Sparking limits, cavity loading, and beam breakup instability associated with high-current rf linacs

The limitations on high-current rf linacs due to gap sparking, cavity loading, and the beam breakup instability are studied. It appears possible to achieve cavity accelerating gradients as high as 35 MV/m without sparking. Furthermore, a linear analysis, as well as self-consistent particle simulations of a multipulsed 10 kA beam, indicated that only a negligible small fraction of energy is radiated into nonfundamental cavity modes. Finally, the beam breakup instability is analyzed and found to be able to magnify initial radial perturbations by a factor of no more than about 20 during the beam transit time through a 1 GeV accelerator

Batteries and fuel cells working group report

Electrochemical energy systems are dominated by interfacial phenomena. Catalysis, corrosion, electrical and ionic contact, and wetting behavior are critical to the performance of fuel cells and batteries. Accordingly, development of processing techniques to control these surface properties is important to successful commercialization of advanced batteries and fuel cells. Many of the surface processing issues are specific to a particular electrochemical system. Therefore, the working group focused on systems that are of specific interest to DOE/Conservation and Renewable Energy. These systems addressed were: Polymer Electrolyte Membrane (PEM) Fuel Cells, Direct Methanol Oxidation (DMO) Fuel Cells, and Lithium/Polymer Batteries. The approach used by the working group for each of these systems was to follow the current path through the system and to identify the principal interfaces. The function of each interface was specified together with its desired properties. The degree to which surface properties limit performance in present systems was rated. Finally, the surface processing needs associated with the performance limiting interfaces were identified. This report summarizes this information

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

A student's guide to dimensional analysis

This introduction to dimensional analysis covers the methods, history and formalisation of the field, and provides physics and engineering applications. Covering topics from mechanics, hydro- and electrodynamics to thermal and quantum physics, it illustrates the possibilities and limitations of dimensional analysis. Introducing basic physics and fluid engineering topics through the mathematical methods of dimensional analysis, this book is perfect for students in physics, engineering and mathematics. Explaining potentially unfamiliar concepts such as viscosity and diffusivity, the text includes worked examples and end-of-chapter problems with answers provided in an accompanying appendix, which help make it ideal for self-study. Long-standing methodological problems arising in popular presentations of dimensional analysis are also identified and solved, making the book a useful text for advanced students and professionals

Thermodynamic weirdness: from Fahrenheit to Clausius

Students of physics, chemistry, and engineering are taught classical thermodynamics through its methods―a “problems first” approach that neglects the subject's concepts and intellectual structure. In Thermodynamic Weirdness, Don Lemons fills this gap, offering a nonmathematical account of the ideas of classical thermodynamics in all its non-Newtonian “weirdness.” By emphasizing the ideas and their relationship to one another, Lemons reveals the simplicity and coherence of classical thermodynamics. Lemons presents concepts in an order that is both chronological and logical, mapping the rise and fall of ideas in such a way that the ideas that were abandoned illuminate the ideas that took their place. Selections from primary sources, including writings by Daniel Fahrenheit, Antoine Lavoisier, James Joule, and others, appear at the end of most chapters. Lemons covers the invention of temperature; heat as a form of motion or as a material fluid; Carnot's analysis of heat engines; William Thomson (later Lord Kelvin) and his two definitions of absolute temperature; and energy as the mechanical equivalent of heat. He explains early versions of the first and second laws of thermodynamics; entropy and the law of entropy non-decrease; the differing views of Lord Kelvin and Rudolf Clausius on the fate of the universe; the zeroth and third laws of thermodynamics; and Einstein's assessment of classical thermodynamics as “the only physical theory of universal content which I am convinced will never be overthrown.

Electron-temperature requirements for neutralized inertial-confinement-fusion light-ion beams

Because of their large self-space-charge fields, light ion beam drivers of energy and power sufficient to achieve inertial confinement fusion (ICF) cannot be focused on a small fuel pellet unless neutralized. Even if initially neutralized with comoving electrons, these beams will not stay neutralized and focus during propagation through a vacuum chamber unless the initial thermal energy of the neutralizing electrons is sufficiently small. In this paper we discuss the effects which contribute to the effective initial temperature of the neutralizing electrons, including compressional shock heating. We also employ a simple heuristic model to construct envelope equations which govern axial as well as radial beam compression and use them to predict the largest initial electron temperature consistent with the required beam compression. This temperature for typical light ion beam systems is about ten eV - a temperature which may be possible to achieve

Ion beam propagation simulations

A series of numerical particle-in-cell simulations of ion beam propagation have been performed with the LASL two-dimensional electromagnetic code, CCUBE. A few results for each of two different simulations are presented. They are intended to illustrate plasma effects relevant to (1) ion propagation in a relatively dense plasma background, and (2) ion vacuum propagation with co-moving electrons