19 research outputs found
Measurement of the Charged Multiplicities in b, c and Light Quark Events from Z0 Decays
Average charged multiplicities have been measured separately in , and
light quark () events from decays measured in the SLD experiment.
Impact parameters of charged tracks were used to select enriched samples of
and light quark events, and reconstructed charmed mesons were used to select
quark events. We measured the charged multiplicities:
,
, from
which we derived the differences between the total average charged
multiplicities of or quark events and light quark events: and . We compared
these measurements with those at lower center-of-mass energies and with
perturbative QCD predictions. These combined results are in agreement with the
QCD expectations and disfavor the hypothesis of flavor-independent
fragmentation.Comment: 19 pages LaTex, 4 EPS figures, to appear in Physics Letters
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Development of cost-effective Nb3Sn conductors for the next generation hadron colliders
Significant progress has been made in demonstrating that reliable, efficient high field dipole magnets can be made with Nb{sub 3}Sn superconductors. A key factor in determining whether these magnets will be a cost-effective solution for the next generation hadron collider is the conductor cost. Consequently, DOE initiated a conductor development program to demonstrate that Nb{sub 3}Sn can be improved to reach a cost/performance value of $1.50/kA-m at 12T, 4.2K. The first phase of this program was initiated in Jan 2000, with the goal of improving the key properties of interest for accelerator dipole magnets--high critical current density and low magnetization. New world record critical current densities have been reported recently, and it appears that significant potential exists for further improvement. Although new techniques for compensating for magnetization effects have reduced the requirements somewhat, techniques for lowering the effective filament size while maintaining these high Jc values are a program priority. The next phase of this program is focused on reducing the conductor cost through substitution of lower cost raw materials and through process improvements. The cost drivers for materials and fabrication have been identified, and projects are being initiated to demonstrate cost reductions
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Fast ramp superconductor for ohmic heating coils
The present study was conducted to consider practical 10,000 ampere conductor designs to meet the operating constraints for the ohmic heating coils of TNS and experimental Tokamak reactors. The conductor must simultaneously meet the requirements for mechanical support, cryostabilization, high overall winding current density, low mechanical and electrical losses, and mechanical and electrical integrity for cyclic pulsed operation for -7 T to +7 T in one second. A suggested winding is a set of nested tubes, each made up of a stack of pancake-wound bobbins. Each pancake is co-wound of a flat open superconductor braid, steel tape, and Kapton insulation. The strands of the braid consist of sectored copper regions separated by copper-nickel and surrounding a mixed-matrix copper, copper-nickel, and NbTi multifilament core. Strands 1.5 mm in diameter provide conservative cryostabilization at overall winding current densities adequate for the OH winding of an EPR-1 or TNS sized coil (approx.1500 amperes/cm/sup 2/). Eddy current and coupling losses are at acceptable levels, and hysteresis losses can be reduced within acceptable limits with 10 ..mu.. diameter filaments, providing the winding is graded, tube to tube. The basic conductor and winding concept can be extended to provide conductors of higher currents. A 2000 ampere model conductor has been fabricated from 0.94 mm diameter strands and tested in a reinforced pancake configuration. The measured maximum recovery current corresponds to a current density of 3500 amperes/cm/sup 2/ over the entire coil cross section
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Integrated composite conductor for the LCS program
The design of a 10 kA 8 T conductor intended for the LCS test program is presented. The interaction of mechanical, thermal, and electrical design requirements are emphasized in the selection of the basic conductor configuration. Evolution of the conductor design from its inception to the final manufactured configuration is traced. Details of the conductor configuration, a steel core about which composite rectangular superconducting elements are cabled, will be given. Using the parameters of this configuration, calculations of electrical loss from a 0.35 T/second and 0.15 T/second pulse are presented. Consideration of possible mechanical motion from the pulsed field is also discussed and analyzed