Summary of session 3 on synchrotron radiation and beam dynamics

Below we summarize presentations, discussions and general conclusions of the Workshop session on "Beam Dynamics Issues". Major subjects include effects due to synchrotron radiation (SR), cryogenic loads, electron cloud, impedances, intra-beam scattering (IBS) and beam-beam interactions.Comment: 2 pp. EuCARD HE-LHC10 AccNet mini-workshop on a High-Energy LHC, 14-16 Oct 2010: Villa Bighi, Malt

Transverse Instabilities of Coasting Beams with Space Charge

Transverse beam stability is strongly affected by the beam space charge. Usually it is analyzed with the rigid-beam model. However this model is only valid when a bare (not affected by the space charge) tune spread is small compared to the space charge tune shift. This condition specifies a relatively small area of parameters which, however, is the most interesting for practical applications. The Landau damping rate and the beam Schottky spectra are computed assuming that validity condition is satisfied. The results are applied to a round Gaussian beam. The stability thresholds are described by simple fits for the cases of chromatic and octupole tune spreads.Comment: 6 pages, 2 figures, accepted by Phys. Rev. ST - Accel. Beam

Concevoir en partenariat une EcoViticulture ECOnomiquement viable et ECOlogiquement responsable par rapport aux pesticides (EcoViti)

Initié en 2010, le projet Casdar EcoViti a proposé et testé une démarche s’appuyant sur des connaissances expertes pour la conception de systèmes viticoles innovants à bas intrants phytosanitaires. L’évaluation des performances et le ré-ajustement des prototypes conçus se fait au sein d’un réseau de plateformes d’expérimentation installées dans les grandes régions viticoles françaises. Une méthode et des outils adaptés à la viticulture ont été produits et formalisés. Les premiers résultats d’EcoViti montrent des performances environnementales et économiques satisfaisantes pour encourager l’évolution des systèmes viticoles vers une moindre dépendance aux intrants

Evaluation of the Beam Coupling Impedance of New Beam Screen Designs for the LHC Injection Kicker Magnets

During the 2011 run of the LHC there was a significant measured temperature increase in the LHC Injection Kicker Magnets (MKI) during operation with 50ns bunch spacing. This was due to increased beam-induced heating of the magnet due to beam impedance. Due to concerns about future heating with the increased total intensity to nominal and ultimate luminosities a review of the impedance reduction techniques within the magnet was required. A number of new beam screen designs are proposed and their impedance evaluated. Heating estimates are also given with a particular attention paid to future intensity upgrades to ultimate parameters

Simulations of Coaxial Wire Measurements of the Impedance of Asymmetric Structures

Coaxial wire measurements have provided a simple and effective way to measure the beam coupling impedance of accelerator structures for a number of years. It has been known how to measure the longitudinal and dipolar transverse impedance using one and two wires for some time. Recently the ability to measure the quadrupolar impedance of structures exhibiting top/bottom and left/right symmetry has been demonstrated. A method for measuring the beam coupling impedance of asymmetric structures using displaced single wires and two wire measurements is proposed. Simulations of the measurement system are presented with further work proposed

Comparison of the current LHC Collimators and the SLAC Phase 2 Collimator Impedances

One of the key sources of transverse impedance in the LHC has been the secondary graphite collimators that sit close to the beam at all energies. This limits the stable bunch intensity due to transverse coupled-bunch instabilities and transverse mode coupling instability. To counteract this, new secondary collimators have been proposed for the phase II upgrade of the LHC collimation system. A number of designs based on different jaw materials and mechanical designs have been proposed. A comparison of the beam coupling impedance of these different designs derived from simulations are presented, with reference to the existing phase I secondary collimator design

