Distortion Free Large-Area Detector for Neutron Scattering

Single crystal diffractometers that require large solid angle coverage for optimum performance typically have large gaps in detector coverage. Moreover, the detector edges exhibit degraded resolution, distortion and gamma rejection. These issues complicate data acquisition, which requires additional beam time to collect sufficient data for analysis. This effect is due in large part to using a flat sensor surface that requires tiling to approximate a spherical surface. A spherical detector surface effectively addresses this issue while eliminating most boundary ‘dead’ areas. We are addressing these specific issues in the proposed program. The problem will be addressed by developing a spherical detector with the desired radius of curvature, high spatial resolution which would translate into fine angular resolution, high detection efficiency for neutron wavelengths of interest, and large active area. The spherical area will be constructed from a set of modules, arrayed to form the sensor. The sensor with the desired curvature will be coupled to a readout array via suitable conduit, the electronics for which will be developed by our collaborators. In Phase I, we have brought our design from concept level to full implementation and testing with one of several modules needed to form the spherical active surface. The Phase I research demonstrated the feasibility of this unique detector, where tests at HFIR confirmed two critical operational details that are a major upgrade over the current detector; 1) The curved detector behaves as expected, and eliminates parallax effects due to interaction depth variations in the scintillator, and 2) There is no loss of resolution or additional distortion at the edge of the detector. The goal of the proposed Phase II is to develop a fully functional spherical detector and deliver it to ORNL for tests and evaluation. Both scientific and engineering efforts in many areas will be pursued to realize the detector. In parallel, we will initiate technology commercialization efforts through various avenues outlined in the commercialization plan included in this application. A spherical detector providing angular coverage >2π solid angle with minimal dead area between active regions is needed for single crystal diffractometers, for protein crystallography instruments, and for Laue diffraction studies. Such a detector will be well suited to studying the structure of 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 and will permit widening of our nation’s technology base.