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Sunlight-like lasers that have a continuous broad frequency spectrum, random phase spectrum, and random polarization are formulated theoretically. With a sunlight-like laser beam consisting of a sequence of temporal speckles, the resonant three-wave coupling that underlies parametric instabilities in laser–plasma interactions can be greatly degraded owing to the limited duration of each speckle and the frequency shift between two adjacent speckles. The wave coupling can be further weakened by the random polarization of such beams. Numerical simulations demonstrate that the intensity threshold of stimulated Raman scattering in homogeneous plasmas can be doubled by using a sunlight-like laser beam with a relative bandwidth of ∼1% as compared with a monochromatic laser beam. Consequently, the hot-electron generation harmful to inertial confinement fusion can be effectively controlled by using sunlight-like laser drivers. Such drivers may be realized in the next generation of broadband lasers by combining two or more broadband beams with independent phase spectra or by applying polarization smoothing to a single broadband beam.

An ion beam has a unique feature to deposit its main energy inside a human body to kill cancer cells or inside material. In this paper, a future intense laser ion accelerator is discussed to make the laser-based ion accelerator compact and controllable. The issues in the laser ion accelerator include the energy efficiency from the laser to the ions, the ion beam collimation, the ion energy spectrum control, the ion beam bunching, and the ion particle energy control. The energy efficiency from the laser to ions is improved by using a solid target with a fine sub-wavelength structure. The ion beam collimation is performed by larger holes behind the solid target. An ion beam bunching and a post-acceleration are successfully realized by a multi-stage laser-target interaction. The controllable laser ion acceleration would become viable based on the study discussed in this paper. In this paper, we present 3D PIC simulation results for the controllability of laser ion acceleration system.

A dynamic smoothing method was proposed based on a phase control to stabilize plasma instabilities and smooth plasma non-uniformities. In this paper, the dynamic smoothing method is applied to a spherical fuel target implosion in heavy ion inertial fusion (HIF). We found that the wobbling motion of each heavy ion beam (HIB) axis induces a phase-controlled HIBs energy deposition, and consequently the phase-controlled implosion acceleration is realized, so that the HIBs illumination non-uniformity is successfully smoothed. HIB accelerators provide a well-established capability to oscillate the HIBs axes with a high frequency. In inertial confinement fusion, a fuel implosion uniformity is essentially important to compress the DT fuel and release the fusion energy, and the non-uniformity of the implosion acceleration should be less than a few %. The results in this paper also demonstrate that the wobbling HIBs would provide an improvement in the fusion energy output gain.

A few percent wobbling-beam illumination nonuniformity is realized in heavy ion inertial confinement fusion (HIF) by a spiraling beam axis motion in the paper. The wobbling heavy ion beam (HIB) illumination was proposed to realize a uniform implosion in HIF. However, the initial imprint of the wobbling HIBs was a serious problem and introduces a large unacceptable energy deposition nonuniformity. In wobbling the HIBs illumination, the illumination nonuniformity oscillates in time and space. The oscillating-HIB energy deposition may contribute to the reduction of the HIBs' illumination nonuniformity and also the mitigation of the Rayleigh–Taylor instability. The wobbling HIBs can be generated in HIB accelerators and the oscillating frequency may be from several 100 MHz to 1 GHz. Three-dimensional HIBs illumination computations presented here show that the few percent wobbling HIBs illumination nonuniformity oscillates successfully with the same wobbling HIBs frequency.

