[en] Japan Atomic Energy Research Institute (JAERI) was qualified, in January 2003, as a member of the IAEA network analytical laboratories (NWALs) for particle and bulk analyses of safeguards environmental samples. The particle analysis gives more detailed information on nuclear facility operation than the bulk analysis because the isotope ratios of nuclear materials in the samples collected inside nuclear facilities (swipe samples) can be determined for individual particles. We applied secondary ion mass spectrometry (SIMS) to the uranium isotope ratio measurement for particle analysis. Prior to the SIMS analysis, the particles in a swipe sample are recovered onto a carrier by impaction. The carriers with the recovered particles are then screened by total reflection X-ray fluorescence spectrometry. We integrated these techniques into a standard procedure, which is applied to domestic and IAEA swipe samples routinely. For the analysis of the particles with the diameter smaller than 1 μm, with which the SIMS has insufficient sensitivity, we are developing a more sensitive method, the combination of fission track detection and thermal ionization mass spectrometry. (author)

[en] In the development of high quality and large laser crystals suitable for ultra high peak power CPA (Chirped Pulse Amplification) laser systems, a non-destructive method is essential to detect micro defects occurring in the crystal growth. A laser tomography method is devised and applied to measure micro defect density in different types of optical materials such as silicate glass, YAG crystal, sapphire crystals, and Ti:sapphire laser crystals. As a result, the accurate densities of micro defects are measured in four different samples: 2 x 10¹⁰/cm³ for a silicate glass: 5 x 10⁷/cm³ for a YAG; 1 x 10⁸/cm³ for a sapphire; 1 x 10¹⁰/cm³ for Ti:sapphire crystals, respectively. We also measure the defect densities in Ti:sapphire with different doped concentrations. The results show that measured defect densities increase in proportion to the doped concentration. (author)

[en] In developments of high quality and large laser crystals suitable for ultra high peak power CPA (Chirped Pulse Amplification) laser systems, non-destructive method is absolutely essential to detect micro defects occurred in the crystal growth. A laser tomography method was devised and applied to measure micro defect density in different types of optical materials such as silicate glass, YAG crystal, sapphire crystals, and Ti:sapphire laser crystals. To ensure accurate measurement of scattering signals generated from micro defects by a probe laser, several data handling techniques were used: (1) background noise reduction in a CCD camera; (2) data correction taking into account of optical absorption of samples; (3) normalization of scattering signal; (4) a signal enhancement based on a binary-bit-pattern operational method. As a result, the accurate densities of micro defects were measured in four different samples: 2x10¹⁰/cm³ for a silicate glass: 5x10⁷/cm³ for a YAG; 1x10⁸/cm³ for a sapphire; 1x10¹⁰/cm³ for Ti:sapphire crystals. We also measured the defect densities in Ti:sapphire with different doped concentrations. The results showed that measured defect densities increased in proportion to the doped concentration. In successive measurements of the defect in Ti:sapphire crystals produced by several types of crystal growth methods, a crystal grown by HEM (Heat Exchange Method) had the smallest defect density of 6.4x10⁸/cm³, over one order magnitude smaller than those in any other crystals. (author)

[en] Laser crystals doped with ytterbium trivalent ions are of interest for the development of advanced high-peak power lasers. To evaluate the spectroscopic properties of the crystals, we established a photo-luminescence system and measured absorption spectrum under cold ambient in three different laser crystals (Yb:YLF, Yb:CaF₂, Yb:YCOB) doped with Yb³⁺ ions. We also consider the spectroscopic properties with the crystal-field theory. (author)

[en] Direct bonding without the use of adhesives was demonstrated on Ti:sapphire laser crystals with a bonding surface of 12 mm x 6 mm and the bonded region was evaluated from the macroscopic to the atomic level by three different methods. Wavefront distortion caused by the bonded region of 10 mm x 5 mm was estimated at 0.031 wavelengths (λ) at 633 nm. Micro defect measurements by a laser tomography method showed that the number of micro defects on the bonded region were much smaller than that of the intrinsic ones inside the crystal. From a magnified inspection, atoms in the bonded region were well arranged with the same regularity as inside the crystal. In addition, we discussed reasons of ion distribution around the bonded interface measured by quantitative EDX analysis for three elements composed of Ti:sapphire crystal. (author)

