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We developed an optically synchronized highly stable frequency-doubled Nd:YAG laser with sub-nanosecond pulse duration. The 1064 nm seed pulses generated by soliton self-frequency shift in a photonic crystal fiber from Ti:sapphire oscillator pulses were stabilized by controlling input pulse polarization. The seed pulses were amplified to 200 mJ by diode-pumped amplifiers with a high stability of only

Atomically thin graphene is a transparent, highly electrically and thermally conductive, light-weight, and the strongest material. To date, graphene has found applications in many aspects including transport, medicine, electronics, energy, defense, and desalination. We demonstrate another disruptive application of graphene in the field of laser-ion acceleration, in which the unique features of graphene play indispensable role. Laser driven ion sources have been widely investigated for pure science, plasma diagnostics, medical and engineering applications. Recent developments of laser technologies allow us to access radiation regime of laser ion acceleration with relatively thin targets. However, the thinner target is the less durable and can be easily broken by the pedestal or prepulse through impact and heating prior to the main laser arrival. One of the solutions to avoid this is plasma mirror, which is a surface plasma created by the foot of the laser pulse on an optically transparent material working as an effective mirror only for the main laser peak. So far diamond like carbon (DLC) is used to explore the ion acceleration in extremely thin target regime (< 10 nm) with plasma mirrors, and it is necessary to use plasma mirrors even in moderately thin target regime (10-100 nm) to realize energetic ion generation. However, firstly DLC is not 2D material, and therefore, it is very expensive to make it thin and flat. Moreover, graphene is stronger than diamond at extremely thin regime, and much more reasonable for mass-production. Furthermore, installing and operating plasma mirrors at high repetition rate is also costly. Here we show another direct solution using graphene as the thinnest and strongest target ever made. We develop a facile transfer method to fabricate large-area suspended graphene (LSG) as target for laser ion acceleration with precision down to a single atomic layer. Direct irradiation of the LSG targets with an ultra intense laser generates energetic carbons and protons evidently showing the durability of graphene without plasma mirror. This extends the new frontier of science on graphene under extreme electromagnetic field, such as energy frontier and nuclear fusion.

We have experimentally improved the temporal contrast of the petawatt J-KAREN-P laser facility. We have investigated how the generation of pre-pulses by post-pulses changes due to the temporal overlap between the stretched pulse and the post-pulse in a chirped-pulse amplification system. We have shown that the time at which the pre-pulse is generated by the post-pulse and its shape are related to the time difference between the stretched main pulse and the post-pulse. With this investigation, we have found and identified the origins of the pre-pulses and have demonstrated the removal of most pre-pulses by eliminating the post-pulse with wedged optics. We have also demonstrated the impact of stretcher optics on the picosecond pedestal. We have realized orders of magnitude enhancement of the pedestal by improving the optical quality of a key component in the stretcher.

We demonstrate the removal of the pre-pulses based on the exploration of the generation of pre-pulses by post-pulses through the nonlinear process associated with the B-integral in the laser chain of the petawatt facility J-KAREN-P.

Ultra-high intensity femtosecond lasers have now become excellent scientific tools for the study of extreme material states in small-scale laboratory settings. The invention of chirped-pulse amplification (CPA) combined with titanium-doped sapphire (Ti:sapphire) crystals have enabled realization of such lasers. The pursuit of ultra-high intensity science and applications is driving worldwide development of new capabilities. A petawatt (PW = 1015 W), femtosecond (fs = 10&minus, 15 s), repetitive (0.1 Hz), high beam quality J-KAREN-P (Japan Kansai Advanced Relativistic ENgineering Petawatt) Ti:sapphire CPA laser has been recently constructed and used for accelerating charged particles (ions and electrons) and generating coherent and incoherent ultra-short-pulse, high-energy photon (X-ray) radiation. Ultra-high intensities of 1022 W/cm2 with high temporal contrast of 10&minus, 12 and a minimal number of pre-pulses on target has been demonstrated with the J-KAREN-P laser. Here, worldwide ultra-high intensity laser development is summarized, the output performance and spatiotemporal quality improvement of the J-KAREN-P laser are described, and some experimental results are briefly introduced.

