Search

This paper presents the brushless electrical excited synchronous machine drive system. A rotary transformer transfers the power to the rotor field winding of synchronous machine. A 12 slot - 10 pole brushless excited synchronous machine (BESM) is designed and analyzed. The super-twisting sliding mode direct torque and flux controller (STSM-DTC) is investigated for this motor drives. The tests show that STSM-DTC displays a very robust behavior.

Great efforts have been made to create a bright K-shell source using the thin metal cylindrical cavities in the past few decades. Several metal materials such as titanium (Ti), iron, and so on have been tested for high x-ray conversion efficiency mainly at the OMEGA and NIF laser facilities. Recently, x-ray sources in Ti K-shell transition energy range were investigated at the Shenguang-III prototype laser facility with ∼5 kJ laser energy. The experiments were aimed to reproduce the previous ones at OMEGA, but with an extraordinarily small volume of cylindrical cavity and detailed characterizations of the x-ray source. The cavities were 800 μm inner diameter, 800 μm length, and 30 μm thick plastic tubes supporting 1 μm thick Ti. Seven laser beams were focused to 200 μm diameter. The combination of the small cavity volume and the focused laser spots is intended to improve the electron temperature with limited laser energy since the electron temperature is a key issue for high x-ray conversion efficiency. Thomson scattering was adopted to experimentally probe the electron temperatures at special time and space zones as well as the average temperature obtained from the Ti K-shell spectrum. The evolutions of the electron temperature and density are predicted by the radiation hydrodynamic simulation. A top view and two photon energy bands of x-ray source images provide a way to directly observe the plasma movement toward the cavity axis and distinguish the different emission mechanisms between the Ti K-shell and lower energy x rays. Six Higher-energy x-ray detectors located at different angles were used to record the Ti K-shell x-ray emission and demonstrate its isotropic feature. The characteristics of the x-ray radiate intensity including the time evolution, the angular distribution, and the total yields for both the photon energy regions above and below 4 keV are compared between the cavity and planar targets. Obviously, different behaviors were found between the two photon energy regions and the two types of targets. The x-ray conversion efficiency of the Ti cylinder was determined to be ∼ 4 % and ∼ 21 % in 4 π sr in the Ti K-shell (4–7 keV) and

An experiment was performed on the Shenguang III prototype laser facility to continue the study on hohlraum radiation source with approximately constant radiation temperature using a continuously shaped laser pulse. A radiation source with a flattop temperature of about 130 eV that lasted about 5 ns was obtained. The previous analytical iteration method based on power balance and self-similar solution of ablation was modified taking into account the plasma movements and it was used to design the laser pulse shape for experiment. A comparison between experimental results and simulation is presented and better agreement was achieved using the modified method. Further improvements are discussed.

To produce a plasma layer (area of 1.3 m2 and power of 1.8 kW) covering the inner surface of a metal cavity (diameter of 45 cm and length of 120 cm), a certain number of standard commercial fluorescent lamps were placed directly against one another. Electromagnetic (EM) scattering of a 1- to 3-GHz EM wave has been studied experimentally and theoretically for a metal cavity and a plasma-covered metal cavity. When the EM wave hits the cavity at the front aspect angle, a significant return loss of as large as 10 dB in the frequency of 1-2 GHz and trends to a peak of 20-30 dB near 1.25-1.5 GHz were observed. Using the finite-difference time-domain method, transient scattered fields of EM wave from cavities were achieved. The loss of the EM wave with covered plasma was proved to be a result of the absorption by the plasma, but not from the turning or bending of the wave entering the plasma.

An experimental method has been developed to measure the X-ray polarization of the Beamline 4B7 on Beijing Synchrotron Radiation Facility in the X-ray energy range 2100-5600 eV by using a PET crystal diagnostic system and rotating the system around the incident X-ray beam by 90 degrees. The experimental results show that the measured X-ray polarization is more than 0.88 in the photon energy range 2100-3600 eV with maximum of 0.99 at 2707.3 eV, and quickly decreases to about 0.38 at 4719.2 eV with photon energy increasing from 3600 to 4719.2 eV, then it keeps almost constant as the photon energy increases further to 5600 eV. (C) 2010 Elsevier B.V. All rights reserved.

