Optimization and control of the field quality, the mechanical structure and the quench protection of superconducting dipoles for future accelerators

Future particle accelerators will require future magnets, this work addresses most of the problems involved in designing and building state-of-the-art superconducting magnets for particle accelerators. These issues are field quality control, mechanical design, and quench protection. This thesis includes, for each of these three topics, a general introduction, a case study, and the specific solutions implemented for it. In particular, in the case of field quality and quench protection analysis the case study is the MBRD separation/recombination dipole (Main Bending Recombination Dipole, or D2 for short) for the high luminosity upgrade of the LHC, while for the optimization of the mechanical design it is the FalconD magnet (Future Accelerator post-LHC Cos-theta Optimized Nb3Sn Dipole), which is a prototype that represents an intermediate step between the high-field magnets obtainable with today's technology and the magnets that will be required for the Future Circular Collider (FCC), a 100 TeV hadron accelerator. As regards the analysis of the quality of the field, it was possible to define the stability of the magnetic design of D2 the magnet by evaluating the sensitivity of the harmonic content of the field generated as the tolerances of the components involved in the coils varied. In addition, the optimal shimming strategy needed to finalize production of the D2 prototype and another one to meet the field quality acceptance criteria for the series magnets was found. For what concerns the studies on quench protection, one of the most recent computational tools specialized in the simulation of quench phenomena (LEDET) was used, calibrated, and validated both by using another older software (ROXIE) and by the measurements carried out on the short model of the D2 magnet. Thanks to this simulation campaign it was possible to set up the tests that will be performed on the D2 prototype and to update the quench protection strategy, since these simulations demonstrated that the previous one did not comply with the safety limits imposed on the project. The forthcoming measurements on the D2 prototype will validate both the quality of the construction process, the simulation models used and the design choices that have been made. Finally, the mechanical optimization work (performed with the f.e.m. software ANSYS) consists of the design of both the 2D and 3D mechanical structure of the Falcon Dipole, which is both a high field magnet (12 T of bore field) and a brittle superconductor (Nb3Sn). For these reasons, the success of the project strongly depends on the optimal management of the high Lorentz forces generated in the coils

Absolute frequency measurement of the 1S0 - 3P0 transition of 171Yb

We report the absolute frequency measurement of the unperturbed transition 1S0 - 3P0 at 578 nm in 171Yb realized in an optical lattice frequency standard. The absolute frequency is measured 518 295 836 590 863.55(28) Hz relative to a cryogenic caesium fountain with a fractional uncertainty of 5.4x10-16 . This value is in agreement with the ytterbium frequency recommended as a secondary representation of the second in the International System of Units.Comment: This is an author-created, un-copyedited version of an article accepted for publication/published in Metrologia. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/1681-7575/aa4e62. It is published under a CC BY licenc

Measurement of the Blackbody Radiation Shift of the 133Cs Hyperfine Transition in an Atomic Fountain

We used a Cs atomic fountain frequency standard to measure the Stark shift on the ground state hyperfine transiton frequency in cesium (9.2 GHz) due to the electric field generated by the blackbody radiation. The measures relative shift at 300 K is -1.43(11)e-14 and agrees with our theoretical evaluation -1.49(07)e-14. This value differs from the currently accepted one -1.69(04)e-14. The difference has a significant implication on the accuracy of frequency standards, in clocks comparison, and in a variety of high precision physics tests such as the time stability of fundamental constants.Comment: 4 pages, 2 figures, 2 table

Distributed Raman optical amplification in phase coherent transfer of optical frequencies

We describe the application of Raman Optical-fiber Amplification (ROA) for the phase coherent transfer of optical frequencies in an optical fiber link. ROA uses the transmission fiber itself as a gain medium for bi-directional coherent amplification. In a test setup we evaluated the ROA in terms of on-off gain, signal-to-noise ratio, and phase noise added to the carrier. We transferred a laser frequency in a 200 km optical fiber link with an additional 16 dB fixed attenuator (equivalent to 275 km of fiber on a single span), and evaluated both co-propagating and counter-propagating amplification pump schemes, demonstrating nonlinear effects limiting the co-propagating pump configuration. The frequency at the remote end has a fractional frequency instability of 3e-19 over 1000 s with the optical fiber link noise compensation

