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

Abstract

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.

Demonstration of Shape Analysis of Neutron Resonance Transmission Spectrum Measured with a Laser-driven Neutron Source

“…A PMT with gated voltage can reduce the impact of the flash signals [27][28][29] . Neutron resonance transmission experiments using LDNSs have been reported [30][31][32] . Drops in neutron counts at the neutron resonance energies in a spectrum were observed from 18 laser shots using a borated microchannel plate (MCP) detector, which has low sensitivity to gamma rays 30 .…”

“…Drops in neutron counts at the neutron resonance energies in a spectrum were observed from 18 laser shots using a borated microchannel plate (MCP) detector, which has low sensitivity to gamma rays 30 . The changes in neutron transmission at the neutron resonance energies were observed by monitoring the output level of a time-gated 6 Li glass scintillation neutron detector with a single laser shot 31,32 . This study observed the neutron resonance transmission spectrum using a counting method with a time-gated 6 Li glass scintillation neutron detector.…”