16 research outputs found

    Overview of the JET results in support to ITER

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    Underdiagnosis and undertreatment of osteoporotic patients admitted in internal medicine wards in Italy between 2010 and 2016 (the REPOSI Register)

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    Purpose: To evaluate clinical features, treatments, and outcomes of osteoporotic patients admitted to internal medicine and geriatric wards compared with non-osteoporotic patients (REPOSI registry). Methods: We studied 4714 patients hospitalized between 2010 and 2016. We reported age, sex, educational level, living status, comorbidities and drugs taken, Cumulative Illness Rating Scale (CIRS), Barthel Index, Short-Blessed Test, 4-item Geriatric Depression Scale, serum hemoglobin, creatinine, and clinical outcomes. Osteoporosis was defined based on the diagnoses recorded at admission, according to the following ICD9: 733, 805–813, 820–823. Results: Twelve percent of the patients had a preadmission diagnosis of osteoporosis. Only 20% of these had been prescribed oral bisphosphonates; 34% were taking vitamin D supplements. Osteoporotic patients were significantly older, with lower BMI, higher CIRS, and taking more drugs. They were significantly more depressed, less independent, with a higher severity of cognitive impairment compared with non-osteoporotic patients. At discharge, the number of patients receiving treatment for osteoporosis did not change. Length of stay and inhospital mortality did not differ between groups. Osteoporotic patients were more frequently nonhome discharged compared with those without osteoporosis (14.8 vs. 7.9%, p = 0.0007), mostly discharged to physical therapy or rehabilitation (8.8 vs. 2.5% of patients, p < 0.0001). Among osteoporotic patients deceased 3 months after discharge, the number of those treated with vitamin D, with or without calcium supplements, was significantly lower compared with survivors (12 vs. 32%, p = 0.0168). Conclusions: The diagnosis of osteoporosis is poorly considered both during hospital stay and at discharge; osteoporotic patients are frailer compared to non-osteoporotic patients

    Ion cyclotron resonance heating for tungsten control in various JET H-mode scenarios

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    Ion cyclotron resonance heating (ICRH) in the hydrogen minority scheme provides central ion heating and acts favorably on the core tungsten transport. Full wave modeling shows that, at medium power level (4 MW), after collisional redistribution, the ratio of power transferred to the ions and the electrons vary little with the minority (hydrogen) concentration n H/n e but the high-Z impurity screening provided by the fast ions temperature increases with the concentration. The power radiated by tungsten in the core of the JET discharges has been analyzed on a large database covering the 2013-2014 campaign. In the baseline scenario with moderate plasma current (I p = 2.5 MA) ICRH modifies efficiently tungsten transport to avoid its accumulation in the plasma centre and, when the ICRH power is increased, the tungsten radiation peaking evolves as predicted by the neo-classical theory. At higher current (3-4 MA), tungsten accumulation can be only avoided with 5 MW of ICRH power with high gas injection rate. For discharges in the hybrid scenario, the strong initial peaking of the density leads to strong tungsten accumulation. When this initial density peaking is slightly reduced, with an ICRH power in excess of 4 MW,very low tungsten concentration in the core (∼10-5) is maintained for 3 s. MHD activity plays a key role in tungsten transport and modulation of the tungsten radiation during a sawtooth cycle is correlated to the fishbone activity triggered by the fast ion pressure gradient

    Calculations to support JET neutron yield calibration: Modelling of neutron emission from a compact DT neutron generator

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    At the Joint European Torus (JET) the ex-vessel fission chambers and in-vessel activation detectors are used as the neutron production rate and neutron yield monitors respectively. In order to ensure that these detectors produce accurate measurements they need to be experimentally calibrated. A new calibration of neutron detectors to 14 MeV neutrons, resulting from deuterium–tritium (DT) plasmas, is planned at JET using a compact accelerator based neutron generator (NG) in which a D/T beam impinges on a solid target containing T/D, producing neutrons by DT fusion reactions. This paper presents the analysis that was performed to model the neutron source characteristics in terms of energy spectrum, angle–energy distribution and the effect of the neutron generator geometry. Different codes capable of simulating the accelerator based DT neutron sources are compared and sensitivities to uncertainties in the generator's internal structure analysed. The analysis was performed to support preparation to the experimental measurements performed to characterize the NG as a calibration source. Further extensive neutronics analyses, performed with this model of the NG, will be needed to support the neutron calibration experiments and take into account various differences between the calibration experiment and experiments using the plasma as a source of neutrons

    Thermal analysis of protruding surfaces in the JET divertor

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    3D simulations of gas puff effects on edge plasma and ICRF coupling in JET

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    Recent JET (ITER-Like Wall) experiments have shown that the fueling gas puffed from different locations of the vessel can result in different scrape-off layer (SOL) density profiles and therefore different radio frequency (RF) coupling. To reproduce the experimental observations, to understand the associated physics and to optimize the gas puff methods, we have carried out three-dimensional (3D) simulations with the EMC3-EIRENE code in JET-ILW including a realistic description of the vessel geometry and the gas injection modules (GIMs) configuration. Various gas puffing methods have been investigated, in which the location of gas fueling is the only variable parameter. The simulation results are in quantitative agreement with the experimental measurements. They confirm that compared to divertor gas fueling, mid-plane gas puffing increases the SOL density most significantly but locally, while top gas puffing increases it uniformly in toroidal direction but to a lower degree. Moreover, the present analysis corroborates the experimental findings that combined gas puff scenarios - based on distributed main chamber gas puffing - can be effective in increasing the RF coupling for multiple antennas simultaneously. The results indicate that the spreading of the gas, the local ionization and the transport of the ionized gas along the magnetic field lines connecting the local gas cloud in front of the GIMs to the antennas are responsible for the enhanced SOL density and thus the larger RF coupling

    Real-time-capable prediction of temperature and density profiles in a tokamak using RAPTOR and a first-principle-based transport model

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    The RAPTOR code is a control-oriented core plasma profile simulator with various applications in control design and verification, discharge optimization and real-time plasma simulation. To date, RAPTOR was capable of simulating the evolution of poloidal flux and electron temperature using empirical transport models, and required the user to input assumptions on the other profiles and plasma parameters. We present an extension of the code to simulate the temperature evolution of both ions and electrons, as well as the particle density transport. A proof-of-principle neural-network emulation of the quasilinear gyrokinetic QuaLiKiz transport model is coupled to RAPTOR for the calculation of first-principle-based heat and particle turbulent transport. These extended capabilities are demonstrated in a simulation of a JET discharge. The multi-channel simulation requires ∼0.2 s to simulate 1 second of a JET plasma, corresponding to ∼20 energy confinement times, while predicting experimental profiles within the limits of the transport model. The transport model requires no external inputs except for the boundary condition at the top of the H-mode pedestal. This marks the first time that simultaneous, accurate predictions of Te, Tiand nehave been obtained using a first-principle-based transport code that can run in faster-than-real-time for present-day tokamaks
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