265 research outputs found
Measuring the Magnetic Flux Density in the CMS Steel Yoke
The Compact Muon Solenoid (CMS) is a general purpose detector, designed to
run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its
distinctive features include a 4 T superconducting solenoid with 6-m-diameter
by 12.5-m-length free bore, enclosed inside a 10000-ton return yoke made of
construction steel. The return yoke consists of five dodecagonal three-layered
barrel wheels and four end-cap disks at each end comprised of steel blocks up
to 620 mm thick, which serve as the absorber plates of the muon detection
system. Accurate characterization of the magnetic field everywhere in the CMS
detector is required. To measure the field in and around the steel, a system of
22 flux-loops and 82 3-D Hall sensors is installed on the return yoke blocks.
Fast discharges of the solenoid (190 s time-constant) made during the CMS
magnet surface commissioning test at the solenoid central fields of 2.64, 3.16,
3.68 and 4.01 T were used to induce voltages in the flux-loops. The voltages
are measured on-line and integrated off-line to obtain the magnetic flux in the
steel yoke close to the muon chambers at full excitations of the solenoid. The
3-D Hall sensors installed on the steel-air interfaces give supplementary
information on the components of magnetic field and permit to estimate the
remanent field in steel to be added to the magnetic flux density obtained by
the voltages integration. A TOSCA 3-D model of the CMS magnet is developed to
describe the magnetic field everywhere outside the tracking volume measured
with the field-mapping machine. The results of the measurements and
calculations are presented, compared and discussed.Comment: 9 pages, 7 figures, 16 references, presented at the III International
Conference on Superconductivity and Magnetism (ICSM-2012), Kumburgaz,
Istanbul, Turkey, 29 April - 4 May 201
Measuring the Magnetic Flux Density with Flux Loops and Hall Probes in the CMS Magnet Flux Return Yoke
The Compact Muon Solenoid (CMS) is a general purpose detector, designed to
run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its
distinctive features include a 4 T superconducting solenoid with 6-m-diameter
by 12.5-m-length free bore, enclosed inside a 10,000-ton return yoke made of
construction steel. The flux return yoke consists of five dodecagonal
three-layered barrel wheels and four end-cap disks at each end comprised of
steel blocks up to 620 mm thick, which serve as the absorber plates of the muon
detection system. To measure the field in and around the steel, a system of 22
flux loops and 82 3-D Hall sensors is installed on the return yoke blocks. A
TOSCA 3-D model of the CMS magnet is developed to describe the magnetic field
everywhere outside the tracking volume that was measured with the field-mapping
machine. The voltages induced in the flux loops by the magnetic flux changing
during the CMS magnet standard ramps down are measured with six 16-bit DAQ
modules. The off-line integration of the induced voltages reconstructs the
magnetic flux density in the yoke steel blocks at the operational magnet
current of 18.164 kA. The results of the flux loop measurements during three
magnet ramps down are presented and discussed.Comment: 3 pages, 6 figures, presented at the IEEE Nuclear Science Symposium
2016 (NSS) in Strasbourg, France on November 3, 2016. arXiv admin note: text
overlap with arXiv:1605.0877
Flux Loop Measurements of the Magnetic Flux Density in the CMS Magnet Yoke
The Compact Muon Solenoid (CMS) is a general purpose detector, designed to
run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its
distinctive features include a 4 T superconducting solenoid with 6-m-diameter
by 12.5-m-length free bore, enclosed inside a 10,000-ton return yoke made of
construction steel. The return yoke consists of five dodecagonal three-layered
barrel wheels and four end-cap disks at each end comprised of steel blocks up
to 620 mm thick, which serve as the absorber plates of the muon detection
system. To measure the field in and around the steel, a system of 22 flux loops
and 82 3-D Hall sensors is installed on the return yoke blocks. A TOSCA 3-D
model of the CMS magnet is developed to describe the magnetic field everywhere
outside the tracking volume measured with the field-mapping machine. The first
attempt is made to measure the magnetic flux density in the steel blocks of the
CMS magnet yoke using the standard magnet discharge with the current ramp down
speed of 1.5 A/s.Comment: 7 pages, 5 figures, presented at ISCM2016 - 5th International
Conference on Superconductivity and Magnetism on April 28, 2016 at Fethiye,
Turke
Developing the Technique of Measurements of Magnetic Field in the CMS Steel Yoke Elements With Flux-Loops and Hall Probes
Compact muon solenoid (CMS) is a general-purpose detector designed to run at
the highest luminosity at the CERN large hadron collider (LHC). Its distinctive
features include a 4 T superconducting solenoid with 6 m diameter by 12.5 m
long free bore, enclosed inside a 10000-ton return yoke made of construction
steel. Accurate characterization of the magnetic field everywhere in
theCMSdetector, including the large ferromagnetic parts of the yoke, is
required. To measure the field in and around ferromagnetic parts, a set of
flux-loops and Hall probe sensors will be installed on several of the steel
pieces. Fast discharges of the solenoid during system commissioning tests will
be used to induce voltages in the flux-loops that can be integrated to measure
