An experimentally robust technique for halo measurement using the IPM at the Fermilab Booster

We propose a model-independent quantity, $L/G$, to characterize non-Gaussian tails in beam profiles observed with the Fermilab Booster Ion Profile Monitor. This quantity can be considered a measure of beam halo in the Booster. We use beam dynamics and detector simulations to demonstrate that $L/G$ is superior to kurtosis as an experimental measurement of beam halo when realistic beam shapes, detector effects and uncertainties are taken into account. We include the rationale and method of calculation for $L/G$ in addition to results of the experimental studies in the Booster where we show that $L/G$ is a useful halo discriminator

Photocathode Quantum Efficiency of Ultra-Thin Cs2Te Layers On Nb Substrates

The quantum efficiencies (QE) of photocathodes consisting of bulk Nb substrates coated with thin films of Cs2Te are reported. Using the standard recipe for Cs2Te deposition developed for Mo substrates (220 {\AA} Te thickness), a QE ~11% - 13% at light wavelength of 248 nm is achieved for the Nb substrates, consistent with that found on Mo. Systematic reduction of the Te thickness for both Mo and Nb substrates reveals a surprisingly high residual QE ~ 6% for a Te layer as thin as 15 {\AA}. A phenomenological model based on the Spicer 3-Step model along with a solution of the Fresnel equations for reflectance, R, leads to a reasonable fit of the thickness dependence of QE and suggests that layers thinner than 15 {\AA} may still have a relatively high QE. Preliminary investigation suggests an increased operational lifetime as well. Such an ultra-thin, semiconducting Cs2Te layer may be expected to produce minimal ohmic losses for RF frequencies ~ 1 GHz. The result thus opens the door to the potential development of a Nb (or Nb3Sn) superconducting photocathode with relatively high QE and minimal RF impedance to be used in a superconducting radiofrequency (SRF) photoinjector.Comment: 12 pages, 3 figure

Comparative study on disinfection efficacy of Thymus Vulgaris and Aloe Vera extracts with commercial disinfectants, on bacteria isolated in nosocomial environmental

Health concerns, environmental issues, resistance development of microbes and financial constraints drive hygienists to explore alternative disinfection methods to the commonly used, in order to address these issues. One possible solution may be the utilization towards that direction of materials used traditionally in food industry such as plants and herbs, directly consumed or used to flavour foods. Thymus Vulgaris, a plant with substantial antimicrobial activity, and Aloe Vera, a plant with great therapeutic capabilities, are examined in this study for their potential to be the main substance of new disinfection products, intended to be used in nosocomial environments. The extracts, obtained by hydrodistilation (thyme) and ethanol solution (Aloe), were evaluated through antimicrobial screening of their efficacy in comparison with commercial disinfectants, widely used in health care units. Their efficacy was tested against bacteria isolated from hospital environment, responsible for the half of nosocomial infections worldwide namely: Methicillin Resistant Staphylococcus Aureus, Staphylococcus Aureus, Escherichia coli, Pseudomonas aeroginosa, Klebsiella pneumoniae and Acinetobacter baumanii), diluted in deionized water and in reconstituted skim milk. The sensitivity evaluation was performed by broth dilution followed by viable count of the bacteria population after being subjected to different concentrations of the disinfectants with and without the presence of organic matter (skimmed milk). Bacteria were enumerated at time 0, 2, 5 and 10 minutes. Bacterial numbers were expressed as log10 CFU ml-1 and the log reduction was calculated. In the tested concentrations of the extracts promising results were obtained from the samples diluted in deionized water, especially from the Thymus extract. More than 2 log reduction was achieved by the thyme essential oil on four out of six tested bacteria populations from the 5.0 ml/L dilution. Similar but lower counts were obtained from the same dilution of ethanol extract of Aloe Vera (1<DR<2). However, in the presence of organic matter their antibacterial activity was greatly inhibited giving less than 1 log reduction for both extracts. Overall, comparing the tested commercial disinfectants with the natural extracts, the latter presented lower disinfection activity, which was expected taking into account the tested concentrations and their chemical complexity. These preliminary results showed that both extracts have the potential to be used as disinfectants and further studies should be conducted in higher concentrations in order to achieve 5 log reduction

A Parallel General Purpose Multi-Objective Optimization Framework, with Application to Beam Dynamics

Particle accelerators are invaluable tools for research in the basic and applied sciences, in fields such as materials science, chemistry, the biosciences, particle physics, nuclear physics and medicine. The design, commissioning, and operation of accelerator facilities is a non-trivial task, due to the large number of control parameters and the complex interplay of several conflicting design goals. We propose to tackle this problem by means of multi-objective optimization algorithms which also facilitate a parallel deployment. In order to compute solutions in a meaningful time frame a fast and scalable software framework is required. In this paper, we present the implementation of such a general-purpose framework for simulation-based multi-objective optimization methods that allows the automatic investigation of optimal sets of machine parameters. The implementation is based on a master/slave paradigm, employing several masters that govern a set of slaves executing simulations and performing optimization tasks. Using evolutionary algorithms as the optimizer and OPAL as the forward solver, validation experiments and results of multi-objective optimization problems in the domain of beam dynamics are presented. The high charge beam line at the Argonne Wakefield Accelerator Facility was used as the beam dynamics model. The 3D beam size, transverse momentum, and energy spread were optimized

Diffusion due to the Beam-Beam Interaction and Fluctuating Fields in Hadron Colliders

Random fluctuations in the tune, beam offsets and beam size in the presence of the beam-beam interaction are shown to lead to significant particle diffusion and emittance growth in hadron colliders. We find that far from resonances high frequency noise causes the most diffusion while near resonances low frequency noise is responsible for the large emittance growth observed. Comparison of different fluctuations shows that offset fluctuations between the beams causes the largest diffusion for particles in the beam core.Comment: 5 pages, 3 postscript figure