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- Litaudon, X., et al.
(författare)
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Development of steady-state scenarios compatible with ITER-like wall conditions
- 2007
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Ingår i: Plasma Physics and Controlled Fusion. - 0741-3335 .- 1361-6587. ; 49:12B, s. B529-B550
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Tidskriftsartikel (refereegranskat)abstract
- A key issue for steady-state tokamak operation is to determine the edge conditions that are compatible both with good core confinement and with the power handling and plasma exhaust capabilities of the plasma facing components (PFCs) and divertor systems. A quantitative response to this open question will provide a robust scientific basis for reliable extrapolation of present regimes to an ITER compatible steady-state scenario. In this context, the JET programme addressing steady-state operation is focused on the development of non-inductive, high confinement plasmas with the constraints imposed by the PFCs. A new beryllium main chamber wall and tungsten divertor together with an upgrade of the heating/fuelling capability are currently in preparation at JET. Operation at higher power with this ITER-like wall will impose new constraints on non-inductive scenarios. Recent experiments have focused on the preparation for this new phase of JET operation. In this paper, progress in the development of advanced tokamak (AT) scenarios at JET is reviewed keeping this long-term objective in mind. The approach has consisted of addressing various critical issues separately during the 2006-2007 campaigns with a view to full scenario integration when the JET upgrades are complete. Regimes with internal transport barriers (ITBs) have been developed at q(95) similar to 5 and high triangularity, 3 (relevant to the ITER steady-state demonstration) by applying more than 30 MW of additional heating power reaching beta(N) similar to 2 at B(o) similar to 3.1 T. Operating at higher 6 has allowed the edge pedestal and core densities to be increased pushing the ion temperature closer to that of the electrons. Although not yet fully integrated into a performance enhancing ITB scenario, Neon seeding has been successfully explored to increase the radiated power fraction (up to 60%), providing significant reduction of target tile power fluxes (and hence temperatures) and mitigation of edge localized mode (ELM) activity. At reduced toroidal magnetic field strength, high beta(N) regimes have been achieved and q-profile optimization investigated for use in steady-state scenarios. Values of beta(N) above the 'no-wall magnetohydrodynamic limit' (beta(N) similar to 3.0) have been sustained for a resistive current diffusion time in high-delta configurations (at 1.2 MA/1.8 T). In this scenario, ELM activity has been mitigated by applying magnetic perturbations using error field correction coils to provide ergodization of the magnetic field at the plasma edge. In a highly shaped, quasi-double null X-point configuration, ITBs have been generated on the ion heat transport channel and combined with 'grassy' ELMs with similar to 30 MW of applied heating power (at 1.2 MA/2.7 T, q(95) similar to 7). Advanced algorithms and system identification procedures have been developed with a view to developing simultaneously temperature and q-profile control in real-time. These techniques have so far been applied to the control of the q-profile evolution in JET AT scenarios.
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- Farinelli, Ugo, et al.
(författare)
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"White and Green": Comparison of market-based instruments to promote energy efficiency
- 2005
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Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526. ; 13:10-11, s. 1015-1026
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Tidskriftsartikel (refereegranskat)abstract
- The "White and Green'' project completed under the EU SAVE Programme reviewed policies and measures to promote energy efficiency, which involved analysing the experience with instruments that are already implemented, and assessing innovative instruments that are proposed. In particular, the practicability of using ''White Certificates" energy efficiency) along the same lines as "Green Certificates" (renewable energy) was explored. Several of the policies. and measures, were simulated using technical-economic model of the MARKAL family. The results show that by 2020 it is possible to increase energy effiency by 15% at no cost without taking externalities into account. If externalities are considered, an increase of 30-35% with respect to the business-as-usual scenario is justified. The wealth of information obtained through the models and analysis provides a set of recommendations for policy-makers including: (1) the need for closer co-ordination between energy policies and environmental and climate policies; (2) the opportunity to establish more ambitious targets for energy efficiency; (3) the scope for increased EU co-ordination; (4) the extension of White Certificates to the medium and low energy-intensive industries; (5) the need to support White Certificates with accompanying actions, such as running information campaigns, promoting energy service companies, and, providing dedicated credit lines; (6) the need to develop similar instruments for transport and(7) the continuing need for energy research and development. (c) 2005 Published by Elsevier Ltd.
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- Farinelli, Ugo, et al.
(författare)
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"White and Green": Conclusions and Recommendations
- 2005
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The move towards the liberalisation of the energy markets in the whole world and the general shift from command-and-control to market mechanisms bring forward new ways of stimulating initiatives to increase the efficiency in the final uses of energy and demand-side management. In the past, energy policies were implemented in most countries by direct action of the governments through state monopolies, prescriptive legislation and in some cases incentives. With the progressive advent of liberalisation of the energy market and privatisation of state companies, the emphasis has shifted toward a regulation of the market that introduces economic corrections to take into account collective interests (such as externalities) and long-term objectives, which generally are not taken into due account by market forces in the absence of corrective measures. Policies based on incentives have also shown their limits. As they rarely use market forces effectively, the results obtained tend to have a higher cost than necessary and they may bring to a non-optimal development of new technology. Recently, the emergence of other problems - as shown by the power crisis in Sweden, the insufficient assurance given by the system to security of supply, some concerns about the quality of the service - have prompted a reconsideration of the regulation of the energy market. In this context, it is important to consider the ways in which the increase of the share of energy supplied by renewable sources and the increase in the efficiency of energy utilisation can be promoted. These two measures are considered the mainframe of any sustainable energy strategy and necessary steps to contrast the threats of climate change.
