Experimental Studies of Magnetically Driven Plasma Jets

We present experimental results on the formation of supersonic, radiatively cooled jets driven by pressure due to the toroidal magnetic field generated by the 1.5 MA, 250 ns current from the MAGPIE generator. The morphology of the jet produced in the experiments is relevant to astrophysical jet scenarios in which a jet on the axis of a magnetic cavity is collimated by a toroidal magnetic field as it expands into the ambient medium. The jets in the experiments have similar Mach number, plasma beta and cooling parameter to those in protostellar jets. Additionally the Reynolds, magnetic Reynolds and Peclet numbers are much larger than unity, allowing the experiments to be scaled to astrophysical flows. The experimental configuration allows for the generation of episodic magnetic cavities, suggesting that periodic fluctuations near the source may be responsible for some of the variability observed in astrophysical jets. Preliminary measurements of kinetic, magnetic and Poynting energy of the jets in our experiments are presented and discussed, together with estimates of their temperature and trapped toroidal magnetic field.Comment: 7 pages, 6 figures, accepted for publication in Astrophysics & Space Scienc

Abundances of the elements in the solar system

A review of the abundances and condensation temperatures of the elements and their nuclides in the solar nebula and in chondritic meteorites. Abundances of the elements in some neighboring stars are also discussed.Comment: 42 pages, 11 tables, 8 figures, chapter, In Landolt- B\"ornstein, New Series, Vol. VI/4B, Chap. 4.4, J.E. Tr\"umper (ed.), Berlin, Heidelberg, New York: Springer-Verlag, p. 560-63

A deep cut ellipsoid algorithm for convex programming

This paper proposes a deep cut version of the ellipsoid algorithm for solving a general class of continuous convex programming problems. In each step the algorithm does not require more computational effort to construct these deep cuts than its corresponding central cut version. Rules that prevent some of the numerical instabilities and theoretical drawbacks usually associated with the algorithm are also provided. Moreover, for a large class of convex programs a simple proof of its rate of convergence is given and the relation with previously known results is discussed. Finally some computational results of the deep and central cut version of the algorithm applied to a min—max stochastic queue location problem are reported

Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV

We report a measurement of the longitudinal double-spin asymmetry A_LL and the differential cross section for inclusive Pi0 production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV. The cross section was measured over a transverse momentum range of 1 < p_T < 17 GeV/c and found to be in good agreement with a next-to-leading order perturbative QCD calculation. The longitudinal double-spin asymmetry was measured in the range of 3.7 < p_T < 11 GeV/c and excludes a maximal positive gluon polarization in the proton. The mean transverse momentum fraction of Pi0's in their parent jets was found to be around 0.7 for electromagnetically triggered events.Comment: 6 pages, 3 figures, submitted to Phys. Rev. D (RC

Oxygen isotopic constraints on the origin and parent bodies of eucrites, diogenites, and howardites

A few eucrites have anomalous oxygen isotopic compositions. To help understand their origin and identify additional samples, we have analyzed the oxygen isotopic compositions of 18 eucrites and four diogenites. Except for five eucrites, these meteorites have ?17O values that lie within 2 of their mean value viz., -0.242±0.016', consistent with igneous isotopic homogenization of Vesta. The five exceptional eucrites–NWA 1240, Pasamonte (both clast and matrix samples), PCA 91007, A-881394, and Ibitira–have ?17O values that lie respectively 4?, 5?, 5?, 15?, and 21 away from this mean value. NWA 1240 has a ?18O value that is 5? below the mean eucrite value. Four of the five outliers are unbrecciated and unshocked basaltic eucrites, like NWA 011, the first eucrite found to have an anomalous oxygen isotopic composition. The fifth outlier, Pasamonte, is composed almost entirely of unequilibrated basaltic clasts. Published chemical data for the six eucrites with anomalous oxygen isotopic compositions (including NWA 011) exclude contamination by chondritic projectiles as a source of the oxygen anomalies. Only NWA 011 has an anomalous Fe/Mn ratio, but several anomalous eucrites have exceptional Na, Ti, or Cr concentrations. We infer that the six anomalous eucrites are probably derived from five distinct Vesta-like parent bodies (Pasamonte and PCA 91007 could come from one body). These anomalous eucrites, like many unbrecciated eucrites from Vesta, are probably deficient in brecciation and shock effects because they were sequestered in small asteroids (~10 km diameter) during the Late Heavy Bombardment following ejection from Vesta-like bodies. The preservation of Vesta's crust and the lack of deeply buried samples from the hypothesized Vesta-like bodies are consistent with the removal of these bodies from the asteroid belt by gravitational perturbations from planets and protoplanets, rather than by collisonal grinding

