Optoacoustic gas analyzer based on a13C16O2 laser for multicomponent pollution of air

A computer-aided optoacoustic gas analyzer based on a continuous¹³C¹⁶C₂ laser for multicomponent pollution of atmospheric air is described. The analyzer has the ability to detect absorption of radiation by detected substances at the level of ∼1·10⁻⁹ cm⁻¹ at a time resolution of 30 sec. Results of an experiment on simultaneous detection of H₂O, CO₂, NO₂, NH₃, HNO₃, OCS, and C₂H₄ in the atmospheric air using 40 laser lines are presented. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 3, pp. 345–350, May–June, 1999.     

Optico-spectroscopic diagnostics of large-scale plasma clouds created above A surface under the action of A single-pulse laser in atmospheric-pressure air

To whom correspondence should be addressd.     

基于聚焦光声层析技术的甲状腺离体组织成像

对人体甲状腺内的病变组织进行定位和成像对于准确诊断和有效治疗甲状腺疾病是至关重要的. 本文评估了利用光声层析技术对离体甲状腺组织进行成像的可行性, 并利用基于30 MHz超声换能器的聚焦光声成像系统对甲状腺进行扫描成像. 实验中成像系统的横向分辨率和纵向分辨率分别达到了350 μupm和74 μupm. 分别对正常离体甲状腺组织和模拟病变甲状腺组织进行光声成像. 实验结果表明, 本成像系统能够有效区分和鉴别正常甲状腺组织和病变组织. 此项技术有望进一步提高甲状腺疾病诊断的准确率, 以便更为有效地指导疾病的治疗, 具有潜在的临床应用前景.     

基于微型非共振腔的石英增强光声光谱用于氦气纯度分析的实验研究

实验中设计了一种基于微型非共振腔的石英增强光声光谱痕量气体传感器, 用来检测非纯氦气中的痕量氨气浓度. 该传感器采用的微型非共振腔只在空间上限制声波扩散以达到增强信号目的, 而不是像传统微型共振腔一样依靠共振效应. 如此的设计使探测小分子无机气体的光谱测声器尺寸远远小于共振腔的配置而有利于准直. 不同气压下的信号和噪声也被研究, 用来优化传感器性能. 在这种配置下和27.7 kPa的最优气压下, 获得的最佳氨气探测灵敏度为463 ppb (1σ , 1 s积分时间), 相应的归一化噪声等效吸收系数为4.3×10^-9cm^-1W/√Hz. 关键词： 气体传感器 石英增强光声光谱 音叉式石英晶振 类氢气体纯度分析     

Design, simulation and structural optimization of a longitudinal acoustic resonator for trace gas detection using laser photoacoustic spectroscopy (LPAS)

The design of the acoustic resonator is critical for the optimization of the sensitivity of laser photoacoustic spectroscopy (LPAS) in trace gas detection applications. In this paper, an LC circuit model is used for the simulation of a 1D acoustic resonator. This acoustic resonator is designed for CO photoacoustic spectroscopy. The effects of the structural parameters, quality factor and resonant frequency on the performance of the device are theoretically analyzed. The role of the buffer volume as an acoustic filter is investigated and optimized dimensions of the buffer volume, to achieve minimum noise transmission coefficient, are calculated. The effects of the ambient temperature, variety of pressure and gas flow velocity on the resonant frequency of photoacoustic resonator and PA signal are simulated. The temperature dependence of the microphone sensitivity is also introduced.     

Application of CCD cameras in spectral analysis

Smolensk Pedagogical Institute, 4 Przhevalskii Str., Smolensk, 214000, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 6, pp. 166–169, November–December, 1995.     

Dynamics of a waveguide pulsed-periodic CO2 laser with loss modulation

The nonlinear dynamics of a waveguide CO₂ laser with combined periodic loss and pumping modulation is investigated theoretically and experimentally. The possibilities of controlling time and energy parameters of the output radiation using the corresponding selection of the detuning of the cavity's longitudinal mode from the center of the amplification line, the amplitude, and the frequency of loss modulation are demonstrated. The observed asymmetric dependence of the lasing-radiation density on the detuning of the cavity frequency is explained by the attendant modulation of the refractive index of the loss modulator. To whom correspondence should be addressed. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 471–478, July–August, 1999.     

Optimization of three gas compositions in a CO2 laser

Three pressures of gases (CO₂, N₂ and He) added into CO₂ laser tube are optimized for obtaining maximal laser output power by applying a genetic algorithm and solving the CO₂ laser kinetics equations. After the optimization, the laser power is increased by 96% as compared with a non-optimal case.     

CO2-laser photoacoustic detection of gaseous n-pentylacetate

The absorption spectra of gaseous n-pentylacetate were investigated by FT IR spectroscopy as well as CO₂-laser photoacoustic spectroscopy for simulation of the dispersion of a nerve agent (sarin) within a modeled atmospheric boundary layer. Three CO₂-laser emission lines were used for photoacoustic detection of n-pentylacetate with detection limit in the range of 1-3 ppm.