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- Brunsell, Per, et al.
(författare)
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Initial results from the rebuilt EXTRAP T2R RFP device
- 2001
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Ingår i: Plasma Physics and Controlled Fusion. - BRISTOL. ENGLAND : IOP PUBLISHING LTD. - 0741-3335 .- 1361-6587. ; 43:11, s. 1457-1470
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Tidskriftsartikel (refereegranskat)abstract
- The EXTRAP T2R thin shell reversed-field pinch (RFP) device has recently resumed operation after a major rebuild including the replacement of the graphite armour with molybdenum limiters, a fourfold increase of the shell time constant, and the replacement of the helical coil used for the toroidal field with a conventional solenoid-type coil. Wall-conditioning using hydrogen glow discharge cleaning was instrumental for successful RFP operation. Carbon was permanently removed from the walls during the first week of operation. The initial results from RFP operation with relatively low plasma currents in the range I-p = 70-100 kA are reported. RFP discharges are sustained for more than three shell times. Significant improvements in plasma parameters are observed, compared to operation before the rebuild. There is a substantial reduction in the carbon impurity level. The electron density behaviour is more shot-to-shot reproducible. The typical density is n(e) = 0.5-1 x 10(19) m(-3). Monitors of H-alpha line radiation indicate that the plasma wall interaction is more toroidally symmetric and that there is less transient gas release from the wall. The minimum loop voltage is in the range V-t = 28-35 V, corresponding to a reduction by a factor of two to three compared to the value before the rebuild.
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- Corre, Y., et al.
(författare)
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Radiated power and impurity concentrations in the EXTRAP-T2R reversed-field pinch
- 2005
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Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; 71:5, s. 523-531
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Tidskriftsartikel (refereegranskat)abstract
- A numerical and experimental study of the impurity concentration and radiation in the EXTRAP-T2R device is reported. The experimental setup consists of an 8-chord bolometer system providing the plasma radiated power and a vacuum-ultraviolet spectrometer providing information on the plasma impurity content. The plasma emissivity profile as measured by the bolometric system is peaked in the plasma centre. A one dimensional Onion Skin Collisional-Radiative model (OSCR) has been developed to compute the density and radiation distributions of the main impurities. The observed centrally peaked emissivity profile can be reproduced by OSCR simulations only if finite particle confinement time and charge-exchange processes between plasma impurities and neutral hydrogen are taken into account. The neutral hydrogen density profile is computed with a recycling code. Simulations show that recycling on metal first wall such as in EXTRAP-T2R (stainless steel vacuum vessel and molybdenum limiters) is compatible with a rather high neutral hydrogen density in the plasma centre. Assuming an impurity concentration of 10% for oxygen and 3% for carbon compared with the electron density, the OSCR calculation including lines and continuum emission reproduces about 60% of the total radiated power with a similarly centrally peaked emmissivity profile. The centrally peaked emissivity profile is due to low ionisation stages and strongly radiating species in the plasma core, mainly O4+ (Be-like) and C3+ (Li-like).
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- Edlund, A, et al.
(författare)
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Clinical profile of delirium in patients treated for femoral neck fractures
- 1999
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Ingår i: Dementia and Geriatric Cognitive Disorders. - : S. Karger AG. - 1420-8008 .- 1421-9824. ; 10:5, s. 325-329
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Tidskriftsartikel (refereegranskat)abstract
- The incidence of delirium, its predisposing factors, clinical profile, associated symptoms and consequences were investigated in 54 consecutive patients, 19 men and 35 women, mean age 77.1 years, admitted to an 'ortho-geriatric unit' with femoral neck fractures. The incidence of postoperative delirium was 15/54 (27.8%) and a logistic regression model found that dementia and a prolonged waiting time for the operation increased the risk of postoperative delirium. Delirium during the night was most common but in 5 patients the delirium was worst in the morning. Patients with delirium suffered more anxiety, depressed mood, emotionalism, delusions and hallucinations. A larger proportion of patients with delirium could not return to their previous dwelling, and a larger proportion of delirious patients were either dead, wheelchair-bound or bedridden at the 6-month follow-up (p < 0.005). The conclusion is that delirium is common and has a serious impact on the outcome after hip fracture surgery.
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