天野 壮

We have completed a system that can achieve both deep x-ray lithography and submicron x-ray lithography with a single beamline by introducing the combination of x-ray plane and cylindrical mirrors. This x-ray lithography system can provide a large-scale microfabrication processing with 210 × 300 mm2 (A4 size). To exploit multiscale lithography, the beamline has a beam transport vacuum duct with a two-stage stacked structure and a 5-axis stage. This two-stage stacked structure allows us to fabricate both micron scale structures with high aspect ratios and submicron scale structures using the same beamline. In addition, x-ray imaging and computer tomography (CT) system are connected to the x-ray lithography system for nondestructive inspection and evaluation of the fabricated microstructures. The x-ray imaging system constructed this study has a relatively low energy range of x-ray energy in the beamline, which is in the range of 2–15 keV or less. Therefore, relatively good absorption contrast can be obtained for plastic materials, biomaterials, and the like. Since nondestructive imaging of the processed shape by x-ray lithography is possible, it is a very useful system in processing and evaluation can be performed simultaneously. This system also enables us to obtain the live images with keeping the creature alive in liquid using an indirect x-ray imaging system which converts x-ray images to visible light images through the fluorescent plate.

We demonstrated soft X-ray lithography at a wavelength of 3.37 nm using a laser-plasma source and a multi-layer mirror, where the resist was poly(methyl methacrylate) and the developer was ethanol. A nickel mesh was used as a contact mask. The results of lithography showed that the poly(methyl methacrylate) could be etched highly efficiently using X-ray pulses with an intensity of 6.5 μJ/cm2, where the dose required for an etching depth of 0.1 μm was 5.3 mJ/cm2. Additionally, in a proof-of-principle study of the concept that more efficient X-ray lithography can be achieved through the simultaneous excitation of inner- and outer-shell electrons, lithography through double-beam irradiation was tested. The etching efficiency was increased by a factor of 2 using an ultraviolet lamp and a factor of 1.7 using a CO2 infrared laser, relative to the use of X-ray irradiation alone. It is expected that the adoption of the concept will be effective in X-ray micromachining.

We discuss the role of photoneutron reaction data in nuclear physics and astrophysics in conjunction with the Coordinated Research Project of the International Atomic Energy Agency with the code F41032 (IAEA-CRP F41032).

To generate continuously repetitive soft X-ray pulses in the water window from laser-produced plasmas, a one-dimensionally translating substrate system with a closed He gas cryostat that can continuously supply various cryogenic targets has been developed. The system was successfully operated at a lowest temperature of 15 K and at a maximum up-down speed of 12 mm/s. Solid Ar and N-2 layers were formed, and the water-window spectra from them were studied. The emission intensity from Ar was found to be about eight times stronger than that from N-2. Developed laser-plasma source demonstrated high average power of 140 mW in the water-window soft X-ray, when a commercial Nd:YAG Q-switched laser was used to irradiate a solid Ar target with energy of 1 J at a repetition rate of 1 Hz. It can be used for various applications, including soft X-ray microscopy, in place of synchrotron facilities.

New data of total and partial (γ,xn) cross sections with x = 1-3 are proposed to be measured by direct neutron multiplicity sorting using Laser Compton scattering (LCS) gamma ray beams at the ELI-NP to solve long standing discrepancies between existing Lawrence Livermore National Laboratory (USA) and France Centre d'Etudes Nucleaires de Saclay photonuclear data. Pioneering experiments are currently performed at the NewSUBARU facility. We present here preliminary results on 209Bi(g,xn) cross section measurements.

Current gamma-ray telescopes based on photon conversions to electron-positron pairs, such as Fermi, use tungsten converters. They suffer of limited angular resolution at low energies, and their sensitivity drops below 1 GeV. The low multiple scattering in a gaseous detector gives access to higher angular resolution in the MeV-GeV range, and to the linear polarisation of the photons through the azimuthal angle of the electron-positron pair. HARPO is an R&D programme to characterise the operation of a TPC (Time Projection Chamber) as a high angular-resolution and sensitivity telescope and polarimeter for gamma rays from cosmic sources. It represents a first step towards a future space instrument. A 30 cm cubic TPC demonstrator was built, and filled with 2 bar argon-based gas. It was put in a polarised gamma-ray beam at the NewSUBARU accelerator in Japan in November 2014. Data were taken at different photon energies from 1.7 MeV to 74 MeV, and with different polarisation configurations. The electronics setup is described, with an emphasis on the trigger system. The event reconstruction algorithm is quickly described, and preliminary measurements of the polarisation of 11 MeV photons are shown. (C) 2016 Elsevier B.V. All rights reserved.

