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- Eriksson, Frida, 1986, et al.
(author)
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Impact of fast ions on density peaking in JET : fluid and gyrokinetic modeling
- 2019
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In: Plasma Physics and Controlled Fusion. - : Institute of Physics Publishing (IOPP). - 0741-3335 .- 1361-6587. ; 61:7
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Journal article (peer-reviewed)abstract
- The effect of fast ions on turbulent particle transport, driven by ion temperature gradient (ITG)/trapped electron mode turbulence, is studied. Two neutral beam injection (NBI) heated JET discharges in different regimes are analyzed at the radial position rho(t) = 0.6, one of them an L-mode and the other one an H-mode discharge. Results obtained from the computationally efficient fluid model EDWM and the gyro-fluid model TGLF are compared to linear and nonlinear gyrokinetic GENE simulations as well as the experimentally obtained density peaking. In these models, the fast ions are treated as a dynamic species with a Maxwellian background distribution. The dependence of the zero particle flux density gradient (peaking factor) on fast ion density, temperature and corresponding gradients, is investigated. The simulations show that the inclusion of a fast ion species has a stabilizing influence on the ITG mode and reduces the peaking of the main ion and electron density profiles in the absence of sources. The models mostly reproduce the experimentally obtained density peaking for the L-mode discharge whereas the H-mode density peaking is significantly underpredicted, indicating the importance of the NBI particle source for the H-mode density profile.
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| 4. |
- Krat, S., et al.
(author)
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Beryllium film deposition in cavity samples in remote areas of the JET divertor during the 2011-2012 ITER-like wall campaign
- 2017
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In: Nuclear Materials and Energy. - : Elsevier. - 2352-1791. ; 12, s. 548-552
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Journal article (peer-reviewed)abstract
- Beryllium film deposition was studied with cavity samples in remote areas of the inner and outer JET divertor and below divertor tile 5 during the 2011-2012 campaign with the ITER-like wall. Predominantly beryllium films were formed inside the cavities with some additional carbon, the ratio Be/C was > 2. These deposited layers had high D/(Be+C) ratios of about 0.3. The formation of these films is mainly due to sticking of beryllium-containing particles with low sticking coefficients < 0.5. The observed surface loss probabilities depend on the position in the divertor. The particles responsible for film deposition originated from the location of in the divertor strike points.
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| 5. |
- Maggi, C. F., et al.
(author)
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Isotope identity experiments in JET-ILW with H and D L-mode plasmas
- 2019
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In: Nuclear Fusion. - : Institute of Physics Publishing (IOPP). - 0029-5515 .- 1741-4326. ; 59:7
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Journal article (peer-reviewed)abstract
- NBI-heated L-mode plasmas have been obtained in JET with the Be/W ITER-like wall (JET-ILW) in H and D, with matched profiles of the dimensionless plasma parameters, rho*, nu*, beta and q in the plasma core confinement region and same T-i/T-e and Z(eff). The achieved isotope identity indicates that the confinement scale invariance principle is satisfied in the core confinement region of these plasmas, where the dominant instabilities are Ion Temperature Gradient (ITG) modes. The dimensionless thermal energy confinement time, Omega(i) tau(E,th), and the scaled core plasma heat diffusivity, A chi(eff)/B-T, are identical in H and D within error bars, indicating lack of isotope mass dependence of the dimensionless L-mode thermal energy confinement time in JET-ILW. Predictive flux driven simulations with JETTO-TGLF of the H and D identity pair is in very good agreement with experiment for both isotopes: the stiff core heat transport, typical of JET-ILW NBI heated L-modes, overcomes the local gyro-Bohm scaling of gradient-driven TGLF, explaining the lack of isotope mass dependence in the confinement region of these plasmas. The effect of E x B shearing on the predicted heat and particle transport channels is found to be negligible for these low beta and low momentum input plasmas.
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| 6. |
- Nocente, M., et al.
