Highly bent (110) Ge crystals for efficient steering of ultrarelativistic beams

Salvador, D. De; Maggioni, G.; Carturan, S.; Bazzan, M.; Argiolas, N.; Carnera, A.; Palma, Matteo Dalla; Mea, G. Della; Bagli, E.; Mazzolari, A.; Bandiera, L.; Guidi, V.; Lietti, D.; Berra, A.; Guffanti, D.; Prest, M.; Vallazza, E.

doi:10.1063/1.4824798

Cited by 11 publications

(22 citation statements)

References 29 publications

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“…Indeed, since a Ge crystal provides a stronger potential, one expects an increase in the angular acceptance for channeling and an enhancement of e.m. radiation emission. Currently, a few channeling experiments have been performed with bent Ge, only with positively charged particles and only in the hundreds GeV energy range [27,28,29,30], while with electrons and at lower energies there are no data in literature due to the technical difficulties of fabrication of an ultra-short bent Ge crystal.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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We report the observation of the steering of 855 MeV electrons by bent silicon and germanium crystals at the MAinzer MIkrotron. Crystals with 15 µm 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.

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Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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“…Figure 3 shows the distribution of particle deflection angles after the interaction with the crystals for channeling and volume reflection orientations. For the channeling case, a fraction of 3% AE 1% of the beam is deflected by the nominal bending angle (190 AE 3 μrad), in contrast to what was obtainable with a Si (66%) [11] or a Ge (72%) [30] strip of the same geometrical properties. The deflection efficiency of channeling and volume reflection and the statistical error are calculated according to Ref.…”

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confidence: 54%

“…The concentration of dislocations is traditionally referred to the length of dislocation lines by unit volume, i.e., for randomly distributed dislocations, the areal density of dislocations intercepted by a random plane. Germanium (Ge), the natural alternative to Si, demonstrated an ability to overcome the performances of Si owing to its deeper potential well [29][30][31]. However, particular care is needed in the selection of starting material in terms of defect concentration.…”

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confidence: 99%

“…The dechanneling length, i.e., the length for which a 1=e fraction of the initially channeled particles have left the channeling state, was measured to be 0.35 mm, lower than 1.5 mm for Si [45]. As the crystal was oriented in order to excite volume reflection, most of the particles (83% AE 2%) were deflected at an angle of 11.9 AE 0.5 μrad, comparable to Si (97.5% and 11.7 μrad) [9] and Ge (96.6% and 17.3 μrad) [30]. The lower value for the dechanneling length suggests that the particle trajectories are largely altered by the presence of dislocations in the LiNbO 3 .…”

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confidence: 99%

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Orientational Coherent Effects of High-Energy Particles in aLiNbO3Crystal

et al. 2015

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A bent lithium niobate strip was exposed to a 400-GeV/c proton beam at the external lines of CERN Super Proton Synchrotron to probe its capabilities versus coherent interactions of the particles with the crystal such as channeling and volume reflection. Lithium niobate (LiNbO3) exhibits an interplanar electric field comparable to that of Silicon (Si) and remarkable piezoelectric properties, which could be exploited for the realization of piezo-actuated devices for the control of high-energy particle beams. In contrast to Si and germanium (Ge), LiNbO3 shows an intriguing effect; in spite of a low channeling efficiency (3%), the volume reflection maintains a high deflection efficiency (83%). Such discrepancy was ascribed to the high concentration (10(4) per cm2) of dislocations in our sample, which was obtained from a commercial wafer. Indeed, it has been theoretically shown that a channeling efficiency comparable with that of Si or Ge would be attained with a crystal at low defect concentration (less than ten per cm2). To better understand the role of dislocations on volume reflection, we have worked out computer simulation via dynecharm++ Monte Carlo code to study the effect of dislocations on volume reflection. The results of the simulations agree with experimental records, demonstrating that volume reflection is more robust than channeling in the presence of dislocations.

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“…In order to increase the efficiency of deflection, material with higher Z were also tested. As an example, Ge crystals with a sufficiently high crystalline perfection demonstrated to overcome the performances of Si crystals under the same condition [8,9]. Recently, a new collimation scheme based on self-bent graded Si x Ge 1Àx crystal was proposed, by exploiting the volume reflection effect [10].…”

Section: Introductionmentioning

confidence: 98%