Acceleration of High Intensity Proton Beams

In 1998 the CERN SPS accelerator finished a five years long program providing 450GeV proton beams for neutrino physics. These experiments required the highest possible beam intensity the SPS can deliver. During the last five years the maximum proton intensity in the SPS has steadily been increased to a maximum of 4.8 1013 protons per cycle. In order to achieve these intensities a careful monitoring and improvement of the vertical aperture was necessary. Improved feedback systems on the different RF cavities were needed in order to avoid instabilities. Also the quality (emittance and extraction spill) of the injector, the CERN PS, had be optimised

Measurement of bunch length in LEP

Bunch lengths under various beam conditions were measured with the button electrode. From the data it may be concluded that this system has a quadratic error of ~ 15 mm2. However, it is not entirely constant over the range of bunch lengths and this may be attributed to deviations from the ideal Gaussian profile that is assumed. A cross-check measurement was also performed to create a link to the measurements with the streak camera done in an earlier MD

In situ investigation of the ionisation of silica in aqueous ammonia by using a high frequency dielectric method

International audienceThe reaction of silica gel and Stöber beads of silica with ammonia was studied in aqueous medium using a high frequency dielectric method. Measurements of the complex impedance of silica pulps in both static and dynamic modes were found to be a new rapid, sensitive and non-destructive way for the in situ characterisation of the surface silica ionisation process in aqueous ammonia. The influence of various parameters (field frequency, ionic strength, ammonia concentration) was discussed. The apparent equilibrium constant for the following reaction (SiOH) + NH(3)(SiO(-)NH(4)(+)) was found to be strongly affected by the degree of dissociation of both silica samples, so that the complete neutralisation was never observed. The porosity of the Stöber silica towards the NH(3) species was demonstrated experimentally through the formation of (SiO(-)NH(4)(+)) entities in the interior of the silica beads. The reversibility of the neutralisation reaction was applied to successive on-column analysis for which the hydrolysis of ammoniated silica was found to be catalysed by the presence of acids

Selective monitoring of Cu(II) species using a silica modified carbon paste electrode

International audienceThe incorporation of silica particles within carbon paste leads to improved amperometric detection of copper(II) in ammoniacal medium. The enhanced sensitivity was attributed to the accumulation of copper(II) by adsorption on the ionised surface silanol groups of silica. The sensor was found to be highly selective to copper(II) with respect to alkali and alkaline earth metal cations and transition metal–ammonia complex species. The improved selectivity was explained by the strong silanolate–copper interactions, leading to appreciable accumulation even in high ionic strength media, as ascertained by measurements performed in synthetic ground and sea waters. Moreover, cyclic voltammetry using the silica modified carbon paste electrode was applied to the in situ investigation of copper(II) sorption processes on silica. Various silica-based materials were used to shed useful insights into these sorption processes, in relation to their capacity for copper(II) as well as their specific surface area and porosity

Carbonated ferric green rust as a new material for efficient phosphate removal

International audienc

Betatron and Dispersion Matching of the TT2/TT10 Transfer Line for the 26 GeV/c Fast Extraction

Introduction The TT2/TT10 beam line connects the PS and SPS machines. It is used to transfer a variety of positively charged particles into the SPS, such as protons and lead ions for the fixed-target physics, protons to simulate the future LHC-type beam and positrons for LEP. In recent years, there has been a renewed interest in the optics of the transfer line, the main reason being that it will play an important role in the LHC injection chain. The maximum emittance growth allowed for the transport of the LHC beam from PS extraction to SPS extraction is 0.5 m [1] (i.e. a 17% emittance blow-up). However, only a small fraction of this is assigned to mismatch at injection [2]. Since this beam has a small emittance and a large momentum spread, dispersion mismatch is a major concern. Simultaneous Twiss parameter and dispersion matching is therefore mandatory in order to prevent beam blow-up at injection into the SPS. 2 Mismatch of Opt