(author)
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Fast ion energy distribution from third harmonic radio frequency heating measured with a single crystal diamond detector at the Joint European Torus
- 2015
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In: Review of Scientific Instruments. - : AMER INST PHYSICS. - 0034-6748 .- 1089-7623. ; 86:10
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Journal article (peer-reviewed)abstract
- Neutron spectroscopy measurements with a single crystal diamond detector have been carried out at JET, for the first time in an experiment aimed at accelerating deuterons to MeV energies with radio frequency heating at the third harmonic. Data are interpreted by means of the expected response function of the detector and are used to extract parameters of the highly non-Maxwellian distribution function generated in this scenario. A comparison with observations using a time of flight and liquid scintillator neutron spectrometers is also presented. The results demonstrate the capability of diamond detectors to contribute to fast ion physics studies at JET and are of more general relevance in view of the application of such detectors for spectroscopy measurements in the neutron camera of next step tokamak devices.
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- Pillon, Mario, et al.
(author)
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Characterization of a diamond detector to be used as neutron yield monitor during the in-vessel calibration of JET neutron detectors in preparation of the DT experiment
- 2016
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In: Fusion engineering and design. - : Elsevier. - 0920-3796 .- 1873-7196. ; 106, s. 93-98
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Journal article (peer-reviewed)abstract
- A new Deuterium-Tritium (DT) campaign is planned at JET. An accurate calibration for the 14 MeV neutron yield monitors is necessary. In order to perform the calibration a 14 MeV Neutron Generator with suitable intensity (similar to 10(8) n/s) will be used. Due to the intensity change during the Neutron Generator lifetime it would be necessary to monitor continuously the neutron emission intensity during the calibration using a compact detector attached to it. A high quality diamond detector has been chosen as one of the monitors. This detector has been fully characterized at the 14 MeV Frascati Neutron Generator facility. The characterization procedure and the resulting 14 MeV neutron response of the detector are described in this paper together with the obtained uncertainties.
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| 8. |
- Slabkowska, K., et al.
(author)
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On the interpretation of high-resolution x-ray spectra from JET with an ITER-like wall
- 2015
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In: Journal of Physics B. - : Institute of Physics (IOP). - 0953-4075 .- 1361-6455. ; 48:14
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Journal article (peer-reviewed)abstract
- The upgraded x-ray crystal spectrometer KX1 on the Joint European Torus (JET) can now measure the M x-ray lines from tungsten with sufficiently high resolution to evaluate how much tungsten may sputter from the plasma-facing tungsten wall planned for the International Thermonuclear Experimental Reactor (ITER). However, a test run on JET found that the L x-ray lines of a molybdenum impurity, which happen to occur in the targeted wavelength region of 5.00-5.35 angstrom, must be taken into account together with the radiation from the M x-ray lines of tungsten to match the high-resolution spectra. Such detailed radiation modeling is expected to be needed for ASDEX Upgrade tokamak, and for other tokamaks such as ITER and tungsten (W) Environment in Steady-state Tokamak (WEST), which will implement tungsten plasma-facing components and a high-resolution spectrometer to keep track of with a similar x-ray diagnostics.
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| 9. |
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- 2018
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:9
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Journal article (peer-reviewed)
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| 10. |
- Itala, Eero, et al.
(author)
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Gas-phase study on uridine : Conformation and X-ray photofragmentation
- 2015
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 142:19
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Journal article (peer-reviewed)abstract
- Fragmentation of RNA nucleoside uridine, induced by carbon 1s core ionization, has been studied. The measurements by combined electron and ion spectroscopy have been performed in gas phase utilizing synchrotron radiation. As uridine is a combination of d-ribose and uracil, which have been studied earlier with the same method, this study also considers the effect of chemical environment and the relevant functional groups. Furthermore, since in core ionization the initial core hole is always highly localized, charge migration prior to fragmentation has been studied here. This study also demonstrates the destructive nature of core ionization as in most cases the C 1s ionization of uridine leads to concerted explosions producing only small fragments with masses <= 43 amu. In addition to fragmentation patterns, we found out that upon evaporation the sugar part of the uridine molecule attains hexagonal form.
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