92 research outputs found
SRF cavity geometry optimization for the ILC with minimized surface e.m. fields and superior bandwidth
The main linacs of the ILC consist of nine-cell cavities based on the TESLA
design. In order to facilitate reaching higher gradients we have re-designed
the cavity shape. This leads to a reduction, comparable to several current
designs, in both the ratio of the surface electric field to the accelerating
field (Es/Ea) and the magnetic field to the accelerating field (Bs/Ea). The
bandwidth of the accelerating mode is also optimized. This new shape, which we
refer to as the New Low Surface Field (NLSF) design, bears comparison with the
Ichiro, Re-entrant and LSF designs.Comment: Presented at the 23rd Particle Accelerator Conference (PAC09)
Vancouver, Canad
Third Harmonic Cavity Modal Analysis
Third harmonic cavities have been designed and fabricated by FNAL to be used
at the FLASH/XFEL facility at DESY to minimise the energy spread along the
bunches. Modes in these cavities are analysed and the sensitivity to frequency
errors are assessed. A circuit model is employed to model the monopole bands.
The monopole circuit model is enhanced to include successive cell coupling, in
addition to the usual nearest neighbour coupling. A mode matching code is used
to facilitate rapid simulations, incorporating fabrication errors. Curves
surfaces are approximated by a series of abrupt transitions and the validity of
this approach is examinedComment: Proceedings of 14th International Conference on RF Superconductivity
(SRF 2009), 2009, Berlin, German
Study of Beam Diagnostics with Trapped Modes in Third Harmonic Superconducting Cavities at FLASH
Off-axis beams passing through an accelerating cavity excite dipole modes
among other higher order modes (HOMs). These modes have linear dependence on
the transverse beam offset from the cavity axis. Therefore they can be used to
monitor the beam position within the cavity. The fifth dipole passband of the
third harmonic superconducting cavities at FLASH has modes trapped within each
cavity and do not propagate through the adjacent beam pipes, while most other
cavity modes do. This could enable the beam position measurement in individual
cavities. This paper investigates the possibility to use the fifth dipole band
for beam alignment in the third harmonic cavity module. Simulations and
measurements both with and without beam-excitations are presented. Various
analysis methods are used and compared. A good correlation of HOM signals to
the beam position is observed.Comment: 2nd International Particle Accelerator Conference (IPAC '11), San
Sebastian, Spain, Sep 4-9, 201
Rapid cavity prototyping using mode matching and globalised scattering matrix
Cavity design using traditional mesh based numerical means (such as the
finite element or finite difference methods) require large mesh calculations in
order to obtain accurate values and cavity optimisation is often not achieved.
Here we present a mode matching scheme which utilises a globalised scattering
matrix approach that allows cavities with curved surfaces (i.e. cavities with
elliptical irises and or equators) to be accurately simulated allowing rapid
cavity prototyping and optimisation to be achieved. Results on structures in
the CLIC mainComment: Proceedings of X-Band Structures and Beam Dynamics Workshop (XB08),
44th ICFA beam dynamics workshop, cockcroft institute, uk, 1-4 dec. 200
Status of COLDDIAG: A Cold Vacuum Chamber for Diagnostics
One of the still open issues for the development of superconducting insertion
devices is the understanding of the beam heat load. With the aim of measuring
the beam heat load to a cold bore and the hope to gain a deeper understanding
in the beam heat load mechanisms, a cold vacuum chamber for diagnostics is
under construction. The following diagnostics will be implemented: i) retarding
field analyzers to measure the electron energy and flux, ii) temperature
sensors to measure the total heat load, iii) pressure gauges, iv) and mass
spectrometers to measure the gas content. The inner vacuum chamber will be
removable in order to test different geometries and materials. This will allow
the installation of the cryostat in different synchrotron light sources.
COLDDIAG will be built to fit in a short straight section at ANKA. A first
installation at the synchrotron light source Diamond is foreseen in June 2011.
Here we describe the technical design report of this device and the planned
measurements with beam.Comment: Presented at First International Particle Accelerator Conference,
IPAC'10, Kyoto, Japan, from 23 to 28 May 201
Reductions in cardiovascular, cerebrovascular, and respiratory mortality following the national Irish smoking ban: Interrupted time-series analysis
Copyright @ 2013 Stallings-Smith et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.This article has been made available through the Brunel Open Access Publishing Fund.Background: Previous studies have shown decreases in cardiovascular mortality following the implementation of comprehensive smoking bans. It is not known whether cerebrovascular or respiratory mortality decreases post-ban. On March 29, 2004, the Republic of Ireland became the first country in the world to implement a national workplace smoking ban. The aim of this study was to assess the effect of this policy on all-cause and cause-specific, non-trauma mortality. Methods: A time-series epidemiologic assessment was conducted, utilizing Poisson regression to examine weekly age and gender-standardized rates for 215,878 non-trauma deaths in the Irish population, ages ≥35 years. The study period was from January 1, 2000, to December 31, 2007, with a post-ban follow-up of 3.75 years. All models were adjusted for time trend, season, influenza, and smoking prevalence. Results: Following ban implementation, an immediate 13% decrease in all-cause mortality (RR: 0.87; 95% CI: 0.76-0.99), a 26% reduction in ischemic heart disease (IHD) (RR: 0.74; 95% CI: 0.63-0.88), a 32% reduction in stroke (RR: 0.68; 95% CI: 0.54-0.85), and a 38% reduction in chronic obstructive pulmonary disease (COPD) (RR: 0.62; 95% CI: 0.46-0.83) mortality was observed. Post-ban reductions in IHD, stroke, and COPD mortalities were seen in ages ≥65 years, but not in ages 35-64 years. COPD mortality reductions were found only in females (RR: 0.47; 95% CI: 0.32-0.70). Post-ban annual trend reductions were not detected for any smoking-related causes of death. Unadjusted estimates indicate that 3,726 (95% CI: 2,305-4,629) smoking-related deaths were likely prevented post-ban. Mortality decreases were primarily due to reductions in passive smoking. Conclusions: The national Irish smoking ban was associated with immediate reductions in early mortality. Importantly, post-ban risk differences did not change with a longer follow-up period. This study corroborates previous evidence for cardiovascular causes, and is the first to demonstrate reductions in cerebrovascular and respiratory causes
A systematic review of physical activity promotion strategies
This article was first published in:British Journal of Sports Medicine:1996:30:84-89We have reviewed randomised controlled trials of physical activity promotion to provide recent and reliable information on the effectiveness of physical activity promotion. Computerised databases and references of references were searched. Experts were contacted and asked for information about existing work. Studies assessed were randomised controlled trials of healthy, free living, adult subjects, where exercise behaviour was the dependent variable. Eleven trials were identified. No United Kingdom based studies were found. Interventions that encourage walking and do not require attendance at a facility are most likely to lead to sustainable increases in overall physical activity. Brisk walking has the greatest potential for increasing overall activity levels of a sedentary population and meeting current public health recommendations. The small number of trials limits the strength of any conclusions and highlights the need for more research
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