Sangjin Lee

Sanjin Lee Education

B.S. Pukyung National University 2001 Physics
M.S. Florida State University 2004 Physics
Ph.D. Florida State University 2008 Physics

Contact Informaton
(812) 855-3613



Neutron Radiation Effects Program

The Low Energy Neutron Source (LENS) is a novel, university-based pulsed neutron source located within the Center for Exploration of Energy and Matter (CEEM) at Indiana University. The source utilizes a low energy p-n reaction in Beryllium coupled with a high-current, variable-pulse-width proton accelerator to produce either short or long neutron pulses.  One of the target stations has been optimized for neutron radiation effects studies of device and board level electronics testing with quasi monochromatic high flux neutron beams (~1 MeV equivalent silicon).  The total neutron flux at the device under test (DUT) is approximately 2 × 10^10 (n/cm^2/sec) with low gamma contamination, 1 × 10^9 (n/cm^2/sec). The neutron spectrum at the DUT position has been calculated using MCNP-X and has been characterized using foil activation measurements. Inverse gain degradations of 2N222A BJT device have also been characterized and Sulfur and Iron foils have been used as dosimetry monitor foils. Measured neutron intensities are compared to MCNPX calculations and legacy systems.


Advanced Fast Neutron Radiography and Tomography

In contrast to many existing neutron imaging stations we have chosen to utilize a broad range of neutron energies extending into the fast neutron regime to take advantage of the higher fluxes and larger penetrating power of these high energy neutrons.  The imaging station consists of a collimator to define the beam, a rotating sample stage and a cooled CCD camera (Alta U6) utilizing a scintillator.  Polypropylene + ZnS are used for fast neutrons and LiF +ZnS screen are used for thermal neutrons.  Typical image collection times are a few seconds for a l/d ratio of 100 yielding and a spatial resolution of 0.2 x 0.2 mm2. Examples of several scanned images will be presented. 

Tomographic reconstructions can be carried out by placing the sample on a rotating sample stage and collecting neutron images at different orientations.  Scanned 2D images are reconstructed using Feldkamp filtered back-projection algorithm. 3D image is produced using the slice volume rendering code with reconstructed 2D slice images.  An automated procedure for collecting 400 slice images has been developed and a full CT scan can be completed in approximately one hour.