Study on heat transfer behavior of a rectangular particle bed with volumetric heating

Wen, J.*; Kamada, Yuto*; Yokoyama, Kosei*; Matsumoto, Tatsuya*; Liu, W.*; Morita, Koji*; Imaizumi, Yuya; Tagami, Hirotaka; Matsuba, Kenichi; Kamiyama, Kenji

Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 8 Pages, 2024/08

Isotope-selective ionization utilizing field-free alignment of isotopologues with a train of femtosecond laser pulses

Akagi, Hiroshi; Kasajima, Tatsuya*; Kumada, Takayuki; Itakura, Ryuji; Yokoyama, Atsushi; Hasegawa, Hirokazu*; Oshima, Yasuhiro*

Physical Review A, 91(6), p.063416_1 - 063416_7, 2015/06

https://doi.org/10.1103/PhysRevA.91.063416

We propose a strategy of isotope-selective ionization for a binary mixture of isotopologues of homonuclear diatomic molecules, utilizing field-free alignment with a train of femtosecond laser pulses. Field-free alignment can be achieved simultaneously for two isotopologues consisting of two atoms with the same atomic mass number or , utilizing a pulse train with their time interval of T = T() = T(), where T() and T() are the rotational revival times of the isotopologues. We demonstrate experimentally that a train of four alignment pulses with their interval of T ( = 14, = 15) creates transiently aligned N and anti-aligned N just before T/2 after the last pulse, and vice versa just after T/2. Highly isotope-selective N ionization is achieved at these timings with another femtosecond laser pulse, which induces the non-resonant multiphoton ionization with the cross section remarkably depending on the angle between the molecular axis and the laser electric field direction. The ion yield ratio I(N)/I(N) ranges from 0.49 to 2.00, which is wider than the range obtained with single alignment pulse.

In-situ stress measurement in the Mizunami Underground Research Laboratory; A New test of strain sensitivity method applying to CCBO

Tanno, Takeo; Sato, Toshinori; Sanada, Hiroyuki; Hikima, Ryoichi*; Yokoyama, Tatsuya*; Shimoyama, Masahiro*

Heisei-25 Nendo (2013 Nen) Shigen, Sozai Gakkai Shuki Taikai Koenshu, p.255 - 256, 2013/09

rock stresses were measured by Compact Conical-ended Borehole Overcoring (CCBO) technique in the 300m depth gallery at the Mizunami Underground Research Laboratory and the measurement results were evaluated using a conventional method and a new test of strain sensitivity method. To compare the rock stress evaluated by both methods, the new test of strain sensitivity method resulted in more accurate evaluation than the conventional method, because of its improved stress deviations.

Change of Si(110) reconstructed structure by Ge nanocluster formation

Yokoyama, Yuta; Yamazaki, Tatsuya; Asaoka, Hidehito

Journal of Crystal Growth, 378, p.230 - 232, 2013/09

https://doi.org/10.1016/j.jcrysgro.2012.10.047

The initial processes of Ge nano cluster formation on Si(110)-162 reconstructed structure were investigated via scanning tunneling microscopy. For a small amount of Ge deposited on Si(110)-162 single-domain structure at room temperature, the surface structure did not change significantly. After direct current heating at 973 K for 20 min, the striped structure almost broken and disordered-like structure was formed on the terrace. With increasing the annealing time, the surface structure changed from disordered-like structure to the 162 double-domain structure and pyramidal nano clusters were formed at the domain boundary. These results suggest that the surface stress was induced by Ge nano cluster formation and the double-domain structure was formed in order to relax the stress.

