Hydrogen/deuterium absorption capacity of Pd nanomaterials and its relation with heat generated upon loading of hydrogen isotope gases

Abstract: Using Sievert's method, hydrogen/deuterium absorption capacity was measured for Pd nanopowder and nanocomposites of nanoPd/ γ Al2O3 and nanoPd/ZrO2. For these materials, heat evolution upon loading of hydrogen isotope gases was also measured by a flow calorimeter. In order to identify the properties of metallic Pd nanoparticles, both measurements were conducted repeatedly three or four times without exposing the samples to air. It was found that both apparent absorption capacity and heat evolution depended strongly on the degree of oxidation of Pd. The amount of the oxidized Pd in each sample was estimated from the difference between the apparent and the true values of hydrogen/deuterium absorption capacity and used to evaluate the heat generated from chemical reactions. The hydrogen absorption capacity at 1MPa was found to be slightly smaller than that of Pd bulk for all the Pd nanomaterials studied. The heat evolution was composed of two stages, i.e., the first stage during pressurizing the samples from 0 to 1MPa and the second stage where the the sample was kept under a fixed pressure of 1MPa. The heat generated in the first stage was largely explained by taking into account two chemical reactions, i.e., the water formation reaction and the hydride/deuteride formation reaction. It was noted that in the second stage, where the heat generated from chemical reactions was hardly expected to occur, a small heat power was observed intermittently when the samples were loaded with deuterium gas

Direct fast heating efficiency of a counter-imploded core plasma employing a laser for fast ignition experiments (LFEX)

Fast heating efficiency when a pre-imploded core is directly heated with an ultraintense laser (heating laser) was investigated. \u27Direct heating\u27 means that a heating laser hits a pre-imploded core without applying either a laser guiding cone or an external field. The efficiency, η, is defined as the increase in the internal core energy divided by the energy of the heating laser. Six beams (output of 1.6 kJ) from the GEKKO XII (GXII) green laser system at the Institute of Laser Engineering (ILE), Osaka University were applied to implode a spherical deuterated polystyrene (CD) shell target to form a dense core. The DD-reacted protons and the core x-ray emissions showed a core density of 2.8 ± 0.7 g cm−3, or 2.6 times the solid density. Furthermore, DD-reacted thermal neutrons were utilized to estimate the core temperature between 600 and 750 eV. Thereafter, the core was directly heated by a laser for fast-ignition experiments (LFEX, an extremely energetic ultrashort pulse laser) at ILE with its axis lying along or perpendicular to the GXII bundle axis, respectively. The former and latter laser configurations were termed \u27axial\u27 and \u27transverse modes\u27, respectively. The η was estimated from three independent methods: (1) the core x-ray emission, (2) the thermal neutron yield, and (3) the runaway hot electron spectra. For the axial mode, 0.8%< η <2.1% at low power (low LFEX energy) and 0.4%< η <2.5% at high power (high LFEX energy). For the transverse mode, 2.6%< η <7% at low power and 1.5%< η <7.7% at high power. Their efficiencies were compared with that in the uniform implosion mode using 12 GXII beams, 6% < η <12%, which appeared near to the η for the transverse mode, except that the error bar is very large

Amorphous nanostructuralization in HOPG by 10(14) W cm(-2) laser

This reports provide an amorphous nanostructuralization technique on the surface modification in Highly Oriented Pyrolytic Graphite (HOPG) by using a femtosecond laser. We showed, for the first time, that the surface of HOPG is changed to the amorphous nanostructuralization graphite by using a femtosecond laser-driven compression technique. Our results also suggest that the HOPG surface is changed until the deeper area from the surface by the laser-driven shock wave. A single shot of a femtosecond laser beam (1.27,similar to,1.33x10(14) W cm(-2) in intensity, with 2mm-diameter, and 110 fs in pulse width) is irradiated under the vacuum ambience onto a 2mm-thick of HOPG. The calculated impact pressures on a sample was 8.3 similar to 8.7 GPa. Crystal structure in the HOPG were analyzed using a Raman spectroscopy and an X-ray diffraction, those analyzing depth from the surface were 50 nm and 350pm, respectively

