Plasma polarization spectroscopy

Plasma Polarization Spectroscopy (PPS) is now becoming a standard diagnostic technique for working with laboratory plasmas. This new area needs a comprehensive framework, both experimental and theoretical. This book reviews the historical development of PPS, develops a general theoretical formulation to deal with this phenomenon, along with an overview of relevant cross sections, and reports on laboratory experiments so far performed. It also includes various facets that are interesting from this standpoint, e.g. X-ray lasers and effects of microwave irradiation. It also offers a timely discussion of instrumentation that is quite important in a practical PPS experiment

TURING INSTABILITY IN THE OREGONATOR MODEL(Session IV : Structures & Patterns, The 1st Tohwa University International Meeting on Statistical Physics Theories, Experiments and Computer Simulations)

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Relations between the ionization or recombination flux and the emission radiation for hydrogen and helium in plasma

On the basis of the collisional-radiative models for neutral hydrogen, and neutral and ionized helium, the relationship between the ionization flux or the recombination flux and the photon emission rate of a representative visible line of each species is investigated. It is found that both fluxes are proportional to the photon emission rate and that the proportionality factor depends rather weakly on the plasma parameters in the ranges of practical interest. This implies that the observed emission line intensity can be a good measure of the ionization flux or the recombination flux. The relation between the total radiation power rate and the ionization or recombination flux is also considered. For a hydrogen plasma in ionization balance the Balmer-alpha line intensity takes the maximum value near the optimum temperature of 1.3 eV, while for plasmas out of ionization balance it takes the minimum near that temperature. This latter characteristic corresponds to the recently observed "inverse edge-localized mode" in divertor plasmas. For neutral hydrogen and ionized helium, it is found that in the recombining plasma of low electron temperature, T_e, and density, n_e, the radiation energy close to the ionization potential of the ground state is emitted during one recombination event. In the ionizing plasma of high Te and low n_e, a similar amount of energy is emitted during one ionization event. Emission line intensities of hydrogen and helium were measured in the Large Helical Device, and the time variation of n_e at the initial and final phases of a discharge was estimated. The results agreed well with the interferometer measurement, and this indicated that the variation of n_e was dominated by their ionization or recombination processes rather than by diffusion. The total radiation energy of hydrogen and helium in the recombining phase was found to be less than 1% of the stored energy of the plasma

Collisional-Radiative Coefficients and Population Coefficients of Hydrogen Plasma

Numerical calculation based on the collisional-radiative model is made for rate equations of optically thin hydrogen plasma to give the collisional-radiative and population coefficients. Results are tabulated for the range of plasma parameters of 1×10³≼Tₑ≼2.56×10⁵ °K and 10⁶≼nₑ≼10²⁰ cm⁻³. Behavior of all the coefficients is analyzed as a function of electron density and as a result the asymptotic expressions of the coefficients at low and high electron-density limits as well as the approximate expressions of the critical electron densities for these asymptotic behaviors are obtained in terms of the rate coefficients for atomic transitions. Effect of trapping of resonance radiations on the coefficients is discussed

A Novel Strategy for Xeno-Regenerative Therapy

The shortage of organs for transplantation is of critical importance worldwide. Xenotransplantation or xeno-embryonic organ transplantation can stably supply organs and is considered to be an established alternative treatment. Regenerative medicine is another option, and recent advances in stem cell research have enabled the reproduction of miniature organs, called organoids, derived in vitro from human induced pluripotent stem cells. However, the in vitro production of large and complex organs that can efficiently function in vivo is not yet accomplished. We proposed a novel strategy for xenotransplantation in which a chimeric kidney is constructed by injecting human nephron progenitor cells into a porcine embryonic kidney, thereby eliminating pig nephron progenitor cells and allowing transplantation into a human and long-term survival. In this chapter, we discussed advantages and pitfalls of xenotransplantation and xeno-embryonic kidney transplantation. Recent attempts of human organoids and blastocyst complementation were reviewed. Finally, we proposed our novel xeno-regenerative therapeutic strategy

Reflection of Metastable Atoms by a Glass Wall in a Positive Column Discharge Plasma

The leser-induced-fluorescence-spectroscopy (LIFS) method has been applied to a dc discharge plasma, and the radial density distribution of metastable ( 2 ¹S) helium atoms has been measured. It was found that the density did not tend to zero at the discharge tube wall. Rather, the density was about 20-30% of the value on the tube axis. By using the collisional-radiative model, we interpreted the result. As the origin of this finite population at the wall we considered two possibilities, namely, 1 ) the helium ions which recombine at the wall converted partly into the metastable atoms and 2 ) the metastable atoms were not quenched completely at the wall, but were reflected by a certain amount. We found that the first process could not reproduce the experimental population distribution, and that the second process with the reflection coefficient of the metastable atoms of 80-90% accounted for the experiment

Spectroscopic Studies of an Electron-Beam-Produced Plasma

An electron beam operating in medium-pressure gases has been constructed, and its operating characteristics investigated. Helium, neon and argon have been excited by the electron beam, and it has been found that for lower pressures, less than 1 torr in the case of helium, accelerated electrons directly excite the ionic excited level. The population densities in the neutral series levels have been observed up to n＝15, and have been found to be roughly proportional to n⁻⁴. A possible explanation is proposed that is based on a direct excitation from the ground state and a depopulation by l-changing collisions