Feasibility study of an optical resonator for applications in neutral-beam injection systems for the next generation of nuclear fusion reactors

Cette étude fait partie d'un projet plus large appelé SIPHORE (SIngle gap PHOtoneutralizer energy REcovery injector), visant à améliorer l'efficacité globale de l'un des mécanismes par lesquels le plasma est chauffe, dans un réacteur de fusion nucléaire, à savoir le système d'injection de neutres (IDN). Une composante importante d'un système IDN est le neutraliseur de faisceaux d'ions de haute énergie. SIPHORE propose de substituer le neutraliseur à cellule à gaz, utilisé dans les systèmes IDN actuels, par un photo-neutraliseur exploitant le processus de photo-détachement dans des cavités Fabry Perot. Ce mécanisme devrait permettre une efficacité globale η> 60% du système IDN, nettement plus élevée que celle actuellement possible (η 60%, significantly higher than the one currently possible (η<25% for ITER). The present work concerns the feasibility study of an optical cavity with suitable properties for applications in NBI systems. Within this context, the issue of the determination of an appropriated optical cavity design has been firstly considered and the theoretical and experimental analysis of a particular optical resonator has been carried on. The problems associated with the high levels of intracavity optical power (~3 MW) required for an adequate photo-neutralization rate have then been faced. In this respect, we addressed both the problem of the thermal effects on the cavity mirrors due to their absorption of intra-cavity optical power (~1W) and the one associated to the necessity of a high powerful input laser beam (~1 kW) to feed the optical resonator

Étude de faisabilité d'un résonateur optique pour des applications aux systèmes d'injection de neutres pour la prochaine génération de réacteurs à fusion nucléaire

This work is part of a larger project called SIPHORE (SIngle gap PHOtoneutralizer energy RE-covery injector), which aims to enhance the overall efficiency of one of the mechanisms through which the plasma is heated, in a nuclear fusion reactor, i.e. the Neutral Beam Injection (NBI) system. An important component of a NBI system is the neutralizer of high energetic ion beams. SIPHORE proposes to substitute the gas cell neutralizer, used in the current NBI systems, with a photo-neutralizer exploiting the photo-detachment process within Fabry Perot cavities. This mechanism should allow a relevant NBI global efficiency of η> 60%, significantly higher than the one currently possible (η 60% du système IDN, nettement plus élevée que celle actuellement possible (η <25% pour ITER). Le travail de thèse porte sur l'étude de faisabilité d'une cavité optique avec des propriétés adaptées aux systèmes IDN. Dans ce contexte, le problème de la détermination d'une conception de la cavité optique appropriée a été tout d'abord pris en considération et l'analyse théorique ainsi qu'expérimentale d'un résonateur optique ont été effectuées. Les problèmes lies aux niveaux élevés de puissance optique intracavité (~3 MW) nécessaire pour un taux de photo-neutralisation adéquat ont ensuite été prises en compte. A cet égard, nous avons traite a la fois le problème des effets thermiques sur les miroirs de la cavité en raison de leur absorption de la puissance optique intra-cavite (~1 W) et celui associe à la nécessité d'un faisceau laser d'entrée de puissance élevée (~1 kW) pour alimenter le résonateur optique

Overview of photo-neutralization techniques for negative ion-based neutral beam injectors in future fusion reactors

Photo-neutralization of negative ions ($$H^-/D^-$$) is now regarded as a promising technique to increase the efficiency of neutral beam heating systems in future fusions reactors. In a gas or plasma neutralizer, the extra electron in the negative ion is detached by stripping, while in photo-neutralizers it detaches by absorbing a visible or near-infrared photon. The main technological challenge is the level of optical power required (several MW), which forbids the use of direct illumination and requires some form of light trapping: the research focuses on the development of suitable coherent sources and enhancement cavities. This overview discusses the different concepts so far developed, describing their working principles, advantages and critical points as well as new possible methodologies to realize photo-neutralization for nuclear fusion reactor applications

Telescope-based cavity for negative ion beam neutralization in future fusion reactors

International audienc

Impact of infrasound atmospheric noise on gravity detectors used for astrophysical and geophysical applications

International audienceDensity changes in the atmosphere produce a fluctuating gravity field that affects gravity strainmeters or gravity gradiometers used for the detection of gravitational waves and for geophysical applications. This work addresses the impact of the atmospheric local gravity noise on such detectors, extending previous analyses. In particular we present the effect introduced by the building housing the detectors, and we analyze local gravity-noise suppression by constructing the detector underground. We present also new sound spectra and correlation measurements. The results obtained are important for the design of future gravitational-wave detectors and gravity gradiometers used to detect prompt gravity perturbations from earthquakes

Adaptive Denoising of Acoustic Noise Injections Performed at the Virgo Interferometer

