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Il Tempo della Scienza

Seminari tecnici 2015

Sala Conferenze (Edificio M)
Strada delle Cacce 91, Torino

Data Relatore Titolo
15 luglio
ore 12
James Camparo
The Aerospace Corporation, Physical Sciences Laboratories

Basic Physics and Atomic Timekeeping in Space

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The presentation will begin with a very brief overview of The Aerospace Corporation, and its mission to support various space programs of the United States, for example GPS. The talk will then focus on the development of next generation atomic clocks to support navigation and communication space missions; and how improving atomic clocks for space requires a better understanding basic atomic physics, in particular the ac-Stark shift. The talk will conclude with an outline of collaborative efforts between INRIM and Aerospace examining the basic physics of the ac Stark shift, and the influence of the ac Stark shift on the performance of GPS rubidium atomic clocks.
14 luglio
ore 11
Ed. D
Sébastien Pruvost
Ingénierie des Matériaux Polyméres - INSA de Lyon, France

Electrothermal properties of polymers: electrocaloric effect and energy harvesting

21 maggio
ore 10
Andrei Slavin
Department of Physics, Oakland University

Autonomous and Non-Autonomous Dynamics of Spin Hall Auto-Oscillators

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A novel type of spin-torque nano-oscillators driven by pure spin current generated via the spin Hall effect has been demonstrated recently. The study of the effects of external microwave signals on these Spin Hall oscillators (SHO) is reported. It is shown that SHO can be efficiently synchronized by applying a microwave signal at approximately twice the frequency of the auto-oscillation, which opens additional possibilities for the development of novel spintronic devices. It is found that the synchronization exhibits an apparent threshold determined by magnetic fluctuations pumped above their thermal level by the spin current, and is significantly influenced by the nonlinear self-localized nature of the auto-oscillatory mode.
15 maggio
ore 16:30
Roberto Cingolani
Direttore Scientifico Istituto Italiano di Tecnologia (ITT), Genova


Nanotechnologies for humans and humanoids

14 maggio
ore 14
Thorsten Schumm
Vienna University of Technology
Towards a nuclear clock with Thorium-229

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The radio isotope Thorium-229 is expected to present a remarkably low-energy excited (isomer) state of the nucleus which is expected around 7.8(5) eV. It might hence be possible to directly excite the atomic nucleus with UV (laser) radiation, creating a bridge between atomic and nuclear physics. The (expected) narrow line width of the transition makes it a promising candidate for a new frequency standard. Furthermore, Nuclear transitions are intrinsically more robust against external fields. This allows to implant (dope) Thorium-229 into UV transparent crystals and hence the realization of a "solid state nuclear clock".
In this presentation we will review the current state of knowledge on the low-energy nuclear transition in Thorium-229 and the ongoing quest to measure it’s exact energy. We will discuss in particular solid-state approaches and the interaction of the nuclear states with the surrounding crystal structure and estimate line shifts and broadenings.
14 aprile
ore 14:30
John Bennett
Australian Nuclear Science and Technology Organisation (ANSTO)
Head of the Centre for Nuclear Applications
Neutron activation analysis in Australia using the OPAL Research Reactor

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The Australian Nuclear Science and Technology Organisation operates the 20 MW OPAL research reactor. It is a multipurpose reactor, serving the needs of researchers and industry. It is a major producer of medical radioisotopes and semiconductor silicon, as well as providing thermal and cold neutron beams for neutron scattering and irradiation facilities for research.
Dr John Bennett will describe the excellent neutron activation analysis (NAA) facilities that are available and the implementation of the k0-method of standardisation. He will provide examples of NAA applications and describe the linkages that have been formed through international networks.

