Observation of coherent synchrotron, Čerenkov, and wake-field radiation at millimeter wavelengths using an<i>L</i>-band linear accelerator

Abstract

Spectra of synchrotron radiation (SR) and \ifmmode \check{C}\else \v{C}\fi{}erenkov radiation (CR) in air have been observed in the wavelength range of 1.15--8 mm using bunched electrons accelerated by an L-band linac, whose energy and radio frequency are 40 MeV and 1300 MHz. The observed intensities of SR and CR at \ensuremath{\lambda}=4 mm are enhanced by factors of 9\ifmmode\times\else\texttimes\fi{}${10}^{7}$ and 1\ifmmode\times\else\texttimes\fi{}${10}^{7}$ in comparison with calculated intensities of ordinary SR and CR, respectively. Radiation of the rf wake induced in a chamber has also been observed. Bunch form factors are derived from the observed spectra, and the electron distribution in a bunch is discussed.