Observation of frequency-locked coherent terahertz Smith-Purcell radiation.
PHYSICAL REVIEW LETTERS 2005;
94:054803. [PMID:
15783652 DOI:
10.1103/physrevlett.94.054803]
[Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2004] [Indexed: 05/24/2023]
Abstract
We report the observation of enhanced coherent Smith-Purcell radiation (SPR) at terahertz (THz) frequencies from a train of picosecond bunches of 15 MeV electrons passing above a grating. SPR is more intense than other sources, such as transition radiation, by a factor of Ng, the number of grating periods. For electron bunches that are short compared with the radiation wavelength, coherent emission occurs, enhanced by a factor of Ne, the number of electrons in the bunch. The electron beam consists of a train of Nb bunches, giving an energy density spectrum restricted to harmonics of the 17 GHz bunch train frequency, with an increased energy density at these frequencies by a factor of Nb. We report the first observation of SPR displaying all three of these enhancements, NgNeNb. This powerful SPR THz radiation can be detected with a high signal to noise ratio by a heterodyne receiver.
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