Assessing habitat-suitability models with a virtual species

This paper compares two habitat-suitability assessing methods, the Ecological Niche Factor Analysis (ENFA) and the Generalised Linear Model (GLM), to see how well they cope with three different scenarios. The main difference between these two analyses is that GLM is based on species presence/absence data while ENFA on presence data only. A virtual species was created and then dispatched in a GIS-model of a real landscape following three historic scenarios: 1° spreading, 2° at equilibrium and 3° overabundant species. In each situation, the virtual species was sampled and these simulated data sets were used as input for the ENFA and GLM to reconstruct the habitat suitability model. The results showed that ENFA is very robust to the quality and quantity of the data, giving good results in the three scenarios. GLM was badly affected in the case of the spreading species but produced slightly better results than ENFA when the species was overabundant; at equilibrium, both methods produced equivalent results. The use of a virtual species proved to be a very efficient method, allowing to fully control the quality of the input data as well as to accurately evaluate the predictive power of both analyses

Chromaticity dependence of the transverse effective impedance in the CERN Proton Synchrotron

The current knowledge of the transverse beam coupling impedance of the CERN Proton Synchrotron (PS) has been established with beam-based measurements at different energies. The transverse coherent tune shift as a function of the beam intensity has been measured in order to evaluate the total effective imaginary part of the transverse impedance in the accelerator at the energies of 7, 13 and 25 GeV. Measurements have been performed changing the vertical chromaticity for each vertical tune scan with intensity. The data analysis revealed an increase of impedance with chromaticity for all the considered energies. The transverse impedance can be compared with the previously evaluated theoretical impedance budget taking into account the individual contribution of several machine devices

Baseline LHC machine parameters and configuration of the 2015 proton run

This paper shows the baseline LHC machine parameters for the 2015 start-up. Many systems have been upgraded during LS1 and in 2015 the LHC will operate at a higher energy than before and with a tighter filling scheme. Therefore, the 2015 commissioning phase risks to be less smooth than in 2012. The proposed starting configuration puts the focus on feasibility rather than peak performance and includes margins for operational uncertainties. Instead, once beam experience and a better machine knowledge has been obtained, a push in $\beta^*$ and performance can be envisaged. In this paper, the focus is on collimation settings and reach in $\beta^*$---other parameters are covered in greater depth by other papers in these proceedings.Comment: submitted for publication in a CERN yellow report (Proceedings of the LHC Performance Workshop - Chamonix 2014

Progress of guayule trials in Europe (Spain and France) : early evaluation

The main objectives of the project were to define the potential for cultivation of guayule (#Parthenium Argentatum#) in Southern Europe and to assess the economical justification as an alternative source for natural rubber produced in Europe. The best available subsets of guayule lines from Arizona germplasm were collected from USDA, National germplasm and US Universities (Arizona, Texas). The seeds from the germplasm collection both in France and Spain were used to produce enough guayule plants for local field trials and to settle a guayule collection of selected accessions to produce seeds for European projects. The genetic diversity of 40 guayule imported varieties was tested in two locations: Murcia in Spain, and Montpellier in France. The results showed clear genetic differences. First results showed that Mexican varieties are best adapted to South of Spain. Germination rates of seeds produced by the project varied from 5% to 60% depending on origin, age, line and seeds cleaning. A fertilization and irrigation trial was set-up in Murcia and Montpellier in May 2009. Three levels of irrigation and 3 levels of fertilization were compared using AZ2 seeds as genetic material. In Montpellier, different levels of irrigation did not alter the growth, but less watering reduced the mortality rate. While in Murcia, watering resulted in significantly higher yields. The low rubber content (3.2% in March 2010) and a high mortality of the plants (> 60%) observed in Montpellier after the 2009-2010 winter showed that France is not yet adapted for commercial cultivation of guayule. Rubber content of guayule plants in Murcia (Spain) harvested was 7.4% in March 2010 (for 17-months-old plants). Less than 1% mortality was observed, and the average yields of the irrigation trial was above 10 tons of dry matter (i.e.: 700 kg/ha of rubber) after two years, showing that the area is fully adapted for commercial cultivation of guayule, provided good watering. (Résumé d'auteur