Laser spectroscopy for measuring the parameters of a plasma containing helium and argon

Laser spectroscopy diagnostics used in experiments on the PNX-U facility are described. The working gas was argon with an additive of helium. The 2³ P → 3³ D transition was excited by means of optical pumping, and helium fluorescence at wavelengths of 388 and 706.5 nm was observed. The Doppler temperature of helium atoms was determined by scanning the profile of the absorption line with the help of a tunable laser. The sum of the signals so obtained provides information on the local density of helium atoms. It was proposed to determine the local value of the electron density N _e (R) from the ratio between the fluorescence intensities at wavelengths of 388 and 706.5 nm. The ratio of these intensities as a function of N _e for He I was calculated in the collisional-radiative model, and relevant measurements of N _e in the PNX-U facility were performed. When diagnosing the argon component, the main attention was paid to measurements of the ion temperature T _i (R, t). In the course these measurements, anomalous heating of Ar II ions was revealed. The concentration of singly charged argon ions was estimated.     

Emission spectroscopy diagnostics of rare gases in the PNX-U facility

Results are presented from measurements of the electron temperature and neutral atom density in a low-temperature microwave plasma by the method of emission spectroscopy. The measurements were conducted in the PNX-U facility—a magnetic confinement system with a “magnetic wall.” Multichord measurements of plasma radiation at a wavelength of 750.37 nm were performed with the help of an absolutely calibrated monochromator. The neutral atom density was calculated using the collisional-radiative model. The degree of plasma ionization near the axis of the facility was found to be close to unity. The electron temperature of the argon plasma was measured from the relative intensities of the spectral lines of neutral helium injected in small amounts into the plasma (the so-called helium thermometer method). At a low microwave heating power, the results of these measurements agree well with the results of probe measurements.     

Spectroscopic and probe measurements of the electron temperature in the plasma of a pulse-periodic microwave discharge in argon

A pulse-periodic 2.45-GHz electron-cyclotron resonance plasma source on the basis of a permanent- magnet mirror trap has been constructed and tested. Variations in the discharge parameters and the electron temperature of argon plasma have been investigated in the argon pressure range of 1 × 10^–4 to 4 × 10^–3 Torr at a net pulsed input microwave power of up to 600 W. The plasma electron temperature in the above ranges of gas pressures and input powers has been measured by a Langmuir probe and determined using optical emission spectroscopy (OES) from the intensity ratios of spectral lines. The OES results agree qualitatively and quantitatively with the data obtained using the double probe.     

Scanning calorimetry measurements of the gas temperature in an RF-discharge fluorine-containing plasma

The neutral-gas temperature in a low-pressure (50 Pa) capacitive RF discharge in a CF₄+O₂ mixture is determined from the heating kinetics of a gallium arsenide single crystal, which is chemically inert to any radicals in a fluorine-containing plasma. Experimental methods are discussed that make it possible to confirm the absence of heat sources capable of additional heating of the calorimeter in the discharge. The features and applicability limits of the method of non-steady-state gas thermometry in a weakly ionized nonequilibrium plasma are discussed. The method proposed is compared with conventional steady-state methods based on measurements of the established temperature of a thermal probe in the discharge. Temperature scanning makes it possible to study dependences that cannot be investigated by steady-state methods, in particular, the temperature dependence of the calorimeter heating power, which is very important for diagnosing the processes of plasma-surface heat transfer.     

A method for calculating the effective charge of ions decelerated in a hot dense plasma

A method for calculating the effective charge of fast ions decelerated in a hot dense plasma is proposed. The method is based on the known experimental dependence of the effective charge of an ion decelerated in cold matter on its velocity. The ion velocity in this dependence is replaced with the velocity of an ion relative to plasma electrons, averaged over the Fermi-Dirac distribution. Using results of numerical calculations performed in a wide range of plasma parameters (from a Maxwellian plasma to a fully degenerate one), a scale-invariant representation of the effective charge of a decelerating ion as a function of its initial velocity and the plasma temperature and density is obtained. An analytical formula fitting the calculated results to within 5% is derived. The obtained dependences of the effective charge are incorporated in the model describing deceleration of fast ions in plasma. Using this model, the stopping powers of krypton and lead ions in a relatively cold rarefied gas-discharge plasma and hot ICF plasma are calculated. The results of calculations are shown to agree satisfactorily with available experimental data.     

