Masami Chiba

SIGNIFICANT IMPROVEMENT OF PBWO4 SCINTILLATING CRYSTALS BY DOPING WITH TRIVALENT IONS

Abstract Doping by different trivalent ions (La3+, Lu3+, Gd3+, Y3+, Sc3+) was systematically studied in PbWO4 crystals in the same way, using raw material from the same source. The result was compared with an undoped sample (actually a Pb-rich one) and samples doped with divalent (Cd2+) and pentavalent (Nb5+) ions. All the trivalent ions but Sc3+ gave a significant improvement in transmittance in the short wavelength region (330–450 nm) and in radiation hardness. Among all the tested dopants, Y3+ and Gd3+ showed the best result; these dopants may be worth further studies, since they have another advantage of the segregation coefficient close to unity.

DIRAC: A High Resolution Spectrometer for Pionium Detection

The DIRAC spectