Existing focusing crystal devices can be used at TeV-class accelerators because they have small transverse dimensions. A device consisting of several crystals assembled into an array is proposed to increase their acceptance. Results are presented from testing the new device on the U-70 beam.

Annotation. The use of channeling in crystals is quite effective for controlling the primary proton beam, but to manipulate secondary beams pi, K , etc., it is necessary not only to deflect them, but also to focus them, since here the beam divergences are much higher. Focusing devices created to date are suitable for applications at TeV-class accelerators because they have small transverse dimensions. To increase the angular acceptance, a device consisting of several crystals assembled into an array is proposed. In this case, two problems are solved: a large bending angle and acceptable angular acceptance of the device are ensured, which makes it possible to use it at a beam energy of 50 GeV on the domestic U-70 accelerator. The paper presents the results of testing a new device on the U-70 beam.

It becomes difficult and expensive to control TeV-particle trajectories using electromagnets to obtain extracted beams at accelerators. For these purposes, high-gradient devices based on bent crystals are more suitable. These crystals can serve as superstrong lenses with a focal length of less than 1 m with an equivalent magnetic field of 1000 T. In this work, a scheme based on two successive focusing crystals has been implemented to form a 50 GeV axially symmetric beam with a small divergence of 30 μrad in both the horizontal and vertical planes. One of the promising applications of this scheme is the creation of high-energy neutrino beams.

In the TeV energy domain, it becomes difficult and very costly to control the trajectories of particles using electromagnets to obtain the extracted beams on accelerators. Highly gradient devices based on curved crystals are more suitable for these purposes. These crystals can work as super-strong lenses with a focal length of less than 1 m and with an equivalent magnetic field of 1000 T. In this paper, a scheme for the formation of a divergent beam with an energy of 50 GeV by two sequentially arranged focusing crystals is implemented to create an axially symmetric beam with a small divergence of 30 µrad in both horizontal and vertical planes. One promising application of such a scheme is the creation of high-energy neutrino beams.

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.

A radiation source based on the emission of electrons and positrons moving in a short bent crystal has been recently discovered. The emission of particles is due to oscillations of their trajectories near the point of reflections, where trajectories approach a tangent to bent atomic planes. In the experiment performed with the secondary electron beam of the U70 accelerator, it has been shown that the emission intensity can be increased by using a sequence of oriented bent crystals. Passing through six 2.5-mm-long silicon crystals, 7-GeV electrons lose on average 2.0 GeV on emission. This value is several times larger than that in an amorphous medium. Thus, an intense source of radiation has been demonstrated with prospects of application at accelerators.

It has recently been realized that the focusing of high-energy particle beams at a distance of about 1 cm is promising. A new idea is proposed in this work to focus the beam at a short distance by using a bent plane–parallel silicon plate whose side edges are rotated at a small angle with respect to crystallographic planes. At the U-70 accelerator (IHEP, Protvino), a 50-GeV proton beam has been focused to a narrow line with a width of no more than 30 μm at a distance of 17 cm.

The carbon ion C+6 beam with energy 25 GeV/nucleon was extracted by bent crystal from the U-70 ring. The bent angle of silicon crystal was 85 mrad. About 2x10(5) particles for 10(9) circulated ions in the ring were observed in beam line 4a after bent crystal. Geometrical parameters, time structure and ion beam structure were measured. The ability of the bent monocrystal to extract and generate ion beam with necessary parameters for regular usage in physical experiments is shown in the first time.

At large accelerators, bent crystals are employed to deflect weakly divergent proton beams at the stages of extraction and collimation. We demonstrate that a divergent particle beam may be efficiently deflected using a crystal with a focusing edge. A proton beam with divergence near 1 mrad, which exceeds the Lindhard angle by a factor of 30, has been experimentally deflected by 1.8 mrad with efficiency near 15%. The proposed focusing crystal may serve as an element of a novel optical system for secondary-particle beams in the TeV energy region.

A beam of six-charged carbon ions with an energy of 24.8 GeV/nucleon is extracted from the U-70 synchrotron by means of a silicon crystal bent through 85 mrad. A total of 200000 particles are observed in beamline 4a upon forcing 10 9 circulating ions to the crystal. The geometrical parameters, timing structure, and composition of the beam have been measured. It has been shown for the first time that, using a bent single crystal, an ion beam with required parameters can be extracted from the accelerator ring and formed for regular use in physics experiments.