4,054 research outputs found

    Anisotropy-driven collisional separation of impurities in magnetized compressing and expanding cylindrical plasmas

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    When a cylindrically-symmetric magnetized plasma compresses or expands, velocity-space anisotropy is naturally generated as a result of the different adiabatic conservation laws parallel and perpendicular to the magnetic field. When the compression timescale is comparable to the collision timescale, and both are much longer than the gyroperiod, this pressure anisotropy can become significant. We show that this naturally-generated anisotropy can dramatically affect the transport of impurities in the compressing plasma, even in the absence of scalar temperature or density gradients, by modifying the azimuthal frictions that give rise to radial particle transport. Although the impurity transport direction depends only on the sign of the pressure anisotropy, the anisotropy itself depends on the pitch magnitude of the magnetic field and the sign of the radial velocity. Thus, pressure anisotropy effects can drive impurities either towards or away from the plasma core. These anisotropy-dependent terms represent a qualitatively new effect, influencing transport particularly in the sparse edge regions of dynamically-compressing screw pinch plasmas. Such plasmas are used for both X-ray generation and magneto-inertial fusion, applications which are sensitive to impurity concentrations.Comment: 11 pages, 3 figure

    Particle Orbits in a Force-Balanced, Wave-Driven, Rotating Torus

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    The wave-driven rotating torus (WDRT) is a recently proposed fusion concept where the rotational transform is provided by the E x B drift resulting from a minor radial electric field. This field can be produced, for instance, by the RF-wave-mediated extraction of fusion-born alpha particles. In this paper, we discuss how macroscopic force balance, i.e. balance of the thermal hoop force, can be achieved in such a device. We show that this requires the inclusion of a small plasma current and vertical magnetic field, and identify the desirable reactor regime through free energy considerations. We then analyze particle orbits in this desirable regime, identifying velocity-space anisotropies in trapped (banana) orbits, resulting from the cancellation of rotational transforms due to the radial electric and poloidal magnetic fields. The potential neoclassical effects of these orbits on the perpendicular conductivity, current drive, and transport are discussed.Comment: 13 pages, 7 figure

    Analytical QCD and multiparticle production

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    We review the perturbative approach to multiparticle production in hard collision processes. It is investigated to what extent parton level analytical calculations at low momentum cut-off can reproduce experimental data on the hadronic final state. Systematic results are available for various observables with the next-to-leading logarithmic accuracy (the so-called modified leading logarithmic approximation - MLLA). We introduce the analytical formalism and then discuss recent applications concerning multiplicities, inclusive spectra, correlations and angular flows in multi-jet events. In various cases the perturbative picture is surprisingly successful, even for very soft particle production.Comment: 97 pages, LaTeX, 22 figures, uses sprocl.sty (included

    Alpha Channeling with High-field Launch of Lower Hybrid Waves

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    Although lower hybrid waves are effective at driving currents in present-day tokamaks, they are expected to interact strongly with high-energy particles in extrapolating to reactors. In the presence of a radial alpha particle birth gradient, this interaction can take the form of wave amplification rather than damping. While it is known that this amplification more easily occurs when launching from the tokamak high-field side, the extent of this amplification has not been made quantitative. Here, by tracing rays launched from the high- field-side of a tokamak, the required radial gradients to achieve amplification are calculated for a temperature and density regime consistent with a hot-ion-mode fusion reactor. These simulations, while valid only in the linear regime of wave amplification, nonetheless illustrate the possibilities for wave amplification using high-field launch of the lower hybrid wave.Comment: 7 pages, 7 figure

    The Development of Eastern Illinois University\u27s Beginning Teacher Induction Program

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    Throughout the nation programs are being developed that provide support for teachers in their initial years in the profession. Program philosophies emphasize the importance of beginning teachers experiencing a smooth transition from the preservice experiences or student teaching to becoming an employed classroom teacher. Eastern Illiois University’s Beginning Teacher Induction Program is designed to provide free assistance and support to any Eastern graduate employed as a first or second year teacher in the State of Illinois. Beginning teachers may receive individual assistance and support from university faculty. Professional consultation and services are provided to the teacher and his/her supervisor in planning a program of support. Group support is also available through Beginning Teacher Seminars where teachers are given the opportunity to discuss their varied experiences and concerns with other teachers and university faculty in developing new ideas and techniques to be used in their classrooms. The purpose of this study was to compile information needed to develop a program model where adaptation by other educational institutions and agencies could be possible

    Test anxiety: effects on standardized testing, average classroom assessments, and fourth grade students

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    The purpose of this study was to compare the effects of both standardized testing and average classroom assessments on the levels of test anxiety. The study was a correlation study. with a sample of 42 fourth grade students. The students came from four separate classrooms within the same elementary school. This study adapted Wren and Benson\u27s (2004) Children\u27s Test Anxiety Scale (CTAS). The subjects in this study were administered two identical questionnaires entitled, How I Feel About Tests. The first CTAS was administered in the week following the New Jersey Assessment of Skills and Knowledge (NJ ASK). The second CTAS was administered one month later. Each subject\u27s CTAS was studied individually and compared to the group. It was found that 88 percent of the subjects experienced higher levels of test anxiety during the first CTAS. This CTAS was utilized to determine the level of test anxiety students experience during standardized testing. Twelve percent of the subjects showed a heightened level of test anxiety during the second CTAS. The second CTAS was used to rate students\u27 level of test anxiety during average classroom tests and quizzes
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