Bacteria have transient influences on marine corrosion of steel

The contribution of bacteria to the corrosion mass loss and to pitting of mild steel was observed over 2.5 years using parallel streams of unpolluted natural (biotic) and nominally sterilized (abiotic) Pacific Ocean coastal seawater. As also observed by others, in artificial laboratory exposures, corrosion mass loss within the first few days of exposure was much greater in the biotic stream. However, after only about 10 days the difference in mass losses were gradually reduced and were very similar up to about one year of exposure. Thereafter, the corrosion loss in the biotic stream again became more severe. Pitting corrosion in the biotic stream was more severe from the very first exposure throughout the 2.5 years. Corrosion in both seawater streams exhibited three distinct but transient time-dependent phases. Of these only the first and third obviously involve bacteria. Similar longer-term observations in real seawaters have not been described previously but are generally consistent with some long-term field data. The results show that longer-term corrosion behavior and possible microbial influences cannot be predicted from short-term laboratory observations, even if natural seawater is used

Implications of a 20-Hz Booster cycle-rate for Slip-stacking

We examine the potential impacts to slip-stacking from a change of the Booster cycle-rate from 15- to 20-Hz. We find that changing the Booster cycle-rate to 20-Hz would greatly increase the slip-stacking bucket area, while potentially requiring greater usage of the Recycler momentum aperture and additional power dissipation in the RF cavities. In particular, the losses from RF interference can be reduced by a factor of 4-10 (depending on Booster beam longitudinal parameters). We discuss the aspect ratio and beam emittance requirements for efficient slip-stacking in both cycle-rate cases. Using a different injection scheme can eliminate the need for greater momentum aperture in the Recycler.Comment: Fermilab Technical Memo 2587-AP

Dynamical Stability of Slip-stacking Particles

We study the stability of particles in slip-stacking configuration, used to nearly double proton beam intensity at Fermilab. We introduce universal area factors to calculate the available phase space area for any set of beam parameters without individual simulation. We find perturbative solutions for stable particle trajectories. We establish Booster beam quality requirements to achieve 97\% slip-stacking efficiency. We show that slip-stacking dynamics directly correspond to the driven pendulum and to the system of two standing-wave traps moving with respect to each other.Comment: Supplemental Material appended to pape

Non-deterministic dynamics of a mechanical system

A mechanical system is presented exhibiting a non-deterministic singularity, that is, a point in an otherwise deterministic system where forward time trajectories become non-unique. A Coulomb friction force applies linear and angular forces to a wheel mounted on a turntable. In certain configurations the friction force is not uniquely determined. When the dynamics evolves past the singularity and the mechanism slips, the future state becomes uncertain up to a set of possible values. For certain parameters the system repeatedly returns to the singularity, giving recurrent yet unpredictable behaviour that constitutes non-deterministic chaotic dynamics. The robustness of the phenomenon is such that we expect it to persist with more sophisticated friction models, manifesting as extreme sensitivity to initial conditions, and complex global dynamics attributable to a local loss of determinism in the limit of discontinuous friction.Comment: 22 pages, 8 figure