Based on the Rytov approximation of light propagation in weak turbulent atmosphere, the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG) beams: cosine-Gauss beams, stationary Mathieu-Gauss beams, stationary parabolic-Gauss beams, and Bessel-Gauss beams, which are propagating in weak turbulent atmosphere, are obtained. The results show that the field and average irradiance can be written as the product of four factors: complex amplitude depending on the z-coordinate only, a Gaussian beam, a factor of complex phase perturbation induced by atmospheric turbulence, and a complex scaled version of the transverse shape of the non-diffracting beam. The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.

It is reported that in National Ignition Facility's shock timing campaign, there is a 2 μm layer of residual air condensation on the cold laser entrance hole window, and residual gas level of ∼5×10−6 Torr ( ∼6.6×10−4 Pa) in the chamber [Robey et al., Phys. Plasmas 19, 042706 (2012)]. On Shenguang (SG) II and III laser facilities, a nominal residual gas level in the chamber is ∼10−2 Pa in experiment. In this work, the residual Carbon (C) level in the SG II chamber is investigated experimentally using a transmission grating spectrometer (TGS). The experimental result shows that there is a clear C K edge (280–300 eV), which implies that there is residual C condensation on the charge-coupled device (CCD) silicon oxide layer. The effect of the C condensation on the CCD response is studied with a condensed-C-foil model. With the modified CCD responses, the unfolded spectra by TGS are shown, and the significant C K edge decreases as the C foil thickness increases. Compared to the simulated C K edge depth, the me...

Time-resolved x-ray self-emission imaging was used to study the dynamic evolution of a laser-produced gold plasma tamped by plastic (CH), and a significant plasma collapse was observed during the laser irradiation. The plasma collapse, a kind of transverse contraction, has been ascribed to the radial compression caused by the different radiative cooling rates and thus different pressures between the central high-Z gold plasma and the surrounding low-Z CH plasma, and this has been reproduced by numerical simulations using the two-dimensional radiation-hydrodynamics code Multi2D. The experimental results represent an observation of the radiative cooling induced plasma jet within a 1 ns laser pulse duration, much more quickly than those reported previously. In addition, our experiment design may offer a method to study the radiative cooling rates of high-Z plasmas. The measured cooling rate is a factor of 2 higher than the theoretical result [Post et al., At. Data Nucl. Data Tables 20, 397 (1977)], but is wi...

We describe an experimental technique to measure the drive symmetry of M-band radiation on the capsule in hohlraum. M-band radiation from the corona of the laser-produced gold plasma, especially the laser spot regions in the cavity, was used to pump x-ray fluorescence of a thin layer of Si-tracer coated on a solid CH-ball. The fluorescence images were time resolvedly recorded by an x-ray framing camera and the drive asymmetry due to M-band radiation was deduced from these fluorescence images. Moreover, a Si-doped gold cavity was used with the initial purpose of maximizing the fluorescence signal through resonance transitions. Since the Si-plasma expands more rapidly than the gold-plasma, the evolution of drive asymmetry was accelerated in Si-doped hohlraum.

A design of secondary hohlraum radiation source with laser focal spots blocked is introduced. The hard x-ray radiation such as the gold M-band emission and hot electrons from the coronal plasma were designed to be shielded using a cylindrical shield. Three-dimensional view factor analysis was carried out to optimize the shield structure to achieve higher radiation temperature. An experiment was performed at Shenguang III prototype laser facility to verify the design. Velocity Interferometer System for Any Reflector was used to measure the shock wave speed in a three-stepped Al sample driven by this radiation source and the peak radiation temperature of the radiation source was estimated to be about 90 eV.

Streak camera is widely used in continuous time diagnostics in fast physical process. To produce accurate result, it requires delicate calibration and a reliable analysis method. High quality sweep-rate data with uncertainty smaller than 0.5% are obtained over the full record area by a constrained fitting method of peak position measurement, with a short pulse laser and an etalon as the fiducial source. The temporal response is linearized by this full-screen sweep-rate data, which eliminates errors in measurement due to nonlinearity and space-distortion inherent in streak camera.

