Papers by Nobuhiko Sarukura
Response time-improved, impurity-doped ZnO scintillator for precise synchronization of femtosecond pulses from XFEL and conventional ultrafast laser
Response time of an Indium ion-doped zinc oxide scintillator is measured to be ~3 ps, an improved... more Response time of an Indium ion-doped zinc oxide scintillator is measured to be ~3 ps, an improved of almost 50 times compared to the previously reported Iron ion-doped counterpart. Intentional impurityion doping introduces additional fluorescence quenching channels that facilitate shortening of the response time. This improved response time allows timing control between x-ray free electron laser pulses and a femtosecond laser to within a few picosecond accuracy.
Epj Web of Conferences, 2013
The FIREX-1 project, the goal of which is to demonstrate fuel heating up to 5 keV by fast ignitio... more The FIREX-1 project, the goal of which is to demonstrate fuel heating up to 5 keV by fast ignition scheme, has been carried out since 2003 including construction and tuning of LFEX laser and integrated experiments. Implosion and heating experiment of Fast Ignition targets have been performed since 2009 with Gekko-XII and LFEX lasers. A deuterated polystyrene shell target was imploded with the 0.53-m Gekko-XII, and the 1.053-m beam of the LFEX laser was injected through a gold cone attached to the shell to generate hot electrons to heat the imploded fuel plasma. Pulse contrast ratio of the LFEX beam was significantly improved. Also a variety of plasma diagnostic instruments were developed to be compatible with harsh environment of intense hard x-rays (rays) and electromagnetic pulses due to the intense LFEX beam on the target. Large background signals around the DD neutron signal in timeof-flight record of neutron detector were found to consist of neutrons via (,n) reactions and scattered gamma rays. Enhanced neutron yield was confirmed by carefully eliminating such backgrounds. Neutron enhancement up to 3.5 × 10 7 was observed. Heating efficiency was estimated to be 10-20% assuming a uniform temperature rise model.
Review of Scientific Instruments, Oct 22, 2014
The Review of Laser Engineering, 2015
Epj Web of Conferences, 2013
A fast-decay and low-afterglow liquid scintillator was developed for the fast ignition experiment... more A fast-decay and low-afterglow liquid scintillator was developed for the fast ignition experiment at the Institute of Laser Engineering (ILE). The liquid scintillator was coupled to a gated photomultiplier (PMT), and the gating performance under high-intensity-rays was experimentally checked. In 2010, a detector with a high detection efficiency of 10 −4 was developed and installed in this experiment. The neutron yield in the fast heating experiment was successfully measured using this detector.
Nuclear Fusion, Sep 26, 2013
Controlled thermonuclear ignition and subsequent burn will be demonstrated in a couple of years o... more Controlled thermonuclear ignition and subsequent burn will be demonstrated in a couple of years on the central ignition scheme. Fast ignition has the high potential to ignite a fuel using only about one tenth of laser energy necessary to the central ignition. This compactness may largely accelerate inertial fusion energy development. One of the most advanced fast ignition programs is the Fast Ignition Realization Experiment (FIREX) [1]. The goal of its first phase is to demonstrate ignition temperature of 5 keV, followed by the second phase to demonstrate ignition-and-burn. The second series experiment of FIREX-I from late 2010 to early 2011 has demonstrated a high (≈20%) coupling efficiency from laser to thermal energy of the compressed core, suggesting that one can achieve the ignition temperature at the laser energy below 10 kJ. Given the demonstrations of the ignition temperature at FIREX-I and the ignition-and-burn at the National Ignition Facility [2], the inertial fusion research would then shift from the plasma physics era to power generation era.
Towards the development of APLF scintillators for neutron detection
Proceedings of the Samahang Pisika ng Pilipinas, 2013
We studied lanthanide-doped 20Al(PO3)3-80LiF, or simply APLF, as scintillator for neutron detecti... more We studied lanthanide-doped 20Al(PO3)3-80LiF, or simply APLF, as scintillator for neutron detection. Lanthanide-doped APLFs had faster fluorescence decay times by about 10 ns compared to a standard scintillator, GS2. Nd-doped APLF exhibited the fastest decay time of 6.6 ns. The fluorescence of the Pr-doped and GS2 using different radiation sources were also compared. The Pr-doped APLF had faster decay time compared to GS2 regardless of the radioactive excitation source. We demonstrated the potential of the Pr-doped APLF as a scintillator by neutron diagnostics. Lanthanide- doped APLFs can be better alternatives to conventional scintillators. We envision further developments of lanthanide-doped APLF-based neutronscintillators.
