C. D’Ambrosio

Antisite defect-free Lu3(GaxAl1−x)5O12:Pr scintillator

Pr-doped Lu3(GaxAl1−x)5O12:Pr, x=0–1, single crystals were grown by the micro-pulling-down method. We study luminescence and scintillation characteristics of the sample set focusing on their dependence on the gallium content. For x=0.4 we obtain the high figure-of-merit material with elevated density, high efficiency, and very fast scintillation response below 20ns without any slower components. Improvement of scintillation performance is explained as due to the absence of the antisite LuAl defects that was for the first time realized in such bulk garnet single crystals grown from the high temperature melt.

Scintillation characteristics of Lu3Al5O12:Ce optical ceramics

Optical absorption, luminescence, and scintillation characteristics of Lu3Al5O12:Ce optical ceramics were measured and compared with an analogous high quality single crystal. Optical absorption of the former shows an additional light scattering loss due to nanovoids and/or refraction index inhomogeneities. Even though radioluminescence intensity of the optical ceramics prepared by a coprecipitation route exceeds that of single crystal, its scintillation light yield is lower due to the charge carrier retrapping in the process of energy transfer towards the Ce3+ emission centers. Retrapping processes are evidenced by thermoluminescence measurements below room temperature. Lu3Al5O12:Ce optical ceramics does not show the presence of the LuAl antisite defects which decreases the scintillation figure of merit in single crystals grown from the melt [M. Nikl, Phys. Status Solidi A 202, 201 (2005)]. Furthermore, using the ceramic technology, one can achieve both the homogeneous doping and higher Ce concentration. ...

Hybrid photon detectors

Abstract Hybrid photon detectors detect light via vacuum photocathodes and accelerate the emitted photoelectrons by an electric field towards inversely polarized silicon anodes, where they are absorbed, thus producing electron–hole pairs. These, in turn, are collected and generate electronic signals on their ohmic contacts. This review first describes the characteristic properties of the main components of hybrid photon detectors: light entrance windows, photocathodes, and silicon anodes. Then, essential relations describing the trajectories of photoelectrons in electric and magnetic fields and their backscattering from the silicon anodes are derived. Depending on their anode configurations, three families of hybrid photon detectors are presented: hybrid photomultiplier tubes with single anodes for photon counting with high sensitivity and for gamma spectroscopy; multi-anode photon detector tubes with anodes subdivided into square or hexagonal pads for position-sensitive photon detection; imaging silicon pixel array tubes with finely segmented anodes for photon-sensitive imaging devices. Some of the hybrid photon detectors’ applications and achievements in radiation detection are discussed and compared with competing devices such as photomultipliers, image intensifiers, photodiodes, silicon drift chambers, charge coupled devices, visible light photon counters, and photographic emulsions.

Precision optical systems for the new generation of Ring Imaging Cherenkov detectors in high energy physics experiments

High precision optical systems are required for the new generation of Ring Imaging Cherenkov detectors in high energy physics experiments. In the framework of the LHCb and COMPASS experiments, we have started an R&D programme to assess and to eventually overcome the limits of present technologies. Here, we present the available mirror technologies and discuss the optical and mechanical parameters.

Growth and Characterization of Y-Lu-Gd Aluminium Perovskites

Y-Lu-Gd pure, mixed and doped aluminium perovskite crystals belong to efficient and durable crystals used in different laser and scintillation applications. This paper will review methods of their growth (the Czochralski, Bridgman, EFG ones and their modifications), their overall growth yield and present performances. Various kinds of spectroscopies are used to characterize the crystals in the range ≈ 0.5 eV to ≈ 1 MeV. Finally, status and possible development of Y-Lu-Gd aluminium perovskite crystals will be evaluated with emphasis to their use in modern applications.