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In order to achieve a nanometer-scale resolution in an x-ray microscopy system, a Gabor-type hologram was produced by eliminating the zero-order term of the object diffraction pattern. In this system, a Fresnel zone plate was used for strong illumination of an object, and the zero-order diffraction was physically eliminated by a center stop. An accurate phase plate of π / 2 in the Zernike method was numerically created, and the phase-contrast image was realized. The theoretical resolution was 19.8 nm. We proved that a gold nanocube with a size of 50 nm can be reconstructed with the predicted resolution.

In this work, the application of an undecimated wavelet transformation together with digital interferometric contrast to improve the resulting reconstructions in a digital hard X-ray Gabor holographic microscope is shown. Specifically, the starlet transform is used together with digital Zernike contrast. With this contrast, the results show that only a small set of scales from the hologram are, in effect, useful, and it is possible to enhance the details of the reconstruction.

A quasi-monochromatic hard X-ray source via laser Compton scattering (LCS) was developed on the basis of an S-band compact electron linac at AIST. The total number of photons generated and the maximum X-ray energy were ∼10 7 photons/s and 41 keV, respectively, when a 42-MeV electron beam was collided with an 800-nm Ti:sapphire laser at a 15° collision angle. We successfully demonstrated K-edge imaging using these LCS X-rays for the high-contrast observation of a human phantom with barium sulfate-concentrated blood vessels. In this paper, we describe the results of the K-edge imaging and analytical estimates of the contrast enhancement effect for the energy range ∼37 keV, which corresponds to the K-edge energy of barium.

In this paper, we show how the starlet transform can be used to process holograms from a digital Gabor holographic microscope. The starlet transform is an undecimated wavelet transform with the property that when performing reconstruction, we only need to add all scales without the use of a synthesis filter bank. When the starlet transform is applied to a hologram, we divide the hologram into a certain number of scales, process them separately, and propagate each one using a numerical diffraction method. After diffraction propagation, we perform processing on complex amplitudes that correspond to individual scales. With the aforementioned procedure, it is possible to reduce the background and effects of parasitic fringes caused by high coherence of a laser, enhance the contrast, and reduce the effects of the twin image. Experimental results confirming the method are presented.

We have been fabricated the multilayer Fresnel zone plate (FZP) for hard X-ray focusing. The multilayer FZP consists of a series of concentric multilayer of low-Z (Al) zone and high-Z (Cu) zone, alternatively. The spatial resolution of the multilayer FZP is related with the outermost zone width and the smoothness of the multilayer. In case of the concentric multilayer FZP, the undulations were often observed. The smoothness of the multilayer is strongly related with he optical resolution. In this study we reported the microscopic structure of the multilayer FZP with a scanning transmission electron microscope (STEM) observation and discussed the seed of the undulation.

We propose a differential interference contrast method for cells using hard x-ray Gabor holography and knife-edge filtering in the spatial frequency domain, without relying on beam shearing. A phase object is holographically recorded and reconstructed by computer. Interference between the wavefronts of zeroth order weighted by ejπ/2 in the positive frequency region produces a dark image. Similarly, interference between the wavefronts of the zeroth order weighted by ej3π/2 in the negative frequency region produces a bright image. By adding these two intensity distributions, good quality phase-contrast images of 8-μm-diameter polystyrene beads and human HeLa cells were obtained.

A high-power terahertz (THz) source for THz time-domain spectroscopy (THz-TDS) and THz imaging has been developed based on an S-band compact electron linac at the National Institute of Advanced Industrial Science and Technology (AIST). A THz pulse was generated as coherent synchrotron radiation (CSR) from an ultra-short electron bunch and expected to have peak power of kW-order with frequency range of 0.1–2 THz. The electro-optic (EO) sampling method with a ZnTe crystal for the THz pulse measurement has been prepared for THz-TDS system. The timing measurement between the THz pulse and a probe laser was carried out. A preliminary experiment of THz transmission imaging of an integrated circuit (IC) card has been successfully demonstrated using the THz CSR pulse and a W-band rf detector. The imaging result was experimentally compared with a result of X-ray imaging. It is confirmed that its intensity and stability are enough to perform for the THz applications.

