Abstract
The 28 GeV proton synchrotron (PS) forms part of the chain of LEP injectors with the rôle to accelerate positrons and electrons from 0.6 GeV, the operating energy of the Electron/Positron Accumulator (EPA), to 3.5 GeV, the positron/electron injection energy of CERN's 400 GeV proton synchrotron (SPS) which then accelerates the particles to 20 GeV. The PS used as an electron synchrotron has to supply the SPS with 8 bunches at an intensity of Nb = 8 × 109 particles per bunch. Bunch length and energy spread must be chosen carefully to avoid transverse and longitudinal single-bunch instabilities (turbulence) associated with high peak currents in the SPS. Analysis of the beam dynamics in the combined function lattice of the PS shows that this requirement can be fulfilled if the damning-partition numbers are changed. A Robinson Wiggler is proposed for this purpose and a new additional RF system is needed to produce the required bunch dimensions in longitudinal phase space.
Highlights
3.5 GeV, the positron/electron injection energy of CERN's 400 GeV proton synchrotron (SPS) which accelerates the particles to 20 GeV')
Bunch length and energy spread must be chosen carefully to avoid transverse and longitudinal single-bunch instabilities associated with high peak currents in the Analysis of the beam dynamics in the combined function lattice of the PS shows that this requirement can be fulfilled if the dam ing-partition numbers are changed
A Robinson Wiggler Q is proposed for this purpose and a new additional
Summary
The required longitudinal and transverse beam dimensions are obtained through adjustment of J, to the value of .16 by means of two Robinson wiggler magnets. The second method - bunch-length compression - makes use of the existing RF system tuned to 7.6 MHz. The second method - bunch-length compression - makes use of the existing RF system tuned to 7.6 MHz Acceleration with this low-frequency system and with a modest wiggler strength (JE = 3.1) results in a correct longitudinal bunch area at 3.5 GeV but the bunch of us = .53 m is too long for the SPS and the energy spread UC/E = .3 x IO-’ is too small. In order to compress the bunch length and to increase the energy spread, the voltage of the 114 MHz. RF system is raised from 5 kV to 1 MV adiabatically but fast compared to the radiation damping time Describes the electron behaviour associated with quantum excitation and radiation damping while the second one relates to the adiabatic damping similar to the proton behaviour
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