153 research outputs found
Influence of specific codopants and post-treatments on Erbium Doped Fibers: Radiation behavior characteristics by CML
No full text
STRATEGIA CHIRURGICA NEL TRATTAMENTO DEI TUMORI NEUROENDOCRINI DEL POLMONE.
No full textIntroduzione. I tumori neuroendocrini bronchiali sono un’entità rarissima, benché rappresentino le neoplasie polmonari più frequenti in età pediatrica. Sono neoplasie a lenta crescita che si presentano con sintomi aspecifici quali febbre, polmoniti ricorrenti, tosse. Tale caratteristica può essere confondente e portare ad un ritardo diagnostico di mesi o anni. La gran parte ha un’istologia ben differenziata (carcinoide tipico) ma forme più aggressive sono segnalate circa in un terzo dei casi.
Materiali e metodi. Sono stati analizzati retrospettivamente tutti i casi di tumore neuroendocrino bronchiale con diagnosi presso il nostro Dipartimento. Dei pazienti identificati, sono stati valutati le caratteristiche demografiche, di presentazione clinica, di trattamento e di follow-up.
Risultati. Sono stati identificati 3 pazienti dal 2015 al 2024. L’età media alla diagnosi è di 131 mesi (96-152), con un ritardo diagnostico medio di 4 mesi. Due neoplasie originavano dal bronco lobare medio destro e una dal bronco principale di sinistra. Sono stati eseguiti una resezione endoscopica e una lobectomia media e per la lesione del bronco principale un debulking endoscopico in previsione di una sleeve bronchoplasty.
Conclusioni. La lung-sparing surgery è considerato l’approccio di scelta per queste neoplasie e, quando non vi sia evidenza di invasione locale o metastasi a distanza, l’enucleazione endoscopica è un’opzione accettabile (a seguito di un prelievo bioptico che escluda una forma più aggressiva), sebbene non permetta un prelievo dei linfonodi regionali. La nostra case series mette in evidenza come la sede anatomica di insorgenza sia fondamentale nel processo decisionale che definisce il controllo locale
Influence of Ce codoping and H2 pre-loading on Er/Yb-doped fiber: Radiation response characterized by Confocal Micro-Luminescence
No full textConfocal microscopy luminescence measurements were applied to study the X-ray radiation response of
Er/Yb-doped optical fibers in connection with H2 pre-loading and with the addition of another lanthanide
element (Cerium) in the core composition. Laser excitations at 488 nm and 325 nm allow deriving the
emission and absorption pattern of Er3+, the latter derived from the dips appearing in a wide luminescence
band related to defects in silica. We found that the luminescence spectrum of the X-irradiated Er/Yb-doped
core fiber evidences an increase in the emission intensity around 520 and 660 nm; in contrast, no changes are
induced by radiation neither after H2 pre-loading nor when the Cerium is added to the core composition. Both
treatments reduce the generation of defects in the Er-doped fibers thus providing hardness in the radiative
environment
Etude spectroscopique de fibres durcies pour un environnement radiatif sévère
No full textLes nouveaux environnements radiatifs, comme LMJ, ITER, ILE/ELI, HiPER, réacteurs nucléaires des générations III+ et IV, nécessitent le développement de nouveaux composants pour le transport et le traitement des signaux. A cause de l’impossibilité d’utiliser les composants électroniques, la recherche est orientée vers les composants à fibres optiques comme vecteur d’information et aussi comme élément de diagnostic. Ils présentent de nombreux avantages, comme leur relative immunité électromagnétique, faible pois, large bande passante, mais les rayonnements gamma et les neutrons dégradent leur transmission. La dégradation dépend principalement de la composition de la fibre. Ainsi, il a été montré que l’une des fibres les plus résistantes aux environnements radiatifs sévères à base de silice est celle dopée au fluor.
Dans ce travail, nous allons présenter les différents effets causés par la radiation gamma et les neutrons sur deux fibres, une multimode et l’autre monomode, dopées au fluor. L’étude de l’atténuation spectrale dans le domaine visible-infrarouge et l’RPE sera présenté.
Ces deux techniques nous permettent de comparer la réponse sous irradiation des deux fibres. Une comparaison sera également faite avec la réponse de la silice pure, dont le comportement a été présenté dans la littérature [1,2].
