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

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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

Test of a low gamma transition optics

By increasing the difference between the beam energy and gamma transition one can, in theory, raise the limit for the on-set of the so-called microwave instability and thus increase the maximum intensity per bunch. This is of interest for the high intensity beams demanded from the SPS by the LHC. A fully fledged realization of a low gamma transition scheme in the SPS would involve the installation of additional quadrupoles, however by moving the tunes near to a multiple of the super period of the SPS it is possible to artificially lower gamma transition. To this end an optics was developed with tunes close to 24. 26 GeV protons were injected into the MD cycle on which this optics had been installed. Comparative longitudinal impedance measurements were made on both the low gamma transition optics and the normal fixed target optics

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

The tight emittance budget for the SPS as LHC injector demands for an accurate matching of the transfer line TT2/TT10 between the PS and SPS machines in order to minimise blow-up at injection into the SPS. Since the LHC beam is characterised by both small emittance and large momentum spread, simultaneous Twiss parameter and dispersion matching is mandatory. The LHC beam is delivered from the PS to the SPS by means of a fast extraction at 26 GeV/c. The optics parameters ot the injection line for the 26 GeV/c fast extraction were carefully measured during the 1998 run in the 26 GeV/c segment in parallel with physics. Such a measurement, combined with a theoretical model of the beam line, allowed to recompute the optics in order to improve the injection matching into the SPS machine. In this note the measurement techniques are presented and the experimental results discussed