In the hohlraum used in laser indirect-drive inertial confinement fusion experiments, hydrodynamic processes of radiation-ablated high-Z plasma have a great effect on laser injection efficiency, radiation uniformity, and diagnosis of hohlraum radiation field from diagnostic windows (DW). To study plasma filling in the DWs, a laser-irradiated Ti disk was used to generate 2–5 keV narrow energy band X-ray as the intense backlighter source, and laser-produced X-ray in a hohlraum with low-Z foam tamper was used to heat a small hole surrounded by gold wall with 150 μm in diameter and 100 μm deep. The hydrodynamic movement of the gold plasma in the small hole was measured by an X-ray framing camera and the results are analyzed. Quantitative measurement of the plasma areal density distribution and evolution in the small hole can be used to assess the effect of plasma filling on the diagnosis from the DWs.

We present a simple experimental method that permits an empirical determination of the effective boundary condition and the extrapolated end point for the diffuse photon density in a homogeneous turbid medium.

There are two sections in this paper. First, by using physical model of -4- bound, the statistics propertiesof scattering particles are studied ; the velocity autocorrelations function and the mean-square displacement ofscattered particle under our physical model are got ; we discuss the different a values for different bound model. Second, the scatteded electrical field autocorrelation function of dynamic light scattering through bound scattering particles is calculated. The resules of this paper, we think can been compared with resules experimentand a value for different solution may been obtained. Keywords : 4 bound, Brownain particles, DLS. 1. INTRODUCTION In the theoretical and experimental study of dynamic light scattering. interparticle interactions are generally interested recently. A lot of physical models of interparticle interactions were studied'5. Tung Tsang andH. T. Tang3 have reported studies of the light scattering and dynamics of interacting Brownian particles byusing a harmonic approximations for the effective potential; P. N. Pusey and W. Van Megen4 researcheddynamic light scattering by non-ergodic media, in which the scattering element's are only able to make limited

The double-passage effects of atmospheric turbulence on the imaging quality and resolution of an optical system , illuminated by the incoherent light ,are discussed in terms of the information content and the nUmber Nd of degrees of freedom of an imaging system. The Van Cittent-Zernike theorem and the Karhunen-Loe've expasion of generalized prolate -spheroidal function for the mutual intensity of stochastic waves is used to calaulate the turbulent average mutual intensity f12 for light from an extended incoherent quasi -monochromatic source and double-passage propagation in weak atmospheric turbulence. It is shown that , for incoherent illumination system and the receiving aperture is larger than the radius A of backscattered beam ,the turbulent spread of the beam may lead a positive effect , and there is a potential supperresolution , the resolution beyond the classical diffraction limit.

Accurate opacity and equation of state (EOS) data are important parameters for reliable modeling and understanding many phenomena of high energy density physics. However, they are difficult to obtain either theoretically or experimentally especially for high-Z plasmas. In this paper, we proposed a simple method to verify the opacity and EOS of high-Z plasmas in rarefactive states, which is build on the two key aspects of ablation processes, i.e., the propagation of heatwave into materials and the hydrodynamic expansion of the blow-off plasmas. Based on the integrated analysis of the Au foil burnthrough and foam-confined plasma expansion experiments performed on the Shenguang II and Shenguang III prototype laser facilities, we suggested two semi-empirical multipliers to adjust the opacity and EOS of Au plasma. These adjusted opacity and EOS may then provide a foundation for other radiation hydrodynamic simulations under similar drive conditions.

A technique of flat crystal x-ray spectrometer for quantitative spectral measurement is described. For the flat crystal spectrograph geometry, the quantitative reduction of relating the CCD counts back to the photon flux from the x-ray source is established. The absolute calibrations of the integral diffraction coefficients of the crystal and the CCD sensitivity make it possible to measure absolute photons flux within the energy range of 2000–5000 eV. The uncertainty analysis of the calibrations is carried out to obtain the energy resolved uncertainties of crystal and CCD. Thus, the experimental spectra with spectral resolved intensity uncertainties are available. Then, a performing experiment of laser-produced Ti plasma is carried out and the absolute x-ray spectra with intensity uncertainty less than 8.5% are obtained. The technique is promising for absolute spectral measurement of high temperature plasmas in a kilo-electron-volt region.

