Dolgashev, V.A. Borchard, P. Kostin, R.A. Krasnykh, A.K. Kuzikov, S.V. Romero, A. JACoW Publishing Geneva, Switzerland 2226-0366 978-3-95450-215-8 10.18429/JACoW-LINAC2022-THPOJO16 English 727-730 linac gun electron cavity GUI Contribution to a conference proceedings 2022 2022-09 https://doi.org/10.18429/JACoW-LINAC2022-THPOJO16 https://jacow.org/linac2022/papers/thpojo16.pdf We will present a physics design of a compact, highly efficient, energy-tunable linac to generate up to 500 W of 10 MeV electron beam power for medical and security applications. This linac will employ a patented travelling wave accelerating structure with outside power flow which combines the advantages of high efficiency with energy tunability of traveling wave cavities. Unlike standing wave structures, the proposed structure has little power reflected back to the RF source, eliminating the need for a heavy, lossy waveguide isolator. In contrast to the side-coupled cavity designs, the proposed structure is symmetrical and therefore it does not have deflecting axial fields that impair the beam transport. The high shunt impedance will allow the linac to achieve an output energy of up to 10 MeV when powered by a compact commercial 9.3 GHz 1.7 MW magnetron. For pulse-to-pulse tuning of the beam output energy we will change of the beam-loaded gradient by varying the triode gun current.