D. Lietti

Silicon Photomultipliers as a Readout System for a Scintillator-Lead Shashlik Calorimeter

Silicon photomultipliers are silicon devices that in recent times have been proposed as candidates for the replacement of photomultiplier tubes in many experimental situations. In this article we describe the performance of SiPMs as a readout system of a shashlik calorimeter composed of 41 8×8 cm2, 3.27-mm-thick tiles of scintillator and 40 8×8 cm2, 3.27-mm-thick tiles of lead, for a total of ~24 radiation lengths; the light is collected by 64 0.8-mm wave-length-shifter (WLS) fibers grouped in bundles of four for, a total of 16 channels. The SiPMs are manufactured by FBK-irst and have a sensitive area of 1 mm2. The calorimeter has been tested at CERN using both a low (PS T10 beamline) and high (SPS H4 beamline) energy beam during the summer 2009 data taking.

Single and Multiple Volume Reflections of Ultra-Relativistic Electrons in a Bent Crystal as Tools for Intense Production of Electromagnetic Radiation

Electromagnetic radiation emitted by ultrarelativistic volume-reflected and multi-volume-reflected electrons in a bent crystal is very intense and takes place over a broad angular range of the incident beam. Such radiation results to be nearly independent from the particles trajectory and charge. This paper describes the possible applications these features allow, from the production of a gamma or a positron source to the crystal-assisted collimation of future linear e+/e− colliders and crystal-based electromagnetic calorimeters.

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

Thanks to the effective electrostatic potential generated by the ordered atomic structure, bent crystals can efficiently deflect ultra relativistic charged beams by means of planar and axial channeling phenomena as well as of the recently discovered volume reflection effect. Most of the experimental knowledge about these phenomena has been gathered with Si crystals, but it has been recently demonstrated that the steering performance can be improved by using high quality Ge materials which have a larger atomic number. In this paper, we investigate channeling and volume reflection of 400 GeV protons from (110) lattice planes in highly bent Ge strips crystals. Both production and characterization of the strips are presented. Herein, the experimental results on deflection are compared with theoretical predictions, with previous published data and with the expected performances of Si crystals in similar experimental conditions.

A topologically connected multistrip crystal for efficient steering of high-energy beam

Multiple volume reflection has been recognized as an efficient method to steer high-energy particle beams for beam extraction or collimation. A multistrip silicon crystal has been designed, consisting in an array of mutually aligned 16 silicon strips to cause multiple volume reflection. The multistrip was fabricated from one individual wafer and given the shape of a topologically connected crystal, which proved to be the best configuration for alignment. Full characterization of such a crystal has been carried out. The crystal was extensively tested at the H8 CERN line with 400 GeV/c protons. Record deflection efficiency of (96.0±0.5)% for a mean deflection angle of (112.2±0.1) μrad was obtained. Since the performance of volume reflection is energy dependent, a specific emulation code has been developed to predict multistrip behavior at various energies.

The experimental setup of the Interaction in Crystals for Emission of RADiation collaboration at Mainzer Mikrotron: Design, commissioning, and tests

Silicon/germanium flat/bent crystals are thin devices able to efficiently deflect charged particle GeV-energy beams up to a few hundreds of μrad; moreover, high intensity photons can be efficiently produced in the so-called Multi-Volume Reflection (MVR) and Multiple Volume Reflections in One Crystal (MVROC) conditions. In the last years, the research interest in this field has moved to the dynamic studies of light negative leptons in the low energy range: the possibility to deflect negative particles and to produce high intensity γ sources via the coherent interactions with crystals in the sub-GeV energy range has been proved by the ICE-RAD (Interaction in Crystals for Emission of RADiation) Collaboration at the MAinzer MIkrotron (MAMI, Germany). This paper describes the setup used by the ICE-RAD experiment for the crystals characterization (both in terms of deflection and radiation emission properties): a high precision goniometer is used to align the crystals with the incoming beam, while a silicon based profilometer and an inorganic scintillator reconstruct, respectively, the particle position and the photon spectra after the samples. The crystals manufacturing process and their characterization, the silicon profilometer commissioning at the CERN PS T9 beamline, and the commissioning of the whole setup installed at MAMI are presented.

Bent crystals as a tool for manipulation of ultrarelativistic electron beams

Channeling and coherent interactions of charged particles in crystals are known since the 60s and used as a tool for material analysis by low-energy ion channeling and for the generation of linearly polarized γ-beams through coherent bremsstrahlung at electron accelerators. We report on an experiment carried out at the MAinzer MIkrotron with the aim of investigating the electromagnetic radiation generated by 855 MeV electrons in a bent crystal. Such study allows one to investigate the influence of the crystalline curvature on the radiation emitted by sub-GeV electrons in a bent crystal and the possible application of this kind of radiation.