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31 marzo
ore 10
Ed. D
Ambra Caprile
INRIM
Ghost imaging protocol for magneto-optical applications

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Imaging techniques for domain analysis are still one of the most important means of investigation in magnetic materials field. In this work, we develop a new approach to perform magneto-optical imaging, applying for the first time a high resolution Ghost Imaging (GI) protocol to perform Faraday microscopy, and thus to reconstruct the image of Weiss domains within a magnetic sample.
Thermal light GI is a technique that exploits intensity correlations between light beams to reconstruct the image of an object. Considering two intensity-correlated multi-speckles light beams, the first one illuminating an object and observed with a "bucket" detector (i.e. without any spatial resolution such as e.g. a pigtailed photodiode), the second one, that has never interacted with the object, revealed by a spatial resolving detector (like a CCD camera), the image of the object can be retrieved by correlating the outputs of the two detectors. The experimental setup that allows the measurement of intensity correlation is similar to the Hanbury-Brown-Twiss (HBT) interferometer, with a beam splitter that generates two spatially correlated thermal beams. Glauber’s second order correlation function normalized to the fluctuations of the beams is used to reconstruct the image of the sample. An imaging setup, implemented in order to obtain a spatial resolution sufficient to perform an efficient imaging of magnetic domains within an yttrium iron garnet (YIG) sample, has been realized.
The outstanding magneto-optical properties of YIG, which possesses one of the highest Faraday rotation angle, make it the perfect material for a feasibility investigation of this new technique. Moreover, YIGs show good transmittance in near infra-red, i.e. in wavelength used for optical telecommunications, and at present time they are a hot topic in applied science, since the exploitation of their properties could lead in perspective to interesting optic and microwaves applications, e.g. investigation of spinwave propagation and spincaloritronic effects, magneto-optic isolators, circulators, TE–TM mode conversion or wavelength accordable filters. The sample used here is a film of YIG of chemical composition (YSmCa)3(FeGe)5O12 grown on gadolinium gallium garnet substrate.
Ghost image reconstructions of domains of average size of 60 µm with opposite magnetization have been successfully retrieved. A careful engineering of the correlated thermal beams has been performed in order to maximize both the resolution and the signal to noise ratio of the final image.
The investigated approach opens to the development of interesting innovative setups for magneto-optics, allowing operations in small volumes such as e.g. in cryostats, since no actuators to scan the sample or CCD close to the sample are needed, where, in perspective, the image of the domains can be obtained just inserting a tiny bundle of optical fibers in the proximity of the sample.
This work has been carried out thanks to a cooperation between the Electromagnetics Division (program E4) and the Optics Division (program O4) in INRIM.
11 marzo
ore 10:30
Ed. D
Samuel Dobák
P. J. Šafárik University in Košice, Faculty of Science, Slovakia
Laboratory of Ferromagnetism at the P. J. Šafárik University in Košice, Slovakia: Introduction and Focus of Activity

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The seminar will be devoted to the introduction of research infrastructure in our Laboratory of Ferromagnetism and its focus on the study of magnetization processes in compacted powder ferromagnets. I will then discuss basic principles of the production of this group of magnetic materials and also our ideas concerning the preparation of the new type of composite materials.
26 febbraio
ore 15
Ed. D
Paolo Bortolotti
Unité Mixte de Physique CNRS/Thales, Palaiseau, France
Novel paths for rf applications based on spintronics

