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A magnetic thrust chamber is an important system of a laser fusion rocket, in which the plasma kinetic energy is converted into vehicle thrust by a magnetic field. To investigate the plasma extraction from the system, the ions in a plasma are diagnosed outside the system by charge collectors. The results clearly show that the ion extraction does not strongly depend on the magnetic field strength when the energy ratio of magnetic field to plasma is greater than 4.3, and the magnetic field pushes back the plasma to generate a thrust, as previously suggested by numerical simulation and experiments.

Reduction-resistant lead-free (Ba,Ca)(Ti,Sn)O3 piezoceramics with high piezoelectric constants were fabricated by optimizing the amount of Li2CO3 added. Oxygen partial pressure was controlled during the sintering of (Ba,Ca)(Ti,Sn)O3 ceramics in a reducing atmosphere using H2–CO2 gas. Enhanced grain growth and a high-polarization state after poling treatment were achieved by adding Li2CO3. Optimizing the amount of Li2CO3 added to (Ba0.95Ca0.05)(Ti0.95Sn0.05)O3 ceramics sintered under a low oxygen partial pressure resulted in improved piezoelectric properties while maintaining the high sintered density. The prepared Li2CO3-added ceramic samples had homogeneous microstructures with a uniform dispersion of each major constituent element. However, the residual Li content in the 3 mol % Li2CO3-added (Ba0.95Ca0.05)(Ti0.95Sn0.05)O3 ceramics after sintering was less than 0.3 mol %. Sintered bodies of this ceramic prepared in a CO2 (1.5%)–H2 (0.3%)/Ar reducing atmosphere (PO2 = 10−8 atm at 1350 °C), exhibited sufficient electrical resistivity and a piezoelectric constant (d 33) exceeding 500 pC/N. The piezoelectric properties of this nonreducible ceramic were comparable or superior to those of the same ceramic sintered in air.

Polarized second-harmonic-generation (SHG) spectroscopy was studied for Au nanorods arrayed on fused silica substrates at localized surface plasmon (LSP) resonances. The geometry of the nanorods is centrosymmetric and electric dipolar second-order nonlinearities are forbidden for such a geometry. However, second-order nonlinearities are permitted for rods with sizes comparable to light wavelengths by taking advantage of the field retardation effect across the rods. In the study, we demonstrated SHG by photoexciting nanorods at an oblique incidence in two optical configurations. Independent of the configuration, efficient SHG was obtained when the excitation light was polarized in the LSP direction. The SHG waves were p-polarized, irrespective of the configuration and the excitation light polarization. The polarization behaviors were well reproduced by using numerically simulated field distributions. This comprehensive study classified the roles of the field retardation in the second-order nonlinearities of Au nanorods.

Lead-free ferroelectric K0.5Na0.5NbO3 (KNN) thin films have been synthesized by the chemical solution deposition. The optimization of excess amounts of K and Na in KNN precursor solutions was found to be effective for achieving perovskite KNN single-phase thin films with improved leakage current properties. It was revealed from Raman spectroscopic analysis data that a change in scattering mode was observed for the KNN thin films fabricated under various processing conditions. This change was due to the chemical composition fluctuation of K and Na in the KNN thin films after heat treatment. The leakage current and ferroelectric properties of the perovskite KNN thin films were strongly affected by the excess amounts of K and Na as well as the heating conditions of the precursor films. Optimized KNN thin films with 10 mol % excess K and Na exhibited a ferroelectric polarization–electric field (P–E) hysteresis loop with 2Pr and 2Ec values of 14 µC/cm2 and 140 kV/cm, respectively.

A laser-driven proton beam with a maximum energy of a few MeV is stably obtained using an ultra-short and high-intensity Ti:sapphire laser. At the same time, keV X-ray is also generated at almost the same place where protons are emitted. Here, we show the successful demonstration of simultaneous proton and X-ray projection images of a test sample placed close to the source with a resolution of ~10 µm, which is determined from the source sizes. Although the experimental configuration is very simple, the simultaneity is better than a few hundreds of ps. A CR-39 track detector and imaging plate, which are placed as close as possible to the CR-39, are used as detectors of protons and X-ray. The technique is applicable to the precise observation of microstructures.

