6,796 research outputs found
Continuation of the mini-technology development center program in Barrow, Madison, and Jackson counties
Issued as Quarterly reports, nos. 1-3, and Final reports, nos. 1-2, Project no. L-30-812(subproject is B-562
Establishment of a mini-advanced technology development center
Issued as Quarterly reports no. [1-3] and Final report, Project no. L-30-802 (subproject is B-558/P.D. Loveless
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
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
Optimizing Neutron Yield for Active Interrogation
Neutrons are commonly used for many applications, including active interrogation and cancer therapy. One critical aspect for active interrogation efficiency is neutron yield, which is more important for successful resolution than the energy spectrum. The typical approach for improving neutron yield entails producing more neutrons, which has motivated multiple studies using the interaction of increasingly more powerful tabletop lasers with plastic targets to generate protons or deuterons that are absorbed by another target to create neutrons [1]. Alternatively, one may use lenses to focus the neutrons to increase yield rather than simply generating more neutrons with more powerful lasers [2]. Assessing either approach requires a comprehensive model simulating neutron generation and transport to optimize the target material, system geometry, and neutron yield. A complete model from laser source to neutron generation is beyond the scope of the current study, so this project focuses on simulating the interaction of deuterons with typical target materials, such as lithium or beryllium. We use the neutron transport code Monte Carlo N-Particles (MCNP), which applies the Monte Carlo method to track particles [3]. The simulations accurately reflected experimental results from several groups [4]. Future analyses will assess improvements in neutron yield and directionality through strategically incorporating neutron lenses
Measurement of the CMS Magnetic Field
The measurement of the magnetic field in the tracking volume inside the
superconducting coil of the Compact Muon Solenoid (CMS) detector under
construction at CERN is done with a fieldmapper designed and produced at
Fermilab. The fieldmapper uses 10 3-D B-sensors (Hall probes) developed at
NIKHEF and calibrated at CERN to precision 0.05% for a nominal 4 T field. The
precise fieldmapper measurements are done in 33840 points inside a cylinder of
1.724 m radius and 7 m long at central fields of 2, 3, 3.5, 3.8, and 4 T. Three
components of the magnetic flux density at the CMS coil maximum excitation and
the remanent fields on the steel-air interface after discharge of the coil are
measured in check-points with 95 3-D B-sensors located near the magnetic flux
return yoke elements. Voltages induced in 22 flux-loops made of 405-turn
installed on selected segments of the yoke are sampled online during the entire
fast discharge (190 s time-constant) of the CMS coil 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. The results of the measurements
made at 4 T are reported and compared with a three-dimensional model of the CMS
magnet system calculated with TOSCA.Comment: 4 pages, 5 figures, 15 reference
Use of high throughput sequencing to observe genome dynamics at a single cell level
With the development of high throughput sequencing technology, it becomes
possible to directly analyze mutation distribution in a genome-wide fashion,
dissociating mutation rate measurements from the traditional underlying
assumptions. Here, we sequenced several genomes of Escherichia coli from
colonies obtained after chemical mutagenesis and observed a strikingly
nonrandom distribution of the induced mutations. These include long stretches
of exclusively G to A or C to T transitions along the genome and orders of
magnitude intra- and inter-genomic differences in mutation density. Whereas
most of these observations can be explained by the known features of enzymatic
processes, the others could reflect stochasticity in the molecular processes at
the single-cell level. Our results demonstrate how analysis of the molecular
records left in the genomes of the descendants of an individual mutagenized
cell allows for genome-scale observations of fixation and segregation of
mutations, as well as recombination events, in the single genome of their
progenitor.Comment: 22 pages, 9 figures (including 5 supplementary), one tabl
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Science career aspiration and science capital in China and UK: a comparative study using PISA data
The concept of science capital has a growing influence in science education research for understanding young people’s science trajectories. Popularised in the UK, this paper aims to extend and evaluate the applicability of science capital in the context of China by drawing on PISA2015. More specifically, we make use of existing items in the PISA2015 survey as a proxy for operationalising the construct of science capital to explore the science career aspirations and attainments of 15-year-old Chinese and UK students (n=23,998). Our findings indicate that science capital has more explanatory power for understanding UK students’ science career aspirations than for Chinese students, where science attainment seems most important. We raise the potential challenge for Chinese students to convert their science capital into scientific self-efficacy and science career aspirations as we highlight the importance of recognising cultural and national differences in operationalising science capital
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