Multi-zone temperature sensor using a multi-wavelength Brillouin fiber ring laser

A simple system for sensing temperature in multiple zones based on a multi-wavelength Brillouin fiber laser ring is presented. Optical fiber reels are serially concatenated and divided in zones (one per sensing area). Setting the Brillouin lasing in each spool of fiber generates a characteristic wavelength that depends on the fiber properties and the temperature in the zone. Thus, it is possible to measure temperature independently and accurately through heterodyne detection between two narrow laser signals. The proposed sensor integrates the temperature along the whole spool of fiber in each zone. These real time measurements were successfully checked in our laboratory

BOTDA sensor network with power by light remote switching

We present and demonstrate a Brillouin Optical Time Domain Analysis (BOTDA) based long range sensor network with remote switching. Two different 5 km long sections were monitored alternatively by using a fast remotely controlled and optically powered up optical switch. The sensed fibers were located 10 km away from the interrogation unit. The BOTDA unit uses a simplified configuration to reduce the sensor network costs. Proof-of-concept experiments were carried out verifying the capacity of the proposed system.This work was supported by the Spanish Government project TEC2010-20224-C0

Microscopic origin of the acceptor removal in neutron-irradiated Si detectors - An atomistic simulation study

Producción CientíficaThe improved radiation hardness of p-type Si detectors is hindered by the radiation-induced acceptor removal process, which is not fully understood yet. Through atomistic modeling of displacement damage and dopant interactions, we analyze the acceptor removal under neutron irradiation, providing physical insight into its microscopic origin. Our results show that the fast decay of the effective dopant concentration (Neff) at low irradiation fluences is due to B deactivation caused by Si self-interstitials. The intriguing increase of the acceptor removal parameter with the initial dopant concentration (Neff,0) is explained by the limited number of mobile Si self-interstitials that survive annihilation and clustering processes. The sublinear dependence of the removal parameter on Neff,0 is associated to the inhomogeneity of damage for low Neff,0 and the formation of B-interstitial clusters with several B atoms for high Neff,0. The presence of O and C modifies B deactivation mechanisms due to the key role of BiO defects and the trapping of vacancies and Si self-interstitials, but for the impurity concentrations analyzed in this work ([O] >> [C]) it has little effect on the overall amount of removed acceptors. At high irradiation fluences, the reported increase of Neff is attributed to the formation of defect-related deep acceptors. From the analysis of the defect concentrations resulting from neutron irradiation and the occupancy of small clusters with acceptor levels reported in literature, we point out the tetra-vacancy cluster as one of the main contributors to Neff with negative space charge.Ministerio de Ciencia, Innovación y Universidades (projects PID2020-115118GB-I00 and PID2019-110189RB-C22

Application of remote power-by-light switching in a simplified BOTDA sensor network

We propose and demonstrate the use of spatial multiplexing as a means to reduce the costs of distributed sensing networks. We propose a new scheme in which remote power-by-light switching is deployed to scan multiple branches of a distributed sensing network based on Brillouin Optical Time Domain Analysis (BOTDA) sensors. A proof-of-concept system is assembled with two 5-km sensor fiber branches that are alternatively monitored using a fast remotely controlled and optically powered optical switch. The multiplexed distributed sensor fibers were located 10 km away from the interrogation unit and a Raman pump is used to remotely power the switch. Furthermore, the deployed BOTDA unit uses an alternative configuration that can lead to simplified setups

Mapping the depleted area of silicon diodes using a micro-focused X-ray beam

For the Phase-II Upgrade of the ATLAS detector at CERN, the current ATLAS Inner Detector will be replaced with the ATLAS Inner Tracker. The ATLAS Inner Tracker will be an all-silicon detector, consisting of a pixel tracker and a strip tracker. Sensors for the ITk strip tracker are required to have a low leakage current up to bias voltages of -700 V to maintain a low noise and power dissipation. In order to minimise sensor leakage currents, particularly in the high-radiation environment inside the ATLAS detector, sensors are foreseen to be operated at low temperatures and to be manufactured from wafers with a high bulk resistivity of several k{\Omega} cm. Simulations showed the electric field inside sensors with high bulk resistivity to extend towards the sensor edge, which could lead to increased surface currents for narrow dicing edges. In order to map the electric field inside biased silicon sensors with high bulk resistivity, three diodes from ATLAS silicon strip sensor prototype wafers were studied with a monochromatic, micro-focused X-ray beam at the Diamond Light Source. For all devices under investigation, the electric field inside the diode was mapped and its dependence on the applied bias voltage was studied. The findings showed that the electric field in each diode under investigation extended beyond its bias ring and reached the dicing edge

Research and development of a gamma-ray imaging spectrometer in the MeV range in Barcelona

