Single-shot laser-driven neutron resonance spectroscopy for temperature profiling

Lan Z., Arikawa Y., Mirfayzi S.R., et al. Single-shot laser-driven neutron resonance spectroscopy for temperature profiling. Nature Communications 15, 5365 (2024); https://doi.org/10.1038/s41467-024-49142-y.The temperature measurement of material inside of an object is one of the key technologies for control of dynamical processes. For this purpose, various techniques such as laser-based thermography and phase-contrast imaging thermography have been studied. However, it is, in principle, impossible to measure the temperature of an element inside of an object using these techniques. One of the possible solutions is measurements of Doppler brooding effect in neutron resonance absorption (NRA). Here we present a method to measure the temperature of an element or an isotope inside of an object using NRA with a single neutron pulse of approximately 100 ns width provided from a high-power laser. We demonstrate temperature measurements of a tantalum (Ta) metallic foil heated from the room temperature up to 617 K. Although the neutron energy resolution is fluctuated from shot to shot, we obtain the temperature dependence of resonance Doppler broadening using a reference of a silver (Ag) foil kept to the room temperature. A free gas model well reproduces the results. This method enables element(isotope)-sensitive thermometry to detect the instantaneous temperature rise in dynamical processes

Direct fast heating efficiency of a counter-imploded core plasma employing a laser for fast ignition experiments (LFEX)

Fast heating efficiency when a pre-imploded core is directly heated with an ultraintense laser (heating laser) was investigated. \u27Direct heating\u27 means that a heating laser hits a pre-imploded core without applying either a laser guiding cone or an external field. The efficiency, η, is defined as the increase in the internal core energy divided by the energy of the heating laser. Six beams (output of 1.6 kJ) from the GEKKO XII (GXII) green laser system at the Institute of Laser Engineering (ILE), Osaka University were applied to implode a spherical deuterated polystyrene (CD) shell target to form a dense core. The DD-reacted protons and the core x-ray emissions showed a core density of 2.8 ± 0.7 g cm−3, or 2.6 times the solid density. Furthermore, DD-reacted thermal neutrons were utilized to estimate the core temperature between 600 and 750 eV. Thereafter, the core was directly heated by a laser for fast-ignition experiments (LFEX, an extremely energetic ultrashort pulse laser) at ILE with its axis lying along or perpendicular to the GXII bundle axis, respectively. The former and latter laser configurations were termed \u27axial\u27 and \u27transverse modes\u27, respectively. The η was estimated from three independent methods: (1) the core x-ray emission, (2) the thermal neutron yield, and (3) the runaway hot electron spectra. For the axial mode, 0.8%< η <2.1% at low power (low LFEX energy) and 0.4%< η <2.5% at high power (high LFEX energy). For the transverse mode, 2.6%< η <7% at low power and 1.5%< η <7.7% at high power. Their efficiencies were compared with that in the uniform implosion mode using 12 GXII beams, 6% < η <12%, which appeared near to the η for the transverse mode, except that the error bar is very large

Development of a Time-Gated Epithermal Neutron Spectrometer for Resonance Absorption Measurements Driven by a High-Intensity Laser

The advance of laser-driven neutron sources (LDNSs) has enabled neutron resonance spectroscopy to be performed with a single shot of a laser. In this study, we describe a detection system of epithermal (∼eV) neutrons especially designed for neutron resonance spectroscopy. A time-gated photomultiplier tube (PMT) with a high cut-off ratio was introduced for epithermal neutron detection in a high-power laser experiment at the Institute of Laser Engineering, Osaka University. We successfully reduced the PMT response to the intense hard X-ray generated as a result of the interaction between laser light and the target material. A time-gated circuit was designed to turn off the response of the PMT during the laser pulse and resume recording the signal when neutrons arrive. The time-gated PMT was coupled with a 6Li glass scintillator, serving as a time-of-flight (TOF) detector to measure the neutron resonance absorption values of 182W and 109Ag in a laser-driven epithermal neutron generation experiment. The neutron resonance peaks at 4.15 eV of 182W and 5.19 eV of 109Ag were detected after a single pulse of laser at a distance of 1.07 m

Non-destructive inspection of water or high-pressure hydrogen gas in metal pipes by the flash of neutrons and X-rays generated by laser

Low-energy neutrons in the thermal and epithermal energy regions are a powerful probe to inspect water or high pressure hydrogen gas because of their large scattering cross-sections with protons. Laser-driven neutron source, whichis able to simultaneously emit different types of radiations such as X-rays, can be used for neutron and X-ray radiography in the same laser shot. In the present paper, we report the demonstration of non-destructive inspection for H2Oinside of a stainless steel pipe using a laser driven thermal neutron source, where water and stainless containers are detected by neutrons and X-rays, respectively. The simulation result indicates that this method is also able to measure accurately the hydrogen density in high-pressure hydrogen gas in metal containers

A miniature thermal neutron source using high power lasers

Dataset underpinning the results presented in the article titled, "A miniature thermal neutron source using high power lasers" published in Journal of Applied Physics (2020) Absstract of the paper: The continuous improvement of high power laser technologies is recasting the prospects of small-scale neutron sources to enable scientific communities and industries performing experiments that are currently offered at extensive accelerator-driven facilities. This paper reports moderation of laser-driven fast neutrons to thermal energies using a compact modular moderator assembly. A significant thermal (25 meV) flux of 106 n/sr/pulse was measured from water and plastic moderators in a proof-of-principle experiment employing a relatively moderate power laser delivering 200 J on the target in 10 ps. Using Monte Carlo N-Particle eXtended simulations, the experimental results are reproduced and discussed

レーザー駆動中性子源の宇宙核物理学への応用 -放射化法による広いエネルギー領域における中性子数の測定-

大強度レーザーを用いて陽子と重陽子を加速して、Beに照射して中性子を生成した。10-20MeVの高エネルギーの中性子を金属試料に照射し、（n,2n)反応で生成された放射性同位体のβ崩壊によるγ線を計測する手法に、中性子の飛行時間計測法から得たエネルギー分布を組み合わせることで中性子の量を評価した。日本物理学会　2021年秋季大