets.

This study attempted to quantify long-term subaerial denudation of bare carbonate rock surfaces by using in situ-produced cosmogenic 36 Cl in calcite. Carbonate samples were collected from the topmost 5 cm of exposed pinnacles at several non-glaciated karst areas in subtropical to subarctic regions in Japan. Concentrations of natural Cl and 36 Cl in calcite were determined by accelerator mass spectrometry with isotope dilution with 35 Cl-enriched carrier spike. The nuclide concentrations were of the order of 10 5 –10 6 atom g −1 , and converted to total denudation rates averaged over a 10 5 yr-timescale of chemical and physical processes acting on the karst surfaces. The denudation rates were 20–60 mm kyr −1 , being lowest in the central part of Japan. This tendency indicates the alternation of relative importance of chemical (dissolution) and physical (frost shattering) processes in denudation, depending on site-specific factors such as mean temperature, annual precipitation, and freeze–thawing intensity.

This paper reports the results of trial measurements of the concentration of cosmogenic 36Cl in an ice core recovered from Dome Fuji Station, Antarctica. Ten ice samples were extracted from depths corresponding to the Last Glacial Maximum and the early Holocene, with each sample comprising ∼150 g for a core length of 0.5 m (∼30–40 yr resolution). Analyses of 36Cl concentrations by accelerator mass spectrometry were successfully performed within ±10% precision, even for samples with low 36Cl/Cl values (∼3 × 10–14). The average 36Cl concentrations were 16 × 103 atoms g–1 for the Last Glacial Maximum, and 7 × 103 atoms g–1 for the early Holocene. The apparent 36Cl depositional flux at Dome Fuji Station during these periods was estimated to be approximately 2.5–3.5 × 104 atoms cm–2 yr–1.

Distribution of 36Cl/Cl ratios in a river-recharged aquifer was investigated in the Oderbruch area, northeastern Germany. The aquifer is confined up to 3.5–4 km inland, where it changes to an unconfined condition. The 36Cl/Cl ratios in the confined area were in the range between 4.6 × 10−14 and 23.1 × 10−14, showing a peak at 2–3 km away from the river. A plot of 36Cl/Cl vs. reciprocal Cl− concentrations indicated possible effect of the Cl− concentration variation on the observed 36Cl/Cl ratios. After accounting for this effect, the estimated 36Cl fallout rates for the last 30 yrs show reasonable agreement with the Dye-3 data and the mid-latitude background value. The results suggest that a local 36Cl fallout curve can be constructed from groundwater when dispersive mixing is of minor importance.

We present the current status and research programs of a multinuclide accelerator mass spectrometry (AMS) system on the 12UD Pelletron tandem accelerator at the University of Tsukuba (Tsukuba AMS system), Japan. A maximum terminal voltage of 12 MV is available for the AMS system. The Tsukuba AMS system can measure environmental levels of long-lived radioisotopes of 14 C, 26 Al, 36 Cl and 129 I by employing a molecular pilot beam. Recently, enhancements in AMS techniques and equipment, including sample preparation, the ion source and the data acquisition system, have improved the performance of 36 Cl-AMS. The standard deviation of fluctuations is typically ±2%, and the machine background level for the 36 Cl/Cl ratio is lower than 1 × 10 −15 with a halite sample. We have measured over 500 samples in 1 year, including samples for earth and environmental sciences and nuclear safety research.

