The impurity dynamics in stellarators has become an issue of moderate concern due to the inherent tendency of the impurities to accumulate in the core when the neoclassical ambipolar radial electric ...field points radially inwards (ion root regime). This accumulation can lead to collapse of the plasma due to radiative losses, and thus limit high performance plasma discharges in non-axisymmetric devices.\\ A quantitative description of the neoclassical impurity transport is complicated by the breakdown of the assumption of small \(\mathbf{E}\times \mathbf{B}\) drift and trapping due to the electrostatic potential variation on a flux surface \(\tilde{\Phi}\) compared to those due to the magnetic field gradient. The present work examines the impact of this potential variation on neoclassical impurity transport in the Large Helical Device (LHD) stellarator. It shows that the neoclassical impurity transport can be strongly affected by \(\tilde{\Phi}\). The central numerical tool used is the \(\delta f\) particle in cell (PIC) Monte Carlo code EUTERPE. The \(\tilde{\Phi}\) used in the calculations is provided by the neoclassical code GSRAKE. The possibility of obtaining a more general \(\tilde{\Phi}\) self-consistently with EUTERPE is also addressed and a preliminary calculation is presented.
Plasma Phys. Control. Fusion 53, 115014 (2011) Calculations of the bootstrap current for the TJ-II stellarator are
presented. DKES and NEO-MC codes are employed; the latter has allowed, for the
first ...time, the precise computation of the bootstrap transport coefficient in
the long mean free path regime of this device. The low error bars allow a
precise convolution of the monoenergetic coefficients, which is confirmed by
error analysis. The radial profile of the bootstrap current is presented for
the first time for the 100_44_64 configuration of TJ-II for three different
collisionality regimes. The bootstrap coefficient is then compared to that of
other configurations of TJ-II regularly operated. The results show qualitative
agreement with toroidal current measurements; precise comparison with real
discharges is ongoing.
Electron cyclotron resonance heating (ECRH) at the W7-AS stellarator is performed two systems of comparable heating power at 70 GHz (0.8 MW, 3 s) and 140 GHz (0.9 MW, 0.4 s). Experiments with 140 GHz ...open a new parameter window with high density operation up to 1.1 × 10
20 m
−3. H mode transitions were observed in high density discharges at 2.5 T and at lower density at 1.25 T. The operational window for the stellarator H mode with emphasis on the density and power threshold and the influence of gas puffing on the H transitions are discussed. Perturbation experiments with modulated ECRH power were performed to determine the heat transport and the power deposition profile. Density control is achieved in combined heating with neutral beam injection (NBI) despite the beam particle fuelling, whereas with NBI alone a steady density rise is observed. The impact of combined heating on the impurity confinement was investigated. Electron cyclotron current drive (ECCD) was studied in different magnetic field configurations and the influence of trapped particles on the ECCD efficiency was examined experimentally and compared with theory.
Study objective: To compare information contained in standard out-of-hospital trauma triage criteria and standard criteria plus advanced emergency medical technician (EMT) injury severity perception ...for determination of patient need for trauma center evaluation.
Design: Prospective, observational cohort analysis of trauma triage by advanced EMTs.
Participants: Out-of-hospital, geographically stratified statewide sample of patients injured in Oregon.
Results: Advanced EMTs provided patient information on demographics, physiologic parameters, injury anatomy and mechanism, premorbid conditions, EMT injury severity perception, and trauma system entry status. A four-point scale was used to grade the injury severity perception. Need for trauma center evaluation was defined as major surgery within 6 hours of hospital arrival, admission to the ICU, death in the hospital, or Injury Severity Scale score of 16 or more. The relative triage information gain with injury severity perception was assessed by use of logistic regression, tree-based models, and receiver operating characteristic (ROC) curves. Of 1,063 patients, 307 (28.9%) warranted trauma center evaluation. With logistic regression modeling, the following standard triage parameters were associated (
P<.05) with the need for trauma center evaluation after inclusion of injury severity perception: systolic blood pressure less than 90 mm Hg, abnormal respiratory rate (less than 10 or more than 29), Glasgow Coma Scale score less than 13, penetrating injury (midthigh to head), two or more obvious proximal long-bone fractures, and fall of more than 20 feet. The two largest injury severity perception categories had the greatest odds ratios (20:1 and 167:1). ROC curve areas improved with injury severity perception (.88 versus .83 without;
P<.0001).
Conclusion: Standard out-of-hospital triage criteria benefit from inclusion of advanced EMT injury severity perception information. Simmons E, Hedges JR, Irwin L, Maassberg W, Kirkwood HA Jr: Paramedic injury severity perception can aid trauma triage.
Ann Emerg Med October 1995;26:461-468.
This work surveys the main results concerning the effects of the rotational transform, its low order rational values and its shear on the confining properties of low shear devices. It is meant to ...promote further studies aimed at clarifying their role in future, reactor grade, devices. 1-D transport studies are encouraged as the effects of rotational transform on confinement appear to be of local nature. Low order rational values of the rotational transform are associated with both degraded and improved confinement, being the magnetic shear a plausible cause for the difference. Very small shear values are enough to avoid deletereous effects of the low order rationals in high rotational transform discharges, but further experiments are needed to elucidate whether there is a threshold shear that depends on the rotational transform itself.
PDF
