482 research outputs found

    The effects of a revised 7^7Be e−^--capture rate on solar neutrino fluxes

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    The electron-capture rate on 7^7Be is the main production channel for 7^7Li in several astrophysical environments. Theoretical evaluations have to account for not only the nuclear interaction, but also the processes in the plasma where 7^7Be ions and electrons interact. In the past decades several estimates were presented, pointing out that the theoretical uncertainty in the rate is in general of few percents. In the framework of fundamental solar physics, we consider here a recent evaluation for the 7^7Be+e−^- rate, not used up to now in the estimate of neutrino fluxes. We analysed the effects of the new assumptions on Standard Solar Models (SSMs) and compared the results obtained by adopting the revised 7^7Be+e−^- rate to those obtained by the one reported in a widely used compilation of reaction rates (ADE11). We found that new SSMs yield a maximum difference in the efficiency of the 7^7Be channel of about -4\% with respect to what is obtained with the previously adopted rate. This fact affects the production of neutrinos from 8^8B, increasing the relative flux up to a maximum of 2.7\%. Negligible variations are found for the physical and chemical properties of the computed solar models. The agreement with the SNO measurements of the neutral current component of the 8^8B neutrino flux is improved.Comment: 7 pages, 3 figures, 4 tables. Accepted for the publication on A&

    NIKEL_AMC: Readout electronics for the NIKA2 experiment

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    The New Iram Kid Arrays-2 (NIKA2) instrument has recently been installed at the IRAM 30 m telescope. NIKA2 is a state-of-art instrument dedicated to mm-wave astronomy using microwave kinetic inductance detectors (KID) as sensors. The three arrays installed in the camera, two at 1.25 mm and one at 2.05 mm, feature a total of 3300 KIDs. To instrument these large array of detectors, a specifically designed electronics, composed of 20 readout boards and hosted in three microTCA crates, has been developed. The implemented solution and the achieved performances are presented in this paper. We find that multiplexing factors of up to 400 detectors per board can be achieved with homogeneous performance across boards in real observing conditions, and a factor of more than 3 decrease in volume with respect to previous generations.Comment: 21 pages; 16 figure

    Electronics and data acquisition demonstrator for a kinetic inductance camera

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    A prototype of digital frequency multiplexing electronics allowing the real time monitoring of kinetic inductance detector (KIDs) arrays for mm-wave astronomy has been developed. It requires only 2 coaxial cables for instrumenting a large array. For that, an excitation comb of frequencies is generated and fed through the detector. The direct frequency synthesis and the data acquisition relies heavily on a large FPGA using parallelized and pipelined processing. The prototype can instrument 128 resonators (pixels) over a bandwidth of 125 MHz. This paper describes the technical solution chosen, the algorithm used and the results obtained
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