Fluid inclusions in quartz from miarolitic cavities, pegmatites, and quartz veins in Miocene biotite-granite plutons, Kofu, Japan, were analyzed by particle-induced X-ray emission to examine chemistries and behaviors of granite-derived fluids in island-arc granite. Most inclusions are aqueous two-phase inclusions, and halite-bearing polyphase inclusions are also observed in quartz veins in the upper part of the plutons. From element contents of fluid inclusions in the miarolitic cavities, the original fluid released from the granite plutons during solidification is inferred to have concentrations of Mn, Fe, Cu, Zn, Ge, Br, Rb, Pb, and Ba of several tens to hundreds of parts per million by weight (ppm) and a salinity of about 10 wt% NaCl equivalent. We estimated the formation conditions of the fluid to have been at about 1.3–1.9 kb and 530–600°C on the basis of the homogenization temperatures of the inclusions and the solidification conditions of the plutons. The polyphase inclusions probably originated from hypersaline fluid by boiling of part of the released fluid during its ascent in the plutons. The polyphase inclusions contain several hundreds to tens of thousands of ppm of Fe and Mn, and tens to several hundreds of ppm of Cu, Zn, Br, Rb, and Pb. The salinities are about 35 wt% NaCl equivalent. Compositional variations in two-phase inclusions from the miarolitic cavities and quartz veins are primarily explained by mineral precipitation with dilution by surface water exerting a secondary influence. Thus, chemistries and behaviors of the granite-derived fluids in the plutons can be explained by mineral precipitation, boiling, and dilution of the originally released fluid.

The evaluation of radioactivity induced in the concrete shield is important for the decommissioning of accelerator facilities. Specific activities of gamma-ray emitters of nuclear spallation produc...

Reduction in polarization dependent loss of a planar lightwave circuit was achieved by asymmetric birefringence formed by ion implantation, in which oxygen ions were implanted along a diagonal of a cross-section of the planar lightwave circuit. The induced birefringence has a slow axis along the line perpendicular to the diagonal. In the present research, a decrease in polarization dependent loss of up to 3.7 dB was obtained, indicating that the method is effective for reducing polarization dependent loss.

Analytical errors in single fluid inclusion analyses by PIXE were investigated to evaluate the accuracy and detection limits of this type of analysis. Analytical errors due to the ellipsoidal approximation of the inclusion shape and the presence of a precipitated halite crystal in the inclusion were much smaller than the total analytical error. The major source of error in the quantification was the uncertainty in the determination of the inclusion depth, which can be minimized by using measurements of the Cl Kβ/Kα intensity ratio. The total analytical error was ±17% relative for most elements and ±40% relative for Cl. Detection limits of 15–40 ppm for elements with mass numbers 25–38 were achieved in analyses of ellipsoidal fluid inclusions (size, 50 μm × 30 μm × 30 μm; depth, 10 μm; bubble size, 15 μm; and NaCl solution, 10 wt%) in quartz, at an integrated charge of 1.0 μC and beam size of 50 μm × 50 μm. The trace-element compositions of single fluid inclusions in quartz crystals from a miarolitic cavity or from quartz veins within a granite body were also determined to investigate the chemical compositions of granite-derived fluids and compositional changes in the fluids during fluid movement in a granite body.

In the process of developing a new dosimetry system for atomic bomb survivors in Hiroshima and Nagasaki (DS02), an intercomparison study between (152)Eu and (36)Cl measurements was proposed, to reconcile the discrepancy previously observed in the Hiroshima data between measurements and calculations of thermal neutron activation products. Nine granite samples, exposed to the atomic-bomb radiation in Hiroshima within 1,200 m of the hypocenter, as well as mixed standard solutions containing known amounts of europium and chlorine that were neutron-activated by a (252)Cf source, were used for the intercomparison. Gamma-ray spectrometry for (152)Eu was carried out with ultra low-background Ge detectors at the Ogoya Underground Laboratory, Kanazawa University, while three laboratories participated in the (36)Cl measurement using accelerator mass spectrometry (AMS): The Technical University of Munich, Germany, the Lawrence Livermore National Laboratory, USA and the University of Tsukuba, Japan. Measured values for the mixed standard solutions showed good agreement among the participant laboratories. They also agreed well with activation calculations, using the neutron fluences monitored during the (252)Cf irradiation, and the corresponding activation cross-sections taken from the JENDL-3.3 library. The measured-to-calculated ratios obtained were 1.02 for (152)Eu and 0.91-1.02 for (36)Cl, respectively. Similarly, the results of the granite intercomparison indicated good agreement with the DS02 calculation for these samples. An average measured-to-calculated ratio of 0.98 was obtained for all granite intercomparison measurements. The so-called neutron discrepancy that was previously observed and that which included increasing measured-to-calculated ratios for thermal neutron activation products for increasing distances beyond 1,000 m from the hypocenter was not seen in the results of the intercomparison study. The previously claimed discrepancy could be explained by insufficient understanding of the measured data.