A compact hard X-ray source via laser Compton scattering (LCS) has been developed for biological and medical applications at the National Institute of Advanced Industrial Science and Technology (AIST) in Japan. The multi-collision LCS has been investigated in order to enhance the X-ray yields. The first observation of multi-pulse X-ray train with 6 pulses via the multi-collision LCS has been successfully demonstrated between the multi-bunch electron train with 6 bunches and the multi-pulse Ti:Sa laser train with 6 pulses. The 32 MeV electron train was generated from a Cs 2 Te photocathode rf gun with a multi-pulse UV laser and the S-band linac. The Ti:Sa laser train was obtained with the chirp pulse amplification (CPA) including the modified regenerative amplifier. The X-ray train with 6 pulses with 12.6 ns spacing was observed with the micro-channel plate (MCP). The maximum energy of the X-ray is analytically estimated to be about 24 keV and the total number of generated photons was calculated to be about 1.8×10 6 photons/train.

The laser-Compton X/gamma-rays produced through the inverse-Compton scattering process are acknowledged as excellent tools in basic science and industrial technologies. At the National Institute of Advanced Industrial Science and Technology (AIST), two Compton systems based on a compact S-band linac and a versatile storage ring are working in photon energy ranges of 10–40 keV and 1–40 MeV. Compton X-rays in the lower energy range are thought to be suitable to make the fine and low-dose imaging in biology or medicine due to their partial spatial coherence and quasi-monochromaticity. Here we report some typical examples for medical imaging by Compton X-rays using the phase-contrast and K-edge-contrast schemes. It will be also shown that a distinctive image was taken by a single-shot picosecond Compton X-ray pulse which will enable us not only to take a still-shot of dynamic behaviour in organs but also to achieve a real-time motion picture using successively obtained single-shot images.

We have developed a multilevel-type multilayer X-ray lens (Fresnel zone plate, FZP) using sputter deposition. Such a multilevel-type FZP can attain high diffraction efficiency which results in the reduction of radiation damage to biological specimens and the simplification of the X-ray optical system because unwanted diffraction orders are considerably suppressed. Previously, we have reported the effectiveness (i.e., realizing high diffraction efficiency) of a multilevel multilayer FZP with 4-step structure. This paper presents two experimental results on the FZP: (1) the focusing test of a multilayer FZP with 6-step structure in order to realize higher efficiency and (2) the change over time of the focusing characteristic of the FZP with 4-step structure. For (1), the diffraction efficiency of the 1st order focus and the focused beam size measured by knife-edge scanning were found to be more than 50% and 0.8 μm, respectively, at 41.3 keV, and superior to the previous results. For (2), no significant differences have been observed: it can be said that the multilevel FZP is stable at least for 9 months.

The high power terahertz (THz)-time domain spectroscopy (TDS) system has been designed based on S-band compact electron linac at Advanced Industrial Science and Technology (AIST). The THz pulse is expected to have the peak power of about 25 kW with frequency range 0.1–2 THz using the 40 MeV electron beam which has about 1 nC bunch charge with 300 fs bunch length (rms). The aptitude discussion of the EO sampling method with ZnTe crystal was accomplished to apply to our THz-TDS system. The preliminary experiment of the absorption measurements of P-PPV on the Si wafer has been successfully demonstrated using the 0.1 THz coherent synchrotron radiation (CSR) pulse and W-band rf detector. It is confirmed that the intense of the THz pulse is enough to perform the THz-TDS analysis of the sample on the Si wafer. In near future, the investigation of the un-researched materials will be started in the frequency range 0.1–2 THz with our high power THz-TDS system.

Cavity-mirror degradation is one of the serious problems especially in short-wavelength storage ring free-electron lasers (FELs). To reduce the degradation problem, we tried to treat the Al 2 O 3 /SiO 2 mirror, degraded through irradiation by undulator radiation, with both oxygen plasma and thermal annealing. As a result, the optical loss of the degraded mirrors optimized around 200 nm was successfully restored. With such efforts, FEL application experiments are being performed. The recent progress on surface observation using a photoelectron emission microscopy (PEEM) at NIJI-IV is also reported.

The 0.1 THz coherent synchrotron radiation (CSR) was successfully generated in the 90° bending magnet of the compact S-band linac with the achromatic arc section using the ultra-short electron bunch which has the energy of 40 MeV, the bunch charge of about 1nc and the bunch length less than 1 ps (rms). The electron bunch compression of 1 nC electron bunch was achieved less than 1 ps (rms) by controlling the Q-magnets in the achromatic arc section as the bunch length was measured by the rms bunch length monitor.