3D MHD Simulations of Laboratory Plasma Jets

Jets and outflows are thought to be an integral part of accretion phenomena and are associated with a large variety of objects. In these systems, the interaction of magnetic fields with an accretion disk and/or a magnetized central object is thought to be responsible for the acceleration and collimation of plasma into jets and wider angle flows. In this paper we present three-dimensional MHD simulations of magnetically driven, radiatively cooled laboratory jets that are produced on the MAGPIE experimental facility. The general outflow structure comprises an expanding magnetic cavity which is collimated by the pressure of an extended plasma background medium, and a magnetically confined jet which develops within the magnetic cavity. Although this structure is intrinsically transient and instabilities in the jet and disruption of the magnetic cavity ultimately lead to its break-up, a well collimated, knotty jet still emerges from the system; such clumpy morphology is reminiscent of that observed in many astrophysical jets. The possible introduction in the experiments of angular momentum and axial magnetic field will also be discussed.Comment: 15 pages, 4 figures, accepted by Astrophysics and Space Science for Special Issue High Energy Density Laboratory Astrophysics Conferenc

Event-plane-dependent Dihadron Correlations With Harmonic Vn Subtraction In Au + Au Collisions At S Nn =200 Gev

STAR measurements of dihadron azimuthal correlations (Δφ) are reported in midcentral (20-60%) Au+Au collisions at sNN=200 GeV as a function of the trigger particle's azimuthal angle relative to the event plane, φs=|φt-ψEP|. The elliptic (v2), triangular (v3), and quadratic (v4) flow harmonic backgrounds are subtracted using the zero yield at minimum (ZYAM) method. The results are compared to minimum-bias d+Au collisions. It is found that a finite near-side (|Δφ|π/2) correlation shows a modification from d+Au data, varying with φs. The modification may be a consequence of path-length-dependent jet quenching and may lead to a better understanding of high-density QCD. © 2014 American Physical Society.894DOE; U.S. Department of EnergyArsene, I., (2005) Nucl. Phys. A, 757, p. 1. , (BRAHMS Collaboration), () NUPABL 0375-9474 10.1016/j.nuclphysa.2005.02. 130;Back, B.B., (2005) Nucl. Phys. 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NUPABL 0375-9474 10.1016/S0375-9474(99)85117-3Adams, J., (2004) Phys. Rev. Lett., 92, p. 112301. , (STAR Collaboration),. PRLTAO 0031-9007 10.1103/PhysRevLett.92.112301Borghini, N., Dinh, P.M., Ollitrault, J.Y., (2000) Phys. Rev. C, 62, p. 034902. , PRVCAN 0556-2813 10.1103/PhysRevC.62.034902Adams, J., (2005) Phys. Rev. C, 72, p. 014904. , (STAR Collaboration),. PRVCAN 0556-2813 10.1103/PhysRevC.72.014904Abelev, B.I., (2009) Phys. Rev. C, 79, p. 034909. , (STAR Collaboration),. PRVCAN 0556-2813 10.1103/PhysRevC.79.034909Bielcikova, J., (2004) Phys. Rev C, 69, p. 021901. , (R) () PRVCAN 0556-2813 10.1103/PhysRevC.69.021901;Konzer, J., Wang, F., (2009) Nucl. Instrum. Meth., A606, p. 713. , NIMAER 0168-9002 10.1016/j.nima.2009.05.011Mishra, A.P., (2008) Phys. Rev. C, 77, p. 064902. , PRVCAN 0556-2813 10.1103/PhysRevC.77.064902;Alver, B., Roland, G., (2010) Phys. Rev. C, 81, p. 054905. , PRVCAN 0556-2813 10.1103/PhysRevC.81.054905Alver, B., Roland, G., (2010) Phys. Rev. C, 82, p. 039903. , 0556-2813 10.1103/PhysRevC.82.039903Xu, J., Ko, C.M., (2011) Phys. Rev. C, 84, p. 014903. , PRVCAN 0556-2813 10.1103/PhysRevC.84.014903Petersen, H., (2010) Phys. Rev. C, 82, p. 041901. , PRVCAN 0556-2813 10.1103/PhysRevC.82.041901Takahashi, J., (2009) Phys. Rev. Lett., 103, p. 242301. , PRLTAO 0031-9007 10.1103/PhysRevLett.103.242301;Andrade, R.P.G., (2012) Phys. Lett. B, 712, p. 226. , PYLBAJ 0370-2693 10.1016/j.physletb.2012.04.044;Qian, W.L., (2013) Phys. Rev. C, 87, p. 014904. , PRVCAN 0556-2813 10.1103/PhysRevC.87.014904Schenke, B., Jeon, S., Gale, C., (2011) Phys. Rev. Lett., 106, p. 042301. , PRLTAO 0031-9007 10.1103/PhysRevLett.106.042301;Qiu, Z., Heinz, U.W., (2011) Phys. Rev. C, 84, p. 024911. , PRVCAN 0556-2813 10.1103/PhysRevC.84.024911;Song, H., (2011) Phys. Rev. Lett., 106, p. 192301. , PRLTAO 0031-9007 10.1103/PhysRevLett.106.192301;Schenke, B., Jeon, S., Gale, C., (2012) Phys. Rev. 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Fluctuations Of Charge Separation Perpendicular To The Event Plane And Local Parity Violation In S Nn = 200 Gev Au + Au Collisions At The Bnl Relativistic Heavy Ion Collider