Laser-irradiated Au layer with CH foam coating is investigated numerically. It is found that when coated with under-critical density CH foam more thermal radiation is produced, while less radiation is produced when coated with over-critical density CH foam. The under-critical density CH foam coating, which is heated supersonically and volumetrically by lasers, hampers the expansion of high-Z plasma and helps increase the density and temperature of Auplasma in the radiation zone. It is a practical and simple way to increase the laser x-ray conversion efficiency of hohlraum by coated with low-Z foam of under-critical density. This idea is tested with an experiment in an analogous geometry. The line emission from laser-irradiated Ti layer coated with CH foam was measured, and the increment of x-ray when coated with under-critical density CH foam was found.

A 1D space resolving x-ray spectrum diagnostic system has been developed to study the radiation opacity of hot plasma on SG-II laser facility. The diagnostic system consists of a 2400 lines/mm flat-field holographic grating and a gated microchannel plate coupled with an optical CCD and covers the wavelength range of 5-50 Å. The holographic grating was compared with a ruled one by measuring the emission spectra from a laser-produced molybdenum plasma. The results indicate that the holographic grating possesses better sensitivity than the ruled grating having nearly similar spectral resolution. The spectrograph has been used in radiative opacity measurement of Fe plasma. Simultaneous measurements of the backlight source and the transmission spectrum in appointed time range in one shot have been accomplished successfully with the holographic grating spectrometer. The 2p-3d transition absorption of Fe plasma near 15.5 Å in has been observed clearly.

Experiments are presented, which demonstrate the properties of x-ray radiation and redistribution of radiant thermal energy in high Z cylindrical cavities filled with low Z CH foam. Time integrated spectra records were obtained by a calibrated space-resolved transmission grating spectrometer. The x-ray radiation became weaker in intensity and was changed to a softer near-Planckian radiation light after a 1500 μm long transport in the foam filling cavity. The experimental redistribution of the radiant thermal energy was plotted and compared to the numerical results of a simplified model. Good agreements have been achieved.

We present a result of studying holographic grating focus both in theory and experiment. It is based on a geometric analysis of a point source grating, through a detailed study of a typical holographic grating we show the grating focus place and its possible application.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Hydrodynamic processes of radiation-ablated high-Z plasmas have great influence on the x-ray radiation transport both in a high-Z tube with low-Z foam filling and in a low-Z filling indirect drive cavity. Using the intense x-ray radiation to heat a low-Z foam-tamped high-Z gold plate from a half cavity, the hydrodynamic moving process of the x-ray-ablated gold plasma has been studied by an imaging method with Ti He-α line emission as the backlighter source. The hydrodynamic trajectory of the x-ray-heated gold plasma was obtained and the average trajectory velocity of (36.5±1.2) km/s was derived. The experimental trajectory was compared with the simulations using the one-dimensional (1D) RDMG [P. Gu et al., Sci. China, Ser. G 48, 345 (2005)] and two-dimensional (2D) LARED-R [K. Lan et al., Laser Part. Beams 23, 275 (2005)] codes separately. It is shown that the 2D LARED-R code simulated the measured plasma trajectory much better than the 1D RDMG code due to the fact that the lateral x-ray radiation loss wa...

X-ray streak cameras are extensively used to study transient x-ray processes in experiments carried out on various laser facilities at the Research Center of Laser Fusion. Precise calibration and clear description of the sweep speed of the x-ray streak camera are vital for obtaining precise temporal information to understand the fast physics phenomena. An x-ray streak camera named wide-slit x-ray streak camera has been calibrated using a small-scale laser facility with pulse duration of 8 ps. Sweep speeds on most part of the output screen (charge coupled device) are obtained. These calibration results can be used to correct the nonlinearity of sweep speed in measurement of temporal processes.

In the study of dynamic light scattering (DLS), the autocorrelation function of the scattered light is one of the most important problems. Through the relationship between autocorrelation function and autocorrelation function of scattered light intensity, using the technology of photon correlation spectroscopy (PCS), we can measure the physical and the chemical properties of the illuminating system. In the illuminated system, the Brownian movement of the scattering particle is a result of dynamic light scattering. In this paper, calculations are presented of the autocorrelation of scattered field by a monodispersion system of spherical particle in colloid following statistical properties of Brownian movement and theory of classical electromagnetic field. The approximation of results which we get was the same single exponential functions in general use, and the results applied to the situation for the Brownian particles in an electric field. The spectral density difference between the two situations is discussed and it is suggested that this result may be employed in the experiments of the quantitative analysis of mixtures of charged macromolecules in colloid.