High power laser systems are an attractive driver for compact energetic ion sources. We demonstrate repetitive acceleration at 0.1 Hz of proton beams up to 40 MeV from a reeled tape target irradiated by ultra-high intensities up to 5 × 1021 Wcm − 2 and laser energies ≈ 15 J using the J-KAREN-P laser system. We investigate the stability of the source and its behaviour with laser spot focal size. We compare the scaling of proton energy with laser energy to a recently developed analytical model, and also demonstrate that it is possible to reach energies up to 50 MeV on a single shot with a lower laser energy ≈ 10 J by using a thinner target, motivating development of high repetition targetry suitable for thinner targets.

The interaction of high-intensity laser pulses with solid targets can be used as a highly charged, energetic heavy ion source. Normally, intrinsic contaminants on the target surface suppress the performance of heavy ion acceleration from a high-intensity laser&ndash, target interaction, resulting in preferential proton acceleration. Here, we demonstrate that CW laser heating of 5 &micro, m titanium tape targets can remove contaminant hydrocarbons in order to expose a thin oxide layer on the metal surface, ideal for the generation of energetic oxygen beams. This is demonstrated by irradiating the heated targets with a PW class high-power laser at an intensity of 5 &times, 1021 W/cm2, showing enhanced acceleration of oxygen ions with a non-thermal-like distribution. Our new scheme using a CW laser-heated Ti tape target is promising for use as a moderate repetition energetic oxygen ion source for future applications.

The importance of heat-resistant optics is increasing together with the average power of high-intensity lasers. A silicon carbide (SiC) ceramic with high thermal conductivity is proposed as an optics substrate to suppress thermal effects. The temperature rise of the substrate and the change in the surface accuracy of the mirror surface, which degrades the laser beam quality, are investigated. Gold mirrors on synthetic fused silica and SiC ceramic substrates are heated with a 532 nm wavelength laser diode. The synthetic fused silica substrate placed on an aluminum block shows a temperature increase by ~32 &deg, C and a large temperature gradient. In contrast, the SiC ceramic substrate shows a uniform temperature distribution and a temperature increase of only ~4 &deg, C with an absorbed power of ~2 W after 20 min laser irradiation. The surface accuracy (roughness) when using the synthetic fused silica substrate changes from /21.8 (29.0 nm) to /7.2 (88.0 nm), increasing by a factor of ~3.0. However, that of the SiC ceramic substrate changes from /21.0 (30.2 nm) to /13.3 (47.7 nm), increasing by only a factor of ~1.6. Based on these experimental results, detailed considerations and calculations of actively cooled SiC ceramic substrates for high-average-power laser systems are also discussed.

We report on femtosecond petawatt laser pulses at 0.1 Hz that combine both Ti:sapphire chirped-pulse amplification (CPA) and optical parametric CPA (OPCPA) techniques. High temporal contrast of 1012 prior to the main pulse of 10 J output energy has been demonstrated with a cleaned high-energy seeded low gain OPCPA preamplifier. Intensities as high as 1022 W∕cm2 on target have been achieved by focusing a wave-front corrected 0.3 PW laser by adaptive optics and reflective-type optics with an f ∕1.3 off-axis parabolic mirror. We describe the origins of the pre-pulses generated by the post-pulses through non-linear processes and demonstrate the removal of the pre-pulses by switching to optical components with a small wedge angle at our petawatt laser facility. We also briefly introduce some experimental results. Exploration of new regimes in high field science is now possible with the unprecedented laser intensity levels of the J-KAREN-P laser.