The effect of accelerated argon ions on the retina

It has been postulated that high energy heavy ions cause a unique form of damage in living tissue, which results from the high linear energy transfer of accelerated single particles. We have searched for these single-particle effects, so-called "microlesions," in composite electron micrographs of retinas of rats which had been irradiated with a dose of 1 Gy of 570 MeV/amu argon ions. The calculated rate of energy deposition of the radiation in the retina was about 100 keV/micron and the influence was four particles per 100 micron 2. Different areas of the irradiated retinas which combined would have been expected to be traversed by approximately 2400 particles were examined. We were unable to detect ultrastructural changes in the irradiated retinas distinct from those of controls. The spatial cellular densities of pigment epithelial and photoreceptor cells remained within the normal range when examined at 24 h and at 6 months after irradiation. These findings suggest that the retina is relatively resistant to heavy-ion irradiation and that under the experimental conditions the passage of high energy argon ions does not cause retinal microlesions that can be detected by ultrastructural analysis.     

Charge-exchange recombination spectroscopy of the plasma ion temperature at the T-10 tokamak

Charge-exchange recombination spectroscopy (CXRS) based on a diagnostic neutral beam has been developed at the T-10 tokamak. The diagnostics allows one to measure the ion temperature profile in the cross section of the plasma column. In T-10 experiments, the measurement technique was adjusted and the elements of the CXRS diagnostics for ITER were tested. The used spectroscopic equipment makes it possible to reliably determine the ion temperature from the Doppler broadening of impurity lines (helium, carbon), as well as of the spectral lines of the working gas. The profiles of the plasma ion temperature in deuterium and helium discharges were measured at different plasma currents and densities, including with the use of active Doppler measurements of lines of different elements. The validity and reliability of ion temperature measurements performed by means of the developed CXRS diagnostics are analyzed.     

Diffuse reflectance spectroscopy as a monitoring tool for gastric mucosal devitalization treatments with argon plasma coagulation

Electrosurgery with argon plasma coagulation is a widespread technique used in various medical fields for applications which range from hemostasis to devitalization processes. Developing tools which provide feedback concerning tissue condition during these surgeries is fundamental for improving the safety and success of this treatment. We present here a method based on diffuse reflectance spectroscopy to monitor gastric mucosal devitalization treatments. The analysis of the diffusely reflected spectra of the tissue allows us to differentiate between ablation states by using linear discriminant analysis (LDA) as a classification algorithm. An ex vivo pilot study on several swine stomachs showed promising results, with 97.8% of correctly classified ablation states on a new unseen stomach, encouraging further tests with human tissue.     

Coagulation of dust grains in the plasma of an RF discharge in argon

Results are presented from experimental studies of coagulation of dust grains of different sizes injected into a low-temperature plasma of an RF discharge in argon. A theoretical model describing the formation of dust clusters in a low-temperature plasma is developed and applied to interpret the results of experiments on the coagulation of dust grains having large negative charges. The grain size at which coagulation under the given plasma conditions is possible is estimated using the developed theory. The theoretical results are compared with the experimental data.     

柏小爪螨发育起点温度和有效积温的研究

在恒温条件下测定了柏小爪螨Oligonychusperditus卵、幼螨、若螨历期 ,成螨产卵前期和世代发育历期 ,用直线回归法和李典谟直接最优法分别计算了柏小爪螨各螨态和 1代的发育起点温度和有效积温 ,并根据有效积温法则预测了该螨在山东泰安地区 1年可能完成代数为 1 1代左右     

灰飞虱发育起点温度及有效积温的探讨

利用培养箱在恒温条件下饲养灰飞虱Laodelphax striatellus Fallén,测定了卵、若虫、成虫繁殖前和全世代发育历期,用直线回归法计算了灰飞虱各虫态和全世代的发育起点温度和有效积温分别为10.06、6.43、10.29、8.08℃和102.3、365.2、87.5、552.1日·度。并根据有效积温法则预测了该虫在济宁市1年完成的代数为4～5代。     

Standardized measurements and differential spectroscopy in microplates

Microplates (MPs) are excellent devices for the parallel processing of multiple samples for the spectroscopic analysis of chromophores and turbidity, for luminometric measurements, for cell culture applications, or simply for sample storage, library organization, and other high-throughput (HTP) processes. Disadvantages include an ill-defined pathlength, meniscus formation, evaporation, and cross-contamination. Here, we have developed a novel MP and lid system which can serve to minimize these drawbacks. Cup-like lids are inserted into MP wells. Thereby, liquid is pushed aside. The flat bottoms of the cup-like lids guarantee a planar interface and a defined pathlength. In addition, the devised MP system allows for differential spectroscopic analysis of multiple samples comparable to measurements in tandem cuvettes. This was shown by the investigation of the binding of reduced nicotinamide adenine dinucleotide to dihydrolipoamide dehydrogenase. The MP lid system described offers a low-cost solution for standardized spectrophotometric quantitations in any solvent compatible with the MP/lid material. In addition to the system's suitability for routine MP application, it should be advantageous as a simple and noninvasive method, i.e., no labeling and immobilization of analytes is required for detection of the interaction of molecules, for various HTP applications and drug screening purposes.     

