Welcome to NARS                               

 

The Nuclear Analysis and Radiation Sensor (NARS) Laboratory was founded by Prof. Lei R. Cao of the Nuclear Engineering Program at The Ohio State University (OSU) in 2010. The NARS has a lab space of approximately 1,000 sq. ft. and is located at Scott Laboratory, the hub laboratory building for Mechanical and Aerospace Engineering at OSU. The lab also includes an external neutron beam facility at the Ohio State University Research Reactor (OSURR).

Dr. Cao's  conducts research at the intersection of nuclear, materials science, and physics. The focus of his group is on the applied radiological nuclear physics and radiation science in addressing the challenging national needs for counter nuclear threats, improving safe production of nuclear energy, and characterizing materials’ property with nuclear methods, including the development of novel sensors to detect radiation, advanced nuclear instrumentation and measurement methodology, the damage caused by radiation on material properties, use of neutrons, gamma- and X-rays as an interrogation or probing tool to study nuclear and non-nuclear materials, and the radiation transport problems.

NARS Group: December 16, 2016

 

The newly-built external neutron beam line at OSURR is able to deliver a relatively-clean, small-sized (< 30 mm diameter) thermal neutron beam to a workbench, where various instruments can be set up for detector evaluation and in situ materials characterization.  The neutron collimator consists of single-crystal sapphire and polycrystalline bismuth filters -- providing fast neutron and gamma-ray filtration, respectivity -- followed by a parallel series of 3-cm apertures for collimation.  The thermal-equivalent neutorn flux is 2.3E6 n/cm^2/s at the sample position in the high-vacuum chamber. The cadmium ratio -- which is defined as the ratio of the activities of bare and cadmium-covered detectors (typically gold foils), and characterizes the epithermal and fast neutron contributions in the neutron spectrum -- was measured to be 92.  Another available sample locations -- with more space available for scientific equipment -- are in front of the vacuum chamber (maximum flux of 4.4E6 n/cm2/s) and behind the vacuum chamber as well.  

The beam profile and uniformity have been studied with digital neutron imaging using off-the-shelf point-and-shoot cameras as well as with scientific cooled-CCD cameras.   The figure below shows the neutron image of the beam and a 3D surface plot of its intensity profile -- revealing uniform intensity over the 3-cm-dimeter beam umbra.  

Neutron image of beamNeutron image of beam3D surface plot of beam's intensity profile3D surface plot of beam's intensity profile

 

Neutron images of the ASTM standards -- the Beam Purity Indicator (BPI) and Sensitivity Indicator (SI) -- demonstrate the excellent radiographic qualities of the neutron beam, as shown in the figure below. 

Neutron images of the ASTM standardsNeutron images of the ASTM standards: (a) the Sensitivity Indicator and (b) its neutron image; (c) the Beam Purity Indicator (BPI) and (d) its neutron image.

 

 

The neutron beam could be used to evaluate neutron scintillation screens, for example. The neutron image below shows the different light yields and emission spectra of our four scintillators available for neutron imaging.  Novel screens are characterized in terms of resolution and response (linearity, light yield, sensitivity, etc.).  

 

Visible light photo and neutron image of four different scintillatorsVisible light photo and neutron image of four different scintillators

We have the capability for precise sample rotation, as demonstrated in the neutron images below: (top) a lithium-ion battery with 15-degree rotations and (bottom) the BPI with 5-degree and 1-degree rotations.

Neutron images of lithium-ion batteryNeutron images of lithium-ion batteryNeutron images of the BPI taken at precise angles (1- and 5-degree rotations).Neutron images of the BPI taken at precise angles (1- and 5-degree rotations).

 

This beam facility is also particularly useful for evaluation of neutron detectors. We have studied the compound of Boron, Li, and Gd for their response to neutron of varying flux.