Climatic variabilities on millennial and longer time scales with a bipolar seesaw pattern have been documented in paleoclimatic records, but their frequencies, relationships with mean climatic state, and mechanisms remain unclear. Understanding the processes and sensitivities that underlie these changes will underpin better understanding of the climate system and projections of its future change. We investigate the long-term characteristics of climatic variability using a new ice-core record from Dome Fuji, East Antarctica, combined with an existing long record from the Dome C ice core. Antarctic warming events over the past 720,000 years are most frequent when the Antarctic temperature is slightly below average on orbital time scales, equivalent to an intermediate climate during glacial periods, whereas interglacial and fully glaciated climates are unfavourable for a millennial-scale bipolar seesaw. Numerical experiments using a fully coupled atmosphere-ocean general circulation model with freshwater hosing in the northern North Atlantic showed that climate becomes most unstable in intermediate glacial conditions associated with large changes in sea ice and the Atlantic Meridional Overturning Circulation. Model sensitivity experiments suggest that the prerequisite for the most frequent climate instability with bipolar seesaw pattern during the late Pleistocene era is associated with reduced atmospheric CO2 concentration via global cooling and sea ice formation in the North Atlantic, in addition to extended Northern Hemisphere ice sheets., SCOPUS: ar.j, info:eu-repo/semantics/published

This study investigates the source and flux of particulate 129I in the downstream reaches of the Niida River system in Fukushima. The upper watershed is a relatively highly contaminated zone located 30–40 km northwest of the Fukushima Daiichi Nuclear Power Plant. Samples of total suspended substance (SS) were collected continuously at Haramachi (5.5 km upstream from the river mouth) from December 2012 to January 2014 using a time-integrative SS sampler. Activity of 129I and the 129I/127I ratio in SS were 0.9–4.1 mBq kg−1 and (2.5–4.4) × 10−8, respectively, and were strongly correlated with the total dry weight of SS samples with R2 of 0.79–0.88. High SS 129I activity and 129I/127I ratios were found in March, April, September, and October 2013. SS 129I activity and 129I/127I ratios are considered to reflect the SS source, i.e., the more contaminated upper watershed or the less contaminated downstream area. The flux of particulate 129I at the Haramachi site was estimated to be 7.6–9.0 kBq month−1 during September–October 2013. A relatively high amount of particulate 129I may have been transported from the upstream to the downstream reaches of the Niida River by high rainfall over this period.

With the current AMS system on the 12UD Pelletron tandem accelerator at the University of Tsukuba, we are able to measure the long-lived radioisotopes of 14 C, 26 Al, 36 Cl and 129 I by employing a molecular pilot beam method that stabilizes the terminal voltage with 0.1% accuracy. Several major improvements have been made to increase the sensitivity of the AMS system to 26 Al and 36 Cl radioisotopes. For 26 Al-AMS, the ions extracted from the ion source have been changed from Al − to AlO − by using an Al 2 O 3 target sample. In addition, 26 MgO − molecular ions are used as a pilot beam to control the terminal voltage through slit current feedback. Also, a fully-stripping AMS technique is used to achieve an effective detection limit of better than 5 × 10 −15 for the 26 Al/ 27 Al ratio. For 36 Cl-AMS, the terminal voltage has been increased from 9 MV to 10 MV, thereby increasing the energy of the 36 Cl 9+ beam to 100 MeV. This energy increment helps us to get a clearer separation between 36 Cl and 36 S in a new Δ E − E detector. In addition, the yield of 36 Cl 9+ is increased by 1.5 times as a result of the higher ion energy at the terminal stripper foil. The standard deviation of the fluctuations of the 36 Cl/ 35 Cl ratio is within ±2%, and the effective detection limit is better than 2.0 × 10 −14 .