A short-pulse (~210 fs) high-power (~1 TW) laser was focused on a tape target 3 and 5 µm in thickness to a size of 11×15 µm2 with an intensity of 3×1017 W/cm2. Protons produced by this laser with an energy spread of 100% were found to be improved to create peaks in the energy distribution with a spread of ~7% by the application of the RF electric field with an amplitude of ±40 kV synchronous to the pulsed laser. This scheme combines the conventional RF acceleration technique with laser-produced protons for the first time. It is possible to be operated up to 10 Hz, and is found to have good reproducibility for every laser shot with the capability of adjusting the peak positions by control of the relative phase between the pulsed laser and the RF electric field.

Perovskite (1-x)BiFeO3–xPbTiO3 thin films have been synthesized by the chemical solution deposition of metalorganic compounds. Homogeneous and stable BiFeO3–PbTiO3 precursor solutions were prepared by selecting appropriate starting materials and 2-methoxyethanol as a solvent. Perovskite BiFeO3–PbTiO3 powder samples with a composition ranging from x=0.1 to 0.5 showed weak ferromagnetism at room temperature. Perovskite BiFeO3–PbTiO3 single-phase thin films on Pt/TiOx/SiO2/Si substrates with good surface morphology were also fabricated by optimizing the PbTiO3 content. Ferroelectric polarization–electric field (P–E) hysteresis loops were observed for 0.7BiFeO3–0.3PbTiO3 thin films, although some leakage current components are included at room temperature. The electrical resistivity of the BiFeO3–PbTiO3 films was improved in the low temperature region, and the remnant polarization and coercive field of the 700 °C-prepared 0.7BiFeO3–0.3PbTiO3 thin films at -190 °C were approximately 50 µC/cm2 and 150 kV/cm, respectively. Furthermore, Mn doping into BiFeO3–PbTiO3 was effective in improving the ferroelectric properties of the resultant thin films at room temperature.

A scheme of the real-time optimization of proton production by an intense short-pulse laser interacting with a foil target was developed using a time-of-flight measurement with a plastic scintillator. Owing to special treatments, the detection of protons using a scintillation counter has become possible under heavy backgrounds such as laser light itself, laser-generated hard X-ray, self-emission light, and electrons from the laser-produced plasma. With such a real-time measurement of protons, the energy spectrum of protons could be obtained shot by shot, and the experimental conditions for optimal proton production could be determined very efficiently.

Ferroelectric (Bi,R)4Ti3O12 [R: rare earth] thin films were synthesized by the chemical solution deposition (CSD) method. Heat treatment above 600°C was required for the fabrication of crystalline (Bi,R)4Ti3O12 thin films of Bi-layered perovskite structure on Pt/TiOx/SiO2/Si substrates. The orientation of the films prepared at 750°C depended upon the kind of substituent rare earth ions. Bi4.12Ti3O12 (BIT) and Bi3.35La0.75Ti3O12 (BLT) thin films revealed (00l) preferred orientation. On the other hand, Bi3.35Nd0.75Ti3O12 (BNT), Bi3.35Sm0.75Ti3O12 (BST) and Bi3.35Gd0.75Ti3O12 (BGT) thin films showed random orientation with strong (117) reflection. Synthesized (Bi,R)4Ti3O12 films exhibited the typical ferroelectric behavior. The BNT thin film showed Pr of 21.6 µC/cm2, which was higher than the values of the other rare earth-doped BIT thin films.

