Seminars Archive

Linear Accelerators for mm-wave and for medical applications state of the art and experimental results

Abstract
The first part of the seminar will explore the physics of vacuum rf breakdowns in high gradient mm-wave accelerating structures. The electromagnetic fields were induced by an ultra-relativistic electron beam generated by the Facility for Advanced Accelerator Experimental Tests (FACET) at SLAC National Accelerator Laboratory. These accelerating structures have a fundamental beam-synchronous mode with a frequency that varies from 95 to 140 GHz depending on the gap width. When the gap is opened by more than half of a free-space wavelength, the corresponding synchronous mode remains trapped demonstrating behavior consistent with the so called “surface wave”. This regime is of potential interest for femtosecond electron beam diagnostics and beam manipulation techniques. The behavior of the surface wave was characterized and the measured synchronous frequency and beam deflection voltage are found to be in good agreement with simulations. The second part will present MRIdian Linac: the next generation radiotherapy technology that integrates a S-band 6 MV linac with a 0.35 T MRI (Magnetic Resonance Imaging) technology in a compact design, together with the proprietary software to locate, target and track the position and shape of tumors while the radiation is delivered. The highlight of the MRIdian Linac design is the patented magnetic and RF shielding that isolates the workings of a linac and the MRI system from each other. The MRI-based technology provides real-time imaging that clearly defines the targeted tumor from the surrounding soft tissue and other critical organs during radiation treatment. MRIdian allows physicians to record the level of radiation exposure that the tumor has received and adapt the prescription as needed. ViewRay believes this combination of enhanced visualization, on-line adapting and accurate dose recording will significantly improve the safety and efficacy of radiation therapy, leading to better outcomes for patients.