The results on the extraction of a proton beam of a varying intensity from the U-70 accelerator using bent silicon single crystals are presented. Stable beam extraction using crystals has been demonstrated for two experiments where smooth adjustment of the beam intensity over a large dynamic range has been required.

The article is devoted to the study of the suppression of multiple scattering of positively charged particles with momenta of 180 GeV/c and 400 GeV/c passing through bent single crystals of silicon at small angles to the plane (111) both in channeling mode and in the above-barrier state. For the first time, the suppression of the effect of multiple scattering of non-channeling particles passing at a small angle to one of the planes of a silicon single crystal was observed. In addition, the asymmetry was observed in the multiple scattering of over-barrier particles with respect to their zero angle of entry into the single crystal.

We present the results of an experimental study of multiple scattering of positively charged high-energy particles in bent samples of monocrystalline silicon. This work confirms the recently discovered effect of a strong reduction in the rms multiple scattering angle of particles channeled in the silicon (111) plane. The effect is observed in the plane orthogonal to the bending plane. We show in detail the influence of angular constraints on the magnitude of the effect. Comparison of the multiple scattering process at different energies indicates a violation of the law of inverse proportionality of the rms angle of channeled particles with energy. By increasing the statistics, we have improved the results of multiple scattering measurements for particles moving, but not channeled, in silicon crystals.

Bent silicon crystals mounted on high-accuracy angular actuators were installed in the CERN Super Proton Synchrotron (SPS) and extensively tested to assess the feasibility of crystal-assisted collimation in circular hadron colliders. The adopted layout was exploited and regularly upgraded for about a decade by the UA9 Collaboration. The investigations provided the compelling evidence of a strong reduction of beam losses induced by nuclear inelastic interactions in the aligned crystals in comparison with amorphous orientation. A conceptually similar device, installed in the betatron cleaning insertion of CERN Large Hadron Collider (LHC), was operated through the complete acceleration and storage cycle and demonstrated a large reduction of the background leaking from the collimation region and radiated into the cold sections of the accelerator and the experimental detectors. The implemented layout and the relevant results of the beam tests performed in the SPS and in the LHC with stored proton and ion beams are extensively discussed.

This paper describes an experiment on focusing a proton beam with an energy of 50 GeV on the U‑70 accelerator using a crystal device. The focusing device is based on the use of bending a plane-parallel silicon wafer in which the side faces are rotated relative to the crystallographic planes by a small angle. The beam is focused at a distance of 10 cm into a narrow line with a width of FWHM ~7 μm. The prospects for using such a short-focus device on modern accelerators are described.

Research of the ionization loss of 50 GeV protons, the path of which in the depleted layer of the silicon detector was smoothly regulated in the range from 0.3 to 10 mm, is presented. In the experiment, we used a flat silicon detector with a fixed thickness of the depleted layer of 300 μm. The smooth regulation of the path was realized due to the variation of the angle between the surface of the detector and the incident proton beam. The comparison of experimental data and theoretical calculations of the ionization loss demonstrates agreement in all range of thicknesses. Results of the research can be used in order to control the angle between the surface of the detector and the incident beam of relativistic particles. Besides, the results can be used in the analysis of data from astrophysical silicon detectors of charged particles if high-energy particles crossed flat detectors at arbitrary angle.

The UA9 setup, installed in the Super Proton Synchrotron (SPS) at CERN, was exploited for a proof of principle of the double-crystal scenario, proposed to measure the electric and the magnetic moments of short-lived baryons in a high-energy hadron collider, such as the Large Hadron Collider (LHC). Linear and angular actuators were used to position the crystals and establish the required beam configuration. Timepix detectors and high-sensitivity Beam Loss Monitors were exploited to observe the deflected beams. Linear and angular scans allowed exploring the particle interactions with the two crystals and recording their efficiency. The measured values of the beam trajectories, profiles and of the channeling efficiency agree with the results of a Monte-Carlo simulation.

In view of the successful experience in the generation of pion and kaon secondary beams using a focusing crystal, it has been proposed to build at the U-70 accelerator a new-type channel of secondary particles that does not consume electric power. It has been shown experimentally that an extraction septum magnet can be protected from radiation by applying a multistrip crystal device through current septum shadowing by the crystal that involves the bulk reflection regime for the deflection of particles. The listed applications of crystals are novel in the world practice with accelerators.