We have been proposing a new photo acoustic spectroscopy (PAS) method with an infrared free electron laser (IR-FEL). The IR-FEL is a continuous tunable laser in the lasing wavelength in an finger-print wavelength region with high peak power. The IR-FEL resonantly induce the specific molecular vibration of the samples, resulting casue the photo acoustic pheneomena with high sensitivity. Thus, the new PAS method with the IR-FEL is high sensitive analysis method applicable to low absorbance measurement. In this study we show the feasibility of application of the MIR-FEL to the photon source of the PAS method by measuring the PAS spectrum of polymers such as a poly ethylene terephthalate (PET) film. In addition, we construct an imaging system of the FEL-PAS to make a map of the PAS signal with a high spatial resolution that is a diffraction limit of the IR-FEL.

Compact hard X-ray source via laser Compton sattering has been developed in SHI and AIST. Our system has the injector and the linac and the high power laser system. The injector has a photo-cathode rf gun with a solenoid magnet. To enhance the X-ray yeild, we are planning to increase electron beam charge up to 5 nC/bunch and to make multi-bunch beam. The beam tracking simulation in the injector have been performed by changing laser spot size, laser pulse width, rf phase and solenoid field to optimize the distance between the injector and the linac for 5 nC/bunch high charge beam. In addition, high charge multi-bunch beam simulation in rf-gun cavity have been carried out to investigate the influence by the beam loading and the wake field.

A multilayer (sputtered-sliced) Fresnel zone plate (FZP) is one of the promising focusing optics with high spatial resolution for the high-energy X-ray region. This is because a large “aspect ratio” can be realized easily. In addition, it is important that the kinoform FZP (theoretical diffraction efficiency=100%) can be fabricated by the sputtered-sliced method. This paper presents the experimental results of two new approaches for fabrication of a multilayer FZP for X-rays. (1) To achieve higher diffraction efficiency, a multilevel-type (4-step: quasi-kinoform type) FZP was fabricated. This FZP was composed of concentric multilayers of alternating high-Z, low-Z, and composite materials. The composite material layer was deposited by co-sputtering of high-Z and low-Z materials. (2) To achieve smoother zones (multilayer interfaces) at the conventional-type FZP, each target of a sputtering apparatus with two DC-sputtering guns was surrounded by a cover with an aperture, and Ar gas was supplied inside the cover, which led to the deposition at lower Ar gas pressure. As a result, for the former, the efficiency was improved markedly as compared with conventional FZP, and for the latter, the zone roughness was reduced, which has resulted in the improvement of the spatial resolution of the FZP.

The proposed Saga two-color IR-FEL facility employs a part of the electron linac injector of the Saga synchrotron light source that is operated in the fall of 2004 in Tosu by a local Government in Kyushu, Japan. It consists of two sets of undulators and optical cavities in series. Its two IR-FEL facilities independently cover most useful wavelength ranges of 4–10 μm and 7–22 μm for biomedical applications and semiconductor applications, respectively. New radio-frequency (RF) system for the ring cavity and the linac accelerating tube has been designed to synchronize the IR-FEL macropulse with the synchrotron radiation (SR) macropulse as much as possible for new applications such as combination of the molecular bond-selective excitation by the IR-FEL and the SR-based X-ray spectro-microscopy of 500 nm spatial resolution. Beam position monitors for the Saga linac and the beam transport lines are also reported.

Laser gain of the NIJI-IV compact storage-ring-based Free Electron Laser (FEL) system at AIST reached ∼9% at 200 nm for an average beam current of 16.3 mA . In addition to such a drastic gain enhancement, improvement of the laser-cavity performance has led to successful FEL lasing in the vacuum ultraviolet below 200 nm even in a compact system. Temporal and spectral characteristics of the NIJI-IV FEL were examined around 200 nm . FEL performance will be briefly discussed from the application point of view.

Generation of the VUV radiation has been numerically studied based on coherent harmonic generation (CHG) scheme at NIJI-IV with a hole-coupled resonator. The optical mode of the light pulse inside the optical cavity in a hole-coupled resonator was simulated by using the code GENESIS 1.3 and its modified version including resonator configurations. In this paper, the expected harmonic radiation power for the different configurations of the hole-coupled resonator combined with a 6.3-m optical klystron ETLOK-II is discussed.

