Novosibirsk terahertz free electron laser: instrumentation development and experimental achievements

Abstract

Nowadays, the Novosibirsk free electron laser (NovoFEL) is the most intense radiation source in the terahertz spectral range. It operates in the continuous mode with a pulse repetition rate of up to 11.2 MHz (5.6 MHz in the standard mode) and an average power of up to 500 W. The radiation wavelength can be precisely tuned from 120 to 240 mm with a relative line width of 0.3-1%, which corresponds to the Fourier transform limit for a micropulse length of 40-100 ps. The laser radiation is plane-polarized and completely spatially coherent. The radiation is transmitted to six user stations through a nitrogen-filled beamline. Characteristics of the NovoFEL radiation differ drastically from those of conventional low-power (and often broadband) terahertz sources, which enables obtaining results impossible with other sources, but necessitates the development of special experimental equipment and techniques. In this paper, we give a review of the instrumentation developed for control and detection of high-power terahertz radiation and for the study of interaction of the radiation with matter. Quasi-optic elements and systems, one-channel detectors, power meters, real-time imagers, spectroscopy devices and other equipment are described. Selected experimental results (continuous optical discharge, material and biology substance ablation, real-time imaging attenuated total reflection spectroscopy, speckle metrology, polarization rotation by an artificial chiral structure, terahertz radioscopy and imaging) are also presented in the paper. In the near future, after commissioning another four electron racetracks and two optical resonators, intense radiation in the range from 5 to 240 μm will be available for user experiments.

Regular Trends of Acousto-Optic Interaction in Terahertz Region of Electromagnetic Radiation

“…We measured transparency of a few AO materials in the THz region of spectrum in a preliminary experiment carried out by means of the Novosibirsk free-electron laser (FEL) [4]. It was found that the majority of known AO-materials were opaque.…”

Efficient power combiner for THz radiation

“…A free electron laser 3 reported by the Institute of Nuclear Physics (Novosibirsk, Russia) generates an average power of 0.5 kW; however, it is as large as a building, housed in a large high bay facility. In addition to that, a gyrotron with pulsed magnetic field operating in a single 50 µs pulse with output power 1.5 kW 4 has been reported by the Institute of Applied Physics (Nizhny Novgorod, Russia).…”

“…In addition to that, a gyrotron with pulsed magnetic field operating in a single 50 µs pulse with output power 1.5 kW 4 has been reported by the Institute of Applied Physics (Nizhny Novgorod, Russia). This gyrotron requires a cryomagnet and a diamond window, and including its power supply is about 2m 3 in volume and not portable.…”

Much Ado about Microbunching: Coherent Bunching in High Brightness Electron Beams

“…Linac driven FELs use each electron pulse once, leading to low duty cycles. (Energy recovery linacs reach high duty cycles by recovering the electron energy [36,37,38].) Storage rings, by contrast, naturally operate at MHz repetition rates (determined by the revolution time of the electrons), and fully filled rings can provide CW radiation.…”