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Carborne surveyAir dose rate Fukushima Daiichi nuclear power plant a b s t r a c t A carborne survey system, named as KURAMA (Kyoto University RAdiation MApping system), was developed as a response to the nuclear accident at TEPCO Fukushima Daiichi Nuclear Power Plant in 2011. Now the system has evolved into KURAMA-II, characterized by its compactness, autonomous operation, and acquisition of pulse-height spectrum data. A two-year field test of radiation monitoring by KURAMA-II on local buses, performed by Kyoto University, has successfully proceeded to the phase of official operation by the Fukushima prefectural government, supported by Kyoto University and JAEA (Japan Atomic Energy Agency). An outline and the current status of KURAMA-II, including some results of the continuous monitoring by KURAMA-II on local buses in Fukushima, are introduced.

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Experimental verification of the effect of depletion-region modulation on photoconductance lifetime measurements

Analysis of modulational instability in optical fibers based on a phase-matched four-photon mixing approach is extended by taking into account higher-order dispersion. Fourth-order dispersion governs the modulation frequency in a region near zero-dispersion wavelength, resulting in frequency saturation. The frequency decreases as group delay dispersion becomes dominant in comparison to the fourth-order dispersion. To deepen the modulation, a phase-matching condition for four-photon mixing must be satisfied. A technique is studied which uses externally controllable birefringence of optical fibers to achieve phase-matching at a given modulation frequency.