<p>To generate continuously repetitive soft X-ray pulses in the water window from laser-produced plasmas, a one-dimensionally translating substrate system with a closed He gas cryostat that can continuously supply various cryogenic targets has been developed. The system was successfully operated at a lowest temperature of 15 K and at a maximum up-down speed of 12 mm/sec. Solid Ar and N₂ layers were formed, and the water window spectra from them were studied. The emission intensity from Ar was found to be about 8 times stronger than that from N₂. Developed laser plasma source demonstrated high average power of 140 mW in the water window soft X-ray, when a commercial Nd:YAG Q-switched laser was used to irradiate a solid Ar target with energy of 1 J at a repetition rate of 1 Hz. It can be used for various applications, including soft X-ray microscopy, in place of synchrotron facilities.</p>

Laser plasma soft X-ray sources that operate in the water window and are based on cryogenic targets have been studied. The cryogenic targets used are composed of solid layers of inert gases and are deposition-free targets, which is advantageous for continuous long-lifetime operation using repetitive pulses. The developed laser plasma source has a translating substrate system with a closed He gas cryostat that can continuously supply the cryogenic target, and the source can generate repetitive X-ray pulses continuously. Cryogenic solid Ar and N-2 targets were compared for the soft X-ray source when operating in the water window between 2.3 nm and 4.4 nm. The intensity of the water window X-rays from the Ar target was approximately eight times stronger than that from the N-2 target at a laser intensity of 5x10(12) W/cm(2). At this laser intensity, the Ar plasma source also demonstrated a higher conversion efficiency of 14% and an average power of 140 mW in the water window for a laser energy of 1 J at 1 Hz. This power compares favorably with that of X-rays produced using a synchrotron radiation source. The results also indicated that our source satisfied the requirements for use as a source for a contact X-ray microscope. The developed laser plasma source can be used not only for soft X-ray microscopy but also may be used to replace synchrotron facilities in a variety of other applications.

A high average power of 140 mW and high conversion efficiency of 14% were demonstrated in "water window" soft X-rays generated using a laser plasma source developed in-house, when a solid Ar target was irradiated by a commercial Nd: YAG Q-switched laser with an energy of 1 J at a repetition rate of 1 Hz. This soft X-ray power compared favorably with that produced using a synchrotron radiation source, and the developed laser plasma source can be used in various applications, such as soft X-ray microscopy, in place of synchrotron facilities. (C) 2016 The Japan Society of Applied Physics

Micromachining of poly(tetrafluoroethylene) (Teflon) and poly(methyl methacrylate) (PMMA) samples was carried out using soft X-rays from a laser-produced Xe plasma source, which we developed. In the Teflon sample, the contact angle with a water droplet on a modified surface increased from 90 degrees to 110 degrees as a result of irradiation without a mirror or mask, while the angle decreased to 50 degrees when using irradiation with them. Scanning electron microscopy showed numerous micro-protuberances and a masked pattern with micro-concavities on each sample surface. These results suggested that a change to the contact angle was caused by the microstructures on the Teflon surface. We succeeded in controlling the wettability of the Teflon surface, from hydrophobic to hydrophilic, by micromachining using laser plasma X-rays. In the PMMA sample, the etching rate was investigated with irradiation using a large number of pulses (192,000 pulses) and a low power density of 8 x 10(4) W/cm(2). The etching rate was calculated to be 5 pm/pulse. This was judged to be due only to photo-etching without any thermal effects. We demonstrated a pure photo-etching depth of about 1 m.

We designed and built an experimental apparatus based on a time projection chamber, a novel scheme for high performance gamma-ray astronomy and polarimetry in the gamma -&gt; e(+)e(-) regime. This presentation focuses on the electronics aspect of the detector and, in particular, on the versatile dedicated trigger system that we have developed which allowed us to take data on beam with a high gamma-conversion signal efficiency and a high rejection factor for single tracks and upstream conversion background events. Our scheme allows for the selective collection of gamma conversions in a high-background-rate environment, such as that which is present in orbit, with a fine 3D imaging of the events and very low (in particular electronics) background, at a mild cost in terms of the number of electronics channels and therefore of electrical power consumption.

Tunable and high-power terahertz radiation sources using relativistic electron beams from a compact linear accelerator (LEENA) are under development. Synchrotron radiation and Smith-Purcell radiation in the THz region were successfully measured. The coherent radiation power from an electron bunch shorter than 1 ps is estimated theoretically to be about 10(7) larger than the incoherent power. Recent experimental results on the generation of THz radiation and numerical results on high-power coherent radiation from a short electron bunch are reported. (C) 2016 Wiley Periodicals, Inc.