A computer simulation for evolution of a storage ring free electron laser (SRFEL) micropulse in a macropulse zone has been performed. The one-dimension simulation based on the bunch heating theory could describe dependence of the macropulse period on the longitudinal detuning length and evolution of the pulse width. We modified the simulation code so as to describe the evolution of the SRFEL spectrum. It can explain the characteristics of the NIJI-IV SRFEL spectrum in the macropulse zone. The evolution of the spectral width and wavelength in the macropulse zone is discussed.

Three new types of optical elements for the synchrotron radiation (SR) high-brilliance X-ray beamlines have been developed: (1) a spatial resolution test pattern for X-ray computed tomography (CT), (2) a spatial resolution test pattern for X-ray scanning microscopy, and (3) a condenser device for X-ray imaging microscopy. These optical elements are composed of concentric multilayers of alternating high-Z and low-Z material deposited on a wire substrate. The characteristics of these elements have been tested at the SR facilities of Super Photon ring-8 GeV.Optical element (1) yielded a pattern of alternating opaque and transparent concentric rings with a film thickness of 1 μm. For (2), the test pattern was shown to work well in the high-energy X-ray region at 28 keV.Use of the condenser device with optical element (3) produced an absorption contrast image of a test pattern without modulation by the coherence of the source. These optical elements may play important roles in the future development of various analytical areas with high spatial resolution in the high-energy X-ray region at the SR high-brilliance X-ray beamlines.

佐賀県鳥栖市の北部丘陵地帯に,第三世代光源としては世界最小規模の1.4GeV放射光用電子加速・蓄積リングをもつ佐賀県立九州シンクロトロン光研究センターの建設が進んでいる。蓄積リングの直線部には,アンジュレーターやウイグラーなどの挿入光源の設置が計画されている。このアンジュレーターからの放射光は軟X線領域をカバーし,集光素子を用いることによって,35nm程度の空間分解能での軟X線イメージング研究が提案されている。

Microfocusing of 100 keV x ray with a sputtered-sliced Fresnel zone plate (ss-FZP) has been performed at the 250-m-long beamline (20XU) of SPring-8. The ss-FZP with an outermost zone width 0.16 μm which is composed of 70 layers of alternating Cu and Al layers and having thickness ∼180 μm was fabricated and characterized. The minimum focal spot size attained for the first order focal beam was 0.5 μm with a focal distance 900 mm at a photon energy 100 keV. The total flux of the microprobe was ∼2×106 photons s−1 μm−2.

The electron-beam qualities with and without free electron laser (FEL) oscillations were investigated in the compact storage ring NIJI-IV. The peak-electron density in a bunch was suppressed by beam instabilies, so that it was limited to about 1.0 ×1017 m-3. The maximum FEL gain estimated for 215 and 300 nm using a well-known one-dimension theory was about 2.8% and 4.6%. The cavity loss at 300 nm was evaluated to be about 2% from the threshold beam current. The bunch length and energy spread with FEL oscillations increased by 1.3 times or more due to bunch heating. The ratio of the FEL gain to a cavity loss estimated from the beam qualities with and without FEL oscillations was almost in accord with the ratio evaluated directly with the measured data of the FEL gain and the cavity loss.

We are planning to develop a kinoform zone plate (ZP) for hard X-ray using a sputtered-sliced (SS) method with two materials (Cu/Al). The SS kinoform ZP is composed of a Cu/Al multilayer that is based on radial modulation of the refractive indices of deposition materials. The X-ray through the zones interferes constructively at the focal point. The kinoform ZP, therefore, has an advantage of high focusing efficiency. According to the our theoretical calculation, the focusing efficiency of the Cu/Al kinoform PZP is up to 86% in the 0-30 keV X-ray energy region, while one of the conventional Cu/Al multilayer Fresnel zone plate is up to 38%.

Concentric multilayers of alternate high-Z material and low-Z one, deposited on the wire substrate, can be applied to various optical elements for synchrotron radiation (SR) high-brilliance X-ray beamlines. We present new application of the concentric multilayer to optical elements for the SR high-brilliance X-ray beamlines at SPring-8. Three types of Cu/ Al concentric multilayer samples have been fabricated and applied to (1) a spatial resolution test pattern for X-ray computed tomography (CT), (2) a spatial resolution test pattern for the X-ray equipment and (3) a condenser device in the X-ray imaging microscopy. These characteristics have been tested. For the (1), alternate opaque and transparent concentric ring pattern with 2 micron film thickness has been clearly resolved. For the (2), the test pattern can work well in the high energy X-ray region. For the (3), absorption contrast image of a test pattern without modulation by the coherence of the source has been obtained by using the condenser device.

