N.A. Vinokurov

Novosibirsk terahertz free electron laser: instrumentation development and experimental achievements

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.

Lasing in visible and ultraviolet regions in an optical klystron installed on the VEPP-3 storage ring

Abstract Lasing in a wide 2400–6900 A spectral range (from visible to ultraviolet) was reached in the optical klystron OK-4 installed on the VEPP-3 storage ring. OK-4 is the first FEL operating in UV.

Novosibirsk Free Electron Laser—Facility Description and Recent Experiments

The design and operational characteristics of the Novosibirsk free electron laser facility are described. Selected experiments in the terahertz range carried out recently at the user stations are surveyed in brief.

The VEPP-3 storage-ring optical klystron: Lasing in the visible and ultraviolet regions

Abstract Lasing in a wide spectral range (from visible to ultraviolet, 2400–6900 A) was reached in the optical klystron OK-4 installed on the VEPP-3 storage ring. OK-4 is the first FEL operating in UV.

Status of the INP optical klystron

Abstract The result of recent experiments with the optical klystron OK-2 installed in the storage ring VEPP-3 are presented. The current status, the new magnetic system design OK-3, and some prospects and plans are described.

The magnetic and diagnostics systems for the Advanced Photon Source self-amplified spontaneously emitting FEL

A self-amplified spontaneously emitting (SASE) free-electron laser (FEL) for the visible-to-ultraviolet spectral range is under construction at the Advanced Photon Source at Argonne National Laboratory. The amplifier part of the FEL consists of twelve identical 2.7-meter-long sections. Each section includes a 2.4-meter-long, 33-mm-period hybrid undulator, a quadruple lens, and a set of electron beam and radiation diagnostics equipment. The undulatory will operate at a fixed magnetic gap (approx. 9.3 mm) with K=3.1. The electron beam position will be monitored using capacitive beam position monitors, YAG scintillators with imaging optics, and secondary emission detectors. The spatial distribution of the photon beam will be monitored by position sensitive detectors equipped with narrow-band filters. A high-resolution spectrograph will be used to observe the spectral distribution of the FEL radiation.

Synchrotron Light Sources and Recent Developments of Accelerator Technology

The main aim of the next-generation synchrotron radiation sources is to provide diffraction-limited undulator radiation in the 0.1-4 nm range with an average power of 10-1000 W and monochromaticity of 10(-3)-10(-4). A review of new accelerator technologies that could be used for the construction of such types of synchrotron radiation sources is given.

Multisegment wigglers for short wavelength FEL

Abstract A high gain FEL with a magnetic system consisting of undulators and dispersive sections between them is considered. Using of achromatic bends between undulators is briefly discussed. A scheme of the beam conditioning applicable for ultrarelativistic electrons is described.

The elliptical multipole wiggler project

The elliptical multipole wiggler (EMW) has been designed, constructed, and installed in the X13 straight section of the NSLS X-ray Ring. The EMW generates circularly polarized photons in the energy range of 0.1-10 keV with AC modulation of polarization helicity. The vertical magnetic field of 0.8 T is produced by a hybrid permanent magnet structure with a period of 16 cm. The horizontal magnetic field of 0.22 T is generated by an electromagnet, the core of which is fabricated from laminated iron to operate with a switching frequency up to 100 Hz. There are dynamic compensation trim magnets at the wiggler ends to control the first and second field integrals with very high accuracy throughout the AC cycle. The residual closed orbit motion due to the electromagnet AC operation is discussed.

Studying the non-thermal effects of terahertz radiation on E. coli/pKatG-GFP biosensor cells

Studies of the impact of terahertz radiation on living objects present a significant interest since its use for security systems is currently considered promising. We studied the non-thermal impact of terahertz radiation on E. coli/pKatG-gfp biosensor cells. The Novosibirsk free electron laser (NovoFEL), which currently has the worlds highest average and peak power, was used as the source of terahertz radiation. We demonstrated that exposure to terahertz radiation at the wavelengths of 130, 150, and 200 µm and a power of 1.4 W/cm(2) induces changes in green fluorescent protein (GFP) fluorescence values and thus induces the expression of GFP in E. coli/pKatG-gfp biosensor cells. Possible mechanisms of the E. coli response to non-thermal exposure to terahertz radiation are discussed.