Crack-free and highly oriented (Ba,Ln)Nb2O6 [Ln: La, Gd, Dy] thin films have been synthesized by a chemical solution deposition (CSD) method. Homogeneous and stable (Ba0.75Ln0.167)Nb2O6 precursor solutions were prepared by optimizing the reaction of metal alkoxides in solution. La, Gd, Dy-substituted BaNb2O6 powders and thin films, such as Ba0.75La0.167Nb2O6 (BLN75), Ba0.75Gd0.167Nb2O6 (BGN75) and Ba0.75Dy0.167Nb2O6 (BDN75), crystallized into the tetragonal tungsten bronze phase above 700°C. The synthesized BLN75, BGN75 and BDN75 thin films on Pt(100)/MgO(100) had a remarkable c-axis preferred orientation and exhibited the diffuse phase transition of e–T curves. The Curie temperatures of the (Ba0.75Ln0.167)Nb2O6 films were found to depend upon the ionic radii of substituted rare earth ions. The BLN75 and BGN75 thin films on Pt(100)/MgO(100) showed typical ferroelectric hysteresis loops below the Curie temperature.

BiFeO3 and Ag nanoparticle-embedded BiFeO3 thin films were prepared on Pt/TiO x /SiO2/Si and MgO(100) substrates using colloidal silver and BiFeO3 metal–organic precursor solutions. Colloidal silver solution was prepared by a chemical reductive method using NaBH4 as a reductant. The prepared Ag nanoparticles exhibited characteristic optical absorption properties based on their surface plasmon resonance related to particle size. The synthesized BiFeO3 and Ag nanoparticle/BiFeO3 thin films demonstrated rapid on/off responses of photocurrent to visible light. The Ag nanoparticle-incorporated BiFeO3 film exhibited a 2–4-fold higher photocurrent than the BiFeO3 film. Optical and ferroelectric properties did not change markedly even when Ag nanoparticles were embedded in the BiFeO3 thin film within the quantities of this study. Furthermore, in the Ag nanoparticle/BiFeO3 composite structure, Ag nanoparticles were introduced in the near-metallic state with maintained their nanometer size. In the Ag nanoparticle-embedded BiFeO3 film, photoinduced charge separation and transport of photoexcited carriers were enhanced by the surface plasmon effect of nanosized Ag particles as well as the internal bias electric field existed in the narrow-bandgap BiFeO3 thin film.

Lead-free piezoelectric K0.5Na0.5NbO3 thin films for microelectromechanical systems were fabricated via chemical solution process using metal alkoxide. Perovskite K0.5Na0.5NbO3 (KNN) single-phase thin films with good leakage current properties were successfully prepared by optimizing the KxNaxNbO3 (x0.5) composition of the precursor solution. The KNN thin films prepared from the solution with K0.55Na0.55NbO3 composition showed typical ferroelectric P–E hysteresis and field-induced strain loops. The 2Pr and 2Ec values of the K0.55Na0.55NbO3 films were 14 µC/cm2 and 140 kV/cm, respectively. From the slope of the field-induced butterfly loop, the effective d33 was found to be 46 pm/V.

BiFeO3 and Ag nanoparticle-embedded BiFeO3 thin films were prepared on Pt/TiO x /SiO2/Si and MgO(100) substrates using colloidal silver and BiFeO3 metal–organic precursor solutions. Colloidal silver solution was prepared by a chemical reductive method using NaBH4 as a reductant. The prepared Ag nanoparticles exhibited characteristic optical absorption properties based on their surface plasmon resonance related to particle size. The synthesized BiFeO3 and Ag nanoparticle/BiFeO3 thin films demonstrated rapid on/off responses of photocurrent to visible light. The Ag nanoparticle-incorporated BiFeO3 film exhibited a 2–4-fold higher photocurrent than the BiFeO3 film. Optical and ferroelectric properties did not change markedly even when Ag nanoparticles were embedded in the BiFeO3 thin film within the quantities of this study. Furthermore, in the Ag nanoparticle/BiFeO3 composite structure, Ag nanoparticles were introduced in the near-metallic state with maintained their nanometer size. In the Ag nanoparticle-embedded BiFeO3 film, photoinduced charge separation and transport of photoexcited carriers were enhanced by the surface plasmon effect of nanosized Ag particles as well as the internal bias electric field existed in the narrow-bandgap BiFeO3 thin film.