A hard X-ray microbeam is a key technology for third-generation high-brilliance synchrotron radiation sources such as SPring-8. A Fresnel zone plate (FZP) is one of the promising focusing elements for X-rays. A multilayer (sputtered–sliced) FZP is suitable for use in hard X-ray region, because large thickness can be available. Zone (multilayer interface) roughness is inevitable to the multilayer FZP, which results in the inferior-focusing characteristic. Some Cu/Al concentric multilayers were fabricated by DC sputtering deposition. In order to reduce the oblique incidence of sputtered atoms on the wire substrate, a cylindrical slit was placed between the target and the wire substrate. As a result, the interface roughness was improved with very good repeatability.

Temporal and spectral characteristics of the NIJI-IV FEL were investigated around 300 nm using a dual-sweep streak camera and a monochromator. It was found that a fine cavity tuning within ∼3.6 μm resulted in an obvious change of the lasing mode from quasi-cw to cw through a pulsed region, though the average laser power is almost the same. By measuring the dynamic behavior of both temporal pulse width and laser line width, FEL brilliance was found to be enhanced by a factor of ∼7.4 in the cw mode, compared with the quasi-cw mode. Phenomena relating to the laser startup were observed in detail with periodic gain switching operation. Laser dynamics of the NIJI-IV FEL will be totally discussed.

We advance the FEL-X project and plan to install a new optical klystron for the infrared FELs within next year. The expected FEL gain at a wavelength of 10.6 μm is over 2% with the present electron-beam qualities in the storage ring NIJI-IV. Infrared FELs based on the fundamental and higher harmonics from the new optical klystron will generate hard X-ray beams with an energy of 0.1–2 MeV by the FEL-Compton backscattering process. Conventional light sources cannot provide sufficient amounts of photons in this energy region. The expected yield of the hard X-ray beam is 105–106 per second with an energy spread of 3%.

A two-color infrared free electron laser (FEL) facility is proposed. This FEL facility will employ a new 250-MeV linac injector of the Saga synchrotron light source (SLS). The linac has two operation modes: short macropulse mode of 1 μs at 250 MeV is for injection to a 1.4-GeV storage ring and long macropulse mode of 13 μs at 40 MeV is for the two-color FEL facility. The two-color FEL uses a single electron beam and simultaneously provides both infrared (IR) and far-IR laser pulses for pump-probe studies of quantum-well structures and studying vibrational relaxation of molecules. The Saga SLS will be operated in 2004 to promote material science, bio-medical and industrial applications in Kyushu.

We propose the novel application of the mid-infrared (MIR) FEL to the thin-film fabrication process. During the application, a substrate on which a thin film is being fabricated by a conventional method is simultaneously irradiated by the MIR FEL. The MIR FEL induces the fabricated molecules into the excited state of the stretching vibration energy, when the photon energy of the MIR FEL corresponds to one of the molecules. Therefore, the method can assist the thin-film fabrication quasi-independent of the substrate temperature. The method has the advantages of application on a temperature sensitive substrate and selective fabrication due to the tunable wavelength of the MIR FEL. In order to realize the method, we developed two thin film fabrication devices; an MIR FEL assisted RF sputtering device and an MIR FEL assisted laser ablation deposition device. For the method, the intensity of the assisted MIR FEL is an important problem. Thus the cross-section of the MIR FEL intensity profile is shown and the propagation discussed.

A zone plate for hard X-rays with outermost zone width as small as 30 nm and thickness ∼14 μm fabricated by sputtered-sliced technology was evaluated. With the brilliant X-ray beam from the undulator at the SPring-8 the minimum focal spot size attained was ∼0.8 μm at the energy of 18.6 keV. The intrinsic diffraction efficiency was determined to be ∼12%.

X-ray imaging microscopy with a sputtered-sliced Fresnel zone plate (SS-FZP) has been developed at an X-ray energy of 25keV. Objects were imaged in transmission with the SS-FZP as an objective with a magnification of 10.2 times, and detected with a X-ray image sensor. The performance of the imaging microscope has been tested with a gold mesh and a resolution test pattern at an undulator beamline 47XU of SPring-8. The resolution test patterns up to 0.5mm line-and-space structures have been resolved. # 2001 Elsevier Science B.V. All rights reserved.

