[en] The development of continuous pumping to the target system is an important issue for realizing an x-ray laser with the high repetition rate. We have developed a 13.9 nm XRL using a silver tape target and demonstrated a highly coherent XRL with an oscillator-amplifier configuration using two tape target systems and the TOPAZ laser system with a 10-J and a 0.1-Hz repetition rate. The output energy is comparable to the x-ray laser generated with a silver-deposited slab target, and the pointing stability using the new tape target system is better than conventional slab target. (author)

[en] A computed tomography (CT) system using high-energy monochromatic photons is one of the best choices for non-destructive tests, to detect flaws or defects in manufactured items for the purpose of improving quality control and quality assurance. We have developed such a CT system based on laser-Compton X-rays, which were generated with an electron accelerator and a laser beam. An experimental study for a CT measurement for non-destructive tests of concrete specimens using laser-Compton X-rays were performed. We successfully obtained CT images. (author)

[en] We have demonstrated a spatially coherent 13.9 nm laser with submicroJoule output energy using a double-target geometry with a new driver system. The new driver was a chirped-pulse amplification laser with zigzag slab Nd:glass power amplifiers providing two beams with an energy of 10 J and picosecond duration at a shot rate of 0.1 Hz. The obtained 13.9 nm laser pulse with 10¹⁰ coherent photons will enable us to carry out single-shot pump-probe observation of nonperiodic ultrafast phenomena. (author)

[en] A highly coherent 13.9 nm x-ray laser (XRL) is generated under an oscillator-amplifier configuration using a new tape target system and a driver laser system with a 0.1 Hz repetition rate. The output energy is comparable to the XRL generated with a silver-deposited slab target, and the pointing stability using the new tape target system is better than conventional slab targets.

[en] To study the interactions between picosecond soft x-ray laser (SXRL) beams and material surfaces, aluminum (Al), gold (Au), copper (Cu), and silicon (Si) surfaces were irradiated with SXRL pulses. Following irradiation, the surfaces of the substrates were observed using a scanning electron microscope and an atomic force microscope. The surface modifications caused by the SXRL beam were clearly seen. With single pulse irradiation, the ablation holes and the conical structures were formed on the Al surface, and the ripple-like structures were formed on the Au and Cu surfaces. On the Si surface, deep holes that seemed to be melted structures induced by the accumulation of multiple pulses of irradiations were found. Therefore, it was concluded that SXRL beam irradiation of various material surfaces causes different types of surface modifications, and the changes in the surface behaviors are attributed to the differences in the elemental properties, such as the attenuation length of x-ray photons. (author)

[en] The ⁸⁰Se(γ, n)⁷⁹Se cross section was measured with laser-Compton scattering (LCS) γ-rays to supply fundamental data for the estimation of the inverse reaction cross sections, i.e., the ⁷⁹Se(n, γ)⁸⁰Se cross section. An enriched ⁸⁰Se sample and a reference ¹⁹⁷Au sample were irradiated with LCS γ-rays whose maximum energy was varied from 10.5 to 16.0 MeV. The energy distributions of LCS γ-rays were precisely determined using a high-resolution high-energy photon spectrometer (HHS). Emitted neutrons were detected by a high-efficiency 4π-³He detector. The excitation function of the ⁸⁰Se(γ, n) cross section was determined for the energy range of 10.2-14.6 MeV. The energy point corresponding to each cross section was deduced using the accurately determined energy distribution of LCS γ-rays. (author)

[en] It was demonstrated that high-energy quasi-monochromatic photon beam was useful in CT for industrial NDT of large concrete specimens. Cross sectional images of the specimens as large as 2 m in diameter was possible. Cracks of 0.2 mm in width 5 mm below the surface of the specimen was observed with the present method. Coarse aggregates and mortars were clearly distinguished. Cupping artifacts were not seen in these results. However, the image quality was rather poor due to a low photon intensity. We must increase the intensity of the photon beam or spend a longer time for a measurement to apply the present method in practical NDT. The linear attenuation coefficient and the average density of concrete was 0.05 cm^-1 for 10 MeV photons and 2.3 g/cm³, respectively. Assuming densities of mortar and coarse aggregates of approximately 2.2 g/cm³ and 2.7 g/cm³, the difference of the linear attenuation coefficients for those two materials is calculated to be 0.01 cm^-1. Because the low-contrast resolution of the present CT system was measured to be 7.4x10^-3 cm^-1, it is understood that the difference was detectable as is shown in Figs. 6 and 7. We plan to use the CT system for a precise NDT of homogeneity, voids, crack and defects in sintered materials, die-casts, concrete and carbon/metal composites. Enhancements of photon yield is being planed using a higher-intensity laser and a state-of-the-art technique of an electron accelerator. Feasibility study to build a compact LCS source using a compact electron storage ring and an injector linac, which can be carried by a trailer is also being performed. These results will be discussed in the next paper. (author)

[en] Soft x-ray microscopes operating in the water window region are capable of imaging living hydrated cells. Up to now, we have been able to take some soft x-ray images of living cells by the use of a contact x-ray microscope system with laser produced plasma soft x-ray source. Since the soft x-ray images are different from the optical images obtained with an ordinary microscope, it is very important to identify what is seen in the x-ray images. Hence, we have demonstrated the direct comparison between the images of organelles obtained with a fluorescence microscope and those with a soft x-ray microscope. Comparing the soft x-ray images to the fluorescence images, the fine structures of the organelles could be identified and observed. (author)

[en] The photon mass attenuation coefficients of the important materials for γ-ray detection, Ge and BGO (Bi₄Ge₃O₁₂) crystals, have been measured for 10.0 MeV γ-rays. The measurement system using the laser-Compton backscattering γ-rays and the high-resolution high-energy photon spectrometer has been developed and utilized. The effectiveness of the system achieving the total systematic uncertainties of 0.5% for the measurements of the photon mass attenuation coefficients was demonstrated. It was shown that the measured photon mass attenuation coefficients, 318.1±1.7 [cm²/g] for the Ge crystal and 425.2±2.4 [cm²/g] for the BGO crystal, agree within the achieved experimental uncertainties with the evaluated values including atomic and nuclear processes at 10.0 MeV. (author)

[en] The spatial resolution of hydrothermal method grown zinc oxide (ZnO) scintillator was evaluated using x-ray laser focused with Fresnel zone plate. The fluorescence image of the ZnO scintillator was measured to be less than 10 μm using CCD camera coupled with a Schbartzchild expander mirror. The availability of large size ZnO crystal up to 3-inch is quite attractive for future lithography and imaging applications. (author)