3,175 research outputs found
Progress in the Next Linear Collider Design
An electron/positron linear collider with a center-of-mass energy between 0.5
and 1 TeV would be an important complement to the physics program of the LHC in
the next decade. The Next Linear Collider (NLC) is being designed by a US
collaboration (FNAL, LBNL, LLNL, and SLAC) which is working closely with the
Japanese collaboration that is designing the Japanese Linear Collider (JLC).
The NLC main linacs are based on normal conducting 11 GHz rf. This paper will
discuss the technical difficulties encountered as well as the many changes that
have been made to the NLC design over the last year. These changes include
improvements to the X-band rf system as well as modifications to the injector
and the beam delivery system. They are based on new conceptual solutions as
well as results from the R&D programs which have exceeded initial
specifications. The net effect has been to reduce the length of the collider
from about 32 km to 25 km and to reduce the number of klystrons and modulators
by a factor of two. Together these lead to significant cost savings
Ground Motion Model of the SLAC Site
We present a ground motion model for the SLAC site. This model is based on
recent ground motion studies performed at SLAC as well as on historical data.
The model includes wave-like, diffusive and systematic types of motion. An
attempt is made to relate measurable secondary properties of the ground motion
with more basic characteristics such as the layered geological structure of the
surrounding earth, depth of the tunnel, etc. This model is an essential step in
evaluating sites for a future linear collider.Comment: submitted to XX International Linac Conferenc
Corpus callosum morphology in children on mid-sagittal MR imaging
Background: There is little published research on the wide variation of corpus callosum (CC) morphology in children, the assessment of which is made difficult by the complex alteration of its appearance in childhood. Objective: The purpose of our study was to assess the morphology of the CC on mid-sagittal T1- weighted magnetic resonance imaging (MRI) in a large number of children and correlate the findings with demographic and clinical criteria. Materials and methods: We reviewed all brain mid-sagittal T1-weighted MRI’s performed from July to December 2015 and obtained relevant demographic and clinical information from the accompanying report and laboratory system. The CC morphology was analysed by three radiologists and compared using cross tabulation with the chi-square test and ANOVA. Interobserver correlation was assessed using Kappa coefficient of conformance. Results: 257 patients with mean age 72±60 months were included, 142 were male (55%). In abnormal MRI’s the CC was less likely to have an identifiable isthmus and was more likely to be convex, thin and have separation of the fornix insertion (all p<0.01). In young children (< 5 years) the CC was also less likely to have an identifiable isthmus (p=0.01) and was more likely to be convex (p=0.04) but the fornix was more likely to insert normally (p<0.01). Children with tuberous sclerosis had significantly thinner splenia (p=0.02). Conclusion: There is a distinct pathological appearance of the CC. The immature appearance of the corpus callosum can mirror this but is distinguished by normal insertion of the fornix and normal quantitative measurements. Splenial thinning in children with tuberous sclerosis warrants further investigation
NLC Luminosity as a Function of Beam Parameters
Realistic calculation of NLC luminosity has been performed using particle
tracking in DIMAD and beam-beam simulations in GUINEA-PIG code for various
values of beam emittance, energy and beta functions at the Interaction Point
(IP). Results of the simulations are compared with analytic luminosity
calculations. The optimum range of IP beta functions for high luminosity was
identified.Comment: 4 pages, 7 figure
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