Background: Ion beam has been used in cancer treatment, and has a unique preferable feature to deposit its main energy inside a human body so that cancer cell could be killed by the ion beam. However, conventional ion accelerator tends to be huge in its size and its cost. In this paper a future intense-laser ion accelerator is proposed to make the ion accelerator compact. Subjects and methods: An intense femtosecond pulsed laser was employed to accelerate ions. The issues in the laser ion accelerator include the energy efficiency from the laser to the ions, the ion beam collimation, the ion energy spectrum control, the ion beam bunching and the ion particle energy control. In the study particle computer simulations were performed to solve the issues, and each component was designed to control the ion beam quality. Results: When an intense laser illuminates a target, electrons in the target are accelerated and leave from the target; temporarily a strong electric field is formed between the high-energy electrons and the target ions, and the target ions are accelerated. The energy efficiency from the laser to ions was improved by using a solid target with a fine sub-wavelength structure or by a near-critical density gas plasma. The ion beam collimation was realized by holes behind the solid target. The control of the ion energy spectrum and the ion particle energy, and the ion beam bunching were successfully realized by a multi-stage laser-target interaction. Conclusions: The present study proposed a novel concept for a future compact laser ion accelerator, based on each component study required to control the ion beam quality and parameters.

In inertial fusion, one of scientific issues is to reduce an implosion non-uniformity of a spherical fuel target. The implosion non-uniformity is caused by several factors, including the driver beam illumination non-uniformity, the Rayleigh-Taylor instability (RTI) growth, etc. In this paper we propose a new control method to reduce the implosion non-uniformity; the oscillating implosion acceleration dg(t) is created by pulsating and dephasing heavy ion beams (HIBs) in heavy ion inertial fusion (HIF). The dg(t) would reduce the RTI growth effectively. The original concept of the non- uniformity control in inertial fusion was proposed in (Kawata, et al., 1993). In this paper it was found that the pulsating and dephasing HIBs illumination provide successfully the controlled dg(t) and that dg(t) induced by the pulsating HIBs reduces well the implosion non-uniformity. Consequently the pulsating HIBs improve a pellet gain remarkably in HIF., 10 pages, 10 figures, 2 tables, submitted to a journal

Energetic electron beam generation from a thin foil target by the ponderomotive force of an ultra-intense circularly polarized laser pulse is investigated. Two-dimensional particle-in-cell (PIC) simulations show that laser pulses with intensity of 1022–1023 Wcm−2 generate about 1–10 GeV electron beams, in agreement with the prediction of one-dimensional theory. When the laser intensity is at 1024–1025 Wcm−2, the beam energy obtained from PIC simulations is lower than the values predicted by the theory. The radiation damping effect is considered, which is found to become important for the laser intensity higher than 1025 Wcm−2. The effect of laser focus positions is also discussed.

Collimated proton beams from laser interaction with a slab having a hole on its backside are investigated using particle-in-cell simulation. The hot target electrons driven by the laser expand rapidly into the hole. However, at the hole's corners the electrons are strongly compressed and an intense electron jet is emitted from each corner, tightly followed by the ions. The plasma jets focus and collimate along the axis of the hole and can propagate without divergence within the hole. The effect of the hole diameter on the collimated proton beam is considered.

The key issues in heavy ion beam (HIB) inertial confinement fusion (ICF) include particle accelerator, physics of intense beam, beam final transport, target-plasma hydrodynamics, etc. In this paper, we focus on fuel implosion. In order to realize an effective implosion, beam illumination non-uniformity on a fuel target must be suppressed less than a few percent. In this study a direct–indirect hybrid implosion mode is discussed in heavy ion beam inertial confinement fusion (HIF) in order to release sufficient fusion energy in a robust manner. In the direct–indirect hybrid mode target, a low-density foam layer is inserted, and the radiation energy is confined in the foam layer. In the foam layer, the radiation transport is expected to smoothen the HIB illumination non-uniformity in the lateral direction. In this paper, we study the influences of the foam thickness and the inner radiation-shield Al density on implosion uniformity. Two-dimensional fluid simulations demonstrate that the hybrid target contributes to the HIB non-uniformity smoothing and releases a sufficient fusion energy output in HIF.

