Comparative results on collimation of the SPS beam of protons and Pb ions with bent crystals (original) (raw)
Related papers
Strong reduction of the off-momentum halo in crystal assisted collimation of the SPS beam
Physics Letters B, 2012
A study of crystal assisted collimation has been continued at the CERN SPS for different energies of stored beams using 120 GeV/c and 270 GeV/c protons and Pb ions with 270 GeV/c per charge. A bent silicon crystal used as a primary collimator deflected halo particles using channeling and directing them into the tungsten absorber. A strong correlation of the beam losses in the crystal and off-momentum halo intensity measured in the first high dispersion (HD) area downstream was observed. In channeling conditions, the beam loss rate induced by inelastic interactions of particles with nuclei is significantly reduced in comparison with the non-oriented crystal. A maximal reduction of beam losses in the crystal larger than 20 was observed with 270 GeV/c protons. The off-momentum halo intensity measured in the HD area was also strongly reduced in channeling conditions. The reduction coefficient was larger than 7 for the case of Pb ions. A strong loss reduction was also detected in regions of the SPS ring far from the collimation area. It was shown by simulations that the miscut angle between the crystal surface and its crystallographic planes doubled the beam losses in the aligned crystal.
Optimization of the crystal assisted collimation of the SPS beam
Physics Letters B, 2013
The possibility for optimization of crystal assisted collimation has been studied at the CERN SPS for stored beams of protons and Pb ions with 270 GeV/c per unit charge. A bent silicon crystal used as a primary collimator deflects halo particles in the channeling regime, directing them into a tungsten absorber. In channeling conditions a strong reduction of off-momentum particle numbers produced in the crystal and absorber, which form collimation leakage, has been observed in the first high dispersion (HD) area downstream. The present study shows that the collimation leakage is minimal for some values of the absorber offset relative to the crystal. The optimal offset value is larger for Pb ions because of their considerably larger ionization losses in the crystal, which cause large increases of particle betatron oscillation amplitudes. The optimal absorber offset allows obtaining maximal efficiency of crystal-assisted collimation.
Observation of channeling for 6500 GeV/c protons in the crystal assisted collimation setup for LHC
Physics Letters B, 2016
Two high-accuracy goniometers equipped with two bent silicon crystals were installed in the betatron cleaning insertion of the CERN Large Hadron Collider (LHC) during its long shutdown. First beam tests were recently performed at the LHC with 450 GeV/c and 6500 GeV/c stored proton beams to investigate the feasibility of beam halo collimation assisted by bent crystals. For the first time channeling of 6500 GeV/c protons was observed in a particle accelerator. A strong reduction of beam losses due to nuclear inelastic interactions in the aligned crystal in comparison with its amorphous orientation was detected. The loss reduction value was about 24. Thus, the results show that deflection of particles by a bent crystal due to channeling is effective for this record particle energy.
New results from the CERN-SPS beam deflection experiments with bent crystals
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1996
Presented at the Workshop on "Channeling and other Coherent Crystal Effects are observed. the beam splits into several beams corresponding to the different planes, and even weak planes 450 GeV/c. Qualitatively similar behaviour as in previous experiments at 12 GeV/c is seen; positive particles using axial alignment of a bent silicon crystal has been investigated at time, and a small reduction in efficiency is seen in the irradiated region. Finally, deflection of deflection efficiencies using a strongly irradiated silicon crystal have been measured for the first significantly smaller than expected for such a crystal with higher atomic number. Fourth, Slightly higher deflection efficiencies than for silicon are seen for large bending angles, but the first results from beam deflection at high energy using a germanium crystal are shown. are seen, but no negative particles are bent through the full bending angle of the crystal. Third, crystal, for incidence along the (1 1 1) plane as well as the <1l0> axis. Small deflection effects silicon crystal. Second, deflection of negative pions at 200 GeV/c is investigated for the same 450 GeV/c proton beam for a bending angle of 3.1 mrad along the (111) plane in a 50 mm presented. First, deflection of a positive pion beam at 200 GeV/c is compared to the standard Results from five distinct bending experiments performed recently in the H8 beam at CERN are
Observation of strong leakage reduction in crystal assisted collimation of the SPS beam
Physics Letters B, 2015
In ideal two-stage collimation systems, the secondary collimator-absorbers should exclude the exit of primary particles with large impact parameters. A strong reduction of leakage for channeling conditions has been observed in the crystal-assisted collimation of the SPS beam of 270 GeV/c protons, approaching the ideal conditions.
The European Physical Journal C, 2018
Inelastic nuclear interaction probability of 400 GeV/c protons interacting with bent silicon crystals was investigated, in particular for both types of crystals installed at the CERN Large Hadron Collider for beam collimation purposes. In comparison to amorphous scattering interaction, in planar channeling this probability is ∼ 36% for the quasimosaic type (planes (111)), and ∼ 27% for the strip type (planes (110)). Moreover, the absolute inelastic nuclear interaction probability in the axial channeling orientation, along the 110 axis, was estimated for the first time, finding a value of 0.6% for a crystal 2 mm long along the beam direction, with a bending angle of 55 µrad. This value is more than two times lower with respect to the planar channeling orientation of the same crystal, and increases with the vertical angular misalignment. Finally, the correlation between the inelastic nuclear interaction probability in the planar channeling and the silicon crystal curvature is reported.
Deflection of 400 GeV/c proton beam with bent silicon crystals at the CERN Super Proton Synchrotron
Physical Review Special …, 2008
This paper presents a detailed study of the deflection phenomena of a 400 GeV=c proton beam impinging on a new generation of bent silicon crystals; the tests have been performed at the CERN Super Proton Synchrotron H8 beam line. Channeling and volume reflection angles are measured with an extremely precise goniometer and with high resolution silicon microstrip detectors. Volume reflection has been observed and measured for the first time at this energy, with a single-pass efficiency as large as 98%, in good agreement with the simulation results. This efficiency makes volume reflection a possible candidate for collimation with bent crystals at the CERN Large Hadron Collider.
The European Physical Journal C, 2019
Beam steering performance of bent silicon crystals irradiated with high-intensity and high-energy protons has been studied. In particular, crystals of the type used for collimation and extraction purposes in the Large Hadron Collider and the Super Proton Synchrotron at CERN have been irradiated at the HiRadMat CERN facility with 2.5 \times 10^{13}$$2.5×1013 440 GeV/c protons, with a pulse length of 7.2 \upmu μs. The purpose is to study possible changes in bending angle and channeling efficiency due to thermo-mechanical stresses in case of accidental irradiation during accelerator operations. A comparison between measurements performed before and after the irradiation does not show any appreciable performance reduction in either crystal.
Physics Letters B, 2015
In ideal two-stage collimation systems, the secondary collimator-absorber should have its length sufficient to exclude practically the exit of halo particles with large impact parameters. In the UA9 experiments on the crystal assisted collimation of the SPS beam a 60 cm long tungsten bar is used as a secondary collimator-absorber which is insufficient for the full absorption of the halo protons. Multi-turn simulation studies of the collimation allowed to select the position for the beam loss monitor downstream the collimation area where the contribution of particles deflected by the crystal in channeling regime but emerging from the secondary collimator-absorber is considerably reduced. This allowed observation of a strong leakage reduction of halo protons from the SPS beam collimation area, thereby approaching the case with an ideal absorber.