<?xml version="1.0" encoding="UTF-8"?> <rss version="2.0" xmlns:media="http://search.yahoo.com/mrss/" xmlns:atom="http://www.w3.org/2005/Atom" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:dcterms="http://purl.org/dc/terms/" xmlns:opensearch="http://a9.com/-/spec/opensearch/1.1/"> <channel> <title>CERN Document Server</title> <link>https://cds.cern.ch</link> <description>CERN Document Server latest documents</description> <language>en</language> <pubDate>Sat, 30 Nov 2024 20:06:09 GMT</pubDate> <category></category> <generator>Invenio 1.1.3.1106-62468</generator> <ttl>360</ttl> <atom:link rel="self" href="/rss?f=author&amp;ln=en&amp;p=Hoell%2C+Stefan" /> <opensearch:totalResults>3</opensearch:totalResults> <opensearch:startIndex>1</opensearch:startIndex> <opensearch:itemsPerPage>25</opensearch:itemsPerPage> <image> <url>https://cds.cern.ch/img/site_logo_rss.png</url> <title>CERN Document Server</title> <link>https://cds.cern.ch</link> </image> <atom:link rel="search" href="https://cds.cern.ch/opensearchdescription" type="application/opensearchdescription+xml" title="Content Search" /> <textInput> <title>Search </title> <description>Search this site:</description> <name>p</name> <link>https://cds.cern.ch/search</link> </textInput> <item> <title>Beam-beam long range compensator mechanical demonstrator</title> <link>https://cds.cern.ch/record/2886519</link> <description>Beam-Beam Long-Range Compensators employing current-carrying wires are considered as valuable options in hadron colliders to increase dynamic aperture at small crossing angles. This paper presents a simple design proposal for application at CERN LHC. The preliminary design allows for a certain scalability of the number of modules, current flowing in the wire, and dimensions. It complies with two key requirements: (a) the use of a thin, bare metal wire that allows for movement as near to the beam as necessary while minimising interactions with beam particles and meeting the specified DC current target; and (b) a wire support that is both an electrical insulator and a thermal conductor (ceramic).A molybdenum wire, vacuum brazed on an aluminium nitride support, is proposed, and the design is conceptually proved through the realisation and extensive test of a demonstrator device. The wire brazing validation, as well as the system's heat management, which are the most critical aspects, are given particular regard.</description> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Sito, Leonardo</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Rossi, Adriana</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Bertarelli, Alessandro</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Accettura, Carlotta</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Carra, Federico</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Motschmann, Fritz</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Sterbini, Guido</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Guardia Valenzuela, J</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Gentini, Luca</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Garlasch猫, Marco</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Guinchard, Michael</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Sacristan De Frutos, Oscar</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Hoell, Stefan</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Papaphilippou, Yannis</dc:creator> <pubDate>Tue, 16 Jan 2024 05:45:23 GMT</pubDate> <guid>https://cds.cern.ch/record/2886519</guid> <media:content xmlns:media="http://search.yahoo.com/mrss/" url="https://cds.cern.ch/record/2886519/files/document.pdf"/> <dc:title xmlns:dc="http://purl.org/dc/elements/1.1/" xml:lang="fr"/> <dc:hasPart xmlns:dc="http://purl.org/dc/elements/1.1/">['']</dc:hasPart> <dc:hasVersion xmlns:dc="http://purl.org/dc/elements/1.1/"/> </item> <item> <title>Optical losses assessment for optical fiber-based strain sensing at cryogenic temperatures</title> <link>https://cds.cern.ch/record/2866079</link> <description>Optical fiber-based sensors are non-invasive and suitable instrumentations for physical sensing. In this technology, signals are transmitted through pulses of light and are not affected by electromagnetic interference or electrical noise. Although optical fibers perform well at typical operating temperatures, their properties at cryogenic temperatures down to 1.6 K under ultrahigh vacuum remain largely unknown. Future applications in quantum computing, superconducting research, and aerospace will all require cryogenic technologies. For such cold applications, a solid understanding of optical fiber performance and losses is crucial. This study evaluates the optical fiber losses for discrete and distributed strain sensing down to cryogenic temperatures (1.6 K).