1,484 research outputs found
Low energy chaos in the Fermi-Pasta-Ulam problem
A possibility that in the FPU problem the critical energy for chaos goes to
zero with the increase of the number of particles in the chain is discussed.
The distribution for long linear waves in this regime is found and an estimate
for new border of transition to energy equipartition is given.Comment: revtex, 12 pages, 5 figures, submitted to Nonlinearit
Asymptotic Statistics of Poincar\'e Recurrences in Hamiltonian Systems with Divided Phase Space
By different methods we show that for dynamical chaos in the standard map
with critical golden curve the Poincar\'e recurrences P(\tau) and correlations
C(\tau) asymptotically decay in time as P ~ C/\tau ~ 1/\tau^3. It is also
explained why this asymptotic behavior starts only at very large times. We
argue that the same exponent p=3 should be also valid for a general chaos
border.Comment: revtex, 4 pages, 3 ps-figure
An Exact Formula to Describe the Amplification Process in a Photomultiplier Tube
An analytical function is derived that exactly describes the amplification
process due to a series of discrete, Poisson-like amplifications like those in
a photo multiplier tube (PMT). A numerical recipe is provided that implements
this function as a computer program. It is shown how the program can be used as
the core-element of a faster, simplified routine to fit PMT spectra with high
efficiency. The functionality of the method is demonstrated by fitting both,
Monte Carlo generated and measured PMT spectra.Comment: 12 pages, 5 figures, with cut-and-paste FORTRAN implementatio
Multianode Photo Multiplier Tubes as Photo Detectors for Ring Imaging Cherenkov Detectors
The 64-channel Multianode Photo Multiplier (MaPMT) has been evaluated as a
candidate for the LHCb Ring Imaging Cherenkov (RICH) photo detectors. We
present result from data taken with a 3x3 array of closely packed MaPMTs
mounted onto the RICH 1 prototype vessel, exposed to charged particle beams at
CERN, and read out at LHC speed. Using a LED light source, we have performed
spatial light scans to study the light collection efficiency of the MaPMTs We
have also measured the performance of the MaPMTs as a function of the applied
high voltage. Different dynode resistor chains have been used to study the
tubes at low gains. In addition, we have studied the behaviour of the MaPMT in
magnetic fields.Comment: 5 pages, 6 figures, 8 .eps files, RICH2002 conference, Pylo
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