Ion acceleration by short, high intensity laser pulses in sets of small targets is treated by an analytical model developed here, and by two-dimensional particle-in-cell simulations. When an intense short laser pulse illuminates a thin foil target at normal incidence, electrons in the target are accelerated by the ponderomotive force. At the rear surface of the foil they generate a strong electric field that accelerates the ions, and generates an ion beam of small divergence. Using a mass-limited small target like a droplet enhances the ion energy, but increases divergence at the same time. In this paper, a combination of several-micron targets in a periodic structure (for example, a droplet chain) is proposed in order to increase the conversion efficiency from the incident laser beam to the emergent protons. Improvement of the energy flux conversion efficiency from the laser to the ion beam at optimal conditions is demonstrated.

In a proton beam generation by a laser-foil interaction, significant improvement of energy-conversion efficiency from laser to proton beam is presented by particle simulations. When an intense short-pulse laser illuminates the thin-foil target, the foil electrons are accelerated around the target by the ponderomotive force. The hot electrons generate a strong electric field, which accelerates the foil protons, and the proton beam is generated. In this paper, a tailored multihole thin-foil target is proposed in order to increase the energy-conversion efficiency from laser to protons. The multiholes transpiercing the foil target enhance the laser-proton energy-conversion efficiency significantly. Particle-in-cell 2.5-dimensional simulations present that the total laser-proton energy-conversion efficiency becomes 9.3% for the tailored multihole target, although the energy-conversion efficiency is 1.5% for a plain thin-foil target. The maximum proton energy is 10.0 MeV for the multihole target and is 3.14 MeV for the plain target. The transpiercing multihole target serves a new method to increase the energy-conversion efficiency from laser to ions.

Divergence suppression of laser-produced proton beam is demonstrated by a tailored thin-foil target with hole. When an intense short-pulse laser illuminates the thin-foil target with the hole, transverse-edge effects of an accelerated electron cloud and an ion source cloud are eliminated by a protuberant part of the hole. The edge fields of the electron cloud and the ion source cloud induce the proton-beam divergence. Therefore, the transverse proton-beam divergence is suppressed by the tailored hole target. First, this paper presents the robustness of the hole target against a contaminated proton-source layer. It may be also difficult to make the laser axis coincide with the target-hole center line in realistic experiments and uses when the target has only one hole. The 2.5-D particle-in-cell simulations present that a multiple-hole target is robust against the laser-alignment and the target-setting errors. The multiple-hole target may serve as a robust target for practical uses to produce a collimated proton beam. In addition, a method for a proton-energy-spectrum control is also proposed by using a hole-cover layer. The hole-cover layer serves a role of high-energy proton selection.

The principle of our proposed lens-less Fourier digital holography is experimentally verified by observing a test target. The reconstruction is performed by using a Fourier integral formula derived from Rayleigh-Sommerfeld diffraction integral and coordinate conversion.

Dynamics of high-current heavy-ion beams are studied during longitudinal bunch compression. Operation regions of particle beams are plotted on a tune depression–wave velocity diagram. Emittance growth due to the transverse focusing field error is investigated during the final beam bunching. The beam bunch is longitudinally compressed during the transport with the field error in continuous focusing (CF) or alternating gradient (AG) field lattices. Numerical calculation results show the difference of the emittance growth is only 2% between the cases with and without field error in the CF lattice. On the other hand, in the case of AG lattice with field error of 10%, the emittance growth of 2.4 times is estimated. The beam behaviors in the CF and AG lattice transport are discussed based on the numerical simulations.

In heavy ion beam (HIB) inertial confinement fusion (HIF), implosion asymmetry should be less than a few percent in order to compress a fuel sufficiently and release fusion energy effectively. It is known that the HIB illumination nonuniformity and implosion symmetry are sensitive to a little pellet displacement from a reactor chamber center. We present a new HIB illumination scheme which is robust against the displacement of a direct-driven fuel pellet in an HIF reactor chamber. In conventional HIB illumination schemes a pellet displacement of 25–100 μm was tolerable. The new robust HIB illumination scheme is examined by three-dimensional computer simulations. In the new HIB illumination scheme the tolerable pellet displacement is about 200–300 μm.