[en] Laser crystal integration using a neodymium-doped yttrium vanadate (or orthovanadate) laser crystal, and non-doped yttrium vanadate crystals that function as cold fingers has been demonstrated. A newly developed dry etching process was adopted in the preparation for contact of mechanically polished surfaces. In the heat treatment process, temperature optimization was essential to get rid of precipitation of vanadic acid caused by the thermo-chemical reaction in a vacuum furnace. The bonded crystal was studied via optical characteristics, magnified inspections, laser output performances pumped by a CW laser diode. From these experiments, it was clear that the integrated Nd:YVO₄ laser crystal, securing the well-improved thermal conductivity, can increase laser output power nearly twice that of the conventional single crystal which was cracked in high power laser pumping of 10 W due to its intrinsic poor thermal conductivity. (author)

[en] A new particle recovery method and a sensitive screening method were developed for subsequent isotope ratio analysis of uranium particles in safeguards swipe samples. The particles in the swipe sample were recovered onto a carrier by means of vacuum suction-impact collection method. When grease coating was applied to the carrier, the recovery efficiency was improved to 48±9%, which is superior to that of conventionally-used ultrasoneration method. Prior to isotope ratio analysis with secondary ion mass spectrometry (SIMS), total reflection X-ray fluorescence spectrometry (TXRF) was applied to screen the sample for the presence of uranium particles. By the use of Si carriers in TXRF analysis, the detection limit of 22 pg was achieved for uranium. By combining these methods with SIMS, the isotope ratios of ²³⁵U/²³⁸U for individual uranium particles were efficiently determined. (author)

[en] JAEA has been developing, under the auspices of the Ministry of Education, Culture, Sports, Science and Technology of Japan, analytical techniques for ultra-trace amounts of nuclear materials in the environmental samples in order to contribute to the strengthened safeguards system. In January 2003, JAEA was qualified as a member of the IAEA Network Analytical Laboratories (NWAL) for environmental sample analysis. Since then, JAEA has conducted the analysis of domestic and the IAEA samples. Two techniques, bulk and particle analyses, are available for the environmental samples and the latter method generally provides more detailed information about history of nuclear materials in a facility. However, isotope ratios of uranium are measured in the particle analysis at present and it is wished to develop analytical method for isotope ratios of plutonium in individual particles. We commence the development of the plutonium particle analysis and the consideration of age-dating for plutonium particles through the atomic ratio of Pu-241 and Am-241. At the presentation, our activities as a member of IAEA NWAL and current status for the development of the analytical methods will be discussed. (author)

[en] In the development of laser crystal suitable for the ultra high peak power CPA (Chirped Pulse Amplification) laser system with a compact size, fluoride YLF laser crystals doped with Yb³⁺ rare earth ion have been grown by a vertical Bridgman method. To prevent opaque crystal growth, one of growth materials, YF₃ and PbF₂ as a scavenger were mixed and heated twice in the vacuum furnace to get rid of YOF. We also adjusted the temperature gradient at the crystal growth surface and a mixing rate of the initial materials of LiF and YF₃. As a result, Yb doped YLF crystal was successfully grown with the optimum temperature gradient of 30 - 40degC/cm, and the rate of 60:40 for LiF:YF₃ in mol-%. (author)

[en] Uniform doped concentration along growth direction of Nd³⁺:YAG crystal with 110 mm length was successfully grown by the Czochralski furnace with a double crucible. The fluctuation of doped concentration was less than 4%, nearly 1/4 of the Nd³⁺:YAG crystal grown by a conventional method. We also demonstrated direct bonding without the use of adhesive materials on Ti:sapphire laser crystals with a bonding surface dimension of 12 mm x 6 mm. The bonding surfaces were treated with chemical processes to clean up and to create a hydrophilic layer for hydrogen bonding in an atmospheric furnace. Successive heat treatment in a vacuum furnace transformed the hydrogen bonding into the direct bonding. From the observation by a transmission electron microscope (Hitachi: HF-2000), atomic level bonding was succeeded in the bonding surface. The performance of the bonded crystal was also tested by laser oscillation with a second harmonics of Q-switched Nd³⁺:YAG at a 20 Hz repetition rate. In comparison with a normal laser crystal, there were no difference in output power or spatial profile in an input condition of 30 mJ. The optical damaged threshold on the bonding surface was estimated over 660 MW/cm². (author)