Jean-Bernard DUCHEZ led his thesis work (defense expected June 12) as part of the ANR project PARADYSIO, supervised by Franck MADY and Mourad BENABDESSELAM, on the study of darkening in Ytterbium-doped optical fibers and more particularly the interaction between photo- and radiation-induced effects.
This award recognizes international doctoral dissertations in the final year for their outstanding work in the fields of IEEE - NPSS : Radiation Instrumentation, Medical Imaging Sciences, Radiation Effects, Plasma Sciences, Fusion Technology, Pulsed Power, Particle Accelerators, Nuclear Power and Technology, Computer Applications.
Jean-Bernard DUCHEZ is one of three winners of the 2015 Paul Phelps Award among all these areas and all international applications. The award ceremony will be on July 13 in Boston (MA, USA).
This thesis deals with the degradation induced by the pump (photodarkening, PN) and ionizing radiations (radiodarkening, RN) in ytterbium-doped optical fiber (YDF) used in harsh environments. Through original experimental characterizations and modeling, it analyses the interplay between PN and RN and reveals important and novel properties of the radiation resistance of pumped YDF.
The first part investigates induced defects (color centers) together with their creation/recovery mechanisms. It used a set of post-irradiation characterizations (ESR, RIA, TSL) conducted on preform samples and benefited from their original correlation (thermal recovery protocols coupling TSL and RIA). A systematic study as a function of composition reveals the influence of co-dopants (Al, Ce) on the trapping of carrier freed during ionization processes.
The second part examines the darkening build-up under the simultaneous action of the pump and an ionizing irradiation. By using a measurement bench that allowed us to follow the real-time “on line” degradation of fiber samples, we showed that photo- and radio-darkening both arise from the same color centers that can be bleached by the pump. On the basis of this finding and of the preceding identified mechanisms, we propose a local physical model of the photo-radio-induced darkening. The latter is thoroughly validated by further successful comparisons of simulated degradation with a wide variety of “on line” original observations. Then, we notably demonstrate that for dose rates lying below a critical value (explicited by our theory), the degradation of pumped and irradiated YDF never exceeds the photo-darkening level.
Article published in "Nice Matin" (regional newspaper) :
MOSAIQ, Doctorants/Post-doctorants, Fibres Optiques
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