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

A G Afonin,D A Savin,V N Gorlov,P N Chirkov,A N Lun’Kov,Yu A Chesnokov,I S Voinov,E A Syshchikov,S F Reshetnikov,V A Maisheev,Н.ф Шульга ,V.b Ganenko ,I.v Kirillin ,И В Иванова ,M.k Bulgakov ,В И Терехов ,Dmitriy Krylov ,I A Yazynin ,V T Baranov ,V I Truten

doi:10.1103/physrevstab.15.081001

Abstract

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.

Highlights

Until recently, extraction/collimation of the beam from accelerators was carried out by crystal atomic planes (111) or (110) [1,2,3]
Extraction/collimation of the beam from accelerators was carried out by crystal atomic planes (111) or (110) [1,2,3]. This mechanism of beam deflection can be realized for positively charged particles for both large and small values of angle c between incident particle momentum and the axis of the crystal atomic strings that form the crystal atomic planes
With decreasing angle c, this mechanism of beam deflection collapses. This collapse takes place if the value c is a few values of the critical angle of axial channeling c c. Such decrease of c opens up new possibilities in the particle beams deflection associated with multiple particle scattering on the bent crystal atomic strings and the phenomenon of axial channeling

Summary

INTRODUCTION

Extraction/collimation of the beam from accelerators was carried out by crystal atomic planes (111) or (110) [1,2,3]. The high axial potential of the crystal field (in Si potential barrier for proton is higher than 100 eV) may be used for charged particle beam deflection in the regime of stochastic deflection proposed in [4,5] and experimentally observed in [6] This mechanism (stochastic mechanism of particle beam deflection by a bent crystal) is due to the multiple particle scattering on the crystal atomic strings in conditions when collisions with different atomic strings may be considered as uncorrelated. The first phase of these studies has been associated with carrying out a comparative analysis of the efficiency of beam deflection/collimation by various planar channels of a crystal in conditions of small angles of particle incidence on the crystal with respect to one of the crystallographic axes, when particles can be captured in the planar channeling regime. The results of this phase of the research are described in this paper

DESCRIPTION OF THE EXPERIMENT

Planar channeling in a bent crystal

Stochastic deflection