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Spintronics consists on manipulating magnetic electronic spins rather than, or in addition to, charges through electrical currents and/or magnetic fields. This technology has revolutionized the market of read-head applications and other types of magnetic sensors. Recently, a lot of promising studies have been done for active elements such as memories (see for example the recent developments on perpendicular STT-MRAM), spin transistors and more generally logic spin gates; however, those functionalities are far from being implemented into real devices. Nevertheless, we believe that concerning radio-frequency (rf) applications, spintronics is now mature enough for proposing interesting and industrially attractive active functionalities and foster the development of a new generation of rf devices such as filters, frequency detectors, synthesizers, etc=85 In this seminar I will present some of the recent works of our laboratory on the subject.
The main brick for this new generation of rf applications [1] is the spin-transfer nano oscillator (STNO), which is a magnetic tunnel junction (MTJ) controlled by a dc current. In particular, we are focusing on vortex-based STNOs, consisting of an MTJ where the free layer is in the magnetic vortex configuration, separated from a synthetic anti-ferromagnetic polarizer layer by an MgO barrier. The vortex consists of a circular in-plane magnetization with a central out-of-plane core, which can be excited by a dc current, Idc, resulting in a steady gyrotropic motion of the vortex core [2]. This motion is transformed into an rf signal in the MHz/GHz range, through the tunnel magnetoresistance (TMR) effect. A phase-locked loop (PLL) implementation can be used to further improve the characteristics of such oscillator. Our latest achievements make us confident that a synthesizer based on vortex STNOs will be good enough for device operations.
Furthermore, the vortex core can be resonantly excited by an rf current, Irf, if the frequency of the current matches the frequency of the gyrotropic mode [3], which is the main ingredient for a spintronic frequency detector. In this context, I will briefly present a new type of STNO frequency detector based on vortex core expulsion, displaying promising features which can potentially constitute the basis of a new generation of rf applications.
I will also present some novel ideas on STNO-based associative memories [4]: by mimicking the behavior of our brain, we will consider an array of STNOs and take advantage of their mutual synchronization to perform associative memory functionalities.
Another interesting use of spintronics for rf application resides in the field of magnonics, i.e., the use of spin waves excitations (magnons) for information treatment. I will show that the information can be encoded in the phase of the magnetostatic spin wave and easily manipulated; miniaturized and low energy consumption devices for both logic [5] and rf functionalities, e.g., a magnonic filter, can be indeed conceived.
I acknowledge financial support from ANR agency (SPINNOVA ANR-11-NANO-0016; MEMOS ANR-14-CE26-0021-03; NANOSWITI ANR-11-BS10-003-05) and EU FP7 grant (MOSAIC No. ICT-FP7-n317950).

References:
1. Building blocks: N. Locatelli et al., Nature Mater. 13, 11 (2014)
2. Vortex STNO: A. Dussaux et al., Nature Commun. 1, 8 (2010)
3. Detection: A. S. Jenkins et al., Appl. Phys. Lett. 105, 17 (2014)
4. Associative memories: MEMOS ANR-14-CE26-0021-03
5. Magnonics: Chumak et al., Nat. Commun. 5, 4700 (2014) & ref. therein
19 febbraio
ore 14:30
Ed. D
Mikhail Aleksandrovich Malygin
Head of the Department of Industrial Metrology
D.I. Mendeleyev Institute for Metrology (VNIIM), Russia
Laboratory of Metrology of magnetic measurements and nondestructive testing at UNIIM

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The talk aims to present our lab, our achievements and perspectives for possible further collaboration and finally to get some experience exchange. The presentation will briefly introduce metrological system of Russia, distribution of centres and institutes in the country. After that location and significance of UNIIM and presented laboratory will be determined, and then presentation will focus on the list of measurement capabilities and activities that our laboratory is specialized on, adding some general information.
19 febbraio
ore 11
Gaetano Scamarcio
Università degli Studi di Bari "Aldo Moro", Politecnico di Bari
Dipartimento Interateneo di Fisica "M. Merlin"
CNR - Istituto di Fotonica e Nanotecnologie
Trace gas sensing and imaging with terahertz quantum cascade lasers

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A wide variety of application areas are eagerly aiming at the development of novel sensing and imaging systems exploiting the availability of quantum cascade laser (QCL) compact semiconductor sources emitting in the mid-infrared and terahertz ranges. After reviewing the state-of-the-art in this fast growing field, I will present our recent demonstration of quartz-enhanced photo-acoustic trace gas sensors based on THz QCLs. Also, I will illustrate our theoretical and experimental results on the coherent multimode dynamics of QCLs and their intrinsic stability under strong optical feedback, showing examples of exploitations in the field of self-mixing interferometry and the development of a novel detectorless contact-free imaging method to monitor the free electron density in semiconductor structures.
12 febbraio
ore 11
Ruggero Vaglio
Dipartimento di Fisica, Università di Napoli Federico II
Role of thermal boundary resistance effects in superconducting cavities for particle accelerators

