External magnetic perturbations are typically utilized in tokamak devices with two operational or experimental purposes: 1) correction of intrinsic 3-D error fields and 2) mitigation or suppression of edge localized modes (ELMs). At Joint European Torus (JET), dedicated coils are used for the generation of these toroidally asymmetric perturbations. While error fields exist even in the absence of plasma, in ELM mitigation experiments, the external fields are meant to slightly ergodize the magnetic topology in the plasma periphery hence reducing the drive for the destabilization of these instabilities. The control of the magnetic field produced by these coils is achieved by controlling the current flowing in them. The real-time system responsible for this control recently underwent a number of functional improvements since its original implementation utilizing the present voltage-controlled voltage sources. This paper describes the overall system, built-in functionality, and control algorithms and presents preliminary experimental results along with performance assessment studies. In particular, the main improvements are: 1) the possibility of automatically reducing the current references in case the plasma amplifies the applied perturbation; 2) a real-time limitation of $dI/dt$ to reduce the electromotive force in machine protection diagnostic systems; 3) implementation of a model predictive controller as an alternative to the proportional integral derivative; and 4) the possibility of adapting the current references, in real time, using an external system. The result is a flexible control system contributing toward state-of-the-art physics research at JET’s international and dynamic scientific environment.

A new Disruption Mitigation System (DMS) based on Massive Gas Injections (MGI) has been installed at the JET-tokamak. The key component of this system is a fast eddy current driven valve, which is capable of injecting up to 4.6 x 10(-3) MPa m(3) in less than 5 ms. Along with this valve a new gas handling system has been installed, whose control had to be integrated into the JET-operation. The operation of the DMS requires interaction with several other systems. Although Massive Gas Injections are used to ameliorate potentially severe damage to the tokamak plant and plasma facing components caused by disruptions, they introduce a high risk for example to auxiliary heating systems or diagnostics, which could be damaged by high vacuum pressures. In addition to this, the presence of high pressure (of noble and flammable gases) in combination with high voltages represents a risk not only to the actual DMS plant itself (in case of a failure) but also to personnel in the vicinity. These varieties of risks have been addressed and are described in this article. (C) 2015 Elsevier B.V. All rights reserved.

Disruptions are a major concern for next-generation tokamaks, including ITER. Heat loads, electromagnetic forces and runaway electrons generated by disruptions have to be mitigated for a reliable operation of future machines. Massive gas injection is one of the methods proposed for disruption mitigation. This article reports the first use of massive gas injection as an active disruption protection system at JET. During the 2011–2012 campaigns, 67 disruptions have been mitigated by the disruption mitigation valve (DMV) following a detection by mode lock amplitude and loop voltage changes. Most of disruptions where the valve was intended to be used were successfully mitigated by the DMV, although at different stages of the typical slow disruptions of the ITER-like wall. The fraction of magnetic and thermal energy radiated during the disruption was found to be increased by the action of the DMV. Vertical forces dispersion was also reduced. No non-sustained breakdown was observed following pulses terminated by the disruption mitigation valve.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChemistry of 8-substituted 1-naphthylmethylenes and 2-substituted benzylidenes. A simple entry to 1H-cyclobuta[de]naphthalenesR. J. Bailey, P. Card, and H. ShechterCite this: J. Am. Chem. Soc. 1983, 105, 19, 6096–6103Publication Date (Print):September 1, 1983Publication History Published online1 May 2002Published inissue 1 September 1983https://doi.org/10.1021/ja00357a021RIGHTS & PERMISSIONSArticle Views1553Altmetric-Citations48LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Chemischer InformationsdienstVolume 8, Issue 24 Physical Organic Chemistry ChemInform Abstract: THE STRUCTURE OF 1-BROMO-1H-CYCLOBUTA(DE)NAPHTHALENE M. GESSNER, M. GESSNERSearch for more papers by this authorP. CARD, P. CARDSearch for more papers by this authorH. SHECHTER, H. SHECHTERSearch for more papers by this authorG. G. CHRISTOPH, G. G. CHRISTOPHSearch for more papers by this author M. GESSNER, M. GESSNERSearch for more papers by this authorP. CARD, P. CARDSearch for more papers by this authorH. SHECHTER, H. SHECHTERSearch for more papers by this authorG. G. CHRISTOPH, G. G. CHRISTOPHSearch for more papers by this author First published: June 14, 1977 https://doi.org/10.1002/chin.197724080AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume8, Issue24June 14, 1977 RelatedInformation