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dc.contributor.advisorJoseph V. Minervini and Joel H. Schultz.en_US
dc.contributor.authorMahar, Scott Ben_US
dc.contributor.otherMassachusetts Institute of Technology. Dept. of Nuclear Science and Engineering.en_US
dc.date.accessioned2010-03-25T15:22:13Z
dc.date.available2010-03-25T15:22:13Z
dc.date.copyright2008en_US
dc.date.issued2008en_US
dc.identifier.urihttp://hdl.handle.net/1721.1/53258
dc.descriptionThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2008.en_US
dc.descriptionCataloged from PDF version of thesis.en_US
dc.descriptionIncludes bibliographical references (p. 243-250).en_US
dc.description.abstractLarge superconducting magnets used in fusion reactors, as well as other applications, need a diagnostic that can non-invasively measure the temperature and strain throughout the magnet in real-time. A new fiber optic sensor has been developed for these long-length superconducting magnets that simultaneously measures the temperature and strain based on spontaneous Brillouin scattering in an optical fiber. Using an extremely narrow (200 Hz) linewidth Brillouin laser with very low noise as a frequency shifted local oscillator, the frequency shift of spontaneous Brillouin scattered light was measured using heterodyne detection. A pulsed laser was used to probe the fiber using Optical Time Domain Reflectometry (OTDR) to define the spatial resolution. The spontaneous Brillouin frequency shift and linewidth as a function of temperature agree well with previous literature of stimulated Brillouin data from room temperature down to 4 K. Analyzing the frequency spectrum of the scattered light after an FFT gives the Brillouin frequency shift, linewidth. and intensity. For the first time, these parameters as a function of strain have been calibrated down to 4 K. Measuring these three parameters allow for simultaneously determining the temperature and strain in real-time throughout a fiber with a spatial resolution on the order of several meters. The accuracy of the temperature and strain measurements vary over temperature-strain space, but an accuracy of better than + 2 K and ± 100 Pe are possible throughout most of the calibrated temperature-strain space (4-298 K and 0-3500 p/g). In the area of interest for low-temperature superconducting magnets (4-25 K), the temperature accuracy is better than + 1 degree.en_US
dc.description.abstract(cont.) This temperature accuracy, along with the sub-second measurement time, allows this system to be used not only as a quench detection system, but also as a quench propagation diagnostic. The sensing fiber can also simultaneously provide the first ever spatially resolved strain measurement in an operating magnet.en_US
dc.description.statementofresponsibilityby Scott Brian Mahar.en_US
dc.format.extent250 p.en_US
dc.language.isoengen_US
dc.publisherMassachusetts Institute of Technologyen_US
dc.rightsM.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.en_US
dc.rights.urihttp://dspace.mit.edu/handle/1721.1/7582en_US
dc.subjectNuclear Science and Engineering.en_US
dc.titleSpontaneous brillouin scattering quench diagnostics for large superconducting magnetsen_US
dc.typeThesisen_US
dc.description.degreePh.D.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Nuclear Science and Engineering
dc.identifier.oclc540741508en_US


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