Current gamma-ray telescopes suffer from a gap in sensitivity in the energy range between 100 keV and 100 MeV, and no polarisation measurement has ever been done on cosmic sources above 1 MeV. Past and present e(+)e(-) pair telescopes are limited at lower energies by the multiple scattering of electrons in passive tungsten converter plates. This results in low angular resolution, and, consequently, a drop in sensitivity to point sources below 1 GeV. The polarisation information, which is carried by the azimuthal angle of the conversion plane, is lost for the same reasons. HARPO (Hermetic ARgon POlarimeter) is an R&D program to characterise the operation of a gaseous detector (a Time Projection Chamber or TPC) as a high angular-resolution and sensitivity telescope and polarimeter for gamma rays from cosmic sources. It represents a first step towards a future space instrument in the MeV-GeV range. We built and characterised a 30cm cubic demonstrator [SPIE 91441M], and put it in a polarised gamma-ray beam at the NewSUBARU accelerator in Japan. Data were taken at photon energies from 1.74 MeV to 74 MeV and with different polarisation configurations. We describe the experimental setup in beam. We then describe the software we developed to reconstruct the photon conversion events, with special focus on low energies. We also describe the thorough simulation of the detector used to compare results. Finally we will present the performance of the detector as extracted from this analysis and preliminary measurements of the polarisation asymmetry. This beam-test qualification of a gas TPC prototype in a gamma-ray beam could open the way to high-performance gamma-ray astronomy and polarimetry in the MeV-GeV energy range in the near future.

A time projection chamber (TPC) can be used to measure the polarization of gamma rays with excellent angular precision and sensitivity in the MeV-GeV energy range through the conversion of photons to e(+)e(-) pairs. The Hermetic ARgon POlarimeter (HARPO) prototype was built to demonstrate this concept. It was recently tested in the polarized photon beam at the NewSUBARU facility in Japan. We present this data-taking run, which demonstrated the excellent performance of the HARPO TPC.

To generate continuously repetitive EUV and soft X-ray pulses with various wavelengths from laser-produced plasmas, a one-dimensionally translating substrate system with a closed He gas cryostat that can continuously supply various cryogenic targets for similar to 10 Hz laser pulses has been developed. The system was successfully operated at a lowest temperature of 15 K and at a maximum up-down speed of 12 mm/s. Solid Ar, Kr, and Xe layers were formed, and their growth rates and the laser crater sizes on them were studied. By optimization of the operational parameters in accordance with our design rule, it was shown that stable output power was achieved continuously from the plasma emission at frequencies of 1-10 Hz. The average soft X-ray and EUV powers obtained were 19 mW at 3.2 nm, 33 mW at 10.0 nm, and 66 mW at 10.8 nm, with 10% bandwidths, from the Ar, Kr, and Xe solid targets, respectively, with a laser power of 1 W. We will be able to achieve higher frequencies using a high beam quality laser that produces smaller craters, and can expect higher powers. Although only Ar, Kr, and Xe gases were tested in this study, the target system achieved a temperature of 15 K and can thus solidify almost all target gases, apart from H and He, and can continuously supply the solid target. The use of various target materials will enable expansion of the EUV and soft X-ray emission wavelength range. (C) 2014 AIP Publishing LLC.

Low-temperature crystallization of Si, Ge and Si_XGe_1−X films by SR-soft x-ray irradiation using short undulator light is examined. By setting the photon energy to that of the core electron orbital, the crystallization is examined experimentally and discussed theoretically from a view point of Ge diffusion. The temperature during the crystallization of Si, Ge or Si_0.5Ge_0.5 by soft x-ray was 80 to 140 degree C lower than that by the conventional rapid thermal annealing. The elementary process of the soft x-ray irradiation is thought to be the atom-diffusion following the localized excitation of the core-electrons and the generation of Coulomb repulsion. For the low-temperature crystallization, the quasi-nuclei are formed via the elementary process.<br>

Tunable and high-power terahertz radiation sources using relativistic electron beams from a compact linear accelerator LEENA are under development. The synchrotron radiation and Smith-Purcell radiation in THz regime were successfully measured. The coherent radiation power from an electron bunch shorter than 1ps is estimated theoretically to be about 10⁷ larger than the incoherent one. Recent experimental results on the generation of the THz radiation and the numerical results on the high-power coherent radiation from a short electron bunch are reported.