The inclusive differential cross sections for the production of $$\pi^{\pm}$$ and $$k^{-}$$ mesons, protons, and antiprotons with momenta between 6 and 50 GeV/c and nuclear fragments of mass number $$1\leq A\leq 10$$ in the momentum range between 20 and 220 GeV/c were measured in carbon–lead collisions at a beam kinetic energy of 19.6 GeV per nucleon ( $$\sqrt{S_{NN}}=6.3$$ GeV). A comparison with the respective cross sections for carbon–carbon interactions is performed, and the dependence on the target mass number ( $$A$$ ) is estimated. The present analysis shows that the observed particles originate predominantly from peripheral interactions.

(SVD-2 Collaboration) A. G. Afonin, E. N. Ardashev, V. F. Golovkin, S. N. Golovnya, S. A. Gorokhov, A. A. Kiryakov, A. G. Kholodenko, V. V. Konstantinov, L. L. Kurchaninov, I. S. Lobanov, E. V. Lobanova, G. A. Mitrofanov, V. S. Petrov, A. V. Pleskach, M. K. Polkovnikov, V. N. Riadovikov*, V. N. Ronzhin, V. A. Senko,N. A. Shalanda, M. M. Soldatov, Yu. P. Tsyupa, A. P. Vorobiev, V. I. Yakimchuk, and V. N. Zapolskii∗ IHEP, Protvino, Moscow region, Russia.

Experiments to measure the electric and the magnetic moments of short-lived baryons using an internal target and two bent crystals in the vicinity of one of the existing LHC detectors were recently proposed, in the frame of the Physics Beyond Colliders Working Group at CERN. Investigating fixed-target physics in the LHC with in-vacuum solid targets is an unprecedented challenge. As a preparatory step, the layout of the UA9 experiment, installed in the CERN SPS to explore beam manipulations assisted by bent crystals, has been modified to study the feasibility of the double-crystal scenario in a circular accelerator. Ideally, the first crystal should capture halo protons in channeling states directing them onto the internal target to produce rare baryons, whilst the second crystal, located just downstream of the target, should channel the baryons, rotate their polarization vector and deflect them towards the detector area. The upgraded UA9 layout is presented. Preliminary measurements providing an insight of the beam behavior are reported.

Strong reduction of multiple scattering for channeled particles has been observed in an experiment on the deflection of a 180 GeV/c π+-meson beam by bent silicon crystals. The RMS deflections due to multiple scattering for the channeled particles were about six times smaller than for non-channeled ones. It was shown that the approach suggested recently for the description of multiple scattering for channeled particles using the experimental data for random crystal orientations gives fair agreement with the experiment.

The inclusive differential cross sections for forward production of nuclear fragments at an angle of 0∘ in CC collisions at beam energy 20.5 GeV/nucleon (SNN=6.3GeV) are presented. Measurements have been performed at the U-70 Accelerator Complex (Protvino) using a combined spectrometer on base of the beamline. Fragments selection was carried out by measuring of ionization in scintillation counters taking into account the data from threshold Cherenkov counters and hadron calorimeter. Fragment mass was determined through Cherenkov light emission angle measured in the spectrometer of ring imaging Cherenkov radiation. Data are given for fragments with charge 1≤Z≤6, atomic number 1≤A≤10 and A/Z<3.4 with momenta from 20 to 210 GeV/c. The measurements are compared with Fritiof model, statistical models and theoretical parameterizations. The discovered differences between theory and experiment are discussed.

The invariant cross sections for forward charged-hadron production at zero angle in carbon–carbon collisions at a beam kinetic energy of 19.6 GeV per nucleon were measured at the U-70 accelerator in an experiment performed with the aid of a combined spectrometer including beam line 22 and detectors of the modified FODS setup. The beam line rigidity was varied between 7 and 70 GeV/$$c$$. The results are compared with the predictions of the FTFP model and a self-similar solution for nucleus–nucleus collisions.

In view of possible future fixed target experiments requiring precisely steered charged particle beams, the UA9 Collaboration has undertaken experimental studies of the use of bent silicon crystals for this purpose. The channeling efficiency of positively charged particles inside the crystalline lattice has been investigated in detail for a setup with a tungsten target installed in front of the crystal. Due to multiple Coulomb scattering inside the target, the channeling efficiency was observed to be reduced by a factor of about 6.1 for a 180 GeV/c quasi-parallel hadron beam. The yield of nuclear interaction secondaries as an estimation of the additional machine background is also discussed.