In this study, a light-driven deformable mirror is fabricated by electron beam lithography. The mirror is consisted of a deformation layer and a micromirror array. The deformation layer is made of an azobenzene polymer and the micromirro array is deposited on the deformation layer. The deformation of azobenzene polymer is induced by illuminating a continuum wave beam or femto-second pulse laser beam. Then, the micromirror is displaced. The displacement modulation is experimentally confirmed by interference measurement.

This paper proposes a method to increase the recording density of binary data pages in holographic memory. The recording density is increased by decreasing the rectangular aperture size on a Fourier plane. To extract the original data page from the low quality image, a four-step phase mask is designed. The principle of the proposed method is numerically verified.

Laser interactions with mass-limited targets are studied here via 2D3V relativistic electromagnetic particle-in-cell (PIC) simulations. We also describe our newly developed code that uses novel efficient algorithms. Damping regions have been implemented in order to eliminate spurious reflection of outgoing electromagnetic waves from boundaries of the simulation box. Mass-limited targets limit undesirable spread of absorbed laser energy out of the interaction zone. Mass-limited target, such as droplets, are shown to enhance the achievable fast ion energy significantly.

Beam dynamics is investigated by multiparticle simulations during final beam bunching and final beam focusing in a driver system for heavy-ion inertial fusion. The particle simulations predict the emittance growth during the longitudinal bunch compression for various particle distributions at initial conditions. Particle distributions in the beam transverse cross-section approach uniform during the final beam bunching. It is found that the distribution has the Gaussian profile at the focal spot in the radial direction after the final focusing.

Dependence in pulse duration of heavy ion beam is investigated for effective pellet implosion in an inertial confinement fusion. Not only the spatial nonuniformity of the beam illumination, but also the errors of the beam pulse duration cause changes of implosion dynamics. The allowable regime of beam pulse duration is given by the implosion calculation using numerical simulation techniques. The regime of the beam pulse duration for the effective fusion output becomes narrow with decreasing the input beam energy. The voltage accuracy requirement at the beam velocity modulator is also estimated for the final beam bunching. The voltage error tolerance is estimated as a few percent.

K-α emission is an intense short-pulse line source well suited for X-ray diagnostic techniques with subpicosecond and micrometer resolution. Numerical simulations are performed here in a search for laser–target interaction regimes where both high efficiency of laser energy transformation to X-ray emission and ultrashort X-ray pulses are achieved. We use the one-dimensional PIC code for the description of the laser interaction with the plasma layer at the target surface. Fast electron transport into the target is treated by our newly developed Monte Carlo code with temporal resolution that is described here in detail. Our simulations reveal extremely short ∼200 fs FWHM bright K-α X-ray pulses emitted from targets heated by 120-fs pulses of a table-top laser. Laser energy conversion efficiency to K-α line emission as high as 6 × 10−5 is noticed. Integration of the emitted energy over the focal spot is carried out to improve the simulation accord with published experimental data. Negligible impact of self-induced electric fields on K-α emission is found for conducting target materials at moderate laser intensities [lsim ]1017 W/cm2.

By utilizing a pulsed laser beam of TEM(1,0)+TEM(0,1) mode, it was found numerically for the first time that an electron bunch can be effectively trapped by the transverse ponderomotive force in the transverse direction and at the same time accelerated by the longitudinal ponderomotive force to about 378 MeV at the laser peak intensity of I∼5.48×1018 W/cm2. In addition, the electron bunch size is preferably small: at this laser intensity the electron bunch thickness is ∼10λ in the longitudinal direction and the bunch radius is about 625λ in the transverse direction.

The generation of a high-energy electron bunch is studied by using an intense fs TEM(1, 0) mode laser in vacuum. We perform three-dimensional particle simulations in which the relativistic equation of motion is solved with an analytically expressed laser field. In this paper, we found that electrons are accelerated longitudinally and confined in the transverse direction by a ponderomotive force of an intense short pulse TEM(1, 0) mode laser. Using a TEM(1, 0) mode laser of 1017 W cm−2, the electrons are successfully trapped in the polarized direction and accelerated to the order of tens of megaelectronvolts with an acceleration gradient of about gigaelectronvolts per metre. The electron bunch generated has a small emittance in the transverse and longitudinal directions, and the spatial size of the electron bunch is about several hundred micrometres in each direction with a high electron number density. This electron acceleration mechanism may open a new engineering world towards a point radiation source, a precise measurement, applications to material sciences, and so on.

