A. N. Starodub

Soft X-ray spectrum of laser-produced aluminum plasma

Soft X-ray spectra (30–70 Å) of aluminum plasma have been measured in experiments carried out at the Kanal-2 laser facility at laser intensities of (1–7) × 1013 W/cm2. It is shown that the measured spectra satisfactory agree with those calculated using the RADIAN numerical code.

Anomalous burn-through of thin foils by high-intensity laser radiation

The paper presents results of experiments performed on the Pico facility in which foils were heated by laser radiation, and anomalously fast burn-through of foils by a structured laser beam was detected. Comparison with two-dimensional calculations has allowed us to suggest a tentative mechanism for the effect under investigation. The targets in the experiments were thin aluminum foils of thickness 3 to 40 μm. The flux density of laser radiation on the target surface varied between 1013 and 1014 W/cm2. We detected a strong dependence of the transmitted energy on the foil thickness and the shortening of the transmitted laser pulse. Penetration of laser radiation through foils with thicknesses considerably larger than 3 μm has been observed, although it was stated in earlier publications [V. V. Ivanov, A. K. Knyazev, A. V. Kutsenko, et al., Kratk. Soobshch. Fiz. FIAN No. 7–8, 37 (1997)]; A. É. Bugrov, I. N. Burdonskii, V. V. Gol’tsov et al., Zh. Éksp. Teor. Fiz. 111, 903 (1997) [JETP 84, 903 (1997)] that, at the laser radiation parameters used in our experiment, the evaporated layer of the foil could not be thicker than 2 μm. Two-dimensional calculations have allowed us to interpret this effect in terms of local “piercing” of the target at spots on the target surface where the radiation intensity has its peaks. The possibility of reducing these peaks by using a symmetrizing prepulse is discussed in the paper.

Measurement of the Dead Time of an Optoelectronic Streak Camera with Different Linear Sweep Ranges

A method for measuring the dead time of an optoelectronic streak camera with different linear sweep ranges is described. The proposed method was used for the PN-1 streak camera. Photographs of the time-resolved emission of a DRSh350-2 mercury arc flash lamp for linear sweep ranges of 50 and 100 ns are presented. The dead times of the PN-1 streak camera for linear sweep ranges of 25, 50, and 100 ns were 5, 75, and 105 ns, respectively. The photographs of time-resolved second-harmonic spectra emitted by plasmas of copper and aluminum targets that were obtained in experiments on the interaction of nanosecond laser radiation with the matter using a streak camera are presented.

The image of a nanosecond laser plasma in its own optical radiation

The results of experiments on the interaction of nanosecond laser radiation (wavelength of 1.06 μm and a radiation power density of 1012–1013 W/cm2) with targets from various materials (Cu, (C2H4)n, TAC) are presented in the paper. In the experiments images of the plasma in own optical radiation in the wavelength range 0.4–1.1 μm were obtained. In one shot of laser images at wavelengths corresponding to the radiation of the harmonics 2ω 0, 3/2ω 0, 5/2ω 0, and at the frequency of laser radiation ω 0 were recorded. Using the obtained images the spatial characteristics of the radiating regions of the plasma, as well as the radiated energy for each of the harmonics, were estimated.

Emission of nanosecond laser plasma of gadolinium

The results of the study of laser plasma generated by nanosecond laser radiation with controlled spatial coherence incident on various targets containing gadolinium are presented. X-ray radiation of such plasma is studied using an X-ray diagnostic system developed and fabricated by the authors. Metal gadolinium, gadolinium oxide, gadolinium and aluminum alloy, and aluminum were used as targets. The electron temperature of generated plasma and the efficiency of laser-to-X-ray radiation conversion are estimated; the emitting region sizes are determined. Particular attention is paid to the study of laser plasma spectra in the X-ray region near the wavelength of 6.7 nm.

Second-harmonic conversion of partially coherent radiation of neodymium glass laser

The experimental results on the conversion of multimode radiation of a neodymium glass laser with controlled spatial and temporal coherence to the second optical harmonic in nonlinear KDP crystal during the oee interaction implementation are presented. The dependence of the efficiency of the conversion to the second harmonic on the fundamental radiation power density on the crystal in the range I = 0.2 − 5 GW/cm2 is studied at the number of transverse modes in the cavity N = 1000; the radiation divergence φ = 3.5, 4.7, and 5 mrad; the emission spectral width δλ = 5and 42 Å; and the pulse duration of 2.5 ns. The breakdown power density of the KDP crystal is determined, the interference properties of the converted radiation of the second harmonic are studied.

Second-harmonic conversion of neodymium glass laser radiation with controlled spatial coherence

The experimental results on the second optical harmonic conversion of neodymium glass laser radiation with controlled spatial coherence in a nonlinear KDP crystal are presented. The conversion efficiency is studied depending on the radiation power density on the crystal and the crystal rotation angle in the principal optical plane with respect to the radiation propagation direction. The experiments were performed in the radiation power density range I = 0.2–3 GW/cm2 for the number of cavity transverse modes N = 100–1000, radiation divergence 2ч = 0.5–3.5 mrad, spectrum width of 26 Å, and pulse duration of 2.5 ns.

Study of the spectral composition of the radiation of the neodymium-glass laser with combined active medium

A method for obtaining a broad (30–100 Å) emission line in neodymium-glass lasers is proposed. In this case, an active medium is a combination of two different glass matrices, silicate and phosphate, doped with Nd3+ ions. The structure and spectrum width of such lasers were experimentally studied depending on the active element properties, cavity type, and pump power. A radiation spectrum width more than twice larger in comparison with silicate-glass lasers was achieved.

Selection of a Master-Oscillator Scheme for a Chemical IR-Initiated Laser

The results of experimental and theoretical studies of operation regimes of a pulsed chemical D2–F2–CO2 UV initiated laser are presented. The influence of particular mixture components, the power of the UV radiation source, and the resonators characteristics on the output radiation parameters are experimentally studied on the “Kaiman” setup. The results of theoretical simulation obtained using the proposed scheme correspond sufficiently to those obtained experimentally. A description is given of the pulsed D2–F2–CO2 UV initiated laser “Flash-1” that provides for radiation pulses of 18 J with a 2.6–3.5 μs duration in the 10-micron range. A detailed description is given of the precision diagnostics of dark reactions occurring during the mixture preparations and affecting the efficiency of energy extraction in the course of generation.

Measurement of Spatial-Frequency and Amplitude Responses of a CCD-Matrix Image-Registration Device

A unique method for studying spatial-frequency and amplitude responses of an image-registration device on the basis of a CCD matrix is developed. A monochromatic light-intensity distribution arising from Fraunhofer diffraction on two equal slits is used as an input signal. A quantitative approach to a spatial resolution of the CCD matrix for registration of a periodic image is developed. The dependence of the rms contrast degree of the output signal on the spatial frequency of the image recorded is studied experimentally. The optical scheme developed and the method proposed for treatment of a digitized signal allow one to determine the amplitude response of the registration device over the whole surface of the CCD matrix and to determine the admissible level of the average intensity of the radiation registered.