6,584 research outputs found
Fractal Electromagnetic Showers
We study the self-similar structure of electromagnetic showers and introduce
the notion of the fractal dimension of a shower. Studies underway of showers in
various materials and at various energies are presented, and the range over
which the fractal scaling behaviour is observed is discussed. Applications to
fast shower simulations and identification, particularly in the context of
extensive air showers, are also discussed.Comment: Talk to be presented at the XI International Symposium on Very High
Energy Cosmic Ray Interaction
Formulation of additional observables for ENTREE
The S-band X and Y angles, SAMS, and TACAN range and bearing were incorporated into the ENTREE software for use by experimenters at LaRC for entry trajectory reconstruction purposes. Background discussions present the need for this added capability. Formulations for the various observables are presented. Both north-south and east-west antenna mounts were provided for in the S-band angle computations. Sub-vehicle terrain height variations are included in the SAMS model. Local magnetic variations were incorporated for the TACAN bearing computations. Observable formulations are discussed in detail along with the partial computations
Geosynchrotron radio emission from CORSIKA-simulated air showers
Simulations of radio emission from extensive air showers we have published so
far were performed with a Monte Carlo code using analytical parametrisations to
describe the spatial, temporal, energy and angular particle distributions in
the air shower. A new version of our simulation code, which replaces these
parametrisations with precise, multi-dimensional histograms derived from
per-shower CORSIKA simulations, is now available. The new code allows an
independent selection between parametrisation and histogram for each of the
relevant distributions, enabling us to study the changes arising from using a
more realistic air shower model in detail. We describe the new simulation
strategy, present some initial results and discuss the new possibilities.Comment: 6 pages, Proceedings of the ARENA2006 workshop, Newcastle, England;
to be published in Journal of Physics: Conference Series (JPCS
Minimal circuit for a flux-controlled Majorana qubit in a quantum spin-Hall insulator
We construct a minimal circuit, based on the top-transmon design, to rotate a
qubit formed out of four Majorana zero-modes at the edge of a two-dimensional
topological insulator. Unlike braiding operations, generic rotations have no
topological protection, but they do allow for a full characterization of the
coherence times of the Majorana qubit. The rotation is controlled by variation
of the flux through a pair of split Josephson junctions in a Cooper pair box,
without any need to adjust gate voltages. The Rabi oscillations of the Majorana
qubit can be monitored via oscillations in the resonance frequency of the
microwave cavity that encloses the Cooper pair box.Comment: Contribution for the proceedings of the Nobel Symposium on
topological insulators. 8 pages, 6 figure
Effects of disorder on Coulomb-assisted braiding of Majorana zero modes
Majorana zero modes in one-dimensional topological superconductors obey
non-Abelian braiding statistics. Braiding manipulations can be realized by
controlling Coulomb couplings in hybrid Majorana-transmon devices. However,
strong disorder may induce accidental Majorana modes, which are expected to
have detrimental effects on braiding statistics. Nevertheless, we show that the
Coulomb-assisted braiding protocol is efficiently realized also in the presence
of accidental modes. The errors occurring during the braiding cycle are small
if the couplings of the computational Majorana modes to the accidental ones are
much weaker than the maximum Coulomb coupling.Comment: 7 pages, 4 figures, this is the final, published versio
Monte Carlo simulations of air showers in atmospheric electric fields
The development of cosmic ray air showers can be influenced by atmospheric
electric fields. Under fair weather conditions these fields are small, but the
strong fields inside thunderstorms can have a significant effect on the
electromagnetic component of a shower. Understanding this effect is
particularly important for radio detection of air showers, since the radio
emission is produced by the shower electrons and positrons. We perform Monte
Carlo simulations to calculate the effects of different electric field
configurations on the shower development. We find that the electric field
becomes important for values of the order of 1 kV/cm. Not only can the energy
distribution of electrons and positrons change significantly for such field
strengths, it is also possible that runaway electron breakdown occurs at high
altitudes, which is an important effect in lightning initiation.Comment: 24 pages, 19 figures, accepted for publication in Astroparticle
Physic
Reconstruction of the 1st Space Shuttle (STS-1) entry trajectory
A discussion of the generation of the best estimate trajectory (BET) of the first Space Shuttle Orbiter entry flight is presented. The BET defines a time history of the state, attitude, and atmospheric relative parameters throughout the Shuttle entry from an altitude of approximately 183 km to rollout. The inertial parameters were estimated utilizing a weighted least squares batch filter algorithm. Spacecraft angular rate and acceleration data derived from the Inertial Measurement Unit were utilized to predict the state and attitude which was constrained in a weighted least squares process to fit external tracking data consisting of ground based S-band and C-band data. Refined spacecraft altitude and velocity during and post rollout were obtained by processing artificial altimeter and Doppler data. The BET generation process is discussed. Software and data interface discussions are included. The variables and coordinate systems utilized are defined. STS-1 mission peculiar inputs are summarized. A listing of the contents of the actual BET is provided
Using {\sc top-c} for Commodity Parallel Computing in Cosmic Ray Physics Simulations
{\sc top-c} (Task Oriented Parallel C) is a freely available package for
parallel computing. It is designed to be easy to learn and to have good
tolerance for the high latencies that are common in commodity networks of
computers. It has been successfully used in a wide range of examples, providing
linear speedup with the number of computers. A brief overview of {\sc top-c} is
provided, along with recent experience with cosmic ray physics simulations.Comment: Talk to be presented at the XI International Symposium on Very High
Energy Cosmic Ray Interaction
STS-8 bet results
The final Best Estimate Trajectory (BET) products, i.e., the reconstructed trajectory, the Extended BET, AEROBET and MMLE input files, generated for the eighth NASA Space Shuttle flight are documented. The reconstructed trajectory (inertial BET) for this Challenger flight, the first night landing is discussed. State (position, velocity, and attitude) plus three accelerometer scale factors were determined from fitting the Guam S-band data, seven C-band passes, and pseudo Doppler and altimeter during rollout on Runway 22. The anchor epoch utilized for the batch weighted-least-squares determination was Sept. 5, 1983 7h1m50s.0 (25310 GMT seconds). The spacecraft altitude at epoch is approx. 617 kft. IMU2 data were selected for the reconstruction
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