In inertial confinement fusion the target implosion non-uniformity is introduced by a driver beams' illumination non-uniformity, a fuel target alignment error in a fusion reactor, the target fabrication defect, et al. For a steady operation of a fusion power plant the target implosion should be robust against the implosion non-uniformities. In this paper the requirement for the implosion uniformity is first discussed. The implosion uniformity should be less than a few percent. A study on the fuel hotspot dynamics is also presented and shows that the stagnating plasma fluid provides a significant enhancement of vorticity at the final stage of the fuel stagnation. Then non-uniformity mitigation mechanisms of the heavy ion beam (HIB) illumination are also briefly discussed in heavy ion inertial fusion (HIF). A density valley appears in the energy absorber, and the large-scale density valley also works as a radiation energy confinement layer, which contributes to a radiation energy smoothing. In HIF a wobbling heavy ion beam illumination was also introduced to realize a uniform implosion. In the wobbling HIBs illumination, the illumination non-uniformity oscillates in time and space on a HIF target. The oscillating-HIB energy deposition may contribute to the reduction of the HIBs' illumination non-uniformity by its smoothing effect on the HIB illumination non-uniformity and also by a growth mitigation effect on the Rayleigh-Taylor instability., Comment: 27 pages, presented at Int. Symposium on HIF 2014 at Lanzhou, China

We focus on a control of generation of high-quality ion beam. In this study, near-critical density plasmas are employed and are illuminated by high intensity short laser pulses; we have successfully generated high-energy ions by multiple-stages acceleration. We performed particle-in-cell simulations in this paper. Near-critical density plasmas are employed at the proton source and also in the post acceleration. A beam bunching method is also proposed to control the ion beam length. Intense short-pulse lasers are now available. Based on the new laser technology, new acceleration mechanisms have been proposed by using the laser pulse, as an alternative of the conventional accelerator. However, there are issues in the laser particle acceleration method: the issues includes a lack of controllability for particle beam quality and for the particle energy. These issues should be addressed toward a realistic laser particle accelerator. In this study we focus a high-quality laser proton beam generation. In the laser ion acceleration, first target electrons are kicked by the incoming intense laser pulse, and form an electron cloud at the target surfaces. The target substrate becomes positively charged, and a strong electric field is created at the target surfaces. At the target rear surface, if source ions are located there, the ions are accelerated. This ion acceleration mechanism is called as the TNSA (Target Normal Sheath Acceleration). In TNSA, the acceleration electric field is normal to the target surface. The TNSA is widely used for the ion source. When the target is a under-dense-gas target, a laser would penetrate the gas plasma target with a lower speed than the speed of light c in vacuum. When the intense laser illuminates the gas plasma target, electrons are also accelerated and propagate in the plasma. Then the strong electron current is generated, and a strong magnetic field is generated. At the increase phase of the strong magnetic

In inertial confinement fusion, the driver beam illumination nonuniformity leads to a degradation of fusion energy output. On the other hand, heavy ion beam accelerator provides a capability to oscillate a beam axis with a high frequency. The wobbling beams may provide a new method to reduce or smooth the beam illumination nonuniformity. A fuel target alignment error may happen in a fusion reactor; the target alignment error induces heavy ion beam illumination nonuniformity on a target. Therefore, first we study the effect of driver irradiation nonuniformity induced by the target alignment error on the target implosion. Then we optimize the wobbling beam illumination; spiral wobbling heavy ion beams provide a lower illumination nonuniformity. In addition, by optimizing the beam irradiation scheme, the illumination nonuniformity is reduced further.

The velocity filtering is achieved utilizing the beat frequency dependence of particle velocity. The principle of the velocity filtering is numerically verified. This method confirmed a spherical wave with a certain velocity can be extracted.