the flux in the steel at full excitation of the solenoid. The Hall sensors will
give supplementary information on the axial magnetic field and permit
estimation of the remanent field in the steel after the fast discharge. An
experimental R&D program has been undertaken, using a test flux-loop, two Hall
sensors, and sample disks made from the same construction steel used for the
CMS magnet yoke. A sample disc, assembled with the test flux-loop and the Hall
sensors, was inserted between the pole tips of a dipole electromagnet equipped
with a computer-controlled power supply to measure the excitation of the steel
from full saturation to zero field. The results of the measurements are
presented and discussed.Comment: 6 pages, 8 figures, 6 reference
Pilot whales attracted to killer whales sounds : acoustically-mediated interspecific interactions in cetaceans
This study was mainly funded by three naval organisations: the US Office of Naval Research, the Norwegian Ministry of Defense and the Netherlands Ministry of Defense. In addition, WWF-Norway, TOTAL Foundation and the Foundation Bleustein-Blanchet also contributed financially. Authors are employed by government (Norwegian Defense Research Establishment), independent no-profit (Netherlands Organization for Applied Scientific Research and Kelp Marine Research), or academic (University of St. Andrews) research organisations. No authors are employed by naval organisations. The funders had no role in study design, data analysis, or preparation of the manuscript.In cetaceans’ communities, interactions between individuals of different species are often observed in the wild. Yet, due to methodological and technical challenges very little is known about the mediation of these interactions and their effect on cetaceans’ behavior. Killer whales (Orcinus orca) are a highly vocal species and can be both food competitors and potential predators of many other cetaceans. Thus, the interception of their vocalizations by unintended cetacean receivers may be particularly important in mediating interspecific interactions. To address this hypothesis, we conducted playbacks of killer whale vocalizations recorded during herring-feeding activity to free-ranging long-finned pilot whales (Globicephala melas). Using a multi-sensor tag, we were able to track the whales and to monitor changes of their movements and social behavior in response to the playbacks. We demonstrated that the playback of killer whale sounds to pilot whales induced a clear increase in group size and a strong attraction of the animals towards the sound source. These findings provide the first experimental evidence that the interception of heterospecific vocalizations can mediate interactions between different cetacean species in previously unrecognized ways.Publisher PDFPeer reviewe
Validation of the CMS Magnetic Field Map
The Compact Muon Solenoid (CMS) is a general purpose detector, designed to
run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its
distinctive features include a 4 T superconducting solenoid with 6-m-diameter
by 12.5-m-length free bore, enclosed inside a 10,000-ton return yoke made of
construction steel. The return yoke consists of five dodecagonal three-layered
barrel wheels and four end-cap disks at each end comprised of steel blocks up
to 620 mm thick, which serve as the absorber plates of the muon detection
system. To measure the field in and around the steel, a system of 22 flux loops
and 82 3-D Hall sensors is installed on the return yoke blocks. A TOSCA 3-D
model of the CMS magnet is developed to describe the magnetic field everywhere
outside the tracking volume measured with the field-mapping machine. The
magnetic field description is compared with the measurements and discussed.Comment: 7 pages, 5 figures, presented at 4th International Conference on
Superconductivity and Magnetism 2014, April 27 - May 2, 2014, Antalya,
Turkey. arXiv admin note: substantial text overlap with arXiv:1605.08778;
text overlap with arXiv:1212.165
3D Magnetic Analysis of the CMS Magnet
The CMS magnetic system consists of a super-conducting solenoid coil, 12.5 m
long and 6 m free bore diameter, and of an iron flux-return yoke, which
includes the central barrel, two end-caps and the ferromagnetic parts of the
hadronic forward calorimeter. The magnetic flux density in the center of the
solenoid is 4 T. To carry out the magnetic analysis of the CMS magnetic system,
several 3D models were developed to perform magnetic field and force
calculations using the Vector Fields code TOSCA. The analysis includes a study
of the general field behavior, the calculation of the forces on the coil
generated by small axial, radial displacements and angular tilts, the
calculation of the forces on the ferromagnetic parts, the calculation of the
fringe field outside the magnetic system, and a study of the field level in the
chimneys for the current leads and the cryogenic lines. A procedure to
reconstruct the field inside a cylindrical volume starting from the values of
the magnetic flux density on the cylinder surface is considered. Special
TOSCA-GEANT interface tools have being developed to input the calculated
magnetic field into the detector simulation package.Comment: 4 pages, 6 figures, 1 equation, 14 reference
Evolution of massive stars with new hydrodynamic wind models
Here we present evolutionary models for a set of massive stars, introducing a
new prescription for the mass-loss rate obtained from hydrodynamical
calculations in which the wind velocity profile, , and the
line-acceleration, , are obtained in a self consistently way.
