Innovative remotely-controlled bending device for thin silicon and germanium crystals

Abstract

Steering of negatively charged particle beams below 1 GeV has demonstrated to be possible with thin bent silicon and germanium crystals. A newly designed mechanical holder was used for bending crystals, since it allows a remotely-controlled adjustment of crystal bending and compensation of unwanted torsion. Bent crystals were installed and tested at the MAMI Mainz MIcrotron to achieve steering of 0.855-GeV electrons at different bending radii. We report the description and characterization of the innovative bending device developed at INFN Laboratori Nazionali di Legnaro (LNL).

First design of a crystal-based extraction of 6 GeV electrons for the DESY II Booster Synchrotron

“…The maximal deflection efficiency is slightly above 1 %. Though this number is considerably lower of the efficiency registrated previously in the experiments [20][21][22][23][24][25][26][27], it doesn't represents itself as an efficiency of extraction. Indeed, not only channeling particles may reach the septum magnet entrance, but also the dechanneled ones.…”

“…However, recent experiments at both the Mainz Microtron MAMI (855 MeV electrons) [20][21][22] and the SLAC FACET facility (multi-GeV electrons) [23][24][25][26][27] with the new generation of bent crystals developed by INFN Ferrara group [22,28,29] demonstrated channeling efficiencies in the range from 10 to 40 %, i.e. of the same order of magnitude as for protons.…”

“…Due to so-called quasimosaic effect [57,58], this primary curvature produces a secondary bending of (111) planes which will be used to deflect charge particles. A technology of dynamical holder [21,22] that allows one to adjust the crystal curvature after the installation of the crystal into the accelerator tube, has been also developed. This option will provide the possibility of deflection angle optimization during the experiment.…”

Investigation on radiation generated by Sub-GeV electrons in ultrashort Si and Ge bent crystals

“…Both crystals were mounted on a piezo-driven dynamical holder [21,35], which allowed to modify the sample curvature (θ b ) without replacing the samples and without break the vacuum of the experimental apparatus. The holder was mounted on a high-precision goniometer with 5 degrees of freedom.…”

Simulation code for modeling of coherent effects of radiation generation in oriented crystals

“…Furthermore, we simulated the expected radiation spectra for experimental cases presented in [45,67]. The scope of the experiment [45,67] was the measurement of channeling characteristics, i.e., channeling efficiency and dechanneling length, in dependence on the radius of bent crystals. Since channeling radiation strongly depends on these characteristics, a study of channeling radiation spectra vs crystal radius could be relevant for the development of novel x-ray and gamma radiation sources.…”