The 36 Cl/Cl ratios of groundwater samples were measured by accelerator mass spectrometry (AMS) in order to investigate the potential use of 36 Cl as a dating tool for modern groundwater. Groundwater samples were obtained from several piezometers in the Oderbruch in northeastern Germany. The shallow confined aquifer of the area is mainly recharged by the infiltration from the River Oder. From the results of measurements, the pre-bomb and the recent background 36 Cl/Cl ratios in the basin of the Oder were estimated to be 7–9 × 10 −14 . The 36 Cl fallout values estimated from the 36 Cl/Cl ratios of the Oderbruch samples, which were dated by the 3 H/ 3 He method, show good agreement with Dye-3 ice core data. These results suggest that the distribution of 36 Cl in groundwaters reflects the influence of the 36 Cl bomb pulse. This, in turn, suggests that the distribution of 36 Cl/Cl in modern groundwaters could reveal groundwater ages and flow systems in a region.

An 129I-AMS system has been developed on the 12UD tandem accelerator at the Tandem Accelerator Complex, University of Tsukuba using a 97Mo16O2 molecular pilot beam method developed at the complex. The acceleration voltage of the tandem is precisely controlled and kept within 0.1% accuracy for several days under the 97Mo16O2 molecular pilot beam method. This stability is enough to maintain a stable transmission of 129I ions through the tandem accelerator. Simultaneously generated 127I negative ions are measured by a Faraday cup installed just after a bending magnet for the ion source. Both 129I− and 97 Mo 16 O 2 - ions are accelerated concurrently and the resultant 129I12+ and 97Mo9+ ions are transported to an AMS beam line. A second stripper foil sweeps out the 97Mo9+ ions from the AMS beam line. The 129I26+ ions are selected over the Mo ions for detection using a pair of magnetic and electrostatic deflectors. Finally, 129I26+ ions are clearly detected using a SSD detector, with no strong background. The accelerator voltage is set to 9.68 MV in order to get the most efficient yields of both 129I12+ and 129I26+. The ratio of the background level of 129I to 127I is ∼1 × 10−13.

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 50 km 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 80 cm depth, the measured ratios, ∼10−12, are much higher than any at Makabe. At depth below 80 cm, 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.

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 ≈5–15 cm 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 400 MeV and 12 GeV. 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.

Accelerator mass spectrometry (AMS) was applied to the analysis of 36Cl induced in concrete samples obtained from accelerator facilities. In order to use a small amount of concrete sample and to separate chlorine as pure as possible, an improvement of separation process was developped. Chlorine was extracted from 1–5 g of concrete into 0.01 M nitric acid in a pressurized decomposition vessel. After determining chlorine using ion chromatography, a certain amount of NaCl solution was added to obtain sufficient amounts of AgCl precipitate and to dilute to a suitable isotope ratio of 36Cl to 35Cl (36Cl/35Cl) for the AMS (10-12–10-10). A careful purification procedure was applied to reduce 36S interference in AMS. Good reproducibility and small error throughout the chemical process for sample preparation was attained. Depth profiles of 36Cl/35Cl in concrete of a medium-energy cyclotron were measured by the developed method and compared with the results of γ-emitters induced by thermal neutrons. Since it was confirmed that 36Cl was produced by thermal neutron capture of 35Cl, the thermal neutron fluence irradiated during accelerator operation could be obtained using 36Cl/35Cl. In order to estimate the neutron fluences, the 36Cl/35Cl measurement by AMS is more useful than radioactivity measurements of other isotopes such as γ-emitters because AMS directly provides the isotope ratio and the half-life of 36Cl is very long.

The first observation of the energy distribution of electrons emitted from solids bombarded by MeV atom clusters is reported. In the backward direction, using graphite and Si bombarded by Cn+ and Aln+ (n ≤8), an appreciable suppression of electron emission has been observed at electron energies lower than ~10 eV. Electron yield per atom decreases with increasing n, and becomes less than 50% at n ≥3, relative to the case of n=1. The experimental results cannot be explained in terms of projectile stopping cross sections nor by the clearing-the-way effect. It is probable that the suppressed electron emission is a result of the suppression of the transport or surface transmission of the produced low-energy electrons, rather than of the suppression of ionization.