Previous experimental results based on data (∼15×106 events) collected by the STAR detector at the BNL Relativistic Heavy Ion Collider suggest event-by-event charge-separation fluctuations perpendicular to the event plane in noncentral heavy-ion collisions. Here we present the correlator previously used split into its two component parts to reveal correlations parallel and perpendicular to the event plane. The results are from a high-statistics 200-GeV Au + Au collisions data set (57×106 events) collected by the STAR experiment. We explicitly count units of charge separation from which we find clear evidence for more charge-separation fluctuations perpendicular than parallel to the event plane. We also employ a modified correlator to study the possible P-even background in same- and opposite-charge correlations, and find that the P-even background may largely be explained by momentum conservation and collective motion. © 2013 American Physical Society.886NRF-2012004024; National Research FoundationLee, T.D., Yang, C.N., (1956) Phys. Rev., 104. , 1, 254. 0031-899X PHRVAO 10.1103/PhysRev.104.254Vafa, C., Witten, E., (1984) Phys. Rev. Lett., 53. , 2, 535. 0031-9007 PRLTAO 10.1103/PhysRevLett.53.535Lee, T.D., (1973) Phys. Rev. D, 8. , 3, 1226. 0556-2821 10.1103/PhysRevD.8.1226Lee, T.D., Wick, G.C., (1974) Phys. Rev. D, 9. , 4, 2291. 0556-2821 10.1103/PhysRevD.9.2291Kharzeev, D., Parity violation in hot QCD: Why it can happen, and how to look for it (2006) Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 633 (2-3), pp. 260-264. , DOI 10.1016/j.physletb.2005.11.075, PII S0370269305017430Kharzeev, D., Zhitnitsky, A., (2007) Nucl. Phys. 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Magnetic structure determination using polarised resonant X-ray scattering

100學年度杜昭宏升等參考著作[[abstract]]Full polarisation analysis of resonant X-ray magnetic scattering (RXMS) is shown to advance the determination of magnetic moment directions of complex magnetic structures within single crystals. Key features of this novel method are the variation of the incident beam polarisation through the use of an X-ray phase plate, and the measurement of the scattered beam polarisation in terms of Poincaré–Stokes parameters. Contrary to the established method, no azimuthal rotation is required. Thus, the major sources of systematic error are eliminated, and the method is compatible with exotic and complex sample environments. The technique is demonstrated with the example of TbMn2O5. The RXMS theory briefly outlined in this paper was fitted to the data, and the local and delocalized, band-specific moment directions associated with the magnetic order of the resonating species was refined with a high degree of accuracy.[[notice]]補正完畢[[journaltype]]國外[[incitationindex]]SCI[[booktype]]紙本[[countrycodes]]NL