Ferroelectric (Bi,Nd)4Ti3O12-based thin films were synthesized by chemical solution deposition. In this study, Ge substitution for the Ti site in (Bi,Nd)4Ti3O12 was studied for the improvement of microstructural and ferroelectric properties of low-temperature-annealed thin films. Bi3.35Nd0.75Ti3-xGexO12 thin films crystallized into the Bi4Ti3O12 phase above 600°C. The surface morphology of Bi3.35Nd0.75Ti3-xGexO12 thin films was greatly improved by optimizing the amount of Ge substitution compared with that of nonsubstituted Bi3.35Nd0.75Ti3O12 films. In addition, the Bi3.35Nd0.75Ti2.9Ge0.1O12 thin films were found to show excellent ferroelectric properties after crystallization even at 600°C.

The microstructure of composites derived from amorphous Zr65Pd35 and Zr65Pd35Ce5 alloys was studied. X-ray diffractograms, Raman spectroscopy profiles and scanning electron micrographs indicated that the mixtures containing ZrO2, metallic Pd, and PdO were formed for both amorphous alloys after heat treatment in air. The amorphous Zr60Pd35Ce5 alloy at temperatures of 280–400 °C changed to the composites in which very small Pd precipitates with a diameter less than 100 nm were embedded in a ZrO2 matrix. The hydrogen-temperature-programmed reduction was applied to study the reactivity of hydrogen gas with the oxidized Zr60Pd35Ce5 material. A rapid hydrogen absorption and release behavior was observed on the composite derived from the amorphous alloy.

A laser Doppler velocimeter (LDV) has been developed that is capable of performing two-dimensional (2D) cross-sectional measurements. It employs two horizontal laser light sheets that intersect at an angle of 13.3°. Since the intersection region is thin, it can be used to approximately determine the 2D flow field. An 8 × 8 array of optical fibers is used to simultaneously measure Doppler frequencies at 64 points. Experiments were conducted to assess the performance of the LDV, and it was found to be capable of obtaining spatial and temporal velocity information at multiple points in a flow field. The technique is fast, noninvasive, and accurate over long sampling periods. Furthermore, its applicability to an actual flow field was confirmed by measuring the temporal velocity distribution of a pulsatile flow in a rectangular flow channel with an obstruction. The proposed device is thus a useful, compact optical instrument for conducting simultaneous 2D cross-sectional multipoint measurements.

The preparation of reduction-resistant (Ba,Ca)TiO3 ceramics as lead-free piezoelectric materials was studied. To improve their electrical properties, (100),(001)-oriented (Ba0.85Ca0.15)TiO3 ceramics were fabricated by the reactive templated grain growth method using a mixture of platelike CaTiO3 and BaTiO3 particles. The platelike CaTiO3 and BaTiO3 particles were prepared through a topochemical microcrystal conversion process using CaBi4Ti4O15 and BaBi4Ti4O15 plate-like precursor crystals. The 100 orientation degree of the grain-oriented (Ba0.85Ca0.15)TiO3 ceramics was 92%, as estimated by Lotgering's equation. In addition, 1 mol % Ba excess and 1 mol % Mn-doped (Ba0.85Ca0.15)TiO3 sintered bodies, which were sintered at 1350 °C in an Ar flow containing H2 (0.3%), had sufficient resistivity to allow the characterization of electrical properties. The ferroelectric and field-induced strain properties of the (Ba0.85Ca0.15)TiO3 ceramics, sintered in the reducing atmosphere, were markedly improved as a result of fabricating grain-oriented samples. The field-induced strain coefficient (estimated from the slope of the unipolar strain loop) of the nonreducible (100),(001)-oriented (Ba0.85Ca0.15)TiO3 ceramics reached 570 pm/V, which was higher than that of polycrystals (260 pm/V) with no preferential orientation.

