Wavelength converter using a highly erbium doped optical fiber ring laser

RESUMEN: En este trabajo se presenta un conversor de longitud de onda ultra-estrecho, de alta eficiencia y todo-fibra basado en el efecto de la competición de modos en un láser de fibra dopada con erbio. Se han llevado a cabo estudios experimentales con frecuencias que van desde varios kilohercios hasta las decenas de gigahercios y para más de una longitud de onda de emisión, demostrando así que este efecto puede ser utilizado para la conversión en longitud de onda de múltiples longitudes de emisión simultáneamente.ABSTRACT: This work presents an all-fiber wavelength converter based on a highly Erdoped fiber laser which has been experimentally demonstrated. Frequencies from several kilohertz up to tens of gigahertz have been investigated. Making use of the gain competition in the amplifying medium, the wavelength conversion can be carried out over not only one lasing wavelength but over several ones. These analyses have been also carried out for more than one all-fiber ring structure, demonstrating the viability of this wavelength converter.Este trabajo ha sido financiado por la Comisión Interministerial de Ciencia y Tecnología dentro de los proyectos TEC2013-47264-C2 y TEC2016-76021-C2

Multi-band high resolution spectroscopy rules out the hot Jupiter BD+20 1790b - First data from the GIARPS Commissioning

Context. Stellar activity is currently challenging the detection of young planets via the radial velocity (RV) technique. Aims. We attempt to definitively discriminate the nature of the RV variations for the young active K5 star BD+20 1790, for which visible (VIS) RV measurements show divergent results on the existence of a substellar companion. Methods. We compare VIS data with high precision RVs in the near infrared (NIR) range by using the GIANO - B and IGRINS spectrographs. In addition, we present for the first time simultaneous VIS-NIR observations obtained with GIARPS (GIANO - B and HARPS - N) at Telescopio Nazionale Galileo (TNG). Orbital RVs are achromatic, so the RV amplitude does not change at different wavelengths, while stellar activity induces wavelength-dependent RV variations, which are significantly reduced in the NIR range with respect to the VIS. Results. The NIR radial velocity measurements from GIANO - B and IGRINS show an average amplitude of about one quarter with respect to previously published VIS data, as expected when the RV jitter is due to stellar activity. Coeval multi-band photometry surprisingly shows larger amplitudes in the NIR range, explainable with a mixture of cool and hot spots in the same active region. Conclusions. In this work, the claimed massive planet around BD+20 1790 is ruled out by our data. We exploited the crucial role of multi- wavelength spectroscopy when observing young active stars: thanks to facilities like GIARPS that provide simultaneous observations, this method can reach its maximum potential.Comment: 12 pages, 7 figure

SIFAP2: a new versatile configuration at the TNG for the MPPC based photometer

The quality of SiFAP (Silicon Fast Astronomical Photometer) at the TNG has already shown its ability to easily detect optical pulses from transitional millisecond pulsars and from other slower neutron stars. Up to now the photometer based on Silicon Photo Multipliers manufactured by Hamamatsu Photonics (MPPC, Multi Pixel Photon Counter) was mounted (on and manually aligned with) a MOS mask at the F/11 focal plane of the telescope. In order to have a more versatile instrument with the possibility to remotely center and point several targets during the night we have decided to build a new mechanical support for the MPPCs and mount it on the Namsyth Interface (NI), where originally OIG and later GIANO were hosted. The MPPC module devoted to observe the target will be placed at the center of the FoV (on-axis), while the reference signal will be collected from a peripheral star in the FoV (Field of view) by means of the MPPC module that will be set at this position by a combination of a linear stage movement and a derotator angle. At the same time we have introduced the option for a polarimetric mode, with a 3rd MPPC module and a polarizing cube beam-splitter that separates the states between this and the on axis MPPC. SiFAP has been developed with 3 independent custom electronic chains for data acquisition, exploiting the 3 different outputs (analog, digital, USB pre-processed) provided by the MPPCs modules. The electronic chain fed by the analog output is able to tag a single photon ToA (Time of Arrival) with a time resolution of 25 ns, while the remaining electronic chains can integrate the signal into time bins from 100 ms down to 20 μs. The absolute time is provided by a GPS unit with a time resolution of 25 ns at 50% of the rising edge of the 1PPS (1 Pulse Per Second) signal which is linked to the UTC (Universal Time Coordinated). Apart from the versatility with the remotely controlled on sky configuration of the MPPCs, the mounting of SiFAP2 at the NI allows for a permanent hosting of the instrument, readily available for observations. The new polarimetric mode will then offer other scientific opportunities that have not been explored so far in high-temporal resolution astronomy

