| 1. |
- Abel, I, et al.
(författare)
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Overview of the JET results with the ITER-like wall
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104002-
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Tidskriftsartikel (refereegranskat)abstract
- Following the completion in May 2011 of the shutdown for the installation of the beryllium wall and the tungsten divertor, the first set of JET campaigns have addressed the investigation of the retention properties and the development of operational scenarios with the new plasma-facing materials. The large reduction in the carbon content (more than a factor ten) led to a much lower Z(eff) (1.2-1.4) during L- and H-mode plasmas, and radiation during the burn-through phase of the plasma initiation with the consequence that breakdown failures are almost absent. Gas balance experiments have shown that the fuel retention rate with the new wall is substantially reduced with respect to the C wall. The re-establishment of the baseline H-mode and hybrid scenarios compatible with the new wall has required an optimization of the control of metallic impurity sources and heat loads. Stable type-I ELMy H-mode regimes with H-98,H-y2 close to 1 and beta(N) similar to 1.6 have been achieved using gas injection. ELM frequency is a key factor for the control of the metallic impurity accumulation. Pedestal temperatures tend to be lower with the new wall, leading to reduced confinement, but nitrogen seeding restores high pedestal temperatures and confinement. Compared with the carbon wall, major disruptions with the new wall show a lower radiated power and a slower current quench. The higher heat loads on Be wall plasma-facing components due to lower radiation made the routine use of massive gas injection for disruption mitigation essential.
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| 2. |
- Romanelli, F, et al.
(författare)
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Overview of the JET results
- 2011
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 51:9
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Tidskriftsartikel (refereegranskat)abstract
- Since the last IAEA Conference JET has been in operation for one year with a programmatic focus on the qualification of ITER operating scenarios, the consolidation of ITER design choices and preparation for plasma operation with the ITER-like wall presently being installed in JET. Good progress has been achieved, including stationary ELMy H-mode operation at 4.5 MA. The high confinement hybrid scenario has been extended to high triangularity, lower ρ*and to pulse lengths comparable to the resistive time. The steady-state scenario has also been extended to lower ρ*and ν*and optimized to simultaneously achieve, under stationary conditions, ITER-like values of all other relevant normalized parameters. A dedicated helium campaign has allowed key aspects of plasma control and H-mode operation for the ITER non-activated phase to be evaluated. Effective sawtooth control by fast ions has been demonstrated with3He minority ICRH, a scenario with negligible minority current drive. Edge localized mode (ELM) control studies using external n = 1 and n = 2 perturbation fields have found a resonance effect in ELM frequency for specific q95values. Complete ELM suppression has, however, not been observed, even with an edge Chirikov parameter larger than 1. Pellet ELM pacing has been demonstrated and the minimum pellet size needed to trigger an ELM has been estimated. For both natural and mitigated ELMs a broadening of the divertor ELM-wetted area with increasing ELM size has been found. In disruption studies with massive gas injection up to 50% of the thermal energy could be radiated before, and 20% during, the thermal quench. Halo currents could be reduced by 60% and, using argon/deuterium and neon/deuterium gas mixtures, runaway electron generation could be avoided. Most objectives of the ITER-like ICRH antenna have been demonstrated; matching with closely packed straps, ELM resilience, scattering matrix arc detection and operation at high power density (6.2 MW m-2) and antenna strap voltages (42 kV). Coupling measurements are in very good agreement with TOPICA modelling. © 2011 IAEA, Vienna.
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| 3. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 4. |
- Menard, J.E., et al.
