Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Report of the 2006 ICCAT workshop for bluefin tuna direct ageing

This report provides the presentations, discussions and conclusions from the ICCAT bluefin tuna workshop for direct ageing held in Santander, Spain, in April 2006. The report summarizes the ageing criteria used in the past and the agreements on future age determination based on otoliths, vertebrae and spines. Advantages and disadvantages of each calcified structure for ageing and border interpretation were discussed. It was considered that bluefin tuna age interpretation becomes very difficult from age ten onwards using the whole vertebra and the spine sections methods, but this last technique continues to be useful for older ages. Otolith sections can be used for the whole age range. Participants agreed that none of these three structures could be excluded from routine ageing because otoliths are not easily available. Age estimations within the same structure and between different structures of the same specimen were compared for several readers. Better precision was found between spine readers compared to vertebra and otolith readers. Good age agreement was also achieved between readers of spines and vertebrae from the same bluefin for ages less than 12 years. Preliminary results from radiocarbon assays on otoliths were presented at the workshop and gave promising outcomes for bluefin tuna age validation. Also, these suggested that bluefin tuna can live longer than had previously been established and that a review is needed of the currently used asymptotic size and growth rate for both stocks. Another important contribution of the workshop was a manual for age interpretation.Le présent rapport recueille les présentations, discussions et conclusions de l’Atelier de l’ICCAT chargé de la détermination directe de l’âge du thon rouge, tenu à Santander (Espagne) au mois d’avril 2006. Le rapport résume les critères employés par le passé pour interpréter l’âge et les accords pour la détermination future de l’âge à partir des otolithes, vertèbres et épines. L’Atelier a discuté des avantages et des inconvénients de chaque structure calcifiée pour déterminer l’âge et l’interprétation du type de bord. On a abordé la difficulté de l’interprétation de l’âge des thons de plus de 10 ans au moyen de la vertèbre entière et des sections des épines, bien que cette dernière méthode continue d’être utile pour les âges avancés. Les sections d’otolithes peuvent être employées pour toute la gamme d’âges. Les participants ont convenu qu’aucune de ces trois structures ne doit être exclue pour l’interprétation de l’âge parce qu’il n’est pas toujours possible d’obtenir des otolithes. On a comparé les lectures de l’âge à l’intérieur de la même structure et entre différentes structures du même exemplaire pour divers lecteurs. On a obtenu une plus grande précision parmi les lecteurs d’épines que parmi les lecteurs de vertèbres et d’otolithes. On a également obtenu un bon accord entre les lecteurs d’épines et de vertèbres originaires du même exemplaire pour les âges inférieurs à 12 ans. Les résultats préliminaires des essais de radiocarbone dans les otolithes ont été présentés à l’Atelier, offrant de bonnes perspectives pour son utilisation dans la validation de l’âge. Ces résultats indiquent aussi que le thon rouge a une plus grande longévité que ce qui avait été auparavant établi et qu’il est nécessaire de réviser la longueur asymptotique et le taux de croissance actuellement utilisés. L’élaboration d’un manuel aux fins de l’interprétation de l’âge a constitué une autre contribution importante de l’Atelier.Este informe recoge las presentaciones, discusiones y conclusiones del congreso de ICCAT para la determinación directa de la edad de atún rojo, celebrado en Santander, España, en abril de 2006. El informe resume los criterios empleados en el pasado para interpretar la edad y los acuerdos para la determinación futura de la edad a partir de otolitos, vértebras y espinas. Se discutieron las ventajas y los inconvenientes de cada estructura calcificada para determinar la edad y la interpretación del tipo borde. Se planteó la dificultad en la interpretación de la edad de atunes mayores de 10 años utilizando la vértebra entera y las secciones de espinas, no obstante este último método continúa siendo útil para edades mayores. Las secciones de otolitos pueden ser empleadas para todo el rango de edades. Los participantes acordaron que ninguna de estas tres estructuras deben excluirse para la interpretación de la edad porque no siempre es posible obtener los otolitos. Se compararon las lecturas de edad dentro de la misma estructura y entre diferentes estructuras del mismo ejemplar para varios lectores. Se obtuvo una mayor precisión entre lectores de espinas comparada con las obtenidas por los lectores de vértebras y otolitos. También se obtuvo un buen acuerdo entre lectores de espinas y vértebras procedentes del mismo ejemplar para edades menores de 12 años. Los resultados preliminares de las pruebas de radiocarbono en otolitos fueron presentados en el congreso, proporcionando buenas expectativas para su uso en la validación de la edad. Estos resultados también indican que el atún rojo es más longevo de lo que se consideraba y que es necesaria una revisión de la longitud asintótica y de la tasa de crecimiento empleadas actualmente. Otra importante contribución del congreso fue la elaboración de un manual para la interpretación de la edad

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

Search for intermediate mass black hole binaries in the first and second observing runs of the Advanced LIGO and Virgo network

Gravitational-wave astronomy has been firmly established with the detection of gravitational waves from the merger of ten stellar-mass binary black holes and a neutron star binary. This paper reports on the all-sky search for gravitational waves from intermediate mass black hole binaries in the first and second observing runs of the Advanced LIGO and Virgo network. The search uses three independent algorithms: two based on matched filtering of the data with waveform templates of gravitational-wave signals from compact binaries, and a third, model-independent algorithm that employs no signal model for the incoming signal. No intermediate mass black hole binary event is detected in this search. Consequently, we place upper limits on the merger rate density for a family of intermediate mass black hole binaries. In particular, we choose sources with total masses M=m1+m2ϵ[120,800] M and mass ratios q=m2/m1ϵ[0.1,1.0]. For the first time, this calculation is done using numerical relativity waveforms (which include higher modes) as models of the real emitted signal. We place a most stringent upper limit of 0.20 Gpc-3 yr-1 (in comoving units at the 90% confidence level) for equal-mass binaries with individual masses m1,2=100 M and dimensionless spins χ1,2=0.8 aligned with the orbital angular momentum of the binary. This improves by a factor of ∼5 that reported after Advanced LIGO's first observing run. © 2019 American Physical Society

First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data

Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signal-to-noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have been developed, allowing a fully coherent search for gravitational waves from known pulsars over a fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of 11 pulsars using data from Advanced LIGO's first observing run. Although we have found several initial outliers, further studies show no significant evidence for the presence of a gravitational wave signal. Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for the first time. For an additional 3 targets, the median upper limit across the search bands is below the spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried out so far. © 2017 American Physical Society