Shock Temperature Measurement Using Neutron Resonance Spectroscopy

Abstract

We report a direct measurement of temperature in a shocked metal using Doppler broadening of neutron resonances. The 21.1-eV resonance in 182 W was used to measure the temperature in molybdenum shocked to 63 GPa. An explosively launched aluminum flyer produced a planar shock in a molybdenum target that contained a 1-mm thick layer doped with 1:7 at: % 182 W. A single neutron pulse, containing resonant neutrons of less than 1 s duration, probed the shocked material. Fits to the neutron time-of-flight data were used to determine the temperature of the shocked molybdenum.

Non-contact measurement of partial gas pressure and distribution of elemental composition using energy-resolved neutron imaging

“…Recent developments of neutron detectors with ∼55 µm spatial and 20 ns -500 µs temporal resolution have enabled neutron resonance imaging with spatial resolution greater than ∼100 µm. 19,28,29 Resonance imaging experiments have been previously performed with solid materials using resonances up to ∼10 keV in energy [15][16][17][18][19][20][21][22][23][24] and we extend these studies to imaging gaseous substances.…”

“…At current facilities the measurable energy range is typically limited to less than ∼10 4 eV by the width of the neutron pulse, the available flux, and by the level of background signal. [17][18][19][20][21][22][23][24] Thus current opportunities are best served for nuclides with resonances between ∼0.1 eV and ∼10 keV energies. Tabulated attenuation cross sections 27 exist for the majority of isotopes and can be used to evaluate experiment feasibility to resolve a particular element in a specific sample.…”

“…By contrast pulsed spallation neutron sources, which typically employ time of flight technique to resolve neutron energy, routinely offer energy resolution to sub-percent levels 4 and extend the spectral range to epithermal neutrons in excess of 10 keV. [15][16][17][18][19][20][21][22][23][24] In the region of ∼1-10 5 eV many elements exhibit isotope-specific resonances that exist over narrow energy ranges specific to a particular isotope. Their existence results in sharp decreases in neutron transmission at discrete energies that indicate the presence of isotopes along the neutron path.…”

“…To date the majority of resonance absorption experiments were conducted with a single pixel device 17,22,23 or with a limited (∼1-2 mm) spatial resolution. 15,16,20 However recent development of fast detection devices with 55 µm detector pixel size enables mapping the distribution of elements (including tomographic 3-dimensional imaging) and temperature in a solid sample with a ∼100 µm resolution.…”

“…Studies that employ resonances appearing in the epithermal range of energies have been also reported for the investigation of elemental composition [15][16][17][18][19][20][21] and remote measurement of temperature. [22][23][24] Energy-resolved measurements can be conducted at reactor sources using velocity selectors 25 and crystal monochromators 26 with energy resolutions (∆E/E) of ∼15% and ∼3%, respectively. By contrast pulsed spallation neutron sources, which typically employ time of flight technique to resolve neutron energy, routinely offer energy resolution to sub-percent levels 4 and extend the spectral range to epithermal neutrons in excess of 10 keV.…”