X線集光素子の1つである多層膜フレネルゾーンプレート (FZP) の作製方法, 開発したFZPを利用した集光実験の成果および関連分野の世界の研究動向を紹介した.大型放射光施設SPring-8における集光実験ではトップレベルのデータが得られ, 多層膜FZPは特に高エネルギー領域 (>25keV) の集光にも有効であることがわかった.FZPは連続100時間以上の使用の間, 放射線損傷は観察されなかった.このことから, 高輝度放射光を利用した硬X線顕微鏡の実用化に大きく前進したと言える.測定された性能値を理論値に限りなく近づけるためには, 成膜工程を中心に一層の工夫が必要である.今後, ゾーン (多層膜界面) の平滑性を改善するために成膜条件の検討, 成膜装置の改良を引き続き行うと共に, 多層膜FZPの結像特性の理論的考察も行いたい.また, マイクロビームを利用して微小領域の元素マッピング, 化学状態のイメージングなどを行う予定である.本報告で紹介した以外にも注目すべき新しい硬X線領域用の集光素子が最近相次いで発表され, 今後の進展が期待される.集光テストを行ったSPring-8での利用研究課題の課題番号は, 1999A0091-NM-np, 1999B0080-CM-np, 1999B0103-NM-np, 2000AO160-NM-npである.

The Fresnel zone plate (FZP) is a type of lens for focusing X-rays. We have fabricated a kinoform style FZP with a 30-step structure composed of concentric multilayer of alternating Cu layer, Al layer, and 28 composite material (Cu, Al) layers. The multilayer was deposited using a magnetron sputtering apparatus with two DC-sputtering guns. The focusing characteristics were evaluated at the synchrotron radiation beamline of SPring-8, and the focused beam size measured by knife-edge scanning was 0.8 μm at 40 keV. The peak diffraction efficiencies measured using ion chambers for 1st- and 2nd-order diffraction were 42% and 12% at 40 keV and 20 keV, respectively. High-order X-ray diffraction was also examined using the data obtained from a CCD camera.

Optical damage of multi-layer mirrors used in an ultraviolet free electron laser (UV-FEL) resonator at linac-based FEL has been observed. The peak power of the UV-FEL at the linac-based FEL is about 100 times as large as that of the ring-based FELs. The mirror degradation mechanism in the linac-based FEL therefore is entirely different from that of the ring-based FEL which has been reported. Several 0.2 mm diameter craters have been found on both surfaces of upstream and downstream Ta 2 O 5 /SiO 2 multi-layer mirrors of the resonator after 50 h UV-FEL oscillation at 310–370 nm. At each crater, several layers near the surface are crushed by ablation induced by the FEL. Results from both the X-ray micro-analysis (XMA) on the craters and luminescence analysis during ablation induced with the pico-second pulsed Nd:YLF laser, which is the same pulse format as the FEL, explain that the pico-second pulses of the laser affect the damages.

In order to attain high diffraction efficiency in high-energy X-ray region, we have developed multilevel-type (6-step) multilayer FZPs with the diameter of 70 μm, which composed of concentric multilayers of alternating high-Z (Cu), low-Z (Al), and four types of composite materials (Cu, Al) layers. Such a multilevel-type FZP with high diffraction efficiency contributes the reduction of the radiation damage to biological specimens, the simplification of the X-ray optical system. Some FZPs are fabricated and their diffraction efficiencies were evaluated at the beamline of SPring-8. For one FZP, the peak efficiency for the 1st-order diffraction of 51% has been obtained at 70 keV. The efficiencies higher than 40% have been achieved in the wide energy range of 70–90 keV. That for the 2nd-order diffraction of 46% has been obtained at 37.5 keV. For another FZP, the peak efficiency for the 1st-order diffraction of 52% has been obtained at 41.3 keV. The efficiencies higher than 45% have been achieved in the wide energy range of 33–49.5 keV.

We investigated a kinoform-style Fresnel zone plate (FZP) that is a high-efficient optical element for hard X-ray focusing. The Cu/Al kinoform-style FZPs were fabricated with a sputtered–sliced method. The FZP was composed of 450 layers (30 layers, 15 pairs) of Al, Cu/Al composite, and Cu. The microstructure of the Cu/Al composite layer was observed by scanning ion microscopy based on a focused ion beam (FIB). In the Cu/Al composite layer, the SIM images obtained by grain orientation contrast observation indicated that the Cu grains were grown gradually with increasing Cu concentration.