Absolute frequency measurement of the 1S0 – 3P0 transition of 171-Yb with a link to International Atomic Time

Dataset of the INRIM Yb clock measured respect to TAI collected between October 2018 to February 2019. YbvsSIm-viaEAL.dat: montly data with columns MJDstart: start date in MJD MJDstop: stop date in MJD MJDmed: mid point date in MJD MJDbaro: baricenter date in MJD Ybduty: Yb clock duty time y0=Yb/HM3: ratio between Yb clock and H Maser 03 u0: statistical uncertainty of y0 uB0: systematic uncertainty of y0 y1=extrap.: extrapolation over HM3 udead1: uncertainty of y1 from dead times udrift1: uncertainty of y1 from HM3 drift HM3drift/d: HM3 drift per day udrift/d: uncertainty of HM3 drift y2=HM3/UTCit: ratio between HM3 and UTC(IT) u2: uncertainty of y2 y3=UTCit/TAI: ratio between UTC(IT) and TAI u3: uncertainty of y3 y4=EALext.: extrapolation over EAL udead4: uncertainty of y4 from dead times udrift4: uncertainty of y4 from EAL drift y5=-d: ratio between TAI and the SI second from Circular T u5: uncertainty of y5 uA5: statistical uncertainty of y5 uB5: systematic uncertainty of y5 y=Yb/SI: final ratio beween the Yb clock and the Si second uA: not used uB: not used u: uncertainty of y YbvsTAId.dat: data every 5 days with columns: MJDstart: start date in MJD MJDstop: stop date in MJD MJDmed: mid point date in MJD MJDbaro: baricenter date in MJD Ybduty: Yb clock duty time y0=Yb/HM3: ratio between Yb clock and H Maser 03 u0: statistical uncertainty of y0 uB0: systematic uncertainty of y0 y1=extrap.: extrapolation over HM3 udead1: uncertainty of y1 from dead times udrift1: uncertainty of y1 from HM3 drift HM3drift/d: HM3 drift per day udrift/d: uncertainty of HM3 drift y2=HM3/UTCit: ratio between HM3 and UTC(IT) u2: uncertainty of y2 y3=UTCit/TAI: ratio between UTC(IT) and TAI u3: uncertainty of y3 y=Yb/TAI: final ratio beween the Yb clock and TAI uA: not used uB: not used u: uncertainty of yWe acknowledge funding from the European Metrology Program for Innovation and Research (EMPIR) project 15SIB03 OC18, from the Horizon 2020 Marie Skłodowska-Curie Research and Innovation Staff Exchange (MSCA-RISE) project Q-SENSE (Grant Agreement Number 691156), from the Italian Space Agency (ASI) funding DTF-Matera, from the EMPIR project 18SIB05 ROCIT. The EMPIR initiative is co-funded by the European Union's Horizon 2020 research and innovation programme and the EMPIR Participating States

Bifurcation analysis in a silicon neuron

International audienceIn this paper, we describe an analysis of the nonlinear dynamical phenomenon associated with a silicon neuron. Our silicon neuron integrates Hodgkin-Huxley (HH) model formalism, including the membrane voltage dependency of temporal dynamics. Analysis of the bifurcation conditions allow us to identify different regimes in the parameter space that are desirable for biasing our silicon neuron. This approach of studying bifurcations is useful because it is believed that computational properties of neurons are based on the bifurcations exhibited by these dynamical systems in response to some changing stimulus. We describe numerical simulations and measurements of the Hopf bifurcation which is characteristic of class 2 excitability in the HH model. We also show a phenomenon observed in biological neurons and termed excitation block. Hence, by showing that this silicon neuron has similar bifurcations to a certain class of biological neurons, we can claim that the silicon neuron can also perform similar computation

