Compact, Large Solid Angle Coverage Neutron Diffractometer

Current single-crystal neutron diffractometers have performed remarkably well and have contributed significantly to the research of structural problems in diverse areas including chemistry, earth sciences, materials science, engineering, and solid-state physics. The current instruments, however, are associated with three main issues: 1) lack of portability due to complexity of detector arrangements which increases its physical size, 2) performance issues due to physical gaps between the detector coverage, and 3) high cost. We are addressing these specific issues in the proposed program with a goal of developing a compact, large solid angle coverage single crystal neutron diffractometer. The problem will be addressed by developing the desired diffractometer using truly hemispherical, portable thermal neutron detectors recently developed at RMD. These detectors will use an advanced sensor capable of simultaneously providing high signal strength to enhance the signal to noise ratio (SNR), very high spatial resolution, high detection efficiency and excellent gamma rejection commensurate with the diffractometer needs and can be economically implemented to provide the desired angular coverage. A suitably designed sample handling system will be included in the final deliverable unit. The goal of the proposed Phase I is to demonstrate feasibility of our approach. During Phase I, we will develop the instrument design and conduct experiments at HFIR to establish performance parameters for the final unit. To accomplish this, the following Phase I specific aims have been established: 1) Explore ways to enhance solid angle coverage, design hardware to hold the detector modules, and outline data acquisition and software processing needs. 2) Develop sample manipulator design in consultation with our subcontractors, consultants, and the end-users and 3) Demonstrate feasibility through experiments to be conducted at ORNL. A compact diffractometer providing angular coverage >2p solid angle with minimal or no dead area between active regions will find numerous uses at conventional beamlines, and even in laboratory setups that make use of portable neutron sources. Such an instrument will be well suited for determining atomic positions and displacement parameters of light elements (such as hydrogen) next to heavy metals in advanced materials or new drugs, and will be an ideal solution for studying magnetic structures, phase transitions, disorder, and local structure phenomena. Research in each of these areas will directly benefit public as it will accelerate the development of new drugs, novel materials, and systems, all of which have a direct impact on health care, quality of life, addressing nation’s future energy needs, and will permit widening of our technology base.