Chirp / Chirping
Chirping the beam means introducing a linear correlation into its longitudinal phase space. Usually, it is accomplished by running the beam at the slope of a linac phase, so that the beam head and tail are accelerated with slightly different pace. A natural chirping of the beam occurs in a strong wake-field environment.
CTR
Coherent transition radiation. An OTR from a multi-particle beam may add up coherently for long wavelengths, forming CTR. CTR intensity is by many orders of magnitude exceeds OTR, yet the high frequency cut-off in the CTR spectrum is defined by the longitudinal shape of the electron bunch, and typically is in THz range.
CSR
Coherent synchrotron radiation occurs when an electron beam passes through the bending magnet. As in the CTR case, for the wavelengths reflected in the beam structure, the synchrotron radiation from individual electrons in the beam adds up coherently. Unlike CTR, however, CSR is a continuous process, and may affect the phase space distribution of the source beam. Experimental studies of the CSR instabilities in chicanes are essential in understanding the limits of the bunch compression implementation.
Edge Radiation
A special case of CSR, when the electron beam enters the bending magnet. The Edge radiation spectrum is shifted towards longer wavelengths, compare to CSR.
Gain Length
A length over which the radiation intensity in the laser is amplified by the e-fold.
Golay Cell
A thermal bolometer, working at room temperature and sensitive to far-infrared radiation.
OTR
Optical transition radiation. When a charged particle propagates across the media boundary, it generates surface currents (or polarization in the dielectric), which in turn radiate into the media. OTR spectrum is flat, with the high frequency cut-off determined by the dispersive properties of the media (for a metal it is a plasma frequency).
Saturation
A state of physical system performance, when further improvement is not conceivable within the limits of given system.
Slippage
In FEL, a radiation front moves faster than the particle which emitted the radiation. The actual separation between the particle and radiation front is called slippage. If slippage over the length of the undulator exceeds the e-beam bunch lengths, the SASE radiation is longitudinally coherent; otherwise the coherence is partial.
Tomography
A process to reconstruct the spatial profile of the 3-D (2-D) object through measuring its 2-D (1-D) projections. The tomographic methods can be applied to reconstruct the phase space of an electron beam.