Copyright 2010 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic electronic or print reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.Gamma-ray astrophysics in the MeV energy range plays an important role for the understanding of cosmic explosions and acceleration mechanisms in a variety of galactic and extragalactic sources, e.g., Supernovae, Classical Novae, Supernova Remnants (SNRs), Gamma-Ray Bursts (GRBs), Pulsars, Active Galactic Nuclei (AGN). Through the development of focusing telescopes in the MeV energy range, it will be possible to reach unprecedented sensitivities, compared with those of the currently operating gamma ray telescopes. In order to achieve the needed performance, a detector with mm spatial resolution and very high peak efficiency is required. It will be also desirable that the detector could detect polarization of the source. Our research and development activities in Barcelona aim to study a gamma-ray imaging spectrometer in the MeV range suited for the focal plane of a gamma-ray telescope mission, based on CdTe pixel detectors arranged in multiple layers with increasing thicknesses, to enhance gamma-ray absorption in the Compton regime. We have developed an initial prototype based on several CdTe module detectors, with 11x11 pixels, a pixel pitch of 1mm and a thickness of 2mm. Each pixel is stud-bump bonded to a fanout board and routed to a readout ASIC to measure pixel position, pulse height and rise time information for each incident gamma-ray photon. We will report on the results of an optimization study based on simulations, to select the optimal thickness of each CdTe detector within the module to get the best energy resolution of the spectrometer.Peer reviewe

Spanish Conference on Electron Devices (CDE 2018)

Producción CientíficaElectronic devices operating in harsh radiation environments must withstand high radiation levels with minimal performance degradation. Recent experiments on the radiation hardness of a new vertical p-type JFET power switch have shown a significant reduction of forward drain current under non-ionizing conditions. In this work, atomistic simulations are used to study the impact of irradiation-induced displacement damage on forward characteristics. Damage models have been updated to produce a better description of damage-dopant interactions at RT. Our results show that excess self-interstitials produced by irradiation deactivate a significant amount of B atoms, thus reducing the effective dopant concentration.Ministerio de Ciencia e Innovación (Project TEC2014-60694-P)Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. VA119G18

Atomistic simulations of acceptor removal in p-type Si irradiated with neutrons

Producción CientíficaThe effective dopant concentration in p-type Si detectors reduces with irradiation fluence at low fluences due to the acceptor removal process, which degrades detector performance and shortens its lifetime. This effect has been experimentally characterized and parametrized, but its microscopic origin is still unknown. We use atomistic simulations to gain insight into acceptor removal in neutron irradiation by modeling damage generation and defect-dopant interactions. We analyze the effect on dopant deactivation of the Si di- and tri-interstitial diffusion, the inhomogeneity of irradiation damage and the wafer temperature rise during irradiation. We characterize defect generation rates and identify the relevant defect-dopant interactions. Acceptor removal occurs mainly through the formation of Bi pairs and small boron-interstitial clusters, and it is limited by the availability of mobile Si interstitials. The presence of impurities (O, C) modifies B-complexes favoring the formation of BiO, but has a limited effect on the amount of removed acceptors.Ministerio de Ciencia e Innovación (project PID2020-115118GB-I00

Técnica y dispositivo para conformar el espectro de ganancia de Brillouin en guías de onda ópticas

Técnica y dispositivo para conformar el espectro de ganancia del efecto Brillouin en guías de onda ópticas (en adelante guías). Inyectando una radiación luminosa o "bombeo" en guías, se puede inducir otra radiación -dispersión (scattering) de Brillouin- centrada en otra frecuencia. Esta dispersión puede ser espontánea o estimulada por otra radiación contra-propagante ("semilla") y amplificarla en la banda espectral de ganancia de Brillouin cuyo perfil depende de las propiedades de la guía y del bombeo. Esta invención propone la conexión de N guías concatenadas y/o en estrella, bombeadas todas ellas con la/s misma/s fuente/s de bombeo como técnica para conformar la respuesta espectral de Brillouin del conjunto de guías que constituyen el dispositivo base. Puede emplearse en la elaboración de dispositivos y subsistemas ópticos (ópticamente sintonizables o no). Puede implementarse en tecnología de fibra óptica y usarse para amplificación, filtrado, medida y en general, procesado de señales ópticas.Solicitud: 200900579 (25.02.2009)Nº Pub. de Solicitud: ES2323565A1 (20.07.2009)Nº de Patente: ES2323565B2 (12.01.2010

Long integral temperature Brillouin sensor for off- shore wind energy power supply lines

A hybrid Erbium-Brillouin fiber laser sensor to measure the temperature along 22 km fiber is proposed and experimentally demonstrated. A multi-line laser oscillation is induced by the Brillouin gain of different concatenated transducer fiber sections placed in the ring cavity. Integral temperature measurements of each fiber section are obtained through each laser line. This sensor can be used to monitor the temperature of off-shore wind energy power cables