Multiple volume reflection from different planes inside one bent crystal

Abstract

It is shown that multiple volume reflections from different planes of one bent crystal becomes possible when particles move at a small angle with respect to a crystal axis. Such a Multiple Volume Reflection makes it possible to increase the particle deflection angle inside one crystal by more than four times and can be used to increase the efficiency of beam extraction and collimation at the LHC and many other accelerators.

Radiation generated by single and multiple volume reflection of ultrarelativistic electrons and positrons in bent crystals

“…Both analytical consideration [14], extensive simulations [14,15], and experiments [16][17][18] demonstrated a fivefold increase in deflection angle with respect to an individual VR onto the vertical plane, irrespective of particle's charge. Since the nondipole radiation nature manifests itself in proximity of each reflection point, its role will be naturally increased as a result of multiple reflection.…”

“…Since a crystal axis is the intersection of crystal planes, repeated VR on each of them may occur as a particle moves at small angle with respect to the axis [14] [see Fig. 9(a)].…”

“…In the last years the effects of volume reflection (VR) [4,[11][12][13] and multiple volume reflection in one crystal (MVROC) [14][15][16][17][18] were observed and widely studied, mainly in connection with the problem of halo cleaning in the large hadron collider (LHC). However, both effects are also interesting from the point of view of radiation emission.…”

“…MVROC [14][15][16][17][18] is realized when particles move at relatively small angles with respect to one of the major crystal axes, so that their trajectories become tangential at some point to most of the crystal planes sharing the same axis. Both analytical consideration [14], extensive simulations [14,15], and experiments [16][17][18] demonstrated a fivefold increase in deflection angle with respect to an individual VR onto the vertical plane, irrespective of particle's charge.…”

Nuclear interactions at volume reflection: Perturbative treatment

“…The price to pay is that volume reflection angle is of the order of the Lindhard's critical angle c ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2V 0 =E p , where V 0 is the interplanar continuous potential well depth, and E the particle energy, so at E) )V 0 the angle of single deflection is pretty small. Fortunately, this difficulty can be surmounted by transmitting the particle through a sequence of bent crystals [6], or arranging a composite volume reflection from several crystallographic planes within one crystal [7], thereby multiplying the deflection angle. Experiments on volume reflection begun within a decade, and are currently continuing.…”