This study investigates a target for heavy ion fusion (HIF) using light target materials. In this study, the target structure, the heavy ion beam (HIB) input pulse shape and the HIB input pulse energy are optimized for the maximal fusion energy output. We performed two-dimensional fluid implosion simulations to obtain a high pellet gain. The optimized target shows a high yield of a gain 223. The input Pb beam energy is 1.8 MJ.

A method based on digital holography to reconstruct Fourier vector wave memory is proposed. It is numerically confirmed that the signal vector wave from a recording medium is recorded as a digital hologram and reconstructed.

Holographic memory is expected as a next- generation optical memory because it potentially has terabyte data capacity per disk and gigabit data transfer rate. Furthermore, when a polarization-sensitive medium is used as a recording medium, a vector wave can be recorded so that few times data capacity and data transfer rate are expected. However, the optical system for the vector wave recording technique such as dualchannel polarization holography[1,2] is complicated. Therefore, simple recording and reconstruction methods have been investigated. In this paper, a digital holographic reconstruction method with spatial phase-shifting is proposed.

High-energy-density electron–positron pairs play an increasingly important role in many potential applications. Here, we propose a scheme for enhanced positron production by an ultra intense laser irradiating a gas-Al compound target via the multi-photon Breit–Wheeler (BW) process. The laser pulse first ionizes the gas and interacts with a near-critical-density plasma, forming an electron bubble behind the laser pulse. A great deal of electrons are trapped and accelerated in the bubble, while the laser front hole-bores the Al target and deforms its front surface. A part of the laser wave is thus reflected by the inner curved target surface and collides with the accelerated electron bunch. Finally, a large number of γ photons are emitted in the forward direction via the Compton back-scattering process and the BW process is initiated. Dense electron–positron pairs are produced with a maximum density of m−3. Simulation results show that the positron generation is greatly enhanced in the compound target, where the positron yield is two orders of magnitude greater than that in only the solid slab case. The influences of the laser intensity, gas density and length on the positron beam quality are also discussed, which demonstrates the feasibility of the scheme in practice.

In intense-laser plasma interaction, several issues still remain to be solved for a future laser particle acceleration. In this paper we focus on a bunching of ion beam, which is preaccelerated by a strong electric field generated in a laser plasma interaction. In this study, a nearcritical-density plasma target is illuminated by an intense short laser pulse. A moving strong inductive electric field is generated inside of the target. We have successfully obtained a bunched ion beam in our particle-in-cell simulations in this paper.

For a steady operation of a fusion power plant the target implosion should be robust against the implosion non-uniformities. In this paper the non-uniformity mitigation mechanisms in the heavy ion beam (HIB) illumination are discussed in heavy ion inertial fusion (HIF). A density valley appears in the energy absorber, and the large-scale density valley also works as a radiation energy confinement layer, which contributes to the radiation energy smoothing for the HIB illumination non-uniformity. The large density-gradient scale, which is typically ~500μm in HIF targets, also contributes to a reduction of the Rayleigh- Taylor instability growth rate. In HIF a wobbling HIBs illumination would also reduce the Rayleigh-Taylor instability growth and to realize a uniform implosion.

In inertial confinement fusion, the driver beam illumination non-uniformity leads a degradation of fusion energy output. A fuel target alignment error would happen in a fusion reactor; the target alignment error induces heavy ion beam illumination non-uniformity on a target. On the other hand, heavy ion beam accelerator provides a capability to oscillate a beam axis with a high frequency. The wobbling beams may provide a new method to reduce or smooth the beam illumination non-uniformity. First we study the effect of driver irradiation non-uniformity induced by the target alignment error (dz) on the target implosion. We found that dz should be less than about 130 μm for a sufficient fusion energy output. We also optimize the wobbling scheme. The spiral wobbling heavy ion beams would provide a promissing scheme to the uniform beam illumination.

