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

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.

Laser-driven neutron source and nuclear resonance absorption imaging at ILE, Osaka University: review.

Here, we present an overview on the recent progress in the development of the laser-driven neutron source (LDNS) and nuclear resonance absorption (NRA) imaging at the Institute of Laser Engineering (ILE), Osaka University. The LDNS is unique because the number of neutrons per micro pulse is very large, and the source size and the pulse width are small. Consequently, extensive research and development of LDNSs is going on around the world. In this paper, a typical neutron generation process by the laser-driven ion beam, called the pitcher-catcher scheme, is described. The characteristics of the LDNS are compared with those of the accelerator-driven neutron source (ADNS), and unique application of the LDNS, such as NRA imaging, is presented. In the LDNS, NRA imaging is possible with a relatively short beam line in comparison with that of the ADNS since the neutron pulse width and the source size of the LDNS are small. Future prospects in research and development of NRA imaging with the LDNS at ILE Osaka University are also described.