International audienceA methodology using adaptive time series analysis is tested on data from a seismometer monitoring the north end building (NEB) of the Virgo interferometer during four acoustic noise injections. Empirical mode decomposition (EMD) is used for adaptive detrending, while the recently developed time-varying filter EMD algorithm is used for narrowband mode extraction. Mode persistency is evaluated with detrended fluctuation analysis, and denoising is achieved by setting a threshold Hthr on the Hurst exponent of the obtained modes. The adopted methodology is proven useful in adaptively separating the seismic noise induced by the acoustic noise injections from the underlying nonlinear non-stationary recordings of the seismometer monitoring NEB. The Hilbert–Huang transform provides a high-resolution time–frequency representation of the data. Furthermore, the local Hurst exponent exhibits a drop due to the injections that is of the same order of Hthr. This suggests that the local Hurst exponent could be calculated as an initial step in order to select the threshold Hthr. The algorithms could be used for detector characterisation purposes such as the investigation of non-Gaussian noise

Vol. 3, n. 1 (2021), Special Issue: Pedagogia e Politica. Costruire comunità pensanti

Vol. 3, n. 1, 2021 Special Issue: Mannese, E., Presentazione, P. 1 ; Violante, L., La politica come pedagogia, P. 3 ; Buttafuoco, P., Ancora un bicchiere di cicuta, P. 9 ; Caligiuri, M., Per una pedagogia della nazione. Politica ed educazione in Italia nel XXI secolo, P. 14 ; Carboni, C., Il knowledge gap e come contrastarlo , P. 28 ; Ceruti, M. - Bellusci, F., Governare ed educare al tempo della complessità, P. 37 ; Colosimo, M.L., L’improvviso fiume del vivere, P. 43 ; Dipasquale, G., Edipo, il potente impaurito. Una ipotesi di messinscena, P. 46 ; Elia, G., L’educazione alla politica come esercizio di cittadinanza e fiducia nel futuro, P. 61 ; Ferrari, F., Paideia e Polis nella Repubblica di Platone, P. 69 ; Impagliazzo, M., Le scuole della pace: un modello di educazione alla democrazia e alla pace, P. 83 ; Leganza, G., Leonardo Sciascia e Leonardo Sinisgalli, P. 91 ; Lombardi, M.G., Pedagogia e Politica tra neoliberalismo e responsabilità educative, P. 99 ; Ricci, S., L’educazione alla democrazia e l’esercizio del soft power, P. 103 ; Salmeri, S., Pensare criticamente e educare alla democrazia, P. 111 ; Sirignano, F.M., La crisi delle democrazie europee e l’esigenza di una pedagogia politica, P. 122 ; Interviste di Emiliana Mannese a Marco Damilano, Maria Grazia Riva, Massimiliano Fiorucci, Vincenzo Loia, P. 134 ; Balzano, V., Democrazia, educazione e dignità: la centralità della persona nel rinnovato rapporto tra pedagogia e politica, P. 152 ; Cagol, M., Per una pedagogia etica e politica della complessità, P. 163 ; Castaldi, M.C., Libertà, cura e generatività: le parole comuni della relazione pedagogia-politica, P. 171 ; Della Piana, B., Costruire Spazi di Apprendimento Inclusivi per Pensare Collettivamente: Lo sviluppo di Risorse Umane Culturalmente Intelligenti, P. 181 ; Donato, D. - García de Fez, S., La escuela del siglo XXI: una oportunidad para cogenerar la educación como bien común, P. 192 ; Giordano, M., Ripensare il rapporto dialettico tra Pedagogia e Politica al tempo della complessità, P. 202 ; Rubin, A., Pedagogia e politica: prospettive di ricerca, P. 211.http://www.attualitapedagogiche.it

Search for intermediate mass black hole binaries in the first observing run of Advanced LIGO

International audienceDuring their first observational run, the two Advanced LIGO detectors attained an unprecedented sensitivity, resulting in the first direct detections of gravitational-wave signals produced by stellar-mass binary black hole systems. This paper reports on an all-sky search for gravitational waves (GWs) from merging intermediate mass black hole binaries (IMBHBs). The combined results from two independent search techniques were used in this study: the first employs a matched-filter algorithm that uses a bank of filters covering the GW signal parameter space, while the second is a generic search for GW transients (bursts). No GWs from IMBHBs were detected; therefore, we constrain the rate of several classes of IMBHB mergers. The most stringent limit is obtained for black holes of individual mass 100  M⊙, with spins aligned with the binary orbital angular momentum. For such systems, the merger rate is constrained to be less than 0.93  Gpc−3 yr−1 in comoving units at the 90% confidence level, an improvement of nearly 2 orders of magnitude over previous upper limits