A compact terahertz (THz) SASE-FEL source has been developed with a compact S-band electron linac at AIST. The S-band linac has been improved using a Cs2Te photocathode rf gun with a compact load-lock system. The 40 MeV electron beam which has a bunch charge of more than 2 nC/bunch was stably generated using our system with the Cs2Te photocathode, and the quantum efficiency (QE) typically achieved was about 0.3%. The surface observation of the Cs2Te photocathode to obtain the surface micrographs and QE mapping images was successfully performed with a photoelectron emission microscopy (PEEM).

The development of free electron lasers (FELs) with a compact storage ring NIJI-IV in the near- and middle-infrared regions has been advanced at the National Institute of Advanced Industrial Science and Technology. The optical klystron ETLOK-III was installed in one of the long straight sections of the NIJI-IV, and spontaneous emission spectra were observed in the visible and near-infrared regions. Optical cavity chambers for infrared FELs were installed this February, and it was confirmed that the vibration amplitude of the optical cavity chambers was below 0.5 μm in an optical beam axis. FEL experiments in the near-infrared region will be performed this winter.

The FELI four FEL facilities (FEL-1, FEL-2, FEL-3 and FEL-4) are open for users to supply several MW-level FELs covering a wide wavelength range from 278 nm to 40 μm. The ultraviolet (UV)- and visible-FEL facility (FEL-3) keeps the world record for the shortest wavelength oscillation of linac-based FELs with a thermionic gun since 1995. Technical challenges have been tried at simultaneous FEL beam sharing with fan-shaped mirrors for multistations including two manipulators and at FEL beam diagnostics of micropulse length and beam profile. The latter is for the evaluations of FEL peak power densities at irradiated spots. FEL peak power densities and adequate wavelengths are evaluated at thirteen research subjects performed at the FELI. The application researches have been performed distributed in a wide field of material science, chemical technology and bio-medical applications.

An intense infrared free electron laser (IRFEL) causes laser ablation with an emission of visible luminescence from solids samples. In the case of zinc selenide crystals (ZnSe), the focused IRFEL pulse induces the ablation on the surface because of its high peak power density, despite ZnSe being normally transparent to infrared light. The pulsed IRFELs are at 9.2- and 10.2-μm in wavelength and of several GW/cm2 in power density. The luminescent lines can be identified as the neutral atomic lines originating from the target zinc atoms. The pulsed luminescence from ZnSe is short in width and synchronized with the irradiated IRFEL pulses, which is operated at 22.3 MHz. From the relation of the 9.2-μm FEL fluence and luminescent intensity, the threshold of the ZnSe luminescent emission is found to be ∼13 mJ/cm2 at 9.2-μm IRFEL irradiation.

Four FEL facilities (FEL-1, FEL-2, FEL-3 and FEL-4) achieved lasing at FELI in October 1994, in February 1995, in December 1995 and in October 1996, respectively. They are open for users and can supply several MW-level FELs covering the wavelength range of 0.3–40 μm. Total operation time in 1996 was about 2400 h. The visible- and UV-facility FEL-3 has broken the world record for the shortest wavelength oscillation of linac-based FELs with a thermionic gun up to 0.278 μm. The FEL beams are delivered from the optical cavities to the diagnostic room and four users rooms (18 stations) through the pipe lines. The beam can be shared by using fan-shaped Au-coated mirrors to several stations including two manipulators simultaneously for isotope separation, bio-medical and semiconductor applications.

A microscopic Free Electron Laser (FEL) irradiation system has been developed for bio-medical applications. This system has two major functions; irradiation and observation. This irradiation system cannot only focus the FEL from infrared to ultraviolet in wavelength but can also adjust the area, time and intensity of FEL irradiation. Furthermore, experimental cells are incubated and observed in detail during and after FEL irradiation with an integrated microscope.

First lasings at 5.5 and 1.88 μm were achieved in October 31, 1994 and February 27, 1995 at the FELI using a 2-m long undulator and a 3-m long one installed at 30 and 80-MeV beam lines of the FELI S-band linac with a thermionic gun, respectively. Lasing on the third harmonics at 0.63 μm was also observed in February 28. 24-μs stable rf pulses help FEL oscillations at short wavelengths. At 7.5, 1.88 and 0.63 μm, FEL peak powers are 3.5, 2, and 0.45 MW, respectively. The present maximum average power is 0.14 W around 7.5 μm at a 0.5-mm mirror aperture of the optical cavity for the 2-m long undulator for 4000 micropulses/s.