VIDES AIZSARDZĪBAS MĀCĪBU PRAKSES LABORATORIJA TOP ZEMNIEKU SAIMNIECĪBĀ “ALEKSANDRI” (z/s A)

Laboratorija bijušās Rundānu muižas teritorijā - vietā, kurā jaunieši iepazīsies ar daudziem Latgales pakalnu, purvu vides aizsardzības un izmantošanas praktiskiem un teorētiskiem darbiem. Izmitināšana, ēdināšana, atpūta ar rundāniešu pamestības noskaņu pārvarēšanu. Iesākums krievvalodīgo zonas atdzimšanai...Laboratorijas ideju pamatā ir profesoru G.Novika, A.Ūbeļa, M.Oša u.c. koncepcijas par vidi kā antropogēnu procesu kompleksu, kopu, ieskaitot tajos etniskos un reliģiskos faktorus. Izmantotas etnoekoloģiskās “Eko - Ludzas” zinātniskās grupas atziņas. Ora et labora! - no latīņu valodas var iztulkot, ka oratoram ir jāstrādā, ka vides aizsardzībai nepieciešama trīsvienība Dievs - Daba - Darbs.Laboratorijas vieta Rundānu pagasts - vēsturē reti minēts, jo atrodas pa vidu starp Zilupi, Dagdu, Rēzekni, Ludzu, Nirzu. Z/s A izvietota Latgales augstienes ūdensšķirtnē. Vides tīrības etalons. Te savu tecējumu sāk Sarjanka - Daugavas pieteka. Rundānu strauts aiznes ūdeņus uz Veļikajas upi. Te pēdējā laikā seno latgaļu pilskalnu aizsardzības līnija

Sub-Hz line width diode lasers by stabilization to vibrationally and thermally compensated ULE Fabry-Perot cavities

We achieved a 0.5 Hz optical beat note line width with ~ 0.1 Hz/s frequency drift at 972 nm between two external cavity diode lasers independently stabilized to two vertically mounted Fabry-Perot (FP) reference cavities. Vertical FP reference cavities are suspended in mid-plane such that the influence of vertical vibrations to the mirror separation is significantly suppressed. This makes the setup virtually immune for vertical vibrations that are more difficult to isolate than the horizontal vibrations. To compensate for thermal drifts the FP spacers are made from Ultra-Low-Expansion (ULE) glass which possesses a zero linear expansion coefficient. A new design using Peltier elements in vacuum allows operation at an optimal temperature where the quadratic temperature expansion of the ULE could be eliminated as well. The measured linear drift of such ULE FP cavity of 63 mHz/s was due to material aging and the residual frequency fluctuations were less than 40 Hz during 16 hours of measurement. Some part of the temperature-caused drift is attributed to the thermal expansion of the mirror coatings. High-frequency thermal fluctuations that cause vibrations of the mirror surfaces limit the stability of a well designed reference cavity. By comparing two similar laser systems we obtain an Allan instability of 2*10-15 between 0.1 and 10 s averaging time, which is close to the theoretical thermal noise limit.Comment: submitted to Applied Physics

Gada žurnāls Latvijas Fotogrāfija 2021

publishersversionPeer reviewe

Compact solid-state laser source for 1S-2S spectroscopy in atomic hydrogen

We demonstrate a novel compact solid-state laser source for high-resolution two-photon spectroscopy of the $1S-2S$ transition in atomic hydrogen. The source emits up to 20 mW at 243 nm and consists of a 972 nm diode laser, a tapered amplifier, and two doubling stages. The diode laser is actively stabilized to a high-finesse cavity. We compare the new source to the stable 486 nm dye laser used in previous experiments and record 1S-2S spectra using both systems. With the solid-state laser system we demonstrate a resolution of the hydrogen spectrometer of 6 \times 10^{11} which is promising for a number of high-precision measurements in hydrogen-like systems

Frequency-modulation spectroscopy with blue diode lasers

Frequency-modulation spectroscopy provides ultrasensitive absorption measurements. The technique is especially adaptable to diode lasers, which can be modulated easily, and has been used extensively in the near-infrared and infrared spectral regions. The availability of blue diode lasers now means that the accessible wavelength region can be increased. We successfully demonstrate wavelength-modulation spectroscopy and two-tone frequency-modulation spectroscopy for the weak second resonance line of potassium at 404.8 nm and for the transition at 405.8 nm in lead, starting from the thermally populated 6p(2) P-3(2) metastable level, information on the modulation parameters is obtained with a fitting procedure. Experimental signal-to-noise ratios: at different absorption levels are compared with theoretical signal-to-noise ratios and show good agreement. Detection sensitivities of 2 x 10(-6) and 5 x 10(-6) for wavelength and two-tone frequency-modulation spectroscopy, respectively, for a 120-Hz bandwidth are demonstrated. (C) 2000 Optical Society of America