Abstract
Investigations of particle parallel flow velocities have been carried out for the scrape-off layer (SOL) of the Wendelstein 7-X (W7-X) stellarator, in order to gain insights on the SOL ...transport properties during attached and detached plasma scenarios. The experimental evidence is based on the coherence imaging spectroscopy (CIS) diagnostic, able to measure 2D impurity emission intensity and flow velocity. The impurity monitored by CIS is C
2+
, characterized by a line-emission intensity observed to be linearly proportional to the total plasma radiated power in both attached and detached plasmas. The related C
2+
velocity shows a strong dependence on the line-averaged electron density while remaining insensitive to the input power. During attached plasmas, the velocity increases with increasing line-averaged density. The tendency reverses in the transition to and during detachment, in which the velocity decreases by at least a factor of 2. The sharp drop in velocity, together with a rise in line-emission intensity, is reliably correlated to the detachment transition and can therefore be used as one of its signatures. The impurity flow velocity appears to be well coupled with the main ions’ one, thus implying the dominant role of impurity-main ion friction in the parallelimpurity transport dynamics. In view of this SOL impurity transport regime, the CIS measurement results are here interpreted with the help of EMC3-Eirene simulations, and their major trends are already explainable with a simple 1D fluid model.
Abstract Investigations of particle parallel flow velocities have been carried out for the scrape-off layer (SOL) of the Wendelstein 7-X (W7-X) stellarator, in order to gain insights on the SOL ...transport properties during attached and detached plasma scenarios. The experimental evidence is based on the coherence imaging spectroscopy (CIS) diagnostic, able to measure 2D impurity emission intensity and flow velocity. The impurity monitored by CIS is C2+, characterized by a line-emission intensity observed to be linearly proportional to the total plasma radiated power in both attached and detached plasmas. The related C2+velocity shows a strong dependence on the line-averaged electron density while remaining insensitive to the input power. During attached plasmas, the velocity increases with increasing line-averaged density. The tendency reverses in the transition to and during detachment, in which the velocity decreases by at least a factor of 2. The sharp drop in velocity, together with a rise in line-emission intensity, is reliably correlated to the detachment transition and can therefore be used as one of its signatures. The impurity flow velocity appears to be well coupled with the main ions’ one, thus implying the dominant role of impurity-main ion friction in the parallelimpurity transport dynamics. In view of this SOL impurity transport regime, the CIS measurement results are here interpreted with the help of EMC3-Eirene simulations, and their major trends are already explainable with a simple 1D fluid model.
Wendelstein 7-X (W7-X), the largest advanced stellarator, is built to demonstrate high power, high performance quasi-continuous operation. Therefore, in the recent campaign, experiments were ...performed to prepare for long pulse operation, addressing three critical issues: the development of stable detachment, control of the heat and particle exhaust, and the impact of leading edges on plasma performance. The heat and particle exhaust in W7-X is realized with the help of an island divertor, which utilizes large magnetic islands at the plasma boundary. This concept shows very efficient heat flux spreading and favourable scaling with input power. Experiments performed to overload leading edges showed that the island divertor yields good impurity screening. A highlight of the recent campaign was a robust detachment scenario, which allowed reducing power loads even by a factor of ten. At the same time, neutral pressures at the pumping gap entrance yielded the particle removal rate close to the values required for stable density control in steady-state operation.
Wendelstein 7-X (W7-X), the largest advanced stellarator, is built to demonstrate high power, high performance quasi-continuous operation. Therefore, in the recent campaign, experiments were ...performed to prepare for long pulse operation, addressing three critical issues: the development of stable detachment, control of the heat and particle exhaust, and the impact of leading edges on plasma performance. The heat and particle exhaust in W7-X is realized with the help of an island divertor, which utilizes large magnetic islands at the plasma boundary. This concept shows very efficient heat flux spreading and favourable scaling with input power. Experiments performed to overload leading edges showed that the island divertor yields good impurity screening. A highlight of the recent campaign was a robust detachment scenario, which allowed reducing power loads even by a factor of ten. At the same time, neutral pressures at the pumping gap entrance yielded the particle removal rate close to the values required for stable density control in steady-state operation.
Measurements of the poloidal electron density and temperature distribution in the W7-X island divertor reveal the existence of two distinct scrape-off layer transport regimes. At low and intermediate ...densities, \(T_e\) profiles across the magnetic island are hollow, with a minimum at the island O-point. Above a threshold density \(\overline{n}_e \approx 5 \times 10^{19}\) m\(^{-3}\), the local minimum vanishes and the \(T_e\) profiles become monotonic. At the lowest studied densities, the hollow \(T_e\) profiles imply an electrostatic field of up to \(\textbf{E}_r \sim 6\) kV/m, which can induce \(\textbf{E} \times \textbf{B}\) drifts around the island, with drift velocities of up to \(\sim3\) km/s. These \(\textbf{E} \times \textbf{B}\) drifts result in strong convective heat transport poloidally around the island, binormal to the magnetic field, which supports the hollow radial temperature profile and hence provides a positive feedback to the electric field. Above the threshold density, these drifts strongly diminish, presumably due to increased anomalous diffusion, which causes the profile hollowness and therefore also the radial electric field to strongly diminish. This argument is supported by comparison to EMC3-EIRENE modeling and an analytical transport analyses showing that an additional, non-diffusive transport channel is required to maintain the profile hollowness up to the densities seen in experiment, and that a poloidal drift transport channel supports such hollowness only up to certain densities.
Abstract The purpose of this study was to assess the prevalence of personality disorders (PDs) and their associated factors in prisoners who initiate chronic hepatitis C (CHC) treatment in 25 Spanish ...prisons. The Personality Diagnostic Questionnaire-4 was used to diagnose PDs according to DSM-IV criteria. Factors potentially associated with a PD diagnosis were evaluated by logistic regression analysis. Two hundred and fifty-five patients were initially assessed and 62 (24.3%) were excluded due to an incomplete or invalid self-report screening questionnaire. PD prevalence was 70.5%, with antisocial PD being the most prevalent (46.1%). In terms of PD clusters, the most prevalent was cluster-B (55.4%). PD diagnosis was associated with HCV genotypes 1, 2, or 3 (odds ratio OR 2.14, 95% confidence interval CI 1.02–4.49). Patients with a cluster-B PD were more likely to be infected with HCV genotypes 1, 2, or 3 (OR 2.37, 95% CI 1.08–5.23) and be HIV-infected (OR 2.20, 95% CI 1.10–4.39), to report past-year injection drug use (OR 7.17, 95% CI 1.49–34.58), and to have stage 3 or 4 fibrosis (OR 2.16, 95% CI 1.06–4.49). The prevalence of PDs in Spanish prisoners who initiate CHC treatment is very high. PD management issues should be considered in treating CHC patients in prisons.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abstract
We present recent highlights from the most recent operation phases of Wendelstein 7-X, the most advanced stellarator in the world. Stable detachment with good particle exhaust, low impurity ...content, and energy confinement times exceeding 100 ms, have been maintained for tens of seconds. Pellet fueling allows for plasma phases with reduced ion-temperature-gradient turbulence, and during such phases, the overall confinement is so good (energy confinement times often exceeding 200 ms) that the attained density and temperature profiles would not have been possible in less optimized devices, since they would have had neoclassical transport losses exceeding the heating applied in W7-X. This provides proof that the reduction of neoclassical transport through magnetic field optimization is successful. W7-X plasmas generally show good impurity screening and high plasma purity, but there is evidence of longer impurity confinement times during turbulence-suppressed phases.
PDF
