High Efficiency High Resolution Sensor for Hard X-Ray Microtomography

X-ray microtomography (XMT) is a powerful tool for researchers in a wide range of fields, enabling 3D imaging at the micron scale. Many of the DOE synchrotron tomography facilities are involved in research that requires hard X-rays (high energy, up to 100 keV) in order to get better penetration into metal samples. At these higher energies the scintillator quickly becomes the limiting factor, resulting in poor image quality and very long acquisition times. What is needed is a high-yield scintillator with sufficient stopping power for hard X-rays to allow its fabrication into screens thin enough (and bright enough) to achieve adequate resolution under the relevant measurement conditions. A material that can satisfy all the performance needs for XMT applications already exists. This material, Lu2O3:Eu has the highest density among all known scintillators, very high X-ray absorption, and a bright red emission that matches well to CCD quantum efficiency. However, its high melting point and low vapor pressure has heretofore prevented its fabrication in the form of microcolumnar films. When coupled to a CCD or other suitable detector, such structured films will result in a significant improvement in the overall detective quantum efficiency (DQE) of the XMT detector, and will permit the full potential of this invaluable technique to be realized. The Phase I research has now demonstrated the feasibility of producing this new structured scintillator that will enable the development of XMT detectors with an unprecedented combination of high resolution and high sensitivity for hard X-ray imaging. A vapor deposition process, driven by electron beam, was developed, and its capability for generating structured films thick enough (50 m) and with high enough intrinsic resolution (20 lp/mm) for XMT, has been established and quantified. Tests are under way at Argonne National Laboratory and preliminary results are quite promising. The challenge for Phase II is to develop the new deposition protocol into a full-fledged and viable commercial process. This means a large number of experiments with experimental parameters systematically varied so as to produce material with optimal characteristics and reproducible performance. The scintillation and imaging properties will be quantified, and the films will be integrated into prototype detectors that will be evaluated against conventional commercial detectors both in-house (using X-ray sources) and at XMD beam lines at the Argonne synchrotron facility. Commercial Applications and Other Benefits: Applications for the enhanced structured scintillator developed here are many, and while the initial focus is on XMT with hard X-rays, this new and cost-effective form of this scintillator could also be used in a broad array of applications ranging from macromolecular crystallography to medical imaging, and from nondestructive testing to polymer research. Due to the extraordinary properties of this scintillator, we expect it to have widespread use in many important synchrotron-based applications, and will substantially improve modeling of oil-field extraction potential and CO2 sequestration. The commercial potential for this sensor is thus high.