Isotope-selective ionization utilizing molecular alignment and non-resonant multiphoton ionization

Akagi, Hiroshi; Kasajima, Tatsuya; Kumada, Takayuki; Itakura, Ryuji; Yokoyama, Atsushi; Hasegawa, Hirokazu*; Oshima, Yasuhiro*

Applied Physics B, 109(1), p.75 - 80, 2012/10

https://doi.org/10.1007/s00340-012-5222-3

We demonstrate a laser nitrogen isotope separation, which is based on field-free alignment and angular dependent ionization of N and N isotopomers. A linearly-polarized short laser pulse (795 nm, 60 fs) creates rotational wave packets in the isotopomers, which periodically revive with different revival times as a result of different moments of inertia. Another linearly-polarized short laser pulse (795 nm, 60 fs) ionizes one of the isotopomers selectively as a result of their different angular distributions. In the present experiments, the ion yield ratio [= (N)/(N)] can be changed in the range from 0.85 to 1.22, depending on the time delay between the two laser pulses.

Numerical study on quantum walks implemented on the cascade rotational transitions in a diatomic molecule

Matsuoka, Leo; Kasajima, Tatsuya; Hashimoto, Masashi; Yokoyama, Keiichi

arXiv.org (Internet), 5 Pages, 2011/04

http://arxiv.org/abs/1104.4157

Vibration-selective coherent anti-Stokes Raman scattering with linearly chirped white-light pulses

Kasajima, Tatsuya; Yokoyama, Keiichi; Matsuoka, Leo; Yokoyama, Atsushi

Chemical Physics Letters, 485(1-3), p.45 - 48, 2010/01

https://doi.org/10.1016/j.cplett.2009.12.032

Studies for isotope separation of radioactive waste

Yokoyama, Keiichi; Kasajima, Tatsuya; Matsuoka, Leo; Hashimoto, Masashi; Tsubouchi, Masaaki; Sugiyama, Akira; Yokoyama, Atsushi

no journal, , 

Technological innovation in the isotope separation of long-lived fission products is demanded. Quantum control may provide a breakthrough in such technology. Recently, we proposed a novel scheme based on cascaded excitation of rotation in diatomic molecules. Both (1) demonstration of quantum walk by Raman transition using a conventional Ti:Sapphire laser and (2) development of high-power terahertz-wave source are concurrently proceeded. (1) Cascaded excitation of rotation in the nitrogen molecule N will be induced by impulsive Raman transitions. At present, we are developing a method to observe the incoherent population distribution among rotational states, which involves femotosecond coherent anti-Stokes Raman scattering. Also, current status of (2) development of high-power terahertz-wave source will be briefly introduced, including optical rectification in ZnTe and LiNbO crystals and a plan for construction of a high-power, picosecond laser as a driver laser.

Study of the ion cyclotron emission due to D-D fusion-product H-ions on JT-60U

Sato, Shoichi*; Ichimura, Makoto*; Yamaguchi, Yusuke*; Katano, Makoto*; Imai, Yasutaka*; Murakami, Tatsuya*; Miyake, Yuichiro*; Yokoyama, Takuro*; Moriyama, Shinichi; Kobayashi, Takayuki; et al.

no journal, , 

Ion cyclotron emissions (ICEs) due to deuterium-deuterium fusion-product (FP) ions on JT-60U are studied. ICE due to H-ions is identified from the difference of the toroidal wave number of 2nd ICE(D). The parameter dependence for the appearance of ICE(H) is investigated from the experimental conditions and also is studied by using "Escape Particle Orbit analysis Code (EPOC)".

A New scheme for the laser isotope separation applicable to heavy elements

Yokoyama, Keiichi; Matsuoka, Leo; Kasajima, Tatsuya; Tsubouchi, Masaaki; Hashimoto, Masashi

no journal, , 

Recent progress in laser science enables us precise manipulation of molecules by taking advantages of the wave nature of matter. These techniques are called coherent quantum control. Using coherent quantum control, a breakthrough in laser isotope separation may be realized. Actually, we proposed a novel scheme of isotope selective excitation, which is based on cascaded excitation of rotation in diatomic molecules. A numerical simulation done by solving a coupled Schroedinger equation for the cesium iodide molecule has shown that the separation factor reaches three orders of magnitude higher than that by the conventional scheme. The current status of the experimental demonstration undergoing in our institute will be introduced.