The concentrations of fifty trace elements, including relatively volatile elements and transition metal elements, in fused glasses of Geological Survey of Japan rock reference materials GSJ JR-2, JA-1, JA-2, JB-1a, JB-3, JGb-1 and JF-1 were determined by particle (proton) induced X-ray emission (PIXE) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The fused glasses were prepared by rapid fusion and subsequent quenching in welded platinum capsules and were found to be homogeneous for major elements and for trace elements with concentrations of more than 1 μg g-1 within the observed precision (± 10% mean) on a 70 μm sampling scale. The values obtained by PIXE and LA-ICP-MS for the transition elements (Cr, Mn, Fe, Ni and Cu), the relatively volatile elements (Zn, Ga, Rb and Pb) and the refractory elements (Y, Zr, Nb and Th) with concentrations greater than a few μg g-1 showed good agreement (within 10 % relative difference). The values for almost all the elements detected at concentrations higher than 1 μg g-1 as determined by LA-ICP-MS also agreed well with the reference values (mean relative difference < ± 10%), except for B and Cu. The good agreement confirmed the appropriateness of the NIST SRM 600 series glass calibration reference material for LA-ICP-MS analysis of glasses with variable major-element compositions for almost all elements. The concentrations of Cu in all the samples were lower than the reference values, which was attributed to adsorption of the transition metals onto the platinum capsule during preparation. Les concentrations de cinquante elements en trace, dont des elements relativement volatiles et des elements de transition, ont ete determinees dans des verres obtenus par fusion de materiaux de reference du Service Geologique du Japon JR-2, JA-1, JA-2, JB-1a, JB-3, JGb-1 et JF-1 par analyse PIXE (emission de rayons X induite par bombardement de protons) et par LA-ICP-MS (spectrometrie de masse a plasma induit couplee a une source laser). Les verres ont ete prepares par fusion rapide et refroidissement immediat dans des capsules de platine soudees et se sont reveles homogenes, a une echelle d'echantillonnage de 70 μm, pour les elements majeurs et pour les elements en trace ayant des concentrations superieures a 1 μg g-1, ceci en tenant compte de la precision observee (± 10% en moyenne). Pour les elements de transition (Cr, Mn, Fe, Ni et Cu), les elements relativement volatiles (Zn, Ga, Rb et Pb) et les elements refractaires (Y, Zr, Nb et Th) ayant des concentrations superieures a quelques μg g-1, il y a un bon accord entre les donnees obtenues par PIXE et celles obtenues par LA-ICP-MS (moins de 10% de difference relative). Le dosage par LA-ICP-MS de tous les elements ayant des concentrations superieures a 1 μg g-1 a fourni des valeurs en tres bon accord avec les valeurs de reference (moins de 10% de difference relative), a l'exception de B et Cu. Ce bon accord confirme que la calibration externe par la serie de verres NIST SRM 600 est tout a fait adaptee a l'analyse de verres par ICP-MS ayant des compositions variables en elements majeurs, ceci pour presque tous les elements. Les concentrations en Cu dans tous les echantillons etaient inferieures aux valeurs de reference et on propose que ce soit dua l'adsorption des metaux de transition sur les parois de la capsule de platine durant la preparation des verres.

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.

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.

This report describes our recent development that mainly aims at the quantitative determination of hydrogen concentration in melt inclusions confined in minerals. The method is based on the proton-proton elastic scattering at 20 MeV. Since the stopping power of protons at 20 MeV is very small in materials as silicates, protons pass through a 200 μm thick sample without appreciable energy loss. It is feasible, therefore, to carry out non-destructive hydrogen analysis of melt inclusions with sizes in the range from a few tens to approximately 200 micrometers. Besides the depth profile of hydrogen, a map of the three-dimensional hydrogen concentration is observable using a scanning microbeam. An example is presented on a melt inclusion in quartz from pyroclastic rocks collected at Enda, Zaoh-machi, Miyagi Prefecture, Japan.