The diagnostics of the energy coupling efficiency in the Fast Ignition integrated experiment
Journal of physics, Mar 1, 2016
The energy coupling efficiency (CE) in Fast Ignition (FI) laser fusion was studied at GEKKO XII a... more The energy coupling efficiency (CE) in Fast Ignition (FI) laser fusion was studied at GEKKO XII and LFEx laser facility by using newly developed targets and plasma diagnostic instruments. The gated-liquid scintillator neutron detectors had been upgraded by using neutron collimators for intense background fluxes of γ-rays and neutrons in the FI experiment. Clear fusion neutron signal was successfully recorded in the sub-kJ heating FI experiment. Up to 5 times neutron yield enhancement was observed, and the CE of the heating laser to core plasma was estimated to be 1.6% for cone-in-shell target implosion by 9 beams and core heating by LFEX pulse 115 ps before bang time. The laser-to-electron energy conversion efficiency was separately diagnosed using a newly developed target and resulted to be 45%. The fast electron energy spectrum was estimated to be 2.3 MeV slope temperature by hard x-ray spectroscopy. Monte Carlo simulations demonstrate the consistency of the data set.
Plasma and Fusion Research, 2014
The progress on the neutron time of flight (nTOF) detection system for Fast Ignition (FI) related... more The progress on the neutron time of flight (nTOF) detection system for Fast Ignition (FI) related experiment was presented. The novel nTOF detector consists with custom-developed liquid scintillator and gated PMT was implemented. The origin of the harsh backgrounds which had been observed in previous experiment was identified by Monte Carlo simulation. The neutron yield around 10 6 in the 1 kJ-heating experiment which is 10 times lower than previous lower limit was clearly diagnosed.
Room-temperature optical emission properties of hydrothermal grown zinc oxide nanostructures
We report on the room-temperature optical emissions of hydrothermal-grown zinc oxide (ZnO) nanost... more We report on the room-temperature optical emissions of hydrothermal-grown zinc oxide (ZnO) nanostructures. The nanostructures were fabricated on seeded silicon (Si) substrates by hydrothermal growth method using different zinc acetate dihydrate [Zn(CH3COO)·2H2O, ZnAc] concentrations. Regardless of the ZnAc concentration, all nanostructures exhibit well-defined hexagonal facets and intense near-band-edge ultraviolet (UV) emissions. However, increasing the ZnAc concentration leads ZnO nanostructures which exhibit longer emission lifetimes and a secondary red-shifted UV emission around 392 nm. These changes in the nanostructures' UV emission properties are attributed to the multiple excitation/absorption and emission processes of coalescent structures and/or structures sharing common sides or boundaries. Our results suggest that for UV scintillator applications, this phenomenon in ZnO nanostructures can be reduced by using lower (< 100 mM) ZnAc concentrations during hydrothermal...
Luminescence Properties of Nd3+‐Doped AlF3‐Based Fluoride Glass in the Vacuum Ultraviolet Region
physica status solidi (b), 2020
The development and characterization of the optical properties of a neodymium(III)‐doped 42.75AlF... more The development and characterization of the optical properties of a neodymium(III)‐doped 42.75AlF3–33.25CaF2–19BaF2–5YF3 (Nd3+‐doped BCA‐5Y) glass in the vacuum ultraviolet (VUV) region are reported. Photoluminescence peaks at 180 and 227 nm are observed upon excitation with the 157 nm emission of a F2 laser. The dominant 180 nm emission peak is assigned to the 4f25d–4f3 (4I9/2 level) transition in Nd3+. This emission peak exhibits a fast, single exponential luminescence with a 16 ns decay time. The strong luminescence intensity and the fast decay time allude to its prospects for scintillator applications.
Applied Physics Letters, 2017
First-principles density functional calculations together with experimental measurements demonstr... more First-principles density functional calculations together with experimental measurements demonstrate that pressure (uniform and uniaxial) increases the band gap of a perfect lithium hexafluoroaluminate (LiCaAlF6, LiCAF) crystal. As fluoride crystals can be highly transmitting at vacuum ultraviolet wavelengths, crystal modifications that further increase the band gap are highly sought after for future Vacuum ultraviolet applications. Through an extensive series of density functional theory simulations, we demonstrate that the band gap increases monotonically from 12.2 eV to 14.1 eV with the application of uniform pressure. Through joint theoretical and experimental investigation, we explore different uniaxial compressions that can be achieved through cutting-edge laser-shock compression. We find that uniaxial pressure also increases the LiCAF band gap by 0.3 and 0.4 eV for a- and c-axis compressions, respectively.