High-performing vapor-cell frequency standards

Many nowadays scientific and technological applications need very precise time and frequency reference signals. Very often, only atomic clocks can guarantee the high level of accuracy and stability required by these signals. In the current scenario of atomic frequency standards, vapor-cell clocks are particularly suited to be employed in those activities that demand good frequency stability performances joined to compactness, reliability and low power consumption. Recently, due to better-performing laser sources and to innovative techniques to prepare and detect the atoms, several cell-based prototypes exhibiting unprecedented frequency stability have been developed. We review advances in the field of laser-pumped vapor-cell clocks and we provide an overview of the techniques that allowed to achieve frequency stabilities in the order of 1×10^−13 at 1 s (short term) and in the range of 10^−15 for the medium-long term. These stabilities are two orders of magnitude better than current commercial Rb clocks. We also prospect the possibility of further improving these results.Many nowadays scientific and technological applications need very precise time and frequency reference signals. Very often, only atomic clocks can guarantee the high level of accuracy and stability required by these signals. In the current scenario of atomic frequency standards, vapor-cell clocks are particularly suited to be employed in those activities that demand good frequency stability performances joined to compactness, reliability and low power consumption. Recently, due to better-performing laser sources and to innovative techniques to prepare and detect the atoms, several cell-based prototypes exhibiting unprecedented frequency stability have been developed. We review advances in the field of laser-pumped vapor-cell clocks and we provide an overview of the techniques that allowed to achieve frequency stabilities in the order of 1 x 10(-13) at is (short term) and in the range of 10(-15) for the medium-long term. These stabilities are two orders of magnitude better than current commercial Rb clocks. We also prospect the possibility of further improving these results

In vitro culture from mature seeds of Passiflora species

The genus Passiflora comprises hundred species, mainly native of the South American tropics and rainforests, which are grouped into 21 subgenera. Some species are widely studied for their economic importance and are chiefly cultivated for production of fruit juice. To obtain a continuous source of material for a screening of secondary metabolites, zygotic embryo culture was attempted for 62 Passiflora species, starting from seeds mainly collected in the wild. Twenty nine of these species produced calli, which had very different growth rates. Plants were successfully regenerated from calli of 13 different species. For 25 of the responsive species this is the first report of in vitro culture

Regeneração e cultura in vitro de espécies de Passiflora

O gênero Passiflora compõe centenas de espécies, a maioria de origem dos trópicos e das florestas da América do Sul, as quais são agrupadas em 21 subgêneros. Algumas espécies foram intensamente estudadas por sua importância econômica e são cultivadas principalmente para a produção de suco de fruta. Cultura de 29 espécies de Passiflora foram obtidos a partir de embriões zigóticos e de culturas de endosperma. Foram obtidos diferentes tipos de calos de crescimento, de tal forma que plantas foram regeneradas a partir de calos de 13 espécies diferentes. Não haviam sido ainda relatadas culturas in vitro para 25 das espécies trabalhadas.The genus Passiflora comprises hundred species, mainly native of the South American tropics and rainforests, which are grouped into 21 subgenera. Some species are widely studied for their economic importance and are chiefly cultivated for production of fruit juice. To obtain a continuous source of material for a screening of secondary metabolites, zygotic embryo culture was attempted for 62 Passiflora species, starting from seeds mainly collected in the wild. Twenty nine of these species produced calli, which had very different growth rates. Plants were successfully regenerated from calli of 13 different species. For 25 of the responsive species this is the first report of in vitro culture

Optically loaded Strontium lattice clock with a single multi-wavelength reference cavity

We report on the realization of a new compact strontium optical clock using a 2-D magneto-optical-trap (2D-MOT) as cold atomic source and a multi-wavelength cavity as the frequency stabilization system. All needed optical frequencies are stabilized to a zero-thermal expansion high-finesse optical resonator and can be operated without frequency adjustments for weeks. We present the complete characterization of the apparatus. Optical control of the atomic source allows us to perform low-noise clock operation without atomic signal normalization. Long- and short-term stability tests of the clock have been performed for the 88 Sr bosonic isotope by means of interleaved clock operation. Finally, we present the first preliminary accuracy budget of the system