A microprobe system has been constructed using the 12 MV tandem accelerator in the University of Tsukuba. This system is designed and developed for hydrogen analysis with proton–proton elastic recoil coincidence spectroscopy for thick mineral samples with thicknesses up to 200 μm and with the nuclear reaction H( 19 F, αγ) for thin samples. The focusing lens consists of four quadrupole magnets arranged in a Russian-type configuration. All components of the system are controlled and adjusted by a personal computer. The minimum beam spot size achieved so far is 14 × 6 μm 2 for a 20 MeV proton beam at a beam current of 0.1 nA. First performance tests and results are reported.

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.

Compressively strained SrTaO2N thin films were epitaxially grown on SrTiO3 substrates using nitrogen plasma-assisted pulsed laser deposition. Piezoresponse force microscopy measurements revealed small domains (101–102 nm) that exhibited classical ferroelectricity, a behaviour not previously observed in perovskite oxynitrides. The surrounding matrix region exhibited relaxor ferroelectric-like behaviour, with remanent polarisation invoked by domain poling. First-principles calculations suggested that the small domains and the surrounding matrix had trans-type and a cis-type anion arrangements, respectively. These experiments demonstrate the promise of tailoring the functionality of perovskite oxynitrides by modifying the anion arrangements by using epitaxial strain.

One of the most important success for the theory of nucleosynthesis is the precise reproduction of the mass abundance ration for helium-4 as 25% during the Big Bang. This achievement can be one of the three proves of the existence of the Big Bang. For the comparisons between the theory and the observations, abundances of deutron and helium-3 are also consistent. However, there is a quite large inconsistency for litium-7 where the theoretical result is three times higher than the observations, which are reported by Sipte[1] and Asplund[2]. In order to solve this hard inconsistency we may refine data base of the nuclear reaction information around the Li. Despite the many previous efforts there could still be a region where the experimental information is not sufficient between 0.1 and 0.4 MeV of the c.m. energy[3,4]. Consequently, we have started the experimental study with measuring the astrophysical s-factor for the destruction of Li.

One of the most prominent success with the Big Bang models is the precise reproduction of mass abundance ratio for 4He. In spite of the success, abundances of lithium isotopes are still inconsistent between observations and their calculated results, which is known as lithium abundance problem. Since the calculations were based on the experimental reaction data together with theoretical estimations, more precise experimental measurements may improve the knowledge of the Big Bang nucleosynthesis. As one of the destruction process of lithium-7, we have performed measurements for the reaction cross sections of the 7L(3He,p)9Be reaction.

We have developed a laser coupling with an electron cyclotron resonance (ECR) ion source for trace element analysis of mineral samples at University of Tsukuba. A compact Q-switched Nd:YAG laser at 1064 nm wavelength with a pulse width of 8 ns and a maximum energy of 50 mJ is employed to ablate the sample materials as a means of introducing samples into the ECR plasma. Preliminary experiments were performed to focus the laser beam on a pure metallic target (Cu). The mean kinetic energy of the laser produced Cu ions is measured to 470 eV for the laser energy of 50 mJ by a simple time-of-flight method. Design for a laser coupling with an ECR ion source as a new application of mass spectrometry are reported.

The 12UD Pelletron tandem accelerator at the University of Tsukuba suffered serious damage from the Great East Japan Earthquake on 11 March 2011. A post-quake reconstruction project has been started to construct a new middle-sized tandem accelerator instead of the broken 12UD Pelletron tandem accelerator at the 2nd target room connecting the beam line to existing facilities at the 1st target room. The new accelerator system consists of the 6 MV Pelletron tandem accelerator, new 4 ion sources, an existing Lam-shift polarized ion source and 12 beam lines. It is expected to apply for nuclear physics, accelerator mass spectrometry and ion beam applications. The construction of the new accelerator system will be completed by spring 2014.

