3,358 research outputs found
Overview of progress in European medium sized tokamaks towards an integrated plasma-edge/wall solution
Integrating the plasma core performance with an edge and scrape-off layer (SOL) that leads
to tolerable heat and particle loads on the wall is a major challenge. The new European
medium size tokamak task force (EU-MST) coordinates research on ASDEX Upgrade
(AUG), MAST and TCV. This multi-machine approach within EU-MST, covering a wide
parameter range, is instrumental to progress in the field, as ITER and DEMO core/pedestal
and SOL parameters are not achievable simultaneously in present day devices. A two prong
approach is adopted. On the one hand, scenarios with tolerable transient heat and particle
loads, including active edge localised mode (ELM) control are developed. On the other hand,
divertor solutions including advanced magnetic configurations are studied. Considerable
progress has been made on both approaches, in particular in the fields of: ELM control with
resonant magnetic perturbations (RMP), small ELM regimes, detachment onset and control,
as well as filamentary scrape-off-layer transport. For example full ELM suppression has now
been achieved on AUG at low collisionality with n = 2 RMP maintaining good confinement
HH(98,y2) 0.95. Advances have been made with respect to detachment onset and control.
Studies in advanced divertor configurations (Snowflake, Super-X and X-point target divertor)
shed new light on SOL physics. Cross field filamentary transport has been characterised in a
wide parameter regime on AUG, MAST and TCV progressing the theoretical and experimental
understanding crucial for predicting first wall loads in ITER and DEMO. Conditions in the
SOL also play a crucial role for ELM stability and access to small ELM regimes.European Commission (EUROfusion 633053
Simulation of Main Memory Database Recovery
In a main memory database (MMDB), the primary copy of the database may reside permanently in a volatile memory. When a system failure occurs, the database must be reloaded efficiently from archive memory into main memory. This paper presents four different reload schemes and the simulation models constructed to compare the algorithms. Simulation results indicate that the reload scheme based on freguency of data access gives the best overall performance in terms of transaction response time and system throughput.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
Radiotherapy in langerhans cell histiocytosis - a rare indication in a rare disease
Introduction: Langerhans Cell Histiocytosis (LCH) represents a rare benign disorder, previously designated as “Histiocytosis X”, “Type II Histiocytosis” or “Langerhans Cell Granulomatosis”. Clinical presentation includes osteolysis, ulcerations of skin and soft tissues but also involvement of the CNS is described. Because treatment concepts are not well defined the German Cooperative Group on Radiotherapy for Benign Diseases performed a retrospective analysis. Methods and material: Eight closely cooperating centres collected patients’ data of the past 45 years. As study endpoints disease free survival, recurrent disease, death and therapy related side effects were defined. Results: A total of 80 patients with histologically proven LCH were irradiated within the past 45 years. According to the LCH classification of Greenberger et al. 37 patients had stage Ia, 21 patients stage Ib, 13 patients stage II and 9 patients stage IIIb and the median age was 29 years. The median Follow up was 54 months (range 9–134 months). A total of 39 patients had a surgical intervention and 23 patients a chemotherapy regimen. Radiation treatment was carried out with a median total dose of 15 Gy (range 3–50.4 Gy). The median single fraction was 2 Gy (range 1.8-3 Gy). Overall, 77% patients achieved a complete remission and 12.5% achieved a partial remission. The long-term control rate reached 80%. Within an actuarial overall 5-year survival of 90% no radiogenic side and late effects ≥EORTC/RTOG II° were observed. Conclusion: In the present study a large collective of irradiated patients was analysed. Radiotherapy (RT) is a very effective and safe treatment option and even low RT doses show sufficient local control.<br
Precise Neutron Magnetic Form Factors
Precise data on the neutron magnetic form factor G_{mn} have been obtained
with measurements of the ratio of cross sections of D(e,e'n) and D(e,e'p) up to
momentum transfers of Q^2 = 0.9 (GeV/c)^2. Data with typical uncertainties of
1.5% are presented. These data allow for the first time to extract a precise
value of the magnetic radius of the neutron.Comment: 10 pages, 2 figures, submitted to Physics Letters
Solitary magnetic perturbations at the ELM onset
Edge localised modes (ELMs) allow maintaining sufficient purity of tokamak
H-mode plasmas and thus enable stationary H-mode. On the other hand in a future
device ELMs may cause divertor power flux densities far in excess of tolerable
material limits. The size of the energy loss per ELM is determined by
saturation effects in the non-linear phase of the ELM, which at present is
hardly understood. Solitary magnetic perturbations (SMPs) are identified as
dominant features in the radial magnetic fluctuations below 100kHz. They are
typically observed close (+-0.1ms) to the onset of pedestal erosion. SMPs are
field aligned structures rotating in the electron diamagnetic drift direction
with perpendicular velocities of about 10km/s. A comparison of perpendicular
velocities suggests that the perturbation evoking SMPs is located at or inside
the separatrix. Analysis of very pronounced examples showed that the number of
peaks per toroidal turn is 1 or 2, which is clearly lower than corresponding
numbers in linear stability calculations. In combination with strong peaking of
the magnetic signals this results in a solitary appearance resembling modes
like palm tree modes, edge snakes or outer modes. This behavior has been
quantified as solitariness and correlated to main plasma parameters. SMPs may
be considered as a signature of the non-linear ELM-phase originating at the
separatrix or further inside. Thus they provide a handle to investigate the
transition from linear to non-linear ELM phase. By comparison with data from
gas puff imaging processes in the non-linear phase at or inside the separatrix
and in the scrape-off-layer (SOL) can be correlated. A connection between the
passing of an SMP and the onset of radial filament propagation has been found.
Eventually the findings related to SMPs may contribute to a future quantitative
understanding of the non-linear ELM evolution.Comment: submitted to Nuclear Fusio
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