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New generation of accelerators require increasing superconducting cavity performances. Kapitza thermal resistance and, more in general, thermal boundary resistance effects have been often considered as a possible source of "non-ideal" cavity behavior, through the formation of a temperature difference between the inner cavity superconducting surface and the helium bath. However the general assessment reported in the literature is that such effects can be generally neglected, at least at low or moderate input power.
Here we present new data on small test 6Ghz cavities, showing new evidence of the relevance of thermal effects.
Routes for lowering the Kapitza resistance and to improve the overall cavity performances are finally discussed.
5 febbraio
ore 16
Massimo Inguscio
Presidente INRIM
L'Istituto Nazionale di Ricerca Metrologica (INRIM): una presentazione


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3 febbraio
ore 15
Luca Zilberti
INRIM
Induzione Elettromagnetica, un fenomeno semplice... ma non banale
(Storia, curiosità, paradossi, formulazioni ed interpretazioni attorno alla legge di Faraday)

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Scoperta da Faraday (e, pressoché contemporaneamente, da Henry) nel 1831, l'induzione elettromagnetica è il principio alla base di innumerevoli realizzazioni tecnologiche di uso comune. A dispetto di tale versatilità applicativa, la rappresentazione modellistica di questo fenomeno è tuttavia apparsa critica fin dagli albori dell'elettrotecnica, come testimoniato dai vari esempi di "paradossi" che sembrano smentire la validità della legge usata per descriverlo. Nel corso del seminario si discuteranno alcuni di questi paradossi, insieme agli approcci che sono stati proposti per risolverli, nonché alle più recenti revisioni del problema, atte ad individuare una sua formulazione dall'efficacia generale. Infine saranno proposte riflessioni sull'interpretazione causale dell'induzione elettromagnetica, che ne costituisce un ulteriore aspetto sfuggente. L'intera presentazione sarà scandita da citazioni tratte direttamente dalle opere di alcuni dei "giganti" che hanno contribuito alla costruzione dell'Elettrodinamica Classica.
3 febbraio
ore 10:30
Joachim Ullrich
Presidente Physikalisch-Technische Bundesanstalt (PTB)
Metrology and Light - in the Year of Light and Beyond

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Metrology with and for light has been an ever-increasing field since the invention of the dynamo by W. v. Siemens in 1866 and of the carbon filament lamp by T. A. Edison in 1879. The foundation of the Physikalisch-Technische Reichsanstalt, PTR, in 1887 by H. v. Helmholtz and W. v. Siemens was among others strongly driven by the enormous growth of electric and lighting technologies in those days. Today we are facing a second revolution in light and lighting technologies with innovative laser-, LED- and OLED-source developments, the evolution of nano-photonics, single-photon and quantum-information technologies to name just a view with the quest for state-of-the-art metrology. In the future, light will play an even more important role for metrology with the advent of optical clocks, broad-band and high-precision optical fibre transmission technologies, methods to achieve spatial resolutions below the Abbe limit, with attosecond and free-electron-laser light sources coming online.
In the talk the fascination of light for mankind, the development of light and lightening technologies as well as present and future developments will be highlighted emphasizing in particular the challenges and opportunities for metrology in the future.
28 gennaio
ore 17
Maurizio Prato
Università degli Studi di Trieste
Synergies between Chemistry and Nanotechnology: Applications to Neurosciences and Energy

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Many problems of our times have not been solved yet, mostly due to the complexity of the problems and their difficult solutions. New approaches and new materials are therefore needed, to produce breakthroughs and generate new hopes. Among the wide range of novel materials available today, carbon nanotubes (CNTs) and graphene stand as unique materials for fundamental research and potential applications. During this talk, we will report on the most recent advances in our group, which have led to several interesting applications in many fields. For instance, functionalized carbon nanotubes stimulate neuronal communication or can serve as carriers for innovative drug delivery systems. On the other hand, carbon nanotubes and graphene are ideal supports for catalysis in water splitting devices, for the production of hydrogen as a clean source of energy.



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