We report the generation of 63 J of broadband pulse energies at 0.1 Hz from the J-KAREN-P laser, which is based on an OPCPA/Ti:sapphire hybrid architecture. Pulse compression down to 30 fs indicates a peak power of over 1 PW. High temporal contrast of 1012 prior to the main pulse has been demonstrated with 10 J output energy. High intensities of 1022 W/cm2 on target by focusing a 0.3 PW laser with an f/1.3 off-axis parabolic mirror have been achieved. Fundamental processes of laser matter interaction at over 1022 W/cm2 intensities belong to a new branch of science that will be the principal research task of our infrastructure.

The goal of LIPAc (Linear IFMIF Prototype Accelerator) is to achieve a 125 mA, 9 MeV, CW (continuous wave, i.e. 100% duty cycle) deuteron beam with an average beam power of 1.125 MW. In the beam current measurement, it is considered that calorimetric measurement is advantageous for high current and CW operations since it is not subject to secondary electrons, etc. In calorimetric measurements, it is necessary to measure the temperature rise of the cooling water as accurately as possible. We applied this method to LIPAc proton beams at the Beam Stop unit. In order to check the reliability, we inserted a heater in the cooling loop as a heat source and obtained correlation between the applied and measured power, which was found to be 1.0. Moreover, using this heater, accuracy of this measurement with respect to the flow rate of the cooling water was investigated. Due to heat transfer and the fluctuations of water temperature, etc., there is a range of flow rates in which the measurement error can be minimized with our calorimetric measurement system.

In the present report, we discussed our recent results concerning the investigations of high energy density matter. By using of high-resolution X-ray spectroscopic measurements and kinetic simulations, we demonstrate that the energy of femtosecond laser pulses is efficiently converted to X-ray radiation and produces exotic states in solid density plasma regions. It is shown that exotic hollow multicharged ions states can be obtained and studied not only by ultra-intense X-ray radiation of XFEL lasers, but also upon using optical laser technology. We have concluded that observable features of the hollow-ion spectra are sensitive to such plasma parameters as density, temperature, hot-electron fraction, and intensity of the X-ray pumping radiation and could be used for effective diagnostics of warm dense matter parameters.

We modified a soft X-ray laser (SXRL) interferometer synchronized with a Ti:sapphire laser to observe a single-shot image of the nanoscale structure dynamics of materials induced by an optical laser pulse. The lateral resolution on the sample surface was improved to 0.7 μm using precise imaging optics. Using this system, we succeeded in observing thin film structures above the solid (or liquid) surface in the femtosecond laser ablation process of metals (Au). The thin film worked as soft X-ray beam splitter. This result shows a thin film was smooth and dense (with a roughness of a few nanometers and near sold density). Furthermore, it gave rise to the possibility of generating novel transient soft X-ray optics .

Heterodyne optical phase-locked loop assisted by sum-frequency and second-harmonic generation for non-degenerate phase-sensitive optical amplifier repeaters is proposed. Experiment of offset pump phase-locking to 5-Gbit/s BPSK phase-conjugated twin waves is successfully achieved by our method.

Experimental studies on the formation of highly charged ions of medium-Z elements using femtosecond laser pulses with different contrast levels were carried out. Multiply charged Fe ions were generated by laser pulses with 35 fs duration and an intensity exceeding 1021 W/cm2. Using high-resolution X-ray spectroscopic methods, bulk electron temperature of the generated plasma has been identified. It is shown that the presence of a laser pre-pulse at a contrast level of 105–106 with respect to the main pulse drastically decreases the degree of Fe ionization. We conclude that an effective source of energetic, multiply charged moderate and high-Z ions based on femtosecond laser–plasma interactions can be created only using laser pulses of ultra-high contrast.

