Hand-portable accelerator for radioisotope replacement in field radiography

Radioisotope-based gamma sources are used in many security, industrial and medical applications, such as field radiography. However, this approach has many associated safety and security issues. The isotope must be constantly replenished, adding expense and challenging the safety and quality assurance capabilities of the users. For high-energy radiation, RF accelerator technology is the current method of choice. However, in order to be considered as a suitable replacement, the accelerator must have comparable size, weight, cost and imaging performance as radioisotopes. Technical Approach This project will develop a hand-portable 50 lb. X-ray source based on a 2 MeV Ku-band electron linac. The key innovation is operation of the linac in Ku-band RF frequency. Using such a high frequency allows greatly reducing the dimensions and weight of all components. However it is challenging due to the lack of RF sources and extremely tight fabrication tolerances. We will resolve these problems thanks to the use of compact air-cooled low-power Ku-band magnetrons and a revolutionary approach to fabricate the accelerating waveguide through the split accelerating structure technique. This approach allows machining an accelerating structure from two halves, which not only reduces the cost and complexity of the linac fabrication but also eliminates the need for time-consuming RF tuning. Importantly, this approach enables the fabrication of high-frequency structures due to the elimination of random cell-to-cell errors during structure brazing. Phase I Plans In Phase I we will adapt the design of the Ku-band linac to 2 MeV. We will also develop a build the lightweight Marx modulator to drive the compact air-cooled 250 kW Ku-band magnetron, which is already on hand. These studies will be concluded by high-power testing of the structure and the demonstration of practical feasibility of the proposed approach. Commercial Applications and Other Benefits The goal of his project is to build a hand-portable source of high-energy X-rays that will be used to replace radioisotopes such as Cs-137 and Ir-192 in field radiography, security and medical applications. In addition to filling a market need, it will reduce the risk of accidents and diversion of radioactive materials for terrorist purposes.