Multilayered polycrystallization in single-crystal YSZ by laser-shock compression

A single shot of an ultra-intense laser with 0.8 J of energy and a pulse width of 110 fs (peak intensity of 1.15 x 10(17) W cm(-2)) is divided into two beams and the two beams counter-irradiated onto a 0.5 mm-thick single crystal yttria-stabilized zirconia (YSZ), changing the YSZ into a multilayered polycrystalline state. The laser-driven shock wave of the intensity similar to 7.6x10(12) Pa penetrated the crystal as deep as 96 mu m, causing formation of a four-layered structure (the first layer from the surface to 12 mu m, the second from 12 to 28 mu m, the third from 28 to 96 mu m, and the fourth from 96 to 130 mu m, respectively). The grain size of the first layer was 1 mu m, while that of the second layer was broken into a few tens nanometers. The grain size of the third layer was a few hundred nanometers to a few ten micrometers. The area deeper than 96 mu m remained as a single crystal. The plasma heat wave might remelt the first layer, resulting in the grain size becoming larger than that of the second layer. The surface polycrystallization seems to maintain the residual stresses frozen in the film thickness direction. Our experimentally observed spatial profile of the grain size can be explained by this shock and heat waves model

Upgrade of repetitive fast-heating fusion driver HAMA to implode a shell target by using diode pumped solid state laser

The HAMA is 1-Hz fast heating fusion driver pumped by a 10 J second-harmonic of diode-pumped Nd:glass laser: KURE-1. We have upgraded HAMA to realize an implosion of spherical shell target by using a remaining fundamental beam from KURE-1. This beam of 6 J/1 Hz is transported to the current counter irradiation system. The resulting beam includes three pulses in sequence: 2.2 J/15 ns and 0.7 J/300 ps for implosion, and 0.5 J/190 fs for heating. We estimate the implosion dynamics from 1-D radiation hydrodynamic code (START 1D). It indicates a possibility of tailored-pulse implosion by optimizing the beam spot sizes of imploding beams on the target surface. This upgrade leads to a demonstration of repetitive implosion and additional heating of a spherical shell target in accordance with a repetition of laser operation and that of a target injection system

Target Monitoring and Plasma Diagnosis using 2 omega probe beam for CANDY

We have developed the shadowgraph and interferometer with second-harmonic of heating pulses laser to observe target and plasma in highly-repetitive fusion reaction experiments. In the deuterated polystyrene ((C8D8) n double foil experiment, we confirm implosion plasma and plasma collision. In target injection experiment at a 1 Hz rate, we measure the position of the flying deuterated polystyrene beads at the moment of laser pulse illumination and observe the plasma generation by counter-illumination by 0.63 J, 800 nm, and 104 fs laser pulses

Repetitive Solid Spherical Pellet Injection and Irradiation toward the Repetitive-mode Fast-Ignition Fusion mini-Reactor CANDY.

Pellet injection and repetitive laser illumination are key technologies for realizing inertial fusion energy[1-4]. Neutron generator using lasers also requires a repeating pellet target supplier. Here we present the first demonstration of target injection and neutron generation[5]. We injected more than 1300 spherical deuterated polystyrene(C8D8) bead pellet targets during 23 minutes at 1 Hz(Fig. 1). After the pellet targets fell for a distance of 18 cm, we applied the synchronized laser-diode-pumped ultra-intense laser HAMA. The laser intensity at the focal point is 5 x 10(18) W/cm(2), which is high enough to generate neutrons. As a result of the irradiation, we produced 2.45-MeV DD neutrons. Figure 2 shows the neutron time-of-flight signals detected by plastic scintillators coupled to photomultipliers. The neutron energy was calculated by the time-of-flight method. The maximum neutron yield was 9.5 x 10(4)/4 pi sr. The result is a step toward fusion power and also suggests possible industrial neutron sources