Observation and comparative analysis of proton beam extraction or collimation by different planar channels of a bent crystal

In the experiment the efficiency of the 50 GeV proton beam extraction from accelerator by means of a bent crystal as a function of crystal orientation was measured. This allowed one to make a comparative analysis of efficiencies of high-energy protons deflection by different crystal atomic planes with different values of the electrostatic field. The results of simulation of high-energy protons deflection by means of crystal atomic planes and crystal atomic strings are also presented in the article. In the case of planar channeling the simulation shows a good agreement with experimental data. In the case of proton motion in the regime of stochastic scattering by bent atomic strings the simulation shows that angles of particle deflection are much greater than the critical channeling angle.

Figure 1

The crystal in the double-axis goniometer is set in the ring of U-70.

Figure 2

The experimental setup for the beam extraction and collimation by bent crystals.

Figure 3

The main elements of the experimental equipment: 1—station with a crystal, 2—profilometer, 3—absorber, IC—ionization chambers, M—magnetic blocks of the accelerator.

Figure 4

(a) The efficiency of the accelerated beam extraction as a function of the horizontal angle of the goniometer. The upper curve—the full effect of the deflection due to the planar channeling and incoherent scattering; the lower curve—the contribution of the planar channeling. (b) Stereogram of the most strong atomic planes around the $⟨110⟩$ crystal axis of the silicon crystal.

Figure 5

The comparison of the efficiency of the beam deflection by different crystallographic planes with the extraction by the beam-kicker magnet efficiency.

Figure 6

Beam profiles for different angles of the goniometer [as shown in Fig. 4a] corresponding to the deflection by different crystal planes.

Figure 7

The particle motion in the system defined by the crystallographic axes of the crystal.

Figure 8

Azimuthal shift between the coordinate systems of goniometer and crystal. The dashed line shows the plane with an angle $\beta$.

Figure 9

Beam deflection by the $(klm)$ plane.

Figure 10

Linear approximation of the experimental data.

Figure 11

Simulation results for the efficiency of the proton beam deflection by the bent crystal as a function of the angle ${\theta }_{0x}$. ${\theta }_{0y}=850\mu \mathrm{rad}$.

Figure 12

The angular distribution (left), horizontal (middle), and vertical (right) profiles of the proton beam after passing through the bent crystal. Terms of entrance correspond to the motion of particles in the channeling regime in the vertical plane $(1\overline{1}1)$.

Figure 13

The same as in Fig. 12 for the conditions of particles motion in the channeling mode in the plane $(1\overline{1}0)$.

Figure 14

The same as in Fig. 12 for the conditions of particles motion in the channeling mode in the plane $(1\overline{1}2)$.

Figure 15

The same as in Fig. 12 for the conditions of 50 GeV particles motion in the stochastic deflection regime.

Figure 16

The same as in Fig. 15 for protons with kinetic energy of 1 GeV.