On superluminal tunneling

Photonic tunneling is currently of theoretical and applied interest. In a previous review, faster-than-light (i.e. superluminal) photonic tunneling was discussed (Progr. Quantum Electron. 21 (1997) 81). Recently, superluminal photonic pulse transmission and reflection have been measured at microwave and infrared frequencies. It seems clear that superluminal photonic and electronic devices will become a reality in the near future.

In the present report, we introduce new experimental and theoretical data on superluminal tunneling and reflection. Data of reflection by barriers have evidenced the nonlocal nature of tunneling. Asymmetric barriers have revealed a strange asymmetric reflection behavior in time.

The principle of causality is not violated by a superluminal speed even though the time duration between cause and effect can be shortened compared with a luminal interaction exchange. An empirical relationship independent of the barrier system is found for the photonic tunneling time. This relation seems to be universal for all kind of tunneling processes in the case of single opaque barriers. We show that the superluminal velocity can be applied to speed up photonic modulation and transmission as well as to improve microelectronic devices.     

Development of Output Windows for High-Power Long-Pulse Gyrotrons and EC Wave Applications

Electron cyclotron heating (ECH) is one of the main candidates for heating and current drive on ITER (170 GHz) and W7-X (140 GHz). High unit power (1 MW or greater) and high efficiency single-mode continuous-wave (CW) gyrotrons are under development in order to reduce significantly the systems costs. Face-cooled double-disk sapphire and silicon nitride windows (FC-75 liquid cooling), cryogenically edge-cooled single-disk sapphire (liquid nitrogen, liquid neon or liquid helium cooling) and silicon (230 K refrigerator cooling) windows, water-edge-cooled single-disk CVD-diamond windows and water-cooled distributed windows are being investigated in order to solve the window problem. A water-cooled window has two very important advantages; it employs a cheap and effective coolant and it is compact and probably more reliable than other solutions and thus can also be easily used as a torus window. The present paper summarizes the development status of high-power millimeter-wave windows with emphasis on CVD diamond.     

The role of hydrogen for the long term development of sustainable energy systems—a case study for Germany

Based on different current long-term energy scenarios the paper discusses the future perspectives of hydrogen in the German energy system as a representative example for the development of sustainable energy systems. The scenario analysis offers varying outlines of the future energy system that determine the possible role of hydrogen. The paper discusses the possibilities of expanding the share of renewable energy and the resulting prospects for establishing clean hydrogen production from renewable energy sources. Emphasis is given to the questions of an ecologically efficient allocation of limited renewable energy resources that can only be assessed from a systems analysis perspective. Findings from recent studies for Germany reveal a strong competition between the direct input into the electricity system and an indirect use as fuel in the transport sector. Moreover, the analysis underlines the paramount importance of reducing energy demand as the inevitable prerequisite for any renewable energy system.     

Bericht vom FNN/ETG-Tutorial Schutz- und Leittechnik 2010

Am 9. und 10. Juni 2010 fand in Ulm das "Tutorial Schutz- und Leittechnik 2010" statt, welches vom Forum Netztechnik/Netzbetrieb im VDE (FNN) und der Energietechnischen Gesellschaft im VDE (ETG) in Zusammenarbeit mit der OGE (?sterreichische Gesellschaft für Energietechnik im OVE), der ETG von Electrosuisse und Oesterreichs Energie (vormals VE?) veranstaltet wurde. Das Tutorial war mit rund 300 Teilnehmern sehr gut besucht, was die Aktualit?t der gew?hlten Themen unterstreicht. Die Veranstaltung bestand aus Plenum-Vortr?gen und -Diskussionen, Workshops sowie einer Fachausstellung und bot dem Fachpublikum auf Hersteller- und Anwenderseite die Gelegenheit, die aktuellen Entwicklungen auf dem Gebiet der Schutz- und Leittechnik kennen zu lernen, sich zu informieren und auszutauschen. Zudem war auch eine Postersession in das Programm integriert.     

Effective Cavity Length of Gyrotrons

Megawatt-class gyrotron oscillators for electron cyclotron heating and non-inductive current drive (ECH&CD) in magnetically confined thermonuclear fusion plasmas have relatively low cavity quality factors in the range of 1000 to 2000. The effective length of their cavities cannot be simply deduced from the cavity electric field profile, since this has by far not a Gaussian shape. The present paper presents a novel method to estimate the effective length of a gyrotron cavity just from the eigenvalue of the operating TE_m,n mode, the cavity radius and the exact oscillation frequency which may be numerically computed or precisely measured. This effective cavity length then can be taken to calculate the Fresnel parameter in order to confirm that the cavity is not too short so that the transverse structure of any mode in the cavity is the same as that of the corresponding mode in a long circular waveguide with the same diameter.     

Plant‐oil‐based lubricants and hydraulic fluids

It is estimated that, at present, approximately 50% of all lubricants sold worldwide end up in the environment via total loss applications, volatility, spills or accidents. More than 95% of these materials are currently mineral oil based. In view of their high ecotoxicity and low biodegradability, mineral oil‐based lubricants constitute a considerable threat to the environment. In contrast, most lubricants and hydraulic fluids based on plant oils are rapidly and completely biodegradable and are of low ecotoxicity; moreover, lubricants based on plant oils display excellent tribological properties and generally have very high viscosity indices and flashpoints. However, in order to compete with mineral‐oil‐based products, some of their inherent disadvantages must be corrected, such as their sensitivity to hydrolysis and oxidative attack, and their behaviour at low temperatures. Various methods to improve the undesirable properties of native plant oils will be discussed. In parallel, government regulations that encourage or enforce the use of bio‐based fluids, at least in ecologically sensitive areas, will help to increase their market share. Using the numerous possibilities for selective breeding and/or chemical improvement of the double bond systems of natural fatty acids by increased R&D, the major obstacles regarding the use of plant‐based raw materials for the production of lubricant base fluids can be overcome and bio‐based fluids should expect a future with increasing market shares. Copyright © 2006 Society of Chemical Industry