Compact Electronic X-ray Source for Borehole Logging

Borehole logging tools utilize 137Cs radionuclide sources which are always “on,” imposing significant concerns to radiation safety during handling and transport, potential environmental pollution in case of loss downhole, and security/terrorism activity. RF linacs that are used to replace the radiological sources in other applications are too large and not capable of remotely operating in harsh environment of deep borehole wells at temperatures as high as 150C and in presence of vibrations up to 2G. RadiaBeam Systems is developing a compact and robust X-ray source for well logging using bremsstrahlung radiation of relativistic electrons produced by a linear accelerator operating at up to 150C. A compact “KlyLac” architecture combines an RF linac and klystron, sharing the same electron beam, cathode, and vacuum volume. The conventional linac injector, circulator, RF window, master RF oscillator, waveguides, and control electronics are eliminated. Instead a simple, temperature-independent, ferrite-free, low-level RF feedback loop provides RF self-oscillation of the KlyLac starting quickly from noise with automatic tuning of phase and magnitude of accelerating field keeping it optimal without any temperature-limited electronics. Self-sustained performance of the automatic feedback loop has been confirmed with transient modeling. A stable regime with moderate reflections was found and characterized. A highly efficient, X-band, compact, 650 kW sheet beam klystron (SBK) was designed and modeled. The linac structure was designed and simulated, resulting in a 3.7 MeV beam. We have demonstrated feasibility of the novel cross-rod structure by fabricating and testing a prototype with low level RF. The complete system has been preliminary engineered. In Phase II project, we will design, fabricate, and commission the system prototype. At the end of the Phase II project we will demonstrate operation of the KlyLac system that can to produce several microamperes of beam current at beam energy exceeding one MeV and produce X-rays that correspond to a few Ci activity of a source radiating mostly within 200-500 keV range of photon energies. The goal of his project is to build an ultra-compact portable radioactive material-free source of X-rays that will be used in borehole logging, non-destructive testing and other applications. The addressable market is approximately $50 million per year. The source will also help with the DOE’s goal of reducing the use of radioisotopes in industrial applications.