A tremendous amount of radioactivity was discharged because of the damage to cooling systems of nuclear reactors in the Fukushima No. 1 nuclear power plant in March 2011. Fukushima and its adjacent prefectures were contaminated with fission products from the accident. Here, we show a geographical distribution of radioactive iodine, tellurium, and cesium in the surface soils of central-east Japan as determined by gamma-ray spectrometry. Especially in Fukushima prefecture, contaminated area spreads around Iitate and Naka-Dori for all the radionuclides we measured. Distributions of the radionuclides were affected by the physical state of each nuclide as well as geographical features. Considering meteorological conditions, it is concluded that the radioactive material transported on March 15 was the major contributor to contamination in Fukushima prefecture, whereas the radioactive material transported on March 21 was the major source in Ibaraki, Tochigi, Saitama, and Chiba prefectures and in Tokyo.

Essential parameters for the applications of (36)Cl as a tracer in groundwater studies include the initial (36)Cl/Cl ratio, at the time of recharge, and/or the natural background deposition flux of (36)Cl in the recharge area. To facilitate the hydrological use of (36)Cl in central Japan, this study aimed to obtain a precise estimate of the long-term average local (36)Cl flux and to characterize its seasonal variability. The (36)Cl in precipitation was continuously monitored in Tsukuba, central Japan over a period of >5 years. The (36)Cl flux showed a clear seasonal variation with an annual peak during the spring, which was attributed to the seasonal variability of tropopause height. The long-term average (36)Cl flux (32±2atoms m(-2)s(-1)), estimated from the measured data, was consistent with the prediction from the (36)Cl latitudinal fallout model scaled using the global mean production rate of 20atoms m(-2)s(-1). The initial (36)Cl/Cl ratio was estimated to be (41±6)×10(-15), which is similar to that of pre-bomb groundwater in the Tsukuba Upland. An observation period covering an 11-year solar cycle would yield more accurate estimates of the values, given the increased (36)Cl flux during the solar minimum.

第１回極域科学シンポジウム「極域大気圏を通して探る地球規模環境変動」12月1日（水） 国立極地研究所 ２階大会議室

A multi‐nuclide AMS system on the 12UD Pelletron tandem accelerator at the University of Tsukuba (Tsukuba AMS system) can measure environmental levels of long‐lived radioisotopes of 14C, 26Al, 36Cl and 129I by employing a molecular pilot beam. AMS is an ultrasensitive technique for the study of long‐lived radioisotopes, and stable isotopes at very low abundances. The high terminal voltage has an advantage in the detection of heavy radioisotopes. Much progress has been made in the development of new AMS techniques. For example, a standard deviation of the fluctuation for the 36Cl/Cl ratio is ± 2%, and the effective detection limit is better than 1×10−15. In recent years, the main research field of the 12UD Pelletron tandem accelerator has shifted to accelerator mass spectrometry (AMS) research from nuclear physics. This report presents an overview of the Tsukuba AMS system.

In an effort to develop DS02, a new radiation dosimetry system for the atomic bomb survivors of Hiroshima and Nagasaki, measurements of neutron-induced activities have provided valuable information to reconstruct the radiation situation at the time of the bombings. In Hiroshima, the depth profile of (152)Eu activity measured in a granite pillar of the Motoyasu Bridge (128 m from the hypocenter) was compared with that calculated using the DS02 methodology. For calculation of the (152)Eu production due to the thermal-neutron activation reaction, (151)Eu(n,gamma)(152)Eu, information on the hydrogen content in granite is important because the transport and slowing-down process of neutrons penetrating into the pillar is strongly affected by collisions with the protons of hydrogen. In this study, proton-proton elastic recoil coincidence spectrometry has been used to deduce the proton density in the Motoyasu pillar granite. Slices of granite samples were irradiated by a 20 MeV proton beam, and the energies of scattered and recoil protons were measured with a coincidence method. The water concentration in the pillar granite was evaluated to be 0.30 +/- 0.07%wt. This result is consistent with earlier data on adsorptive water (II) and bound water obtained by the Karl Fisher method.

We have precisely measured the energy loss of carbon cluster ions C{sub n}{sup +} with a kinetic energy of 0.5 MeV/atom. The measured energies, lost in a thin carbon foil by cluster ions, are lower than that of an atomic ion with the equivalent speed [{Delta}E(C{sub n}{sup +})/n