959 research outputs found
Timing jitter in photon detection by straight superconducting nanowires: Effect of magnetic field and photon flux
We studied the effect of the external magnetic field and photon flux on
timing jitter in photon detection by straight superconducting NbN nanowires. At
two wavelengths 800 and 1560 nm, statistical distribution in the appearance
time of the photon count exhibits Gaussian shape at small times and exponential
tail at large times. The characteristic exponential time is larger for photons
with smaller energy and increases with external magnetic field while variations
in the Gaussian part of the distribution are less pronounced. Increasing photon
flux drives the nanowire from quantum detection mode to the bolometric mode
that averages out fluctuations of the total number of nonequilibrium electrons
created by the photon and drastically reduces jitter. The difference between
Gaussian parts of distributions for these two modes provides the measure for
the electron-number fluctuations. Corresponding standard deviation increases
with the photon energy. We show that the two-dimensional hot-spot detection
model explains qualitatively the effect of magnetic field
Scientific, Technical and Economic Committee for Fisheries. Review of scientific advice for 2012 - Consolidated advice on fish stocks of interest to the European Union (STECF-11-18)
Recommended from our members
Argonne National Laboratory Reports
Test data from an in-pile failure experiment of high-power LMFBR-type fuel pins in a simulated $3/s transient-overpower (TOP) accident are reported and analyzed. Major conclusions are that (1) a series of cladding ruptures during the 100-ms period preceding fuel release injected small bursts of fission gas into the flow stream; (2) gas release influenced subsequent cladding melting and fuel release (there were no measurable FCI's (fuel-coolant interactions), and all fuel motion observed by the hodoscope was very slow); (3) the predominant post-failure fuel motion appears to be radial swelling that left a spongy fuel crust on the holder wall; (4) less than 4 to 6 percent of the fuel moved axially out of the original fuel zone, and most of this froze within a 10-cm region above the original top of the fuel zone to form the outlet blockage. An inlet blockage approximately 1 cm long was formed and consisted of large interconnected void regions. Both blockages began just beyond the ends of the fuel pellets
Study of temporal pulse shape effects on W using simulations and laser heating
Transient heat pulses with triangular, square, and ELM-like temporal shapes are investigated in order to further understand how transient plasma instabilities will affect plasma facing components in tokamaks. A solution to the 1D heat equation for triangular pulses allows the peak surface temperature to be written analytically for arbitrary rise times. The solution as well as ANSYS simulations reveal that a positive ramp (maximum rise time) triangular pulse has a higher peak surface temperature by a factor of sqrt{2} compared to that from a negative ramp (rise time = 0) pulse shape with equal energy density, peak power, and pulse width. Translating the results to ITER, an ELM or disruption pulse with the shortest rise time is the most benign compared to other pulse shapes with the same peak heat flux and same energy density.</p
- …