We developed a novel laser melting sampler (LMS) for ice cores to measure the stable water isotope ratios (δ18O and δD) as temperature proxies at sub-centimeter depth resolutions. In this LMS system, a 2 mm diameter movable evacuation nozzle holds an optical fiber through which a laser beam irradiates the ice core. The movable nozzle intrudes into the ice core, the laser radiation meanwhile melts the ice cylindrically, and the meltwater is pumped away simultaneously through the same nozzle and transferred to a vial for analysis. To avoid isotopic fractionation of the ice through vaporization, the laser power is adjusted to ensure that the temperature of the meltwater is always kept well below its boiling point. A segment of a Dome Fuji shallow ice core (Antarctica), using the LMS, was then demonstrated to have been discretely sampled with a depth resolution as small as 3 mm: subsequent analysis of δ18O, δD, and deuterium excess (d) was consistent with results obtained by hand segmentation within measurement uncertainties. With system software to control sampling resolution, the LMS will enable us to identify temperature variations that may be detectable only at sub-centimeter resolutions in ice cores.

Three-dimensional (3D) observation is one of the important trials of future TEM and STEM methods. in the field of biological science, 3D-observation has already become general because the biological materials are usually amorphous and computed tomography (CT) routines can be effectively used. The CT assumes that the image intensity is linearly proportional to the projection of material density. in a crystalline specimen, however, this linearity does not hold due to the dynamical diffraction effect depending on spepimen thickness and incident directions of electron beam. High-angle annular-darkfield STEM (HAADF-STEM) and EDX mapping images could meet this requirement of the linearity because their image intensity are little affected by the dynamical diffraction effect.

Our 3D-STEM is based on a 300 kV FE-TEM/STEM(Hitachi HF-3000) equipped with a specially designed eucentric specimen stage with double spherical fulcra, a newly developed dark/bright field STEM detectors, a 3D-sampling system and a 3D-imaging processor for 3D topography and tomography.