Scintillator for neutron detection and neutron measurement device
EPJ Web of Conferences, 2013
A down-scattered neutron detector operating in the multichannel counting mode was developed for a... more A down-scattered neutron detector operating in the multichannel counting mode was developed for areal density (R) measurement. Equipped with a newly developed 6 Li glass scintillator (APLF80), the detector was tested in a fusion experiment at the GEKKO XII facility, Osaka University, Osaka, Japan. For a low-R fusion shot, the detector clearly discriminated the-rays, primary neutrons,-rays produced via (n,) reactions from the target chamber, and neutrons scattered by the target chamber. Furthermore, the observed signal was in good agreement with predictions made by Monte Carlo simulation.
Scintillation and Optical Properties of Ce-Doped Fluoride Glass Samples with Different Ce Concentrations
Sensors and Materials, 2015
Fast Fe-Doped ZnO Scintillator for Accurate Synchronization of Femtosecond Pulses from XFEL and Conventional Ultrafast Laser
International Conference on Ultrafast Phenomena, 2010
Toshihiko Shimizu,1,4 Kohei Yamamoi,1,4 Tomoharu Nakazato,1,4 Kohei Sakai,1 Nobuhiko Sarukura,1,4... more Toshihiko Shimizu,1,4 Kohei Yamamoi,1,4 Tomoharu Nakazato,1,4 Kohei Sakai,1 Nobuhiko Sarukura,1,4 Dirk Ehrentraut,2 Tsuguo Fukuda,2 Mitsuru Nagasono,4 Tadashi Togashi,4 Shinichi Matsubara,3,4 Kensuke Tono,4 Atsushi Higashiya,4 Makina Yabashi,4 Hiroaki Kimura3,4 ...
Nuclear Power - Operation, Safety and Environment, 2011
Pr Doped Li-6 Glass Scintillator for Inertial Confinement Fusion Neutron Diagnostics
Conference on Lasers and Electro-Optics 2010, 2010
Experimental results are presented on the properties of a custom-designed fast-response lithium-6... more Experimental results are presented on the properties of a custom-designed fast-response lithium-6 glass scintillator for inertial confinement fusion diagnostics. This newly developed scintillator promises as an indispensable tool in the realization of scattered neutron diagnostics.
Terahertz radiation in below-bandgap, optically pumped GaAs/AlGaAs multiple quantum wells in magnetic field
International Quantum Electronics Conference, 2005.
It has been known that the surface-field THz emission in a semiconductor and in a semiconductor q... more It has been known that the surface-field THz emission in a semiconductor and in a semiconductor quantum well occurs when a short laser pulse creates electron-hole (e-h) dipoles that are accelerated in opposite directions by the surface electric field. The accelerating charges emit a THz transient signal [1]. Other mechanisms include intersubband spontaneous emissions and the excitation of quantum beats in the quantum well subbands [2]. In these scenarios, it is always surmised that the energy of the excitation laser pulse is higher than the bandgap of the semiconductor for it to be able to create photogenerated e-h pairs. In this work, we present initial results showing surface field THz radiation of a narrow and wide uncoupled GaAs/AlGaAs multiple quantum well (MQW) heterostructures for excitation energies lower than the bandgap. Furthermore, the emission enhancement and suppression effects of an externally applied magnetic field (B-field) are also investigated.
Action Spectra of GaAs/AlGaAs Multiple Quantum Wells Exhibiting Terahertz Emission Peak at Excitation Energies Below the Bandgap
Springer Series in Optical Sciences, 2007
... E. Estacio,' A. Quema.l' G. Diwa,' G. De los Reyes,' H. Murakami,1 S. Ono... more ... E. Estacio,' A. Quema.l' G. Diwa,' G. De los Reyes,' H. Murakami,1 S. Ono,' N. Sarukura,' A. Somintac.? ... The effect ofthe externally applied magnetic field parallel to the MQW plain is to enhance or reduce the THz emission intensity for the up or down direction, respectively. ...
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Papers by Nobuhiko Sarukura