A photon detector for BNL experiment E949 is described. The detector consists of a lead scintillator "sandwich" of 25 layers of 5 mm thick scintillator BC404 and 24 layers of 2 mm lead absorber. Readout is implemented with 30-60 cm long WLS fibers (BCF 99-29AA) glued into grooves in the BC404. Average yield was measured with cosmic rays to be about 43 p.e./MeV. Extruded plastic scintillation counters developed for sandwich detectors of photons for the KOPIO experiment are also described. For a 7 mm thick counter with 4.3 m long WLS fibers spaced at 7 mm a light yield of 18.7 p.e./MeV and time resolution of 0.71 ns were obtained. A prototype photon veto module consisting of 10 layers of 7 mm thick extruded plastic slabs interleaved with 1 mm lead sheets was tested.
Europium doped alkaline earth fluoride [Eu:AEF 2 (AE = Ca, Sr, Ba)] nanoparticles were synthesized and systematically incorporated into the core of modified chemical vapor deposition (MCVD)-derived silicabased preforms by solution doping. The resulting preforms were examined to determine the impact of the nanoparticles chemistry on the spectroscopic behavior of the glass. The dominant existence of Eu 3+ was demonstrated in all preforms, which is in contrast to conventional solution doped preforms employing dissolved europium salts where Eu 2+ is primarily observed. Raman spectroscopy and fluorescence lifetime measurements indicated that the nanoparticles composition is effective in controlling, at a local chemical and structural level, the spectroscopic properties of active dopants in optical fiber glasses. Further, there is a systematic and marked increase in radiative lifetime, τ, of the Eu 3+ emission that follows the cationic mass; τ Ca < τ Sr < τ Ba with the BaF 2-derived sample yielding a 37% lengthening of the lifetime over the CaF 2-derived one. Such nanoscale control of what otherwise is silica glass could be useful for realizing property-enhanced and tailored spectroscopic performance from otherwise "standard" materials, e.g., vaporderived silica, in next generation optical fibers.
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