K. Abe

M. Teranishi

N. Iwama

Y. Nagayama

National Institute for Fusion Science (NIFS-Repository)

    A small but significant project of imaging science has started.   The numerical techniques of analyzing signals and images that have been developed for nuclear fusion research are applied and extended to other fields: biology and astronomy, particularly, with respect to the electron microscope and the adaptive-optics and radio telescopes.   Results of this academic year are as follows.  (1) Extension to Electron Tomography The phase contrast electron microscope that has been developed by the National Institute of Physiological Sciences (NIPS) [1] is remarkable for its striking feature on biological objects and winning a lot of successes, combined with 3D tomographic techniques of microscopy.  Our research of image processing is firstly focused on the basic problem of “missing wedge” in single-axis specimen rotation; that is, the projection data are missed in the range of tilt angle as large as about ±20° owing to the increase in the effective thickness of the specimen.   We also face the problem of SN ratio for unstained objects that is lowered by weakening the electron beam in order to avoid the specimen damage by repeating the irradiation many times (70 times with an equal tilt angle space of 2°).  With these regards the Hopfield neural network, whose property has been well investigated on the bolometer tomography of plasma [3], was employed as the first test tool for image reconstruction.   A result is shown in Fig. 1.   To test with a decreased size of computation, a 2D section of one virus was targeted with the number of pixels decreased by taking the moving average of noise reduction.  For the resulting number of projection of 3,500 (50 x 70 angles) and that of pixels of 54,634 (W463 x D118), the neural system with the skimmer type of neuron activation function was found favorably to reach the state of minimal energy with 100 iterations. The computing time was greatly decreased to 7.5 min. (with the desktop PC: Dell-Precision 690) by using an improved algorithm of system state updating, which is efficient for the sparse neuron connec-tion.   This technical achievement will be fed back to the 3D tomography being prepared for LHD plasma.   The next challenge in biology is addressed to the 3D image reconstruction over the whole field of view of microscope, that is, an inverse problem of extremely large size.  (2) Extension to Telescope Imaging       Study has just started with an intention of contributing to the adaptive optics related with the 3D tomography of atmospheric turbulence for the Subaru Telescope and also to the image synthesis in the radio telescope ALMA.   The latter subject is an inverse problem of the type that is common to the wavenumber spectrum estimation of plasma fluctuations using the laser phase contrast method and the ECE imaging technique.        The authors thank the staff of Lab. of Nano-Structure Physiology, NIPS, especially Profs. K. Nagayama and K. Murata for valuable discussions and suggestions on the microscopic tomography research.   The research was supported by the budget NIFS10KYBP003.  1) Nagayama, K. : Adv. Imag. Elect. Phys. 138 (2005) 69.  2) Murata, K. et al.: Structure 18 (2010) 903. 3) Iwama, N. et al.: J. Plasma Fusion Res. SERIES 8 (2009) 975.              Fig. 1  Left and middle: a projection image of ε15 bacteriophages obtained by the Zernike phase contrast cryo-electron microscopy [2] (nearly zero tilt angle of −0.53°, data no. 090308e15, 200kV). Image reconstruction was made in the 2D particle section perpendicular to the page surface (indicated in the middle figure by a line segment 22.9 nm long).     Right: 2D image reconstructed by applying the Hopfield neural network to 1D projections as many as 70 (with reversion in black-and-white color). Streaking artifacts seen in the whole picture are related to the electron beams that passed from the right to the left with various tilt angles. With this view of the artifacts, one notes the missing of projection data in the vertical direction. The tailspike of virus is recognized on the left side of the particle.     Ne-like ions are abundant in plasmas of wide ranges of temperatures, because the ground state has an L-shell closed electronic configuration. Since Ne-like Fe XVII lines of extreme ultraviolet wavelengths (EUV) are observed in the active regions of the solar atmosphere, the lines are thought potentially useful to study mechanisms of the corona heating. Doschek et al. 1) examined Skylab observations of a solar flare and reported that lines at 204.6 Å and 254.8 Å, identified as electric-dipole (E1) transitions of 2p53p (1S0) → 2p53s (3/2, 1/2)1 and → 2p53s (1/2, 1/2)1, respectively, had the strongest and almost the same intensities. Since both of the lines share the identical upper level (the lines are indicated by thick dashed arrows in Fig. 1), their line intensity ratio can be evaluated with atomic transition probabilities (branching ratio) only. It is noted that here the plasma is presumably transparent for the lines, though validity of this assumption needs to be studied more rigorously. Fig. 2 shows calculated intermediate-couplings in 2p53p and 2p53s states of Fe XVII by means of grasp2K 2). The nearly equal branching ratio of the atomic data is ascribed to strong intermediate-coupling between 3P and 1P terms in the 2p53s state. However, new observation of a solar flare by means of the EUV Imaging Spectrometer (EIS) on Hinode satellite 3) has shown difficulty in reconciling the available atomic data with observed Fe XVII line intensities. The EIS measurements 4) have shown the branching ratio of the line at 204.6 Å about twice as large as that of the line at 254.8 Å, while the available atomic data gave the almost equal branching ratio for the each line. Although the discrepancy may be ascribed partially to calibration issues, re-investigation of the relevant atomic data seems to be necessary for a better understanding. Recently, benchmark calculations for ions in the iron group have been done by Ishikawa et al. using a relativistic multireference Möller - Plesset scheme 5,6). The high accuracy of these calculations made it possible to revise the identification of several lines. The present work is motivated by the need to extend the term analysis to more highly ionized ions and to give a full set of consistent and high accuracy transition rates including also M1, E2, and M2 multipoles for large parts of the isoelectronic sequence.  In the present work 7), energies, E1, M1, E2, M2 transition rates, oscillator strengths, and lifetimes from relativistic configuration interaction calculations were calculated for the states of the 2p6, 2p53s, 2p53p, and 2p53d, configurations in all Ne-like ions between Mg III and Kr XXVII. Core-valence and core-core correlation effects were accounted for through SD-expansions to increasing sets of active orbitals. The Breit interaction and leading QED effects are included as perturbations. The results were compared with experiments and other recent benchmark calculations. In Mg III, Al IV, Si V, P VI, S VII, and Ar IX, for which experimental energies were known to high accuracy, the mean error in the calculated energies was only 0.011%. This work is supported by the Research Cooperation program in the National Institutes of Natural Sciences (NINS).                              Fig. 1.  Energy level diagram of Ne-like Fe XVII.                       Fig. 2. Intermediate-coupling in 2p53p and 2p53s states of Fe XVII. Coefficients of the intermediate-coupling were calculated by means of grasp2K.     1) Dochek, G.A. et al., Phys. Rev. A 43 (1991) 2565. 2) Jönsson, P. et al., CPC 177 (2007) 597. 3) Culhane, J.L. et al., Sol. Phys. 243 (2007) 19. 4) Warren, H.P. et al., ApJ 685 (2008) 1277. 5)  Ishikawa, Y. et al., Phys. Scr. 79 (2009) 025301. 6)  Del Zanna, G., Ishikawa, Y., A&A 508 (2009) 1517. 7)  Jönsson, P., Kato, D. et al., in preparation.   437§18. Extension of Plasma Imaging Technique to Other Fields: Biology and AstronomyIwama, N. (Daido Univ.),  Teranishi, M. (Hiroshima Inst. of Tech.),  Abe, K. (Gifu Shotoku Gakuen Univ.),  Nagayama, Y.

Extension of Plasma Imaging Technique to Other Fields: Biology and Astronomy

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Extension of Plasma Imaging Technique to Other Fields: Biology and Astronomy

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