Search

In a fast ignition scheme using a cone-guided target, the fusion target is imploded with the inserted cone. Due to the existence of the cone, asymmetric implosion is not avoidable, which has the possibility to degrade fuel compression efficiency. This paper shows how the fuel compression and temperature at the maximum compression time are affected by changing the initial opening angle and position of the cone by the use of two and three dimensional fluid code.

In cone-guiding fast ignition, the guiding of fast electron beam with significantly large beam divergence is one of the most important issues for achieving efficient core heating. We proposed two guiding schemes; one is the “Tongari” tip guiding by resistive magnetic fields and the other is the guiding by externally applying axial magnetic fields. The guiding performances for these two schemes are demonstrated by Particle-In-Cell and Fokker-Planck simulations.

In the implosion phase of the fast ignition scheme, most critical issues are breakup of the cone tip and the formation of high ρ-R core plasma to improve its heating efficiency. For the integrated fast ignition experiment at ILE Osaka University, robust and reliable implosion must be redesign. In this paper, feasible target design under the constraint condition of existing GXII and LFEX facilities is studied using two-dimensional radiation hydrodynamic simulations, and an optimum target design based on low velocity implosion is proposed. The advantages of low velocity implosion are low adiabat, robust against Rayleigh-Taylor instability, which are verified. Also longer life time of compressed core plasma which is preferable for fast ignition is confirmed in this study.

Quasi-static magnetic fields, which are induced by the Weibel instability and grow to more than hundred Megagauss, lead to large divergence angle of fast electrons, hence lower energy coupling. To suppress the divergence, two different structures, namely density trough and punched out holes, are introduced to targets. In the density trough target, the Weibel instability is enhanced and the divergence is getting worse. On the other hand, the divergence angle is improved but the number of electrons is degraded for fast electrons (

The FIREX-1 project, the goal of which is to demonstrate fuel heating up to 5 keV by fast ignition scheme, has been carried out since 2003 including construction and tuning of LFEX laser and integrated experiments. Implosion and heating experiment of Fast Ignition targets have been performed since 2009 with Gekko-XII and LFEX lasers. A deuterated polystyrene shell target was imploded with the 0.53- μm Gekko-XII, and the 1.053- μm beam of the LFEX laser was injected through a gold cone attached to the shell to generate hot electrons to heat the imploded fuel plasma. Pulse contrast ratio of the LFEX beam was significantly improved. Also a variety of plasma diagnostic instruments were developed to be compatible with harsh environment of intense hard x-rays (γ rays) and electromagnetic pulses due to the intense LFEX beam on the target. Large background signals around the DD neutron signal in time-of-flight record of neutron detector were found to consist of neutrons via (γ,n) reactions and scattered gamma rays. Enhanced neutron yield was confirmed by carefully eliminating such backgrounds. Neutron enhancement up to 3.5 × 107 was observed. Heating efficiency was estimated to be 10–20% assuming a uniform temperature rise model.

The collaboration research of ILE and NIFS has made progress on the FIREX target developments. We have two fuel layering strategies: a foam shell method and a conical laser guide heating technique. To date, preliminary and principle demonstration stages on both fuel layering methods have been reached. This paper describes the present status of the target developments.

2D PIC simulations for fast ignition with a planar target and an ultrahigh intensity laser have been performed to investigate effects of laser temporal profile on fast electron characteristics. Six different laser profiles, which are combination of two pulse shapes, namely Flattop and Gaussian shapes, and three different maximum intensities 1 × 1020, 5 × 1019, and 2.5 × 1019 W/cm2, are studied under the condition of fixed laser energy. Time-integrated energy spectra, coupling efficiencies from the heating laser to fast electrons, and divergence angle of fast electrons are shown and discussed.

Considering the occurrence of serious heart failure in a gene knockout mouse of PIP5Kγ and in congenital abnormal cases in humans in which the gene was defective as reported by others, the present study attempted to localize PIP5Kγ in the heart during prenatal stages. It was done on the basis of the supposition that phenotypes caused by gene mutation of a given molecule are owed to the functional deterioration of selective cellular sites normally expressing it at significantly higher levels in wild mice. PIP5Kγ‐immunoreactivity was the highest in the heart at E10 in contrast to almost non‐significant levels of the immunoreactivity in surrounding organs and tissues such as liver. The immunoreactivity gradually weakened in the heart with the prenatal age, and it was at non‐significant levels at newborn and postnatal stages. Six patterns in localization of distinct immunoreactivity for PIP5Kγ were recognized in cardiomyocytes: (1) its localization on the plasma membranes and subjacent cytoplasm without association with short myofibrils and (2) its localization on them as well as short myofibrils in association with them in cardiomyocytes of early differentiation at E10; (3) its spot‐like localization along long myofibrils in cardiomyocytes of advanced differentiation at E10; (4) rare occurrences of such spot‐like localization along long myofibrils in cardiomyocytes of advanced differentiation at E14; (5) its localization at Z‐bands of long myofibrils; and (6) its localization at intercellular junctions including the intercalated discs in cardiomyocytes of advanced differentiation at E10 and E14, especially dominant at the latter stage. No distinct localization of PIP5Kγ‐immunoreactivity of any patterns was seen in the heart at E18 and P1D. The present finding suggests that sites of PIP5Kγ‐appearance and probably of its high activity in cardiomyocytes are shifted from the plasma membranes through short myofibrils subjacent to the plasma membranes and long myofibrils, to Z‐bands as well as to the intercalated discs during the mid‐term gestation. It is further suggested that PIP5Kγ is involved in the differentiation of myofibrils as well as intercellular junctions including the intercalated discs at later stages of the mid‐term gestation. Failures in its involvement in the differentiation of these structural components are thus likely to cause the mid‐term gestation lethality of the mutant mice for PIP5Kγ. [ABSTRACT FROM AUTHOR]