(författare)
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Progress in understanding error-field physics in NSTX spherical torus plasmas
- 2010
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 50:4, s. 045008-
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Tidskriftsartikel (refereegranskat)abstract
- The low-aspect ratio, low magnetic field and wide range of plasma beta of NSTX plasmas provide new insight into the origins and effects of magnetic field errors. An extensive array of magnetic sensors has been used to analyse error fields, to measure error-field amplification and to detect resistive wall modes (RWMs) in real time. The measured normalized error-field threshold for the onset of locked modes shows a linear scaling with plasma density, a weak to inverse dependence on toroidal field and a positive scaling with magnetic shear. These results extrapolate to a favourable error-field threshold for ITER. For these low-beta locked-mode plasmas, perturbed equilibrium calculations find that the plasma response must be included to explain the empirically determined optimal correction of NSTX error fields. In high-beta NSTX plasmas exceeding the n = 1 no-wall stability limit where the RWM is stabilized by plasma rotation, active suppression of n = 1 amplified error fields and the correction of recently discovered intrinsic n = 3 error fields have led to sustained high rotation and record durations free of low-frequency core MHD activity. For sustained rotational stabilization of the n = 1 RWM, both the rotation threshold and the magnitude of the amplification are important. At fixed normalized dissipation, kinetic damping models predict rotation thresholds for RWM stabilization to scale nearly linearly with particle orbit frequency. Studies for NSTX find that orbit frequencies computed in general geometry can deviate significantly from those computed in the high-aspect ratio and circular plasma cross-section limit, and these differences can strongly influence the predicted RWM stability. The measured and predicted RWM stability is found to be very sensitive to the E × B rotation profile near the plasma edge, and the measured critical rotation for the RWM is approximately a factor of two higher than predicted by the MARS-F code using the semi-kinetic damping model.
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| 5. |
- McGinn, Steven, et al.
(författare)
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New Technologies for DNA analysis-A review of the READNA Project.
- 2016
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Ingår i: New Biotechnology. - : Elsevier BV. - 1876-4347 .- 1871-6784.
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Forskningsöversikt (refereegranskat)abstract
- The REvolutionary Approaches and Devices for Nucleic Acid analysis (READNA) project received funding from the European Commission for 4 1/2 years. The objectives of the project revolved around technological developments in nucleic acid analysis. The project partners have discovered, created and developed a huge body of insights into nucleic acid analysis, ranging from improvements and implementation of current technologies to the most promising sequencing technologies that constitute a 3(rd) and 4(th) generation of sequencing methods with nanopores and in situ sequencing, respectively.
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| 6. |
- Sabbagh, S. A., et al.
(författare)
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Resistive wall stabilized operation in rotating high beta NSTX plasmas
- 2006
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 46:5, s. 635-644
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Tidskriftsartikel (refereegranskat)abstract
- The National Spherical Torus Experiment (NSTX) has demonstrated the advantages of low aspect ratio geometry in accessing high toroidal and normalized plasma beta, and βN ≡ 10 8〈βt〉 aB0/Ip. Experiments have reached βt = 39% and βN = 7.2 through boundary and profile optimization. High βN plasmas can exceed the ideal no-wall stability limit, βNno-wall, for periods much greater than the wall eddy current decay time. Resistive wall mode (RWM) physics is studied to understand mode stabilization in these plasmas. The toroidal mode spectrum of unstable RWMs has been measured with mode number n up to 3. The critical rotation frequency of Bondeson-Chu, Ωcrit = ωA/(4q2), describes well the RWM stability of NSTX plasmas when applied over the entire rotation profile and in conjunction with the ideal stability criterion. Rotation damping and global rotation collapse observed in plasmas exceeding βNno-wall differs from the damping observed during tearing mode activity and can be described qualitatively by drag due to neoclassical toroidal viscosity in the helically perturbed field of an ideal displacement. Resonant field amplification of an applied n = 1 field perturbation has been measured and increases with increasing βN. Equilibria are reconstructed including measured ion and electron pressure, toroidal rotation and flux isotherm constraint in plasmas with core rotation ω/ωA up to 0.48. Peak pressure shifts of 18% of the minor radius from the magnetic axis have been reconstructed.
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| 7. |
- Armitage, Emily G, et al.