Microprocessing of poly(tetrafluoroethylene) (Teflon) and poly(methyl methacrylate) (PMMA) samples was carried out using soft X-ray from a laser produced Xe plasma source we developed. In the Teflon sample, a contact angle of a modified surface with a water drop increased from 90° to 110° to by an irradiation without a mirror and a mask, while the angle decreased to 50° by an irradiation with them. Scanning electron microscopy showed numerous microprotuberances and a masked pattern having micro-concavities on the each sample surface. These suggested that the changes of the contact angle were ascribable to the microstructures of the Teflon surface. We succeeded in controlling the wettability of the Teflon surface from hydrophobic to hydrophilic by microprocessing using the laser plasma X-ray. In the PMMA sample, its etching rate was investigated using an irradiation with a large number of pulses (192000 pulses) and a low power density of 8×10⁴ W/cm². The etching rate was calculated to be 5 pm/pulse and this was concluded to be a result by only photo-etching without thermal effect. We demonstrated pure photo-etching depth of ∼1 µm.

The M1 strengths (or level density of 1(+) states) are of importance for estimation of interaction strengths between neutrinos and nuclei for the study of the supernova neutrino-process. In 1957, Agodi predicted theoretically angular distribution of neutrons emitted from states excited via dipole transitions with linearly polarized gamma-ray beam at the polar angle of 0=9 degrees should be followed by a simple function, a + h cos(2 phi), where phi is azimuthal angel. However, this theoretical prediction has not been verified over the wide mass region except for light nuclei as deuteron. We have measured neutron angular distributions with (polarized gamma, n) reactions on Au. NaI, and Cu. We have verified the Agodi's prediction for the first time over the wide mass region. This suggests that (polarized gamma, n) reactions may be useful tools to study M1 strengths in giant resonance regions.

Tunable and high-power terahertz radiation sources using relativistic electron beams from a compact linear accelerator LEENA are under development. The synchrotron radiation and Smith-Purcell radiation in THz regime were successfully measured. The coherent radiation power from an electron bunch shorter than 1ps is estimated theoretically to be about 10⁷ larger than the incoherent one. Recent experimental results on the generation of the THz radiation and the numerical results on the high-power coherent radiation from a short electron bunch are reported.

The characteristics of fast ions generated from laser-induced plasma on a boron solid target have been studied for an application to shallow junction doping. The peak position in the produced B ion energy spectra can be controlled in a 150-550 eV range by changing the laser intensity. From the measurement of B ion energy spectrum which was resolved into charge states at several laser intensities, most part of the energy spectra around the peak position was found to be composed of B ions at the laser intensity less than 3.0 x 10(10) W/cm(2). The number of produced ions around the peak of the energy spectrum was about 2 x 10(12) ions/(eV-Sr) or higher within the emission angle smaller than 45 degrees. These results indicate that the produced B+ ions are applicable to shallow doping in a sub-10 nm range. (C) 2013 Elsevier B.V. All rights reserved.

A diamond-like carbon (DLC) mirror, used as a grazing incident mirror in a plasma x-ray source, exhibits a high resistance to plasma debris sputtering. Good mirror reflectivity at a wavelength of 13.5 nm was confirmed using synchrotron radiation at the NewSUBARU facility. The erosion rate due to plasma debris sputtered at the incident debris angle of 20° was measured using a laser-produced Xe plasma source developed by the authors. The results indicate that the DLC film has a 5- and 15-fold higher sputtering resistance compared to films made of the traditional mirror materials Ru and Au, respectively. Because the DLC mirror retains a high sputtering resistance to Sn ions, it may be effective in Sn plasma source applications. We conclude that a grazing incident x-ray mirror coated with DLC can be of use as a plasma debris sputtering resistant mirror. © 2013 Optical Society of America.

The low-temperature-crystallization effects of soft X-ray irradiation on the structural properties of amorphous Si and amorphous Ge films were investigated. From the differences in crystallization between Si and Ge, it was found that the effects of soft X-ray irradiation on the crystallization strongly depended on the energy band gap and energy level. The crystallization temperatures of the amorphous Si and amorphous Ge films decreased from 953 K to 853 K and 773 K to 663 K, respectively. The decrease in crystallization temperature was also related to atoms transitioning into a quasi-nucleic phase in the films. The ratio of electron excitation andmigration effects to thermal effects was controlled using the storage-ring current (photon flux density). Therefore, we believe that low-temperature crystallization can be realized by controlling atomic migration through electron excitation. (C) 2013 Elsevier B. V. All rights reserved.

A laser-plasma source comprising a rotating cryogenic solid-state Xe target has been studied for use in extreme ultraviolet lithography (EUVL) systems equipped with La/B4C mirrors. The laser-to-EUV power conversion efficiency (CE) of the cryogenic Xe target was improved to achieve a maximum CE of 0.15 % at 6.7 nm with 0.6 % bandwidth. We successfully demonstrated the continuous generation of EUV light with an average power of 80 mW at 6.7 nm with 0.6 % bandwidth using a Nd:YAG slab laser at a repetition rate of 320 Hz and an average power of 100 W. Scaling-up of the laser-plasma source for use as a future EUVL source is also discussed.