Eur. Phys. J. C (2017) 77: 901
https://doi.org/10.1140/epjc/s10052-017-5456-7

Regular Article - Experimental Physics

Steering of Sub-GeV electrons by ultrashort Si and Ge bent crystals

¹ INFN Sezione di Ferrara, Dipartimento di Fisica e Scienze della Terra, Università di Ferrara Via Saragat 1, 44100, Ferrara, Italy
² Institute for Nuclear Problems, Belarusian State University, Bobruiskaya 11, 220030, Minsk, Belarus
³ INFN Laboratori Nazionali di Legnaro, Viale dell’Università 2, 35020, Legnaro, Italy
⁴ Dipartimento di Fisica, Università di Padova, Via Marzolo 8, 35131, Padova, Italy
⁵ Institut für Kernphysik der Universität Mainz, 55099, Mainz, Germany
⁶ Università dell’Insubria, via Valleggio 11, 22100, Como, Italy
⁷ INFN Sezione di Milano Bicocca, Piazza della Scienza 3, 20126, Milan, Italy
⁸ INFN Sezione di Trieste, Via Valerio 2, 34127, Trieste, Italy

^* e-mail: bandiera@fe.infn.it

Received: 6 September 2017
Accepted: 12 December 2017
Published online: 23 December 2017

Abstract

We report the observation of the steering of 855 MeV electrons by bent silicon and germanium crystals at the MAinzer MIkrotron. Crystals with 15 m of length, bent along (111) planes, were exploited to investigate orientational coherent effects. By using a piezo-actuated mechanical holder, which allowed to remotely change the crystal curvature, it was possible to study the steering capability of planar channeling and volume reflection vs. the curvature radius and the atomic number, Z. For silicon, the channeling efficiency exceeds 35%, a record for negatively charged particles. This was possible due to the realization of a crystal with a thickness of the order of the dechanneling length. On the other hand, for germanium the efficiency is slightly below 10% due to the stronger contribution of multiple scattering for a higher-Z material. Nevertheless this is the first evidence of negative beam steering by planar channeling in a Ge crystal. Having determined for the first time the dechanneling length, one may design a Ge crystal based on such knowledge providing nearly the same channeling efficiency of silicon. The presented results are relevant for crystal-based beam manipulation as well as for the generation of e.m. radiation in bent and periodically bent crystals.