</description> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Kandemir, Keziban</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Guinchard, Michael</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Thuliez, David</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Hoell, Stefan</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Mugnier, Sylvain</dc:creator> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Sacristan, Oscar</dc:creator> <pubDate>Thu, 27 Jul 2023 05:46:25 GMT</pubDate> <guid>https://cds.cern.ch/record/2866079</guid> <dc:title xmlns:dc="http://purl.org/dc/elements/1.1/" xml:lang="fr"/> <dc:hasPart xmlns:dc="http://purl.org/dc/elements/1.1/">['']</dc:hasPart> <dc:hasVersion xmlns:dc="http://purl.org/dc/elements/1.1/"/> </item> <item> <title>Characterization of the thermal contraction of superconducting magnet coils for the High-Luminosity upgrade of the Large Hadron Collider (HL-LHC)</title> <link>https://cds.cern.ch/record/2845427</link> <description>The High Luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN comprises several technological improvements such as the new focusing MQXF magnets, which are based on Nb$_3$Sn to increase the magnetic field strength. To optimize the magnet performance by adjustments in design and installation parameters, the thermal contraction of the MQXF magnet coils from room temperature to their operating temperature of 1.9 K was studied. For this purpose, a new and customized optical dilatation test setup capable of measuring thermal contraction at cryogenic temperatures was introduced and commissioned. The cryogenic environment is realized by a closed-cycle cryostat providing dynamic and steady-state operation between 300 and 1.8 K. During an extensive validation campaign, the design and operation of the measurement system has been analyzed and accordingly optimized. Moreover, appropriate sample preparation was established with respect to the reflectivity requirements of the optical displacement sensors. A procedure based on a coating with aluminum foil for materials with insufficient reflectivity was developed to avoid limitations in investigable materials. Conclusively, the system accuracy was determined by the expanded uncertainty under the consideration of two approaches utilizing either the individual error sources or highly accurate reference data. Consequently, the expanded uncertainty in the relative change in length 螖L/L$_0$ at 1.8 K was determined as 0.01脳10$^{-3}$ for uncoated and as 0.03脳10$^{-3}$ for aluminum coated samples. In the coil characterization campaign, each of the three coil axes has been investigated and placed in literature as well as individual constituents. The measurements were performed on several specimens that were obtained from an MQXFB coil and coated with aluminum foil to ensure an appropriate reflectivity. The results in longitudinal direction agree well with several preceding studies on Nb$_3$Sn based coil specimens, indicating a behavior similar to stainless steel with a total contraction of about -2.98脳10$^{-3}$ at 1.8 K. A comparable thermal contraction has also been identified in the literature for the radial axis. The specimen of this study, however, showed a thermal contraction close to Nb$_3$Sn with a shrinkage of -1.61 and -1.75脳10$^{-3}$ for the inner and the outer coil, respectively. In the azimuthal direction, a high dispersion in contraction behavior was observed. Nonetheless, the results indicate an evident increase in contraction from the inner coil with -2.55 to the outer coil with -3.77脳10$^{-3}$, both values at 1.8 K. Several possible causes for this increased shrinkage have been proposed, but further studies are necessary to gain a better understanding of the underlying mechanisms.</description> <dc:creator xmlns:dc="http://purl.org/dc/elements/1.1/">Hoell, Stefan</dc:creator> <pubDate>Thu, 05 Jan 2023 15:01:46 GMT</pubDate> <dc:source xmlns:dc="http://purl.org/dc/elements/1.1/">CERN-THESIS-2022-274</dc:source> <guid>https://cds.cern.ch/record/2845427</guid> <media:content xmlns:media="http://search.yahoo.com/mrss/" url="https://cds.cern.ch/record/2845427/files/CERN-THESIS-2022-274.pdf"/> <dc:title xmlns:dc="http://purl.org/dc/elements/1.1/" xml:lang="fr"/> <dc:hasPart xmlns:dc="http://purl.org/dc/elements/1.1/">2022</dc:hasPart> <dc:hasVersion xmlns:dc="http://purl.org/dc/elements/1.1/">274</dc:hasVersion> </item> </channel> </rss>