3,907 research outputs found
Simulation of Beam-Beam Effects and Tevatron Experience
Effects of electromagnetic interactions of colliding bunches in the Tevatron
had a variety of manifestations in beam dynamics presenting vast opportunities
for development of simulation models and tools. In this paper the computer code
for simulation of weak-strong beam-beam effects in hadron colliders is
described. We report the collider operational experience relevant to beam-beam
interactions, explain major effects limiting the collider performance and
compare results of observations and measurements with simulations.Comment: 23 pages, 17 figure
Transient Cherenkov radiation from an inhomogeneous string excited by an ultrashort laser pulse at superluminal velocity
An optical response of one-dimensional string made of dipoles with a
periodically varying density excited by a spot of light moving along the string
at the superluminal (sub-luminal) velocity is theoretically studied. The
Cherenkov radiation in such system is rather unusual, possessing both transient
and resonant character. We show that under certain conditions, in addition to
the resonant Cherenkov peak another Doppler-like frequency appears in the
radiation spectrum. Both linear (small-signal) and nonlinear regimes as well as
different string topologies are considered.Comment: accepted to Phys. Rev.
Modeling of operating history of the research nuclear reactor
The results of simulation of the IRT-T reactor operation history from 2012 to 2014 are presented. Calculations are performed using continuous energy Monte Carlo code MCU-PTR. Comparison is made between calculation and experimental data for the critical reactor
Size confinement effect in graphene grown on 6H-SiC (0001) substrate
We have observed the energy structure in the density of occupied states of
graphene grown on n-type 6H-SiC (0001). The structure revealed with
photoelectron spectroscopy is described by creation of the quantum well states
whose number and the energy position (E1 = 0.3 eV, E2 = 1.2 eV, E3 = 2.6 eV )
coincide with the calculated ones for deep (V = 2.9 eV) and narrow (d = 2.15 A)
quantum well formed by potential relief of the valence bands in the structure
graphene/n-SiC. We believe that the quantum well states should be formed also
in graphene on dielectric and in suspended graphene.Comment: 7 pages, 4 figure
Hadamard and Vandermonde determinants and Bernoulli-Euler-Lagrange-Aitken-Nikiporets type numerical method for roots of polynomials
In the article we develop Euler-Lagrange method and calculate all the roots
of an arbitrary complex polynomial on the base of calculation (similar
to the Bernoulli-Aitken-Nikiporets methods) of the limits of ratios of Hadamard
determinants built by means of coefficients of expansions into Taylor and
Laurent series of the function~.Comment: 11 page
Electrostatic Patch Effect in Cylindrical Geometry. I. Potential and Energy between Slightly Non-Coaxial Cylinders
We study the effect of any uneven voltage distribution on two close
cylindrical conductors with parallel axes that are slightly shifted in the
radial and by any length in the axial direction. The investigation is
especially motivated by certain precision measurements, such as the Satellite
Test of the Equivalence Principle (STEP). By energy conservation, the force can
be found as the energy gradient in the vector of the shift, which requires
determining potential distribution and energy in the gap. The boundary value
problem for the potential is solved, and energy is thus found to the second
order in the small transverse shift, and to lowest order in the gap to cylinder
radius ratio. The energy consists of three parts: the usual capacitor part due
to the uniform potential difference, the one coming from the interaction
between the voltage patches and the uniform voltage difference, and the energy
of patch interaction, entirely independent of the uniform voltage. Patch effect
forces and torques in the cylindrical configuration are derived and analyzed in
the next two parts of this work.Comment: 26 pages, 1 Figure. Submitted to Classical and Quantum Gravit
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Measurement and correction of the 3rd order resonance in the Tevatron
At Fermilab Tevatron BPM system has been recently upgraded resulting in much better accuracy of beam position measurements and improvements of data acquisition for turn-by-turn measurements. That allows one to record the beam position at each turn for 8000 turns for all BPMs (118 in each plane) with accuracy of about 10-20 ìm. In the last decade a harmonic analysis tool has been developed at CERN that allows relating each FFT line derived from the BPM data with a particular non-linear resonance in the machine. In fact, one can even detect the longitudinal position of the sources of these resonances. Experiments have been performed at the Tevatron in which beams have been kicked to various amplitudes to analyze the 3rd order resonance. It was possible to address this rather large resonance to some regular machine sextupoles. An alternative sextupole scheme allowed the suppression of this resonance by a good factor of 2. Lastly, the experimental data are compared with model calculations
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