Lead-free ferroelectric K0.5Na0.5NbO3–CaZrO3 thin films were prepared by chemical solution deposition. Chemically optimized K0.5Na0.5NbO3–CaZrO3 precursor thin films crystallized in the perovskite single phase on Pt/TiO x /SiO2/Si substrates at 650 °C. The K0.5Na0.5NbO3–CaZrO3 thin films showed poor ferroelectric polarizations due to the insufficient insulating resistance. The leakage current of the K0.5Na0.5NbO3–CaZrO3 films, especially in the high-applied-field region, was markedly reduced by 1 mol % Mn doping for the Nb site. Also, the ferroelectric properties of the K0.5Na0.5NbO3–CaZrO3 thin films depended on CaZrO3 concentration. 1 mol % Mn-doped K0.5Na0.5NbO3–CaZrO3 thin films exhibited slim and small ferroelectric polarization–electric field (P–E) hysteresis loops at room temperature with an increase in CaZrO3 amount. Furthermore, these films showed a typical field-induced displacement curve with a small hysteresis, and the estimated effective d 33 values were 32 pm/V for the 1 mol % Mn-doped 0.95K0.5Na0.5NbO3–0.05CaZrO3 thin films and 21 pm/V for the 1 mol % Mn-doped 0.9K0.5Na0.5NbO3–0.1CaZrO3 thin films.

The precision of the time-of-flight method for measuring proton spectra is confirmed by the activation method using a 7Li(p,n)7Be nuclear reaction. The proton beam driven by a repetitive high-intensity laser is utilized to induce the nuclear reaction. The activity measured by direct gamma-ray measurement after 1912 proton beam shots at 1 Hz is 1.7±0.2 Bq. This is in accordance with the activity of 1.6±0.2 Bq obtained from the shot-to-shot proton energy distribution measured using the time-of-flight detector.

To investigate the radiobiological effects of high dose rates that are attributed to high current, short bunch beam generation with laser-dreven ion acceleration, we have developed an experimental setup that uses laser-accelerated protons. In-vitro human lung cancer cells: A549 pulmonary adenocarcinoma are irradiated with a laser-accelerated proton bunches with a duration of 2×10-8 s and flux of ∼1015 cm-2 s-1, amounting to single bunch absorbed dose at the 1 Gy level. The double-strand break (DSB) yield in cell DNA is analyzed for the laser-accelerated proton beam at an average LET of 41 keV/µm.

Multiferroic BiFeO3–Bi0.5Na0.5TiO3 thin films were synthesized on Pt/TiO x /SiO2/Si substrates by chemical solution deposition. When the amount of Bi0.5Na0.5TiO3 exceeded 30 mol %, perovskite BiFeO3–Bi0.5Na0.5TiO3 single phase thin films were successfully fabricated in the temperature range of 550–700 °C. Also, the surface morphology of the 0.7BiFeO3–0.3Bi0.5Na0.5TiO3 thin films was improved by optimizing the amounts of excess Bi and Na in 0.7BiFeO3–0.3Bi0.5Na0.5TiO3 precursor solutions. However, measurements of ferroelectric polarization-electric field hysteresis loops were difficult for 0.7BiFeO3–0.3Bi0.5Na0.5TiO3 thin films due to the large leakage current densities at room temperature. At low temperatures, the 0.7BiFeO3–0.3Bi0.5Na0.5TiO3 thin films demonstrated improved insulating resistance and exhibited potential ferroelectric properties. Furthermore, by Mn doping of the 0.7BiFeO3–0.3Bi0.5Na0.5TiO3 films, improved ferroelectric properties with weak ferromagnetism were achieved at room temperature. In 0.7Bi(Fe0.95Mn0.05)O3–0.3Bi0.5Na0.5TiO3 thin films, ohmic conduction was dominant in an electric field range of 0–200 kV/cm and the abrupt increase in leakage current was suppressed even at high electric fields, whereas nondoped 0.7BiFeO3–0.3Bi0.5Na0.5TiO3 films exhibited nonohmic conduction with a larger leakage current. The remanent polarization and coercive field of the 0.7Bi(Fe0.95Mn0.05)O3–0.3Bi0.5Na0.5TiO3 films at room temperature were approximately 26 µC/cm2 and 250 kV/cm, respectively.

