Observation of a variable sub-THz radiation driven by a low energy electron beam from a thermionic rf electron gun

• Main Authors: A. V. Smirnov, R. Agustsson, W. J. Berg, S. Boucher, J. Dooling, T. Campese, Y. Chen, L. Erwin, B. Jacobson, J. Hartzell, R. Lindberg, A. Murokh, F. H. O’Shea, E. Spranza, S. Pasky, M. Ruelas, N. S. Sereno, Y. Sun, A. A. Zholents
• Format: Article
• Language: English
• Published: American Physical Society 2015-09-01
• Series: Physical Review Special Topics. Accelerators and Beams
• Online Access: http://doi.org/10.1103/PhysRevSTAB.18.090703

We report observations of an intense sub-THz radiation extracted from a ∼3  MeV electron beam with a flat transverse profile propagating between two parallel oversized copper gratings with side openings. Low-loss radiation outcoupling is accomplished using a horn antenna and a miniature permanent magnet separating sub-THz and electron beams. A tabletop experiment utilizes a radio frequency thermionic electron gun delivering a thousand momentum-chirped microbunches per macropulse and an alpha-magnet with a movable beam scraper producing sub-mm microbunches. The radiated energy of tens of micro-Joules per radio frequency macropulse is demonstrated. The frequency of the radiation peak was generated and tuned across two frequency ranges: (476–584) GHz with 7% instantaneous spectrum bandwidth, and (311–334) GHz with 38% instantaneous bandwidth. This prototype setup features a robust compact source of variable frequency, narrow bandwidth sub-THz pulses.