174 research outputs found
Uni-layer magnets: a new concept for LTS and HTS based superconducting magnets
A novel geometrical configuration to form a magnetic field perpendicular to
an aperture, created by an asymmetric current distribution, within a single
layer, and using a continuous ideal current line, named the uni-layer magnet,
is here presented. The idea is compared to existing concepts in superconducting
magnets, namely, the sector magnet, stress managed
and canted . The uni-layer magnet allows for a
design with a continuous unit length (no layer jump), and an increased minimum
bending radius of the conductor in relation to traditional and
canted designs. The specific characteristics of the uni-layer
design are especially advantageous for strain-sensitive and prone to winding
degradation high-temperature superconductors, in very high field accelerator
magnet applications, in which, high efficiency in the use of conductor, and a
small aperture are required. The advantages with regard to the design and
fabrication of uni-layer magnets in relation to other concepts are also
discussed.Comment: 17 pages, submitted to IOP's Superconductor Science and Technology
Journal (SuST
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Finite Element Model of Training in the superconducting quadrupole magnet SQ02
This paper describes the use of 3D finite element models to study training in superconducting magnets. The simulations are used to examine coil displacements when the electromagnetic forces are cycled, and compute the frictional energy released during conductor motion with the resulting temperature rise. A computed training curve is then presented and discussed. The results from the numerical computations are compared with test results of the Nb{sub 3}Sn racetrack quadrupole magnet SQ02
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LIMITS OF Nb3Sn ACCELERATOR MAGNETS
Pushing accelerator magnets beyond 10 T holds a promise of future upgrades to machines like the Tevatron at Fermilab and the LHC at CERN. Exceeding the current density limits of NbTi superconductor, Nb{sub 3}Sn is at present the only practical superconductor capable of generating fields beyond 10 T. Several Nb{sub 3}Sn pilot magnets, with fields as high as 16 T, have been built and tested, paving the way for future attempts at fields approaching 20 T. High current density conductor is required to generate high fields with reduced conductor volume. However this significantly increases the Lorentz force and stress. Future designs of coils and structures will require managing stresses of several 100's of MPa and forces of 10's of MN/m. The combined engineering requirements on size and cost of accelerator magnets will involve magnet technology that diverges from the one currently used with NbTi conductor. In this paper we shall address how far the engineering of high field magnets can be pushed, and what are the issues and limitations before such magnets can be used in particle accelerators
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TowardsComputing Ratcheting and Training in Superconducting Magnets
The Superconducting Magnet Group at Lawrence Berkeley National Laboratory (LBNL) has been developing 3D finite element models to predict the behavior of high field Nb{sub 3}Sn superconducting magnets. The models track the coil response during assembly, cool-down, and excitation, with particular interest on displacements when frictional forces arise. As Lorentz forces were cycled, irreversible displacements were computed and compared with strain gauge measurements. Additional analysis was done on the local frictional energy released during magnet excitation, and the resulting temperature rise. Magnet quenching and training was correlated to the level of energy release during such mechanical displacements under frictional forces. We report in this paper the computational results of the ratcheting process, the impact of friction, and the path-dependent energy release leading to a computed magnet training curve
Is autopsy tissue a valid control for epilepsy surgery tissue in microRNA studies?
MicroRNAs (miRNAs) are differentially expressed in the brain under pathologic conditions
and may therefore represent both therapeutic targets and diagnostic or prognostic
biomarkers for neurologic diseases, including epilepsy. In fact, miRNA expression
profiles have been investigated in the hippocampi of patients with epilepsy in comparison
with control, nonepileptic cases. Unfortunately, the interpretation of these data is
difficult because surgically resected epileptic tissue is generally compared with control
tissue obtained from autopsies. To challenge the validity of this approach, we performed
an miRNA microarray on the laser microdissected granule cell layer of the
human hippocampus obtained from surgical samples of patients with epilepsy, autoptic
nonepileptic controls, and patients with autoptic epilepsy, using the latter as internal
control. Unfortunately, it is extremely difficult to collect autopsy material from
documented epilepsy individuals who died of non–epilepsy-related causes—we found
only two such cases. However, hierarchical clustering of all samples showed that those
obtained from autopsies of patients with epilepsy segregated with the other autoptic
samples (controls) and not with the bioptic tissues from the surgery patients, suggesting
that the origin of the tissue (surgery or autopsy) may be prevalent over the underlying
pathology (epilepsy or not epilepsy). Even taking into account the limitations due
to the small number of cases, this observation arises concerns on the use of autopsy tissue