Lead-free piezoelectric (K,Na)(Nb,Ta)O3 thin films were prepared by chemical solution deposition. Perovskite single-phase (K0.5Na0.5)(Nb0.8Ta0.2)O3 and Mn-doped (K0.5Na0.5)(Nb0.8Ta0.2)O3 thin films were successfully fabricated at 600 °C on Pt/TiO x /SiO2/Si substrates by controlling the excess amounts of K and Na, and Mn by doping. The (K0.5Na0.5)(Nb0.8Ta0.2)O3 thin films showed poor ferroelectric polarizations due to the insufficient insulating resistance at room temperature. The leakage current density of the (K0.5Na0.5)(Nb0.8Ta0.2)O3 films, especially in the high-applied-field region, was markedly reduced by doping with a small amount of Mn. Also, the ferroelectric properties of the (K0.5Na0.5)(Nb0.8Ta0.2)O3 thin films were markedly improved by Mn doping. 0.5 and 1.0 mol % Mn-doped (K0.5Na0.5)(Nb0.8Ta0.2)O3 thin films exhibited well-shaped ferroelectric polarization–electric field (P–E) hysteresis loops at room temperature. The remanent polarization (P r) and coercive field (E c) values of the 0.5 and 1.0 mol % Mn-doped (K0.5Na0.5)(Nb0.8Ta0.2)O3 thin films at 1 kHz were approximately 14 and 21 µC/cm2, and 111 and 86 kV/cm, respectively. Furthermore, these films showed a typical field-induced butterfly loop, and the estimated effective d 33 values were 58 pm/V for the 0.5 mol % Mn-doped (K0.5Na0.5)(Nb0.8Ta0.2)O3 thin films and 41 pm/V for the 1.0 mol % Mn-doped (K0.5Na0.5)(Nb0.8Ta0.2)O3 thin films.

Lead-free ferroelectric NaNbO3–BaTiO3 thin films were prepared by chemical solution deposition. Perovskite single-phase NaNbO3–BaTiO3 thin films were successfully fabricated at 550 °C on Pt/TiOx/SiO2/Si substrates. The ferroelectric properties of the NaNbO3–BaTiO3 thin films depended on the BaTiO3 content of NaNbO3–BaTiO3. Among NaNbO3–BaTiO3 films with various BaTiO3 concentrations, the 0.95NaNbO3–0.05BaTiO3 thin films showed relatively large polarization at -190 °C, although the insulating resistance of the films was not sufficiently high at room temperature. To improve the electrical resistivity at ambient temperatures, Mn doping of 0.95NaNbO3–0.05BaTiO3 was examined. The leakage current density of the films was found to be greatly reduced by a small amount of Mn doping. 1.0 mol % Mn-doped 0.95NaNbO3–0.05BaTiO3 thin films showed well-shaped slim ferroelectric polarization–electric field (P–E) hysteresis loops at room temperature. The remanent polarization (Pr) and coercive field (Ec) values of the 1.0 mol % Mn-doped 0.95NaNbO3–0.05BaTiO3 thin films at 1 kHz were approximately 5 µC/cm2 and 50 kV/cm, respectively. Furthermore, the ferroelectric P–E loops of the 1.0 mol % Mn-doped 0.95NaNbO3–0.05BaTiO3 thin films showed good frequency dependence and could be characterized at a frequency as low as 1 Hz.