Bhaskar Sur

Atomic structure holography using thermal neutrons.

The idea of atomic-resolution holography has its roots in the X-ray work of Bragg and in Gabors electron interference microscope. Gabors lensless microscope was not realized in his time, but over the past twelve years there has been a steady increase in the number of reports on atomic-resolution holography. All of this work involves the use of electrons or hard X-rays to produce the hologram. Neutrons are often unique among scattering probes in their interaction with materials: for example, the relative visibility of hydrogen and its isotopes is a great advantage in the study of polymers and biologically relevant materials. Recent work proposed that atomic-resolution holography could be achieved with thermal neutrons. Here we use monochromatic thermal neutrons, adopting the inside-source concept of Szöke, to image planes of oxygen atoms located above and below a single hydrogen atom in the oxide mineral simpsonite.

APPLICATION OF GEANT4 TO THE DATA ANALYSIS OF THERMAL NEUTRON SCATTERING EXPERIMENTS

Multiple scattering has been well recognized as an important correction in neutron scattering cross-section measurements. The GEANT4 simulation toolkit includes a special thermal neutron scattering model and a corresponding data library at low neutron energies (<4xa0eV). A new method using GEANT4 to estimate the multiple-scattering effect in thermal neutron scattering experiments is presented. The method was applied to the double differential cross-section measurements of light water with various sample thicknesses under ambient conditions of temperature and pressure. The resulting scattering law for neutron energy transfer from 42.0 to 14.6xa0meV over scattering angles from 10° to 110° is presented and compared with the tabulated Evaluated Nuclear Data File (ENDF/B-VII).

Nuclear Industry Applications of Si-Diode Based High Gamma Dose Rate Detectors

AECL has developed and deployed several high gamma radiation field measurement and profiling systems based on commercial off-the-shelf (COTS) silicon diode sensors and components. These systems have been useful in a number of applications including radiation survey of a medical radioisotope production hot-cell, liquid level measurement in a highly radioactive tank, identification of waste location inside nuclear waste storage structures, imaging of reactivity devices inside a shut-down nuclear reactor, and for scanning and imaging highly radioactive reactor components inside a hot-cell in support of an industrial surveillance project. The measurements ranged from 100 uGy/h (10 mRad/h) to 10 kGy/h (1MRad/h), which covers typical radiation fields in hazardous nuclear facilities. This paper summarizes the development and characterization of the Si-diode based detector system, and describes its performance in a variety of applications.Copyright