The Linear IFMIF (International Fusion Materials Irradiation Facility) Prototype Accelerator (LIPAc) is aiming at demonstrating the low energy section of a 40 MeV/125 mA IFMIF deuteron accelerator up to 9 MeV with a full beam current in cw operation. For such a high-power beam, the LIPAc injector is required to produce a 100 keV D+ beam with 140 mA and match it for injection into the Radio Frequency Quadrupole (RFQ) accelerator. The injector is designed by CEA-Saclay based on the high intensity light ion source (SILHI). In 2019, the commissioning of the RFQ to demonstrate the D+ beam acceleration at a low duty cycle (0.1%) was conducted. A nominal beam current of 125 mA D+ beam was accelerated up to 5 MeV through the RFQ successfully. The LIPAc injector fully satisfied the requirements for RFQ beam commissioning at the pulse mode.

During the EVEDA (engineering validation and engineering design activities) phase of the International Fusion Materials Irradiation Facility (IFMIF) project, a 125 mA/9 MeV linear prototype accelerator (LIPAc) has to be built, tested and operated in Rokkasho-mura (Japan). Involved in this project for several years, CEA-Saclay designed the injector of this accelerator which is composed of an electron cyclotron resonance ion source, delivering a 140 mA deuteron beam at 100 keV, and a low energy beam transport (LEBT) line to match the beam for the injection into the radio-frequency quadrupole. In this paper, the components of the LIPAc injector are described. The commissioning of the ion source and LEBT with beam started in November 2014. The different phases of the commissioning are explained and some noticeable experimental results obtained with a beam at 100 keV are presented.

In this paper, an optical phase-locked loop assisted by sum-frequency and second-harmonic generation (SS-OPLL) for frequency nondegenerate optical parametric phase-sensitive amplifier repeaters is experimentally demonstrated. First, theoretical derivations show that carrier extraction from phase-conjugated twin waves (PCTWs) and reference light generation are achieved by sum-frequency generation; therefore, the SS-OPLL circuit enables optical phase locking between PCTWs and a pump wave by a simple architecture based on a balanced OPLL. Then, optical phase locking between 20-Gbit/s quadrature phase-shift keying PCTWs and an individual pump source is experimentally demonstrated. Experimental results indicate that phase errors were reduced during the SS-OPLL operation.

The authors have demonstrated an optical parametric chirped-pulse amplification (OPCPA)/Yb:YAG ceramic thin disk hybrid laser system having hundred mJ level pulse energy sub-picosecond pulse duration with high temporal contrast. At an input chirped-pulse energy of 3.8 mJ from an OPCPA preamplifier an output energy of 130 mJ has been generated from multipass diode-pumped Yb:YAG ceramic thin disk amplifier. A recompressed pulse duration of 450 fs with a contrast level of less than 7.2×10−9 at −150 ps before the main pulse has been obtained. The contrast level is the highest value achieved in Yb:YAG chirped-pulse amplification (CPA) laser system at 100 mJ level.

We investigated the high intensity plasma generated by using a Nd:YAG laser to apply a laser-produced plasma to the direct plasma injection scheme. The capability of the source to generate high charge state ions strongly depends on the power density of the laser irradiation. Therefore, we focused on using a higher power laser with several hundred picoseconds of pulse width. The iron target was irradiated with the pulsed laser, and the ion current of the laser-produced iron plasma was measured using a Faraday cup and the charge state distribution was investigated using an electrostatic ion analyzer. We found that higher charge state iron ions (up to Fe(21+)) were obtained using a laser pulse of several hundred picoseconds in comparison to those obtained using a laser pulse of several nanoseconds (up to Fe(19+)). We also found that when the laser irradiation area was relatively large, the laser power was absorbed mainly by the contamination on the target surface.

We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 1021 W/cm2 is efficiently converted to X-ray radiation, which is emitted by “hot” electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E4–5 of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~1017 W/cm2, there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. Femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies and radiography of biological systems.