The 33S(n,α)30Si cross section measurement at n-TOF-EAR2 (CERN) : From 0.01 eV to the resonance region

The 33S(n,α)30Si cross section measurement, using 10B(n,α) as reference, at the n-TOF Experimental Area 2 (EAR2) facility at CERN is presented. Data from 0.01 eV to 100 keV are provided and, for the first time, the cross section is measured in the range from 0.01 eV to 10 keV. These data may be used for a future evaluation of the cross section because present evaluations exhibit large discrepancies. The 33S(n,α)30Si reaction is of interest in medical physics because of its possible use as a cooperative target to boron in Neutron Capture Therapy (NCT)

Measurement of the Ge 70 (n,γ) cross section up to 300 keV at the CERN n-TOF facility

©2019 American Physical Society.Neutron capture data on intermediate mass nuclei are of key importance to nucleosynthesis in the weak component of the slow neutron capture processes, which occurs in massive stars. The (n,γ) cross section on Ge70, which is mainly produced in the s process, was measured at the neutron time-of-flight facility n-TOF at CERN. Resonance capture kernels were determined up to 40 keV neutron energy and average cross sections up to 300 keV. Stellar cross sections were calculated from kT=5 keV to kT=100 keV and are in very good agreement with a previous measurement by Walter and Beer (1985) and recent evaluations. Average cross sections are in agreement with Walter and Beer (1985) over most of the neutron energy range covered, while they are systematically smaller for neutron energies above 150 keV. We have calculated isotopic abundances produced in s-process environments in a 25 solar mass star for two initial metallicities (below solar and close to solar). While the low metallicity model reproduces best the solar system germanium isotopic abundances, the close to solar model shows a good global match to solar system abundances in the range of mass numbers A=60-80.Peer reviewedFinal Published versio

Measurement of 73 Ge(n,γ) cross sections and implications for stellar nucleosynthesis

© 2019 The Author(s). Published by Elsevier B.V.73 Ge(n,γ) cross sections were measured at the neutron time-of-flight facility n_TOF at CERN up to neutron energies of 300 keV, providing for the first time experimental data above 8 keV. Results indicate that the stellar cross section at kT=30 keV is 1.5 to 1.7 times higher than most theoretical predictions. The new cross sections result in a substantial decrease of 73 Ge produced in stars, which would explain the low isotopic abundance of 73 Ge in the solar system.Peer reviewe

Characterization of the n-TOF EAR-2 neutron beam

The experimental area 2 (EAR-2) at CERNs neutron time-of-flight facility (n-TOF), which is operational since 2014, is designed and built as a short-distance complement to the experimental area 1 (EAR-1). The Parallel Plate Avalanche Counter (PPAC) monitor experiment was performed to characterize the beam prole and the shape of the neutron 'ux at EAR-2. The prompt γ-flash which is used for calibrating the time-of-flight at EAR-1 is not seen by PPAC at EAR-2, shedding light on the physical origin of this γ-flash

Measurement of the 240Pu(n,f) cross-section at the CERN n-TOF facility : First results from experimental area II (EAR-2)

The accurate knowledge of the neutron-induced fission cross-sections of actinides and other isotopes involved in the nuclear fuel cycle is essential for the design of advanced nuclear systems, such as Generation-IV nuclear reactors. Such experimental data can also provide the necessary feedback for the adjustment of nuclear model parameters used in the evaluation process, resulting in the further development of nuclear fission models. In the present work, the 240Pu(n,f) cross-section was measured at CERN's n-TOF facility relative to the well-known 235U(n,f) cross section, over a wide range of neutron energies, from meV to almost MeV, using the time-of-flight technique and a set-up based on Micromegas detectors. This measurement was the first experiment to be performed at n-TOF's new experimental area (EAR-2), which offers a significantly higher neutron flux compared to the already existing experimental area (EAR-1). Preliminary results as well as the experimental procedure, including a description of the facility and the data handling and analysis, are presented