(författare)
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Time-of-flight SIMS as a novel approach to unlocking the hypoxic properties of cancer
- 2013
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Ingår i: Surface and Interface Analysis. - 1096-9918 .- 0142-2421. ; 45:1, s. 282-285
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Tidskriftsartikel (refereegranskat)abstract
- It is known that hypoxia-inducible factor 1 (HIF-1) activity results in the coordinated up-regulation of a large number of proteins that facilitate cell survival in tumours; however, the effect of HIF-1 on cancer metabolism is less well characterised. With knowledge of the specific effect of HIF-1 on cancer metabolism, biomarkers could be identified for which new drugs could be targeted. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) offers the potential to analyse intact cells in situ and has a mass spectral coverage that is applicable to metabolic profiling. It has been used to analyse the effects of HIF-1 on multicellular tumour models. Multicellular tumour spheroids (MTSs) have been cultured from human colon carcinoma cells with and without the expression of HIF-1, and the surface of the cross sections of each MTS has been analysed. Because metabolic profiling is an emerging field in ToF-SIMS, there is a requirement to determine which metabolites can be detected using this technique and which of those can be identified in complex mixtures within biological samples. For this, a selection of metabolites have been analysed, and the ToF-SIMS standard spectra acquired have been used to localise metabolites in MTS sections. The comparison of metabolic profiles of MTSs with and without the expression of HIF-1 has elucidated potential biomarkers for tumour survival in hypoxia, some of which may be HIF-1 regulated.
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| 8. |
- Kotze, Helen L., et al.
(författare)
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ToF-SIMS as a tool for metabolic profiling small biomolecules in cancer systems
- 2013
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Ingår i: Surface and Interface Analysis. - 1096-9918 .- 0142-2421. ; 45:1, s. 277-281
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Tidskriftsartikel (refereegranskat)abstract
- Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is emerging as a tool for studying the metabolism of disease. ToF-SIMS enables chemical specificity in addition to high spatial resolution imaging of biological samples from cells to tissue. Here, ToF-SIMS has been used to investigate the metabolic regulation of hypoxia-induced chemoresistance to doxorubicin treatment using multicellular tumour spheroids. Imaging principal component analysis (PCA) was used as a tool to identify the regions of chemistry present within the image that differ as a result of drug treatment. A series of metabolite ToF-SIMS spectra were acquired, which were used to identify quasi-molecular ions and fragments correlated to the PCA loading plots. Metabolite patterns have been identified as potential biomarkers of hypoxia-induced chemoresistance.
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| 9. |
- Rafiq, T., et al.
(författare)
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Microtearing instabilities and electron thermal transport in low and high collisionality NSTX discharges
- 2021
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 28:2
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Tidskriftsartikel (refereegranskat)abstract
- Microtearing mode (MTM) real frequency, growth rate, magnetic fluctuation amplitude, and resulting electron thermal transport are studied in systematic NSTX scans of relevant plasma parameters. The dependency of the MTM real frequency and growth rate on plasma parameters, suitable for low and high collision NSTX discharges, is obtained by using the reduced MTM transport model [T. Rafiq et al., Phys. Plasmas 23, 062507 (2016)]. The plasma parameter dependencies are compared and found to be consistent with the results obtained from MTM using the gyrokinetic GYRO code. The scaling trend of collision frequency and plasma beta is found to be consistent with the global energy confinement trend observed in the NSTX experiment. The strength of the magnetic fluctuation is found to be consistent with the gyrokinetic estimate. In earlier studies, it was found that the version of the multi-mode (MM) anomalous transport model, which did not contain the effect of MTMs, provided an appropriate description of the electron temperature profiles in standard tokamak discharges and not in spherical tokamaks. When the MM model, which involves transport associated with MTMs, is incorporated in the TRANSP code and is used in the study of electron thermal transport in NSTX discharges, it is observed that the agreement with the experimental electron temperature profile is substantially improved.
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