Dependence of the energy of ions accelerated during interaction of the laser pulse obliquelly incident on the thin foil target on the laser polarization is studied experimentally and theoretically. We found that the ion energy being maximal for the p-polarization gradually decreases when the pulse becomes s-polarized. The experimentally found dependences of the ion energy are explained by invoking the anomalous electron heating which results in high electrostatic potential formation at the target surface. Anomalous heating of electrons beyond the energy of quiver motion in the laser field is described within the framework of theoretical model of driven oscillator with a step-like nonlinearity. We have demonstrated that the electron anomalous heating can be realized in two regimes: nonlinear resonance and stochastic heating, depending on the extent of stochasticity. We have found the accelerated ion energy scaling determined by the laser intensity, pulse duration, polarization angle and incident angle.

Experimental demonstration of multi-charged heavy ion acceleration from the interaction between the ultra-intense short pulse laser system and the metal target is presented. The laser pulse of

The dependence of the lasing conditions of fast-capillary-discharge plasmas on the initial plasma parameters has been experimentally investigated. The results show that there is an optimum initial condition for lasings and that the initial condition is an important factor for high-energy lasing using capillary plasmas. The experimental results also indicate that the variation in lasing power can be correlated with the electron density of the initial plasmas.

We report about nonlinear growth of x-ray emission intensity emitted from plasma generated by femtosecond petawatt laser pulses irradiating stainless steel foils. X-ray emission intensity increases as ~ I 4.5 with laser intensity I on a target. High spectrally resolved x-ray emission from front and rear surfaces of 5 μm thickness stainless steel targets were obtained at the wavelength range 1.7–2.1 A, for the first time in experiments at femtosecond petawatt laser facility J-KAREN-P. Total intensity of front x-ray spectra three times dominates to rear side spectra for maximum laser intensity I ≈ 3.2×1021 W/cm2. Growth of x-ray emission is mostly determined by contribution of bremsstrahlung radiation that allowed estimating bulk electron plasma temperature for various magnitude of laser intensity on target.

We report on the spectra of x-rays emitted from dense plasma generated via irradiation of thin stainless steel foils by ultra-relativistic femtosecond laser pulses (intensities ~3 × 10^21 W/cm^2). Kinetic modelling was used to estimate electron plasma density and temperature, demonstrating Te ~2.1 keV for Ne ~5 × 10^22 cm^−3 in the hottest emission region. Thus, it is experimentally demonstrated for the first time that the laser pulse of over 10^21 W/cm^2 intensity is absorbed neither in the solid density plasma nor in a pre-plasma of a common critical density, but in the matter of so called relativistic critical density.

In this work we report the successful implementation of plasma mirror (PM) technology on an LFEX laser facility at the Institute of Laser Engineering, Osaka University. The LFEX laser pulse was successfully refocused at the target chamber center (TCC) by means of a spherical plasma mirror, resulting in 5 × 1018 W cm−2 laser intensity, with 45% reflectivity at a laser flux of about 90 J cm−2 on the PM. Experimental results show stable focusing and pointing of the LFEX pulse after PM refocusing. The contrast improvement was demonstrated by both cooler fast electron slope temperature distribution as well as by the ability to shoot sub-µm plastic foils obtaining proton beams with maximum energy exceeding 20 MeV. Experimental results are qualitatively reproduced by 2D particle in cell simulations.

Flyer acceleration experiments are carried out using a KrF laser system with a pulse duration of 10–15 ns and an intensity of ∼1.0 × 1013 W/cm2. Three-layered targets (aluminum–polyimide–tantalum) are used. First, an average velocity of laser-driven tantalum flyers with a thickness of 4 and 8 μm is estimated. Then, in a collision of a flyer with a copper layer attached to a diamond plate, we measure a transit time of a shock wave in the diamond. The impact velocity is estimated based on the transit time and a numerical simulation. This numerical simulation also shows that the initial peak pressure caused by the impact of a 4-μm-thick flyer is kept at 11 Mbar for 12–13 μm in thickness. Finally, whether this thickness is enough for EOS measurements is discussed.