as control for this kind of studies
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Design of Nb3Sn Coils for LARP Long Magnets
The LHC Accelerator Research Program (LARP) has a primary goal to develop, assemble, and test full size Nb{sub 3}Sn quadrupole magnet models for a luminosity upgrade of the Large Hadron Collider (LHC). A major milestone in this development is to assemble and test, by the end of 2009, two 4 m-long quadrupole cold masses, which will be the first Nb{sub 3}Sn accelerator magnet models approaching the length of real accelerator magnets. The design is based on the LARP Technological Quadrupoles (TQ), under development at FNAL and LBNL, with gradient higher than 200 T/m and aperture of 90 mm. The mechanical design will be chosen between two designs presently explored for the TQs: traditional collars and Al-shell based design (preloaded by bladders and keys). The fabrication of the first long quadrupole model is expected to start in the last quarter of 2007. Meanwhile the fabrication of 4 m-long racetrack coils started this year at BNL. These coils will be tested in an Al-shell based supporting structure developed at LBNL. Several challenges have to be addressed for the successful fabrication of long Nb{sub 3}Sn coils. This paper presents these challenges with comments and solutions adopted or under study for these magnets. The coil design of these magnets, including conductor and insulation features, and quench protection studies are also presented
Development and demonstration of next generation technology for Nb_3Sn accelerator magnets with lower cost, improved performance uniformity, and higher operating point in the 12-14 T range
The scope of the proposal outlined in this white paper is the development and
demonstration of the technology needed for next generation of Nb_3Sn
accelerator magnets in the 12-14 T range. The main goal is to cut magnet
cold-mass cost by a factor 2 or higher with respect to the Nb_3Sn magnets
produced by the US Accelerator Upgrade Project (AUP) for the High-Luminosity
Large Hadron Collider (HL-LHC). This goal will be achieved by significant
reduction of labor hours, higher operating point, and improved performance
uniformity. A key factor will be automation that will be achieved through
industry involvement and benefitting from the experience gained in US national
laboratories through the production of the AUP magnets. This partnership will
enable the development of a technology that will be easily transferable to
industry for mid- and large-scale production of Nb_3Sn accelerator magnets in
the 12-14 T range. This step is essential to enable next generation of
colliders such as the FNAL-proposed Muon Collider, FCC and other HEP hadron
colliders.
This is a Directed R&D where direction is given by the field range and
industry involvement for high-automation and industry-ready technology. The
plan includes ten milestones, to be achieved in 6-8 years at the cost of 5-7
$M/year.Comment: White Paper for Snowmass 2022, 8 pages, 2 tables, 1 figur
Non-coding RNAs change their expression profile after Retinoid induced differentiation of the promyelocytic cell line NB4
<p>Abstract</p> <p>Background</p> <p>The importance of non-coding RNAs (ncRNAs) as fine regulators of eukaryotic gene expression has emerged by several studies focusing on microRNAs (miRNAs). miRNAs represent a newly discovered family of non coding-RNAs. They are thought to be crucial players of human hematopoiesis and related tumorigenesis and to represent a potential tool to detect the early stages of cancer. More recently, the expression regulation of numerous long ncRNAs has been linked to cell growth, differentiation and cancer although the molecular mechanism of their function is still unknown.</p> <p>NB4 cells are promyelocytic cells that can be induced to differentiation upon retinoic acid (ATRA) treatment and represent a feasible model to study changes of non coding RNAs expression between cancer cells and their terminally differentiated counterpart.</p> <p>Findings</p> <p>we screened, by microarray analysis, the expression of 243 miRNAs and 492 human genes transcribing for putative long ncRNAs different from miRNAs in NB4 cells before and after ATRA induced differentiation. Our data show that 8 miRNAs, and 58 long ncRNAs were deregulated by ATRA induced NB4 differentiation.</p> <p>Conclusion</p> <p>our data suggest that ATRA-induced differentiation lead to deregulation of a large number of the ncRNAs that can play regulatory roles in both tumorigenesis and differentiation.</p
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RRP Nb3Sn strand studies for LARP
The Nb{sub 3}Sn strand chosen for the next step in the magnet R&D of the U.S. LHC Accelerator Research Program is the 54/61 sub-element Restacked Rod Process by Oxford Instruments, Superconducting Technology. To ensure that the 0.7 mm RRP strands to be used in the upcoming LARP magnets are suitable, extensive studies were performed. Measurements included the critical current, {sub e}, using the voltage-current (V-I) method, the stability current, I{sub S}, as the minimal quench current obtained with the voltage-field (V-H) method, and RRR. Magnetization was measured at low and high fields to determine the effective filament size and to detect flux jumps. Effects of heat treatment temperature and durations on I{sub e} and I{sub S} were also studied. Using strand billet qualification and tests of strands extracted from cables, the short sample limits of magnet performance were obtained. The details and the results of this investigation are herein described
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