Resonant excitation of vortex gyrotropic mode via surface acoustic waves

Finding new energy-efficient methods for exciting magnetization dynamics is one of the key challenges in magnonics. In this work, we present an approach to excite the gyrotropic dynamics of magnetic vortices through the phenomenon of inverse magnetostriction, also known as the Villari effect. We develop an analytical model based on the Thiele formalism that describes the gyrotropic motion of the vortex core including the energy contributions due to inverse magnetostriction. Based on this model, we predict excitations of the vortex core resonances by surface acoustic waves whose frequency is resonant with the frequency of the vortex core. We verify the model's prediction using micromagnetic simulations, and show the dependence of the vortex core's oscillation radius on the surface acoustic wave amplitude and the static bias field. Our study contributes to the advancement of energy-efficient magnetic excitations by relying on voltage-induced driven dynamics, which is an alternative to conventional current-induced excitations

Benefits and medium-term outcome of the Sorin Pericarbon Freedom stentless aortic prosthesis in cases of acute bacterial endocarditis

OBJECTIVES The aim of this study is to evaluate the ease of use and the advantages of Sorin Pericarbon Freedom (SPF) stentless valve in cases of acute bacterial endocarditis and to check the intermediate-term results after the implant of SPF with respect to resistance to infection, valve deterioration and durability. METHODS Between June 2003 and February 2015, 26 patients with active aortic valve bacterial endocarditis underwent aortic valve replacement with SPF pericardial stentless aortic prosthesis. The mean age was 57 \ub1 18 years; 73% of the patients were in preoperative NYHA class III and VI. Mean Logistic EuroSCORE was 14.2 \ub1 12.7. Endocarditis occurred in 18 patients with native valves, and in 9 patients with prosthetic valves (4 mechanical aortic valve prostheses; 5 aortic bioprostheses). Aortic root abscesses were observed in 16 cases (61.5%). Surgery was emergent in 3 cases (11.5%). Redo surgery was performed in 9 cases (35%). Cumulative follow-up was 126.8 patient-years (mean 4.9 \ub1 3.3 years). RESULTS Operative hospital mortality was 0% for all patients. Residual mean prosthetic gradient at discharge was 9.4 \ub1 3.6 mmHg. Neither residual aortic incompetence nor residual abscess cavity was observed at discharge. Mean ejection fraction at discharge was 54 \ub1 8% (Min; Max: 35%; 65%). A total of 4 patients died at follow-up, all for non-cardiac causes. One patient was lost to follow-up. Two patients (8%) underwent non-valve-related reoperation with 0% mortality. Residual mean gradient at follow-up was 7.2 \ub1 2.1 mmHg. Three patients (17%) presented with mild/moderate aortic incompetence and 89% of patients were in NYHA Class I-II at follow-up. At 9 years, actuarial freedom from valve-related reoperation and from structural valve deterioration was 100%. CONCLUSIONS The SPF aortic prosthesis is a true pericardial stentless prosthesis suitable for the treatment of acute bacterial endocarditis. Intermediate-time results in terms of freedom from reoperation, structural valve deterioration and resistance to infections are satisfactory. Haemodynamic performances are excellent since a complete exclusion of aortic root abscesses is achieved without any reduction of the aortic annular diameter, usually due to marsupialization or patch closure of the infected cavities

Intense terahertz pulses from SPARC-LAB coherent radiation source

The linac-based Terahertz source at the SPARC_LAB test facility is able to gene rate highly intense Terahertz broadband pulses via coherent transition radiation (CTR) from high brightness electron beams. The THz pulse duration is typically down to 100 fs RMS and can be tuned through the electron bunch duration and shaping. The measured stored energy in a single THz pulse has reached 40 μ J, which corresponds to a peak electric field of 1.6 MV/cm at the THz focus. Here we present the main features, in particular spatial and sp ectral distributions and energy characterizations of the SPARC_LAB THz source, which is very competitive for investigations in Condensed Matter, as well as a valid tool for electron beam longitudinal diagnostics

Temperature analysis in the shock waves regime for gas-filled plasma capillaries in plasma-based accelerators

Plasma confinement represents a crucial point for plasma-based accelerators and plasma lenses because it can strongly affect the beam properties. For this reason, an accurate measurement of the plasma parameters, as plasma temperature, pressure and electron density, must be performed. In this paper, we introduce a novel method to detect the plasma temperature and the pressure for gas-filled capillaries in use at the SPARC-LAB test facility. The proposed method is based on the shock waves produced at the ends of the capillary during the gas discharge and the subsequent plasma formation inside it. By measuring the supersonic speed of the plasma outflow, the thermodynamic parameters have been obtained both outside and inside the capillary. A plasma temperature around 1.4 eV has been measured, that depends on the geometric properties and the operating conditions of the capillary

The machine protection system for the ELI-NP gamma beam system

The new Gamma Beam System (GBS) of the ELI-NPproject [1], currently under installation in Magurele (RO)by INFN, as part of EuroGammas consortium, can providegamma rays that open new possibilities for nuclear photonicsand nuclear physics.ELI-NP gamma rays are produced by Compton back-scattering to get monochromaticity (0,1% bandwidth), highflux (1013photons), tunable direction and energy up to19.5 MeV. Such gamma beam is obtained when a high-intensity laser collides a high-brightness electron beam withenergies up to740 MeV, a repetition rate of100 Hz, withtrains of 32 bunches within the same RF bucket.An advanced Machine Protection System (MPS) has beendeveloped, in order to ensure proper operation for this chal-lenging facility. The MPS operates on different layers of thecontrol system and is interfaced with all its sub-systems. Forinstance, it comprises different kind of beam loss monitors(based on Cherenkov optical fiber), hall probes, fast currenttransformer together with BPMs, and an embedded systembased on FPGA with distributed I/O over EtherCAT, to mon-itor vacuum and RF systems [2], which require fast responseto be interlocked within one RF pulse

Reducing the impact of radioactivity on quantum circuits in a deep-underground facility

As quantum coherence times of superconducting circuits have increased from nanoseconds to hundreds of microseconds, they are currently one of the leading platforms for quantum information processing. However, coherence needs to further improve by orders of magnitude to reduce the prohibitive hardware overhead of current error correction schemes. Reaching this goal hinges on reducing the density of broken Cooper pairs, so-called quasiparticles. Here, we show that environmental radioactivity is a significant source of nonequilibrium quasiparticles. Moreover, ionizing radiation introduces time-correlated quasiparticle bursts in resonators on the same chip, further complicating quantum error correction. Operating in a deep-underground lead-shielded cryostat decreases the quasiparticle burst rate by a factor fifty and reduces dissipation up to a factor four, showcasing the importance of radiation abatement in future solid-state quantum hardware