[1] D. Bravo, J.C. Lagomacini, M. León, P. Martín, A. Martín, J.F. López and A. Ibarra, Fusion Engineering and Design, vol. 84, pp. 514-517 (2009)
[2] J.C. Lagomacini, D. Bravo, M. León, P. Martín, A. Ibarra, A. Martín and F.J. López, Journal of Nuclear Materials, vol. 417, pp. 802-805 (2011)
Coupled experiment/simulation approach for the design of radiation-hardened rare-earth doped optical fibers and amplifiers
No full textWe developed an approach to design radiation-hardened rare earth -doped fibers and amplifiers. This methodology combines testing experiments on these devices with particle swarm optimization (PSO) calculations. The composition of Er/Yb-doped phosphosilicate fibers was improved by introducing Cerium inside their cores. Such composition strongly reduces the amplifier radiation sensitivity, limiting its degradation: we observed a gain decreasing from 19 dB to 18 dB after 50 krad whereas previous studies reported higher degradations up to 0°dB at such doses. PSO calculations, taking only into account the radiation effects on the absorption efficiency around the pump and emission wavelengths, correctly reproduce the general trends of experimental results. This calculation tool has been used to study the influence of the amplifier design on its radiation response. The fiber length used to ensure the optimal amplification before irradiation may be rather defined and adjusted to optimize the amplifier performance over the whole space mission profile rather than before integration in the harsh environments. Both forward and backward pumping schemes lead to the same kind of degradation with our active fibers. By using this promising coupled approach, radiation-hardened amplifiers nearly insensitive to radiations may be designed in the future
Micro-Raman investigation of X or gamma irradiated Ge doped fibers
No full textInternational audienceMicro-Raman spectra have been recorded on Ge doped optical fibers before and after 10 keV-X or c-ray irradiation up to doses of 1 MGy (X-ray) or 7.8 MGy (-ray). Our data provide evidence that, at such dose levels, the glass matrix is not modified in a detectable way. We observed that varying the Ge doping levels from 0 to about 11 wt.%, X or radiation sensitivity of the overall matrix remains unchanged. Such results are observed for fibers obtained with drawing conditions within the usual range used for the fabrication of specialty fibers as radiation-tolerant waveguides. Our data support the potentiality of fiberbased sensors using glass properties, e.g. Raman scattering, for applications in harsh environments as those encountered in nuclear power plants
Irradiation temperature effects on the induced point defects in Ge-doped optical fibers
No full textWe present an experimental investigation on the combined effects of temperature and irradiation on Ge-doped optical fibers. Our samples were X-ray (10 keV) irradiated up to 5 kGy with a dose rate of 50 Gy(SiO2)/s changing the irradiation temperature in the range 233-573 K. After irradiation we performed electron paramagnetic resonance (EPR) and confocal microscopy luminescence (CML) measurements. The recorded data prove the generation of different Ge related paramagnetic point defects and of a red emission, different from that of the Ge/Si Non-Bridging Oxygen Hole center. Furthermore, by comparing the behaviour of the EPR signal of the Ge(1) as a function of the irradiation temperature with the one of the red emission we can exclude that this emission is originated by the Ge(1)
Origins of radiation-induced attenuation in pure-silica-core and Ge-doped optical fibers under pulsed x-ray irradiation
No full textWe investigated the nature, optical properties, and decay kinetics of point defects causing large transient attenuation increase observed in silica-based optical fibers exposed to short duration and high-dose rate x-ray pulses. The transient radiation-induced attenuation (RIA) spectra of pure-silica-core (PSC), Ge-doped, F-doped, and Ge + F-doped optical fibers (OFs) were acquired after the ionizing pulse in the spectral range of [∼0.8-∼3.2] eV (∼1500-∼380 nm), from a few ms to several minutes after the pulse, at both room temperature (RT) and liquid nitrogen temperature (LNT). Comparing the fiber behavior at both temperatures better highlights the thermally unstable point defects contribution to the RIA. The transient RIA origin and decay kinetics are discussed on the basis of already-known defects absorbing in the investigated spectral range. These measurements reveal the importance of intrinsic metastable defects such as self-trapped holes (STHs), not only for PSC and F-doped fibers but also for germanosilicate optical fibers as clearly evidenced by our LNT measurements. Furthermore, our results show that fluorine co-doping seems to decrease the RIA related to the strain-assisted STHs absorption bands in both types of optical fibers. Regarding Ge-doped glasses, besides a description of the defects responsible of the RIA, highlighting the STHs' role in their transient response, we provide a clear correlation between the GeX and GeY centers' kinetics. In conclusion, the presented results improve our understanding of the transient RIA origin in the ultraviolet and visible domains. The lack of knowledge about the defects causing the RIA in the near-infrared domain will require future studies
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