This paper reviews recent progress in the source development of intense coherent x-rays and the applications in the research fields such as material science and laser processing in Japan Atomic Energy Agency (JAEA). In the source development, the polarization of the fully spatial coherent 13.9 nm soft x-ray laser (SXRL) in the transient collisional excitation (TCE) scheme was investigated experimentally. The result indicated that the SXRL beam was strongly polarized in the direction perpendicular to the target surface. In the alternative schemes toward the short wavelength region, intense higher-order harmonics with the photon energy of more than 300 eV was observed from a relativistic plasma generated with the laser intensity higher than 1018 W/cm2. In the applications of the 13.9 nm TCE laser, we observed temporal evolution of surface distortion of Pt sample pumped by a 80 fs optical pulse by use of x-ray laser interferometer using double Lloyd’s mirrors and reflectometer. In the study of SXRL ablation, the melting depth of the substances using single shot SXRL exposure was measured, and the result was quantitatively consistent with the calculated result based upon the spallative ablation model by molecular-dynamics code.

Almost fully stripped aluminum ion acceleration up to 12 MeV/u from the interaction between the ultra-intense short pulse high contrast laser and the micrometer thick foil target is presented.

A detailed mathematical model is presented for a submicron-sized cluster formation in a binary gas mixture flowing through a three-staged conical nozzle. By measuring the angular distribution of light scattered from the clusters, the size of CO(2) clusters, produced in a supersonic expansion of the mixture gas of CO(2)(30%)/H(2)(70%) or CO(2)(10%)/He(90%), has been evaluated using the Mie scattering method. The mean sizes of CO(2) clusters are estimated to be 0.28 ± 0.03 μm for CO(2)/H(2) and 0.26 ± 0.04 μm for CO(2)/He, respectively. In addition, total gas density profiles in radial direction of the gas jet, measuring the phase shift of the light passing through the target by utilizing an interferometer, are found to be agreed with the numerical modeling within a factor of two. The dryness (= monomer/(monomer + cluster) ratio) in the targets is found to support the numerical modeling. The apparatus developed to evaluate the cluster-gas targets proved that our mathematical model of cluster formation is reliable enough for the binary gas mixture.

We demonstrate a new ion diagnosis method for high energy ions by utilizing a combination of a single CR-39 detector and plastic plates, which enables to detect high energy ions beyond the detection threshold limit of the CR-39. This detection method coupled with a magnetic spectrometer is applied to identify high energy ions of 50 MeV per nucleon in laser-driven ion acceleration experiments using cluster-gas targets.

This paper presents the experimental investigation of laser-driven proton acceleration using a table top Ti:Sapphire laser system interacting with the thin-foil targets during the course of medical application of the laser-driven proton beam. The proton beam with maximum energy of upto 14~MeV is generated in 60 TW mode. The number of protons at ~10 MeV is estimated to be over 105 proton/sr/MeV/shot with beam having half divergence angle of 5~degree. If 10 Hz operation is assumed 2 Gy dose is possible to irradiate during 10 min onto a ~1 mm tumor just under the skin. In contrast to the previous condition of our apparatus with which we demonstrated the DNA double-strand breaking by irradiating the laser-driven proton beam onto the human cancer cells in-vitro test, the result reported here has significant meaning in the sense that pre-clinical in-vivo test can be started by irradiating the laser-driven proton beam onto the skin of the mouse, which is unavoidable step before the real radiation therapy.

Human cancer cells are irradiated by laser-driven quasi-monoenergetic protons. Laser pulse intensities at the 5×10 19 -W/cm 2 level provide the source and acceleration field for protons that are subsequently transported by four energy-selective dipole magnets. The transport line delivers 2.25 MeV protons with an energy spread of 0.66 MeV and a bunch duration of 20 ns. The survival fraction of in-vitro cells from a human salivary gland tumor is measured with a colony formation assay following proton irradiation at dose levels up to 8 Gy, for which the single bunch does rate is 1 × 10 7 Gy/s and the effective dose rate is 0.2 Gy/s for 1-Hz repetition of irradiation. Relative biological effectiveness at the 10% survival fraction is measured to be 1.20 ± 0.11 using protons with a linear energy transfer of 17.1 ± 2.8 keV/μm.

