Mean first passage time for fission potentials having structure

A schematic model of over-damped motion is presented which permits one to calculate the mean first passage time for nuclear fission. Its asymptotic value may exceed considerably the lifetime suggested by Kramers rate formula, which applies only to very special, favorable potentials and temperatures. The additional time obtained in the more general case is seen to allow for a considerable increment in the emission of light particles.Comment: 7 pages, LaTex, 7 postscript figures; Keywords: Decay rate, mean first passage tim

Controlling the quantum number distribution and yield of Rydberg states via the duration of the laser pulse

We show that the distribution of quantum numbers of Rydberg states does not only depend on the field strength and wavelength of the laser which the atom is exposed to, but that it also changes significantly with the duration of the laser pulse. We provide an intuitive explanation for the underlying mechanism and derive a scaling law for the position of the peak in the quantum number distribution on the pulse duration. The new analytic description for the electron's movement in the superposed laser and Coulomb field (applied in the study of quantum numbers) is then used to explain the decrease of the Rydberg yield with longer pulse durations. This description stands in contrast to the concepts that explained the decrease so far and also reveals that approximations which neglect Coulomb effects during propagation are not sufficient in cases such as this.Comment: 8 pages, 8 figure

Wave breaking and particle jets in intense inhomogeneous charged beams

This work analyzes the dynamics of inhomogeneous, magnetically focused high-intensity beams of charged particles. While for homogeneous beams the whole system oscillates with a single frequency, any inhomogeneity leads to propagating transverse density waves which eventually result in a singular density build up, causing wave breaking and jet formation. The theory presented in this paper allows to analytically calculate the time at which the wave breaking takes place. It also gives a good estimate of the time necessary for the beam to relax into the final stationary state consisting of a cold core surrounded by a halo of highly energetic particles.Comment: Accepted in Physics of Plasma Letter

Comparison of techniques to reconstruct VHE gamma-ray showers from multiple stereoscopic Cherenkov images

For air showers observed simultaneously by more than two imaging atmospheric Cherenkov telescopes, the shower geometry is overconstrained by the images and image information should be combined taking into account the quality of the images. Different algorithms are discussed and tested experimentally using data obtained from observations of Mkn 501 with the HEGRA IACT system. Most of these algorithms provide an estimate of the accuracy of the reconstruction of shower geometry on an event-by-event basis, allowing, e.g., to select higher-quality subsamples for precision measurements.Comment: 14 Pages, 6 figures, Late

Quantum parallelism of the controlled-NOT operation: an experimental criterion for the evaluation of device performance

It is shown that a quantum controlled-NOT gate simultaneously performs the logical functions of three distinct conditional local operations. Each of these local operations can be verified by measuring a corresponding truth table of four local inputs and four local outputs. The quantum parallelism of the gate can then be observed directly in a set of three simple experimental tests, each of which has a clear intuitive interpretation in terms of classical logical operations. Specifically, quantum parallelism is achieved if the average fidelity of the three classical operations exceeds 2/3. It is thus possible to evaluate the essential quantum parallelism of an experimental controlled-NOT gate by testing only three characteristic classical operations performed by the gate.Comment: 6 pages, no figures, added references and discussio

Beam Dynamics of Non-Equipartitioned Beams in the Case of the SPL Project at CERN

The SPL [1] working group at CERN is studying a 2.2 GeV H- linac, which recuperates a large amount of RF hardware from the now decommissioned LEP at CERN. During the ongoing design effort for an optimized layout, it was found that in some cases non-equipartitioned beams tend to exchange energy between the longitudinal and the transverse planes. Strict energy equipartition, however, imposes tight restrictions on such a high energy linac and often contradicts the goal of cost effective design. On the other hand, stability charts derived from 2D Vlasov analysis suggest the existence of stable non-equipartitioned equilibria in certain regions of parameter space. Due to the low bunch current (22 mA) in the SPL, these regions are large enough to ensure stable machine operation for non-equipartitioned beams. Systematic multiparticle simulations with IMPACT [2] are used to apply the stability charts to the beam dynamics design of a realistic high energy linac. Using the example of the SPL, it is shown that designs with stable non-equipartitioned bunches are feasible, and how these designs react to mismatched input beams