Nonspecific interactions in AFM force spectroscopy measurements

Sample-probe contact duration (dwell time) and loading force are two important parameters for the atomic force microscopy (AFM) force spectroscopy measurements of ligand-receptor interaction. A prolonged contact time may be required to initiate ligand-receptor binding as a result of slow on-rate kinetics or low reactant density. In general, increasing contact duration promotes nonspecific interactions between the substrate and the functionalized cantilever and, thus, masking the detection of the specific interactions. To reduce the nonspecific interactions in AFM force measurements requiring extended substrate-probe contact, we investigated the interaction of bovine serum albumin (BSA)-functionalized cantilever with BSA-coated glass, polyethylene glycol (PEG)-functionalized glass, Pluronic-treated Petri dishes and agarose beads. The frequency of nonspecific interaction between the BSA-functionalized cantilever and the different samples increased with loading force and dwell time. This increase in nonspecific adhesion can be attributed to the interaction mediated by forced unfolding of BSA. By reducing the loading force, the contact duration of the AFM probe with an agarose bead can be extended to a few minutes without nonspecific adhesion.     

家蝇发育起点温度和有效积温

在5种温度下,对家蝇的发育起点温度和有效积温进行了研究。结果表明,家蝇在不同发育阶段发育起点温度和有效积温不同,且不同发育阶段对两者的要求也不一致。世代的发育起点温度和有效积温分别为13.6℃和196.4日.度,控制发育进度的理论为T=196.4/N+(13.6±0.5)。     

Laser Doppler spectroscopy of biological objects

Laser Doppler spectroscopy permits to investigate the velocity distribution of the biological objects either single cells or ensembles. The main principles of laser Doppler spectroscopy and its practical application connected with the spectral correlation dependence of biological objects have been studied.     

双斑长跗萤叶甲的发育起点温度与有效积温

双斑长跗萤叶甲Monolepta hieroglyphica(Motschulsky)已成为新疆北疆棉区的一重大新害虫,至今该虫各虫态的发育历期都不清楚。在室内5个恒温下(19,22,25,28和31℃),利用有效积温法则和"最小二乘法"对双斑长跗萤叶甲各虫态的发育起点温度和有效积温进行研究。结果表明,卵期、幼虫期、蛹期和产卵前期的发育起点温度分别为9.8,10.8,12.6和10.1℃;有效积温分别为1 182.2,401.2,111.9和269.0日.度;整个世代完成发育所需要的有效积温为1 971.6日.度,预测在新疆北疆1年发生1代。     

Laser probing of the plasma in the S-300 facility

A method for the laser probing of an imploding plasma in the S-300 high-current generator (I=4 MA, Z=0.15 Ω, and τ=100 ns) with the use of a YAG: Nd laser is described. The first version of the method enables obtaining three-frame shadow and schlieren photographs of the plasma of the accelerator load with an exposure of 10 ns and an interval between frames of 25 ns. The second version enables the five-frame probing of the plasma with an exposure of 1 ns and an interval between frames of 10 ns. Stimulated Brillouin scattering in carbon tetrachloride is used to compress the probing laser pulse. A series of shadow and schlieren photographs of the plasma of different liners and Z-pinches are obtained. Mechanisms for the image formation are discussed. The magnitude and gradients of the plasma density are estimated.     

南美斑潜蝇发育起点温度和有效积温的研究

在恒温条件下 ,观察了不同温度对南美斑潜蝇LiriomyzahuidobrensisBlanchard生长发育的影响 ,并用直线回归法测得卵、幼虫、蛹和全世代的发育起点温度分别为 7 2℃ ,7 4℃ ,7 7℃和 7 5℃ ,有效积温分别为 4 0 8,98 6 ,1 4 0 5和 2 79 9日·度     

黄色潜蝇茧蜂发育起点温度与有效积温的研究

在15-30℃温度范围内,观察了不同梯度温度下黄色潜蝇茧蜂Opius flavus Weng etChen生长发育的历期,并对实验数据采用直线性回归的方法处理。结果表明：黄色潜蝇茧蜂卵、幼虫、蛹的发育起点温度分别为8.518℃、9.909℃和8.656℃,其有效积温分别为60.27日度、65.75日度和87.78日度;卵——成虫的发育起点温度是9.631℃,有效积温为203.04日度。