Recent extraordinary developments in synchrotron radiation sources have enabled the growth of powerful research techniques such as time-resolved X-ray diffraction studies, essential for understanding dynamic biological phenomena and recovering phase information in X-ray crystallography. To make the most effective use of these advanced synchrotron sources for important protein studies, however, new, efficient, high-throughput detectors are needed. Such detectors will enhance the quality of the molecular models that are the end product of the macromolecular crystallography process. Toward achieving this goal, several novel readouts based on new designs of charge-coupled devices have been developed. However, current X-ray-to- light converters provide low light conversion efficiency, low X-ray absorption, and a tradeoff between spatial resolution and efficiency, and significantly limit the performance of these powerful new CCD devices. To address these issues, we propose to develop a novel semiconductor scintillator that promises to produce as much as a three-fold increase in light yield over the known brightest scintillators, high X-ray absorption due to its high density and high effective atomic number, a fast decay without any afterglow, emission in the wavelength range that is most suitable for CCD-type devices, and orders of magnitude higher radiation resistance than current scintillators. Beyond the excellent scintillation properties of this new and advanced scintillator, it will be fabricated in a microcolumnar form, which will provide very high spatial resolution. When combined with a suitable readout, this scintillator will enable realization of the high speed, large area, high resolution detectors needed for important time-resolved X-ray diffraction and other studies. During Phase I we successfully accomplished each of our stated goals and demonstrated the feasibility of our new scintillator technology. Building upon this foundation, the goal of the Phase II research is to further develop the technology to grow microcolumnar films capable of providing an as-yet unattained combination of very bright signal, negligible afterglow, high spatial resolution (in excess of 20 lp/mm), and excellent temporal resolution, all of which are necessary for time-resolved X-ray diffraction studies in particular, and for high speed X-ray imaging and digital radiography in general. Our Phase II scintillators are expected to measure 25 x 25 cm2 or larger in area, with efficiency in excess of 98% for X-ray energies typically used in time-resolved studies, and at least 3 orders of magnitude higher radiation resistance compared to current state-of-the-art scintillator screens. After fabrication, the films will be characterized in detail in terms of their morphology, scintillation properties, optical properties and imaging performance at RMD. Films will then be integrated into a specially developed high-speed readout by RMD and evaluated at the BioCAT beam line at the Advanced Photon Source (APS) at ANL, to demonstrate their performance superiority compared to current state-of-the- art scintillator screens. Applications of a scintillator with the exceptional properties described range widely - from macromolecular crystallography to medical imaging, and from nondestructive testing to polymer research. As such, the commercial potential for this sensor is particularly high. We and our collaborators at the APS and our potential commercial partners believe that due to its extraordinary properties, this scintillator will have widespread use in many important synchrotron-based applications. During the proposed Phase II research, we will undertake efforts to successfully develop and market these screens through our own resources and in collaboration with our commercial partners.
The proposed research will develop and evaluate a unique scintillator that will provide a factor of three higher light than the brightest commercial scintillators, emission in the red region of the spectrum, high density and high effective atomic number, fast decay time with no afterglow, and orders of magnitude higher radiation resistance compared to the best current scintillators. The availability of such a sensor will enable advancements in the high speed X-ray imaging detector technology needed for many critically important biological studies, such as static and time-resolved scattering from macromolecules. In turn, this will facilitate addressing the important """"""""protein folding problem"""""""" and the study of phase transitions in model membrane systems, the understanding of which is vital for many biotechnological applications, such as the design of various drug delivery systems.