In inertial confinement fusion, the driver beam illumination non-uniformity leads a degradation of fusion energy output. The illumination non-uniformity allowed is less than a few percent in inertial fusion target implosion. Heavy ion beam (HIB) accelerator provides a capability to oscillate a beam axis with a high frequency. The wobbling beams may provide a new method to reduce or smooth the beam illumination non-uniformity. In this paper the HIBs wobbling illumination scheme was optimized.

In intense laser plasma interaction for particle acceleration several issues remain to be solved. In this paper we focus on a collimation of ion beam, which is produced by a laser plasma interaction. In this study, the ion beam is collimated by a thin film target. When an intense short pulse laser illuminates a target, target electrons are accelerated, and create an electron cloud that generates a sheath electric field at the target surface. Such the ion acceleration mechanism is called the target normal sheath acceleration (TNSA). The TNSA field would be used for the ion beam collimation by the electric field. We have successfully obtained a collimated beam in our particle-in-cell simulations.

In this Letter, the principle of polarization holography for recording an arbitrary vector wave on a thin polarization-sensitive recording medium is proposed. It is analytically shown that the complex amplitudes of p- and s-polarization components are simultaneously recorded and independently reconstructed by using an s-polarized reference beam. The characteristics are experimentally verified.

Multi-valued phase patterns were multiply recorded by retardagraphy in order to improve recording density and data transfer rate. In the experiment, the phase pattern consists of four values were recorded on a polarization-sensitive medium by focusing the recording beam, and three patterns were multiply recorded by shifting the focal point. The recorded patterns could be independently reconstructed.

This paper presents a method based on the use of an image sensor for obtaining the complex amplitudes of beams diffracted from an object at two different wavelengths. The complex amplitude for each wavelength is extracted by the Doppler phase-shifting method. The principle underlying the proposed method is experimentally verified by using the method with two lasers having different wavelengths to measure the surface shape of a concave mirror.

It is shown by simulations that terahertz (THz) radiation can be produced more efficiently by a mid-infrared laser pulse from a gas target. The THz amplitude is enhanced by 35 times as the laser wavelength increases from 1 μm to 4 μm; a 4 μm laser at 10(15) W cm(-2) produces 5 MV/cm THz radiation. The THz amplitude changes oscillatingly with increasing laser intensity for a given laser wavelength. In addition, the laser intensity threshold for the THz emission is lower for a longer laser wavelength.

Multiple recording characteristics of polarization hologram was investigated for high density optical data storage. Polarization and angular multiplexing was performed. Some polarization holograms were independently recorded on the same position of a polarization-sensitive medium. The recorded images could be independently reconstructed.

Two-wavelength digital holography with Doppler-phase shifting method was proposed. Two laser beams with different wavelength was simultaneously illuminated onto a target object, and the surface shape was reconstructed from the digital holograms.

Future ultrashort 10^{22}–10^{25} W cm^{-2} laser pulses offer the possibility of producing ultrashort monoenergetic electron beams in the GeV–TeV level by direct laser ponderomotive force acceleration (LPFA) in distances of millimeters to about 1 m. A scheme is proposed that a thin solid foil and a thick solid foil are placed on the laser axis, where the thin foil supplies the electron source for LPFA and the thick foil reflects the laser away, however allows the accelerated electrons to go through. By optimizing the distance between the foils, one can obtain the maximum electron beam energy. This scheme is demonstrated by particle-in-cell simulations.

Simulation of vacuum laser acceleration, because of its scheme’s simplicity, attracts many people involved in. However, how to put the particle in the initial positions in the field has not been considered seriously in some such schemes. An inattentive choice of electron’s initial conditions may lead to misleading results. Here we show that arbitrarily placing the particle within the laser field leads to an overestimation of its energy gain, and offer suggestions for selecting appropriate initial conditions.

The surface shape of a concave mirror was measured by Doppler phase-shifting digital holography. The surface shape measurement was performed in an environment with external disturbances in order to confirm the robustness of the system.

Polarization gratings were formed on a write-once type polarization-sensitive medium and their polarization characteristics were evaluated. A circularly polarized beam splitting function was observed in an orthogonally circular polarization grating.

