Abstract
In order to have highly flexible secondary beamlines collimation is crucial. Collimators are blocks of material placed along the beamline that let the main beam pass within the collimator aperture limits, while most of the particles beyond it interact in the material and gets absorbed or loses enough energy to be deflected away from the beam core by the magnets placed downstream. Some particles can interact at the edge of the collimators and be accepted within the main beam, creating background for the experiments downstream. The thickness of the layer contributing to this potential background is called Skin Depth. It depends on the material of the collimator, on the beam momentum as well as the acceptance of the beamline in terms of momentum band and divergence. This article presents the first studies with GEANT4 and FLUKA based simulations on the effects of such interactions at the CERN secondary beamlines.
Highlights
The CERN secondary beamlines in the North [1] and the East Area [2] are designed to deliver beams of secondary and tertiary particles as well as attenuated primary protons and ions from the SPS and PS accelerators, see Fig. 1
This paper summarises the effect of the interaction of secondary beams in the collimation system and the impact parameter "Skin Depth" for different incident momenta and materials
First detailed simulation studies have been performed for charged and neutral particle beams at the CERN North Area to estimate this parameter in order to mitigate the background from the scattered products for the downstream experiments
Summary
The CERN secondary beamlines in the North [1] and the East Area [2] are designed to deliver beams of secondary and tertiary particles as well as attenuated primary protons and ions from the SPS and PS accelerators, see Fig. 1. The beamlines deliver secondary and tertiary beams of hadrons, electrons and muons in the energy range < 360 GeV/c at a maximum flux of 107–108 particles/spill to these areas. Secondary beamline collimators are made of heavy materials with a high stopping power that are used to either define the acceptance or momentum of the beam or as a ‘‘cleaning collimators’’ to absorb the secondary particles that escape the acceptance collimator placed upstream. The mean depth of the collimator material that is responsible for such effects will be referred to as the ‘‘Skin Depth’’ (please see the following section for a more detailed definition) As these effects play an important role in the design of the collimation system in a beamline, the skin depth for different materials was studied for charged and neutral particle beams at different incident momenta and for different beam acceptance. The results and estimation for the skin depth are presented in this paper
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