Yb:YAG CPA have a potential to develop a compact, high peak power at high repetition rates. For high energy pulses of short duration Yb:YAG regenerative amplifiers have mainly been studied for which significant prepulse and amplified spontaneous emission (ASE). In laser proton acceleration studies it is very important to suppress the prepulse and ASE levels, because a preplasma is generated before the peak of the laser pulse, therefore the maximum proton energy is limited. To overcome this problem, the OPCPA can efficiently provide high gain for the main pulse while suppressing prepulse amplification. Here we have first demonstrated a hundred mJ level, femtosecond of an OPCPA/Yb:YAG hybrid laser system with a contrast level of 10−9 at −150 ps.

We present substantial enhancement of the accelerated ion energies up to 10–20 MeV per nucleon by utilizing the unique properties of the cluster-gas target irradiated with 40-fs laser pulses of only 150 mJ energy, corresponding to approximately tenfold increase in the ion energies compared to previous experiments using thin foil targets. A particle-in-cell simulation infers that the high energy ions are generated at the rear side of the target due to the formation of a strong dipole vortex structure in subcritical density plasmas. The demonstrated method can be important in the development of efficient laser ion accelerators for hadron therapy and other applications.

In a laser ion source, plasma drift distance is one of the most important design parameters. Ion current density and beam pulse width are defined by plasma drift distance between a laser target and beam extraction position. In direct plasma injection scheme, which uses a laser ion source and a radio frequency quadrupole linac, we can apply relatively higher electric field at beam extraction due to the unique shape of a positively biased electrode. However, when we aim at very high current acceleration such as several tens of milliamperes, we observed mismatched beam extraction conditions. We tested three different ion current at ion extraction region by changing plasma drift distance to study better extraction condition. In this experiment, C(6+) beam was accelerated. We confirmed that matching condition can be improved by controlling plasma drift distance.

Ion species ratio of high current positive hydrogen/deuterium ion beams extracted from an electron-cyclotron-resonance ion source for International Fusion Materials Irradiation Facility accelerator was measured by the Doppler shift Balmer-α line spectroscopy. The proton (H(+)) ratio at the middle of the low energy beam transport reached 80% at the hydrogen ion beam extraction of 100 keV/160 mA and the deuteron (D(+)) ratio reached 75% at the deuterium ion beam extraction of 100 keV/113 mA. It is found that the H(+) ratio measured by the spectroscopy gives lower than that derived from the phase-space diagram measured by an Allison scanner type emittance monitor. The H(+)/D(+) ratio estimated by the emittance monitor was more than 90% at those extraction currents.

The transient lattice deformation of laser-shocked silicon single crystal was studied by picosecond time-resolved X-ray diffraction with laser plasma X-rays. The shock-recovered samples were evaluated by reciprocal space mapping.

The dependence of the lasing condition of fast capillary discharge plasmas on the initial plasma parameters has been experimentally investigated. The results show that there is an optimum initial condition for lasings. The experimental results also indicate that the variation of lasing power can be correlated with the electron density of the initial plasmas and that the initial condition is an important factor for obtaining larger laser energy using capillary discharges.

Kα line emissions from Mo and Ag plates were experimentally studied using clean, ultrahigh-intensity femtosecond laser pulses. The absolute yields of Kα x-rays at 17 keV from Mo and 22 keV from Ag were measured as a function of the laser pulse contrast ratio and irradiation intensity. Significantly enhanced Kα yields were obtained for both Mo and Ag by employing high contrast ratios and irradiances. Conversion efficiencies of 4.28 × 10−5 /sr for Mo and 4.84 × 10−5 /sr for Ag, the highest values obtained to date, were demonstrated with contrast ratios in the range 10−10 to 10−11.