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- McCormick, S. D., et al.
(författare)
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Endocrine disruption of parr-smolt transformation and seawater tolerance of Atlantic salmon by 4-nonylphenol and 17 beta-estradiol
- 2005
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Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 142:3, s. 280-288
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Tidskriftsartikel (refereegranskat)abstract
- Sex steroids are known to interfere with the parr-smolt transformation of anadromous salmonids, and environmental estrogens such as nonylphenol have recently been implicated in reduced returns of Atlantic salmon in the wild. To determine the endocrine pathways by which estrogenic compounds affect smolt development and seawater tolerance, groups of juvenile Atlantic salmon were injected with one of five doses (0.5, 2, 10, 40 or 150 mu g g(-1)) of branched 4-nonylphenol (NP), 2 mu g g(-1) of 17 beta-estradiol (E-2), or vehicle, during the parr-smolt transformation in April, and the treatment was repeated 4, 8, and 11 days after the first injection. Plasma was obtained for biochemical analysis 7 and 14 days after initiation of treatment. After 14 days of treatment, additional fish from each treatment group were exposed to seawater for 24 h to assess salinity tolerance. The E, treatment and the highest NP dose resulted in lower salinity tolerance and decreased plasma insulin-like growth factor I (IGF-I) levels, along with elevated levels of plasma vitellogenin and total calcium. Plasma growth hormone levels were elevated at intermediate NP doses only, and not affected by E-2. After 7 days, plasma thyroxine (T-4) levels decreased in a strong, dose-dependent manner in response to nonylphenol, but after 14 days, this suppressive effect of T-4 occurred at the highest NP dose only. Similarly, E-2 decreased plasma T-4 levels at 7, but not 14 days. Plasma 3,3',5-triodo-L-thyronine was reduced by E-2 and the highest NP dose after 7 and 14 days of treatment. Plasma cortisol levels were not affected by any of the treatments. The results indicate that the parr-smolt transformation and salinity tolerance can be compromised by exposure to estrogenic compounds. Suppression of plasma IGF-I levels is a likely endocrine pathway for the effects of estrogenic compounds on hypo-osmoregulatory capacity, and the detrimental effects of E2 and NP on thyroid hormone levels are also likely to compromise the normal parr-smolt transformation of Atlantic salmon. Published by Elsevier Inc.
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- McCormick, S. D., et al.
(författare)
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Differential hormonal responses of Atlantic salmon parr and smolt to increased daylength: A possible developmental basis for smolting
- 2007
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486. ; 273:2-3, s. 337-344
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Tidskriftsartikel (refereegranskat)abstract
- In order to elucidate the developmental basis for smolting, Atlantic salmon, Salmo salar, parr (< 11.5 cm) and smolts (> 12.5 cm) were exposed to natural daylength (LDN) and increased daylength (LD16:8) starting in late February and gill Na+,K+–ATPase activity and circulating hormone levels monitored from January to May. Gill Na+,K+–ATPase activity remained low and constant in both groups of parr. In smolts, gill Na+,K+–ATPase began increasing in late February in both photoperiods, but was significantly higher in the LD16:8 group from March through April. Smolts exposed to LD16:8 had dramatically elevated plasma GH within one week of increased daylength that remained high through April, whereas plasma GH of LDN smolts increased steadily beginning in late February and peaking in late April. Plasma GH levels of parr remained low in spring and did not respond to increased daylength. Plasma insulin-like growth factor I (IGF-I) levels were substantially higher in smolts than parr in January. Plasma IGF-I levels of parr increased steadily from January to May, but there was no influence of increased daylength. In smolts, plasma IGF-I of LD16:8 fish initially decreased in early March then increased in late March and April, whereas plasma IGF-I of LDN smolts increased steadily to peak levels in early April. Plasma cortisol was low in parr throughout spring and did not differ between photoperiod treatments. Plasma cortisol of LD16:8 smolts increased in early March and remained elevated through April, whereas in LDN smolts plasma cortisol did not increase until early April and peaked in late April. Plasma thyroid hormones were generally higher in smolts than in parr, but there was no clear effect of increased daylength in parr or smolts. The greater capacity of the GH/IGF-I and cortisol axes to respond to increased daylength may be a critical factor underlying smolt development.
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| 11. |
- Zhu, L Y, et al.
(författare)
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Cross section measurements of charged pion photoproduction in hydrogen and deuterium from 1.1 to 5.5 GeV
- 2005
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 71:4
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Tidskriftsartikel (refereegranskat)abstract
- The differential cross sections for the gamma n ->pi(-)p and the gamma p ->pi(+)n processes were measured at Jefferson Lab. The photon energies ranged from 1.1 to 5.5 GeV, corresponding to center-of-mass energies from 1.7 to 3.4 GeV. The pion center-of-mass angles varied from 50(degrees) to 110(degrees). The pi(-) and pi(+) photoproduction data both exhibit a global scaling behavior at high energies and high transverse momenta, consistent with the constituent counting rule prediction and the existing pi(+) data. The data suggest possible substructure of the scaling behavior, which might be oscillations around the scaling value. The data show an enhancement in the scaled cross section at center-of-mass energy near 2.2 GeV. The differential cross section ratios [d sigma/dt(gamma n ->pi(-)p)/d sigma/dt(gamma p ->pi(+)n)] at high energies and high transverse momenta can be described by calculations based on one-hard-gluon-exchange diagrams.
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