Submillimeter local oscillators for heterodyne spectroscopy

The major technological innovations in continuous wave (CW) submillimeter sources which are specifically suitable for application as local oscillators in heterodyne systems are reviewed. A description of the various sources is given which underscores the general principles and operating features for each type of device. Particular emphasis is placed on CW optically pumped lasers, which have had a dramatic impact as widely available sources of narrow linewidth coherent radiation. The state-of-the-art is summarized for these lasers and performance data are presented for several local oscillator packages. Optically pumped lasers are then compared and contrasted with other competing sources such as backward wave oscillators, IMPATT diodes, and Josephson junctions. By comparing their advantages and limitations for use as local oscillators, the potential applications of these different sources are projected. The prospects for increased tunability, reliability, and scalability are briefly considered, and several novel techniques for generating partially tunable radiation using Schottky diode mixers or CW Raman lasers are highlighted

Probing the isospin dependence of the in-medium nucleon-nucleon cross sections with radioactive beams

Within a transport model we search for potential probes of the isospin dependence of the in-medium nucleon-nucleon (NN) cross sections. Traditional measures of the nuclear stopping power are found sensitive to the magnitude but they are ambiguous for determining the isospin dependence of the in-medium NN cross sections. It is shown that isospin tracers, such as the neutron/proton ratio of free nucleons, at backward rapidities/angles in nuclear reactions induced by radioactive beams in inverse kinematics is a sensitive probe of the isospin dependence of the in-medium NN cross sections. At forward rapidities/angles, on the other hand, they are more sensitive to the density dependence of the symmetry energy. Measurements of the rapidity/angular dependence of the isospin transport in nuclear reactions will enable a better understanding of the isospin dependence of in-medium nuclear effective interactions.Comment: 19 pages including 7 figures, submitted to Phys. Rev.

Directed flow at RHIC from Lee-Yang zeroes

Directed flow in ultrarelativistic nucleus-nucleus collisions is analyzed using the reaction plane from elliptic flow, which reduces the bias from nonflow effects. We combine this method with the determination of elliptic flow from Lee-Yang zeroes. The resulting method is more consistent and somewhat easier to implement than the previously used method based on three-particle cumulants, and is also less biased by nonflow correlations. Error terms from residual nonflow correlations are carefully estimated, as well as statistical errors. We discuss the application of the method at RHIC and LHC.Comment: 10 pages. Final version, to appear in Nucl. Phys.

Experimental and analytical performance investigation of air to air two phase closed thermosyphon based heat exchangers

In recent years, the use of wickless heat pipes (thermosyphons) in heat exchangers has been on the rise, particularly in gas to gas heat recovery applications due to their reliability and the level of contingency they offer compared to conventional heat exchangers. Recent technological advances in the manufacturing processes and production of gravity assisted heat pipes (thermosyphons) have resulted in significant improvements in both quality and cost of industrial heat pipe heat exchangers. This in turn has broadened the potential for their usage in industrial waste heat recovery applications. In this paper, a tool to predict the performance of an air to air thermosyphon based heat exchanger using the ε-NTU method is explored. This tool allows the predetermination of variables such as the overall heat transfer coefficient, effectiveness, pressure drop and heat exchanger duty according to the flow characteristics and the thermosyphons configuration within the heat exchanger. The new tool's predictions were validated experimentally and a good correlation between the theoretical predictions and the experimental data, was observed. © 2014 Elsevier Ltd. All rights reserved

Particle production in quantum transport theories

The particle production in the intermediate energy heavy ion collisions is discussed in the framework of the nonequilibrium Green's functions formalism. The evolution equations of the Green's functions for fermions allows for the discussion of the off-shell fermion propagator and of the large momentum component in the initial state. For the case of a homogeneous system numerical calculations of the meson production rate are performed and compared with the semiclassical production rate.Comment: 45 pages, figures included, uses FEYNMAN macro

Determination of the reaction plane in ultrarelativistic nuclear collisions

In the particles produced in a nuclear collision undergo collective flow, the reaction plane can in principle be determined through a global event analysis. We show here that collective flow can be identified by evaluating the reaction plane independently in two separate rapidity intervals, and studying the correlation between the two results. We give an analytical expression for the correlation function between the two planes as a function of their relative angle. We also discuss how this correlation function is related to the anisotropy of the transverse momentum distribution. Email contact: [email protected]: Saclay-T93/026 Email: [email protected]

Transport Dynamics of Broad Resonances

The propagation of short life time particles with consequently broad mass width are discussed in the context of transport descriptions. In the first part some known properties of finite life time particles such as resonances are reviewed and discussed at the example of the $\rho$-meson. Grave deficiencies in some of the transport treatment of broad resonances are disclosed and quantified. The second part addresses the derivation of transport equations which permit to account for the damping width of the particles. Baym's $\Phi$-derivable method is used to derive a self-consistent and conserving scheme, which fulfils detailed balance relations even in the case of particles with broad mass distributions. For this scheme a conserved energy-momentum tensor can be constructed. Furthermore, a kinetic entropy can be derived which besides the standard quasi-particle part also includes contributions from fluctuations.Comment: Talk presented on the Erice School on Nuclear Physics, Erice, Italy, Sept. 17 - 25, 1998 to be published in Progress in Particle and Nuclear Physics, Vol. 42 (10 pages, 5 eps-figures