Replacing mass-loss rates at the Main Sequence stage from the standard Vink's
formula by our new recipe, we generate a new set of evolutionary tracks for
and and metallicities
(Galactic), (LMC), and (SMC).
Our new derived formula for mass-loss rate predicts a dependence , where is not longer constant but dependent on the stellar
mass: ranging from when , to when
.
We found that models adopting the new recipe for retain more mass
during their evolution, which is expressed in larger radii and consequently
more luminous tracks over the Hertzsprung-Russell diagram. These differences
are more prominent for the cases of and 120 at
solar metallicity, where we found self-consistent tracks are dex
brighter and keep extra mass up to 20 , compared with the classical
models using the previous formulation for mass-loss rate.
Moreover, we observed remarkable differences for the evolution of the
radionuclide isotope Al in the core and the surface of the star. Since
are weaker than the commonly adopted values for evolutionary
tracks, self-consistent tracks predict a later modification in the abundance
number of Al in the stellar winds. This new behaviour could provide
useful information about the real contribution of this isotope from massive
stars to the Galactic interstellar medium.Comment: Accepted for publication in Astronomy & Astrophysic
Analysis of eddy current distributions in the CMS magnet yoke during the solenoid discharge
Flux loops have been installed on selected segments of the magnetic flux return yoke of the 4 T superconducting coil of the Compact Muon Solenoid (CMS) detector under construction at CERN. Voltages induced in the loops during discharge of the solenoid will be sampled online during the entire discharge and integrated offline to provide a measurement of the initial magnetic flux density in steel at the maximum field to an accuracy of a few percent. Although the discharge of the solenoid is rather slow (190 s time constant), the influence of eddy currents induced in the yoke elements should be estimated. The calculation of eddy currents is performed with Vector Fields' program ELEKTRA. The results of the calculations are reported.Flux loops have been installed on selected segments of the magnetic flux return yoke of the 4 T superconducting coil of the Compact Muon Solenoid (CMS) detector under construction at CERN. Voltages induced in the loops during discharge of the solenoid will be sampled online during the entire discharge and integrated offline to provide a measurement of the initial magnetic flux density in steel at the maximum field to an accuracy of a few percent. Although the discharge of the solenoid is rather slow (190 s time constant), the influence of eddy currents induced in the yoke elements should be estimated. The calculation of eddy currents is performed with Vector Fields' program ELEKTRA. The results of the calculations are reported
Disturbance-specific social responses in long-finned pilot whales, Globicephala melas
The study was funded by the US Office of Naval Research, The Netherlands Ministry of Defence, Norwegian Ministry of Defence and French Ministry of Defence. F.V., C.C., P.K., F.P.L. and P.M. were supported by one or two of these funders. P.T. received funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland). MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions.Social interactions among animals can influence their response to disturbance. We investigated responses of long-finned pilot whales to killer whale sound playbacks and two anthropogenic sources of disturbance: Tagging effort and naval sonar exposure. The acoustic scene and diving behaviour of tagged individuals were recorded along with the social behaviour of their groups. All three disturbance types resulted in larger group sizes, increasing social cohesion during disturbance. However, the nature and magnitude of other responses differed between disturbance types. Tagging effort resulted in a clear increase in synchrony and a tendency to reduce surface logging and to become silent (21% of cases), whereas pilot whales increased surface resting during sonar exposure. Killer whale sounds elicited increased calling rates and the aggregation of multiple groups, which approached the sound source together. This behaviour appears to represent a mobbing response, a likely adaptive social defence against predators or competitors. All observed response-Tactics would reduce risk of loss of group coordination, suggesting that, in social pilot whales, this could drive behavioural responses to disturbance. However, the behavioural means used to achieve social coordination depends upon other considerations, which are disturbance-specific.Publisher PDFPeer reviewe
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