A direct-indirect hybrid implosion mode is proposed and discussed in heavy ion beam (HIB) inertial confinement fusion (HIF) in order to release sufficient fusion energy in a robust manner. The HIB illumination non-uniformity depends strongly on a target displacement dz from the centre of a fusion reactor chamber. In a direct-driven implosion mode, dz of about 20 micron m was tolerable, and in an indirect- implosion mode, dz of about 100 micron m was allowable. In the direct-indirect mixture mode target, a low-density foam layer is inserted, and the radiation energy is confined in the foam layer. In the foam layer the radiation transport is expected to smooth the HIB illumination non-uniformity in the lateral direction. Two-dimensional implosion simulations are performed, and show that the HIB illumination non- uniformity is well smoothed in the direct-indirect hybrid-mode target. Our simulation results present that a large pellet displacement of about a few hundred micron m is allowed in order to obtain a sufficient fusion energy output in HIF. In fuel target implosion, ICF has two ways of implosion schemes, which are indirect-driven scheme and direct-driven implosion scheme. Each implosion scheme has merits and demerits. The indirect-driven scheme may be robust against the beam non- uniformity and a beam number employed is low compared with that in the direct-driven scheme, though each HIB should carry a larger current and a target structure may be complicated and expensive relatively. The direct-driven pellet structure may be simple, though the scheme may be sensitive to the HIB illumination non-uniformity. In this paper, a direct- indirect mixture implosion mode is proposed and discussed in HIB ICF.

A thin-foil tailored hole target is proposed for an efficient production of a collimated proton beam in a laser target interaction. The tailored target has holes at the target surface. When an intense short pulse laser illuminates the thin foil hole target, transverse edge fields of an accelerated electron cloud and a proton source cloud are shielded by a protuberant part of the hole so that the proton beam divergence is suppressed. This paper presents a robustness of the hole target against laser parameter changes, against a contaminant proton source layer and against a laser alignment error. The 2.5-dimensional PIC (particle-in-cell) simulations also present that a multiple-hole target serves a high energy efficiency of the proton beam generation. Recent researches in this field have demonstrated acceleration of ions to a high energy in an interaction between an intense laser pulse and a thin foil target. The ion beams are expected to be useful for basic particle physics, medical therapy, controlled nuclear fusion, high-energy sources and so on. The important issues of the ion beam production include a quality of the ion beam and an efficient energy convergence to the ion beam from the laser. This paper presents a new method for the efficient collimated proton beam in the laser foil interaction.

It is found that an electron can be efficiently accelerated by a simple system which is composed of a plus plane electromagnetic (EM) wave and a astatic magnetic field. In this system the direction of the magnetic component of the EM wave is pa rallel to that of the static fields. Initialy an electron is positioned in front of the pluse plane EM wave and the electron speed is less than the speed of light(c). The pulse plane EM wave travels across the static magnetic field with the speed of fight(c). Therefore, the pluse EM wave catches up with the electron and leaves it behind. Without the static magnetic field in the system, the electron would not be able to absorb the wave energy because of the symmetry of the EM wave. However, because the static magnetic field breaks the symmetry of the EM wave in the system, the electron can absorb the wave energy and be efficently accelerated in the direction of the electic component of the of the EM wave. We have obtained the optimal magnitude for the static magnetic field and the final γ by a simple analysis.The single particle analyses and the simulations also show that this system ones well for a high-energy electron acceleration and the simulation results agree with the analytical results.

A half-mini beta optics is studied for a warm dense matter science facility in KEK. The irradiation onto a target at a small focal spot (< a few mm) with a short pulse duration (~100 nsec) is required. The final focus is carried out through a half-mini beta beamline placed after the kickout from the 500 MeV Booster improved. The space charge effect is evaluated for the beamline in the high current beam. The beam optics concerned with the effects of space charge and a large momentum spread during the half-mini beta system is investigated for the study of the warm dense matter science in KEK.