V.M. Popik

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.

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.

Visualization of radiation from a high-power terahertz free electron laser with a thermosensitive interferometer

A thermosensitive interferometer based on a plane-parallel glass plate is used for visualization of a high-power terahertz radiation. The plane wavefront of visible radiation emitted by a semiconductor laser is reflected from the two surfaces of the plate and forms on a screen an interference pattern recorded by a digital video camera. Terahertz radiation being measured is incident on the outer surface of the plate and heats a thin surface layer, which causes a shift of interference fringes. For K8 glass, a shift by one fringe corresponds to an absorbed energy of 5.1 J/cm2. The problem of determining the sign of the phase shift was solved by comparing the interference patterns with the images obtained with an infrared imager sensitive to near IR radiation. The processing of interference patterns makes it possible to determine the power density distribution over the beam cross section of the Novosibirsk free electron laser. In these measurements, the absolute value of the beam power determined by integrating over the cross section was 65 ± 7 W for a 130-μm wavelength. Visualization of the complex image with a spatial resolution no worse than 1 mm and a frame repetition rate of 25 Hz is demonstrated.

Status of the Novosibirsk high power free electron laser

The first stage of Novosibirsk high power free electron laser (FEL) was commissioned in 2003. It is based on normal conducting CW energy recovery linac. Now the FEL provides electromagnetic radiation in the wavelength range 120-180 micron. The average power is 100 W. The measured linewidth is 0.3%, which is close to the Fourier-transform limit. The assembly of user beamline is in progress. Plans of future developments are discussed.

Electromagnetic undulators for the VEPP-3 optical klystron

Abstract Two types of electromagnetic undulators are described. The first one has 33.5 periods with a length of 10 cm and a magnetic field amplitude of 5.3 kG. The other, developed for future FEL experiments, has 39.5 periods with 7 cm length and a magnetic field amplitude of 55 kG.

Impact of Terahertz Radiation on Stress-Sensitive Genes of E.Coli Cell

Terahertz (THz) radiation is increasingly used in scientific studies, as well in practical applications, primarily in medicine and safety systems, therefore, exposure of living cells to THz-waves present significant interest. We studied the impact of THz radiation on E. coli biosensor cells containing plasmids with promoters of stress-sensitive genes controlling the expression of GFP. The impact of THz radiation was nonthermal, i.e., special care was taken to keep specimen temperature in the 35±2°C range during irradiation so that heat shock genes would not be induced. GFP level was measured by fluorometry. We found that THz radiation activates genes associated with oxidative stress response. Lower activation levels were found for copper homeostasis genes, while antibiotics resistance genes showed no response. Thus, THz radiation impact varies for different E. coli stress systems. We conclude that THz radiation significantly affects oxidative homeostasis, which is vital for E. coli cells.

First UV/visible lasing with the OK-4/Duke storage-ring FEL: design and initial performance

The OK-4/Duke storage ring FEL was commissioned in November 1996 and demonstrated lasing in the near UV and visible ranges (345 - 413 nm). The OK-4 is the first storage ring FEL with the shortest wavelength and highest power for UV FELs operating in the United States. During one month of operation we have performed preliminary measurements of the main parameters of the OK-4 FEL: its gain, lasing power and temporal structure. In addition to lasing, the OK-4/Duke FEL generated a nearly monochromatic (1% FWHM) 12.2 MeV gamma-ray beam. In this paper we describe the design and initial performance of the OK-4/Duke storage ring FEL. We compare our predictions with lasing results. Our attempt to lase in the deep UV range (around 193 nm) is discussed. The OK-4 diagnostic systems and performance of its optical cavity are briefly described.

Quasi-continuous sub-millimeter optical discharge on Novosibirsk free electron laser: experiments and elementary theory

The first quasi-continuous optical discharge in near sub-millimeter spectral range was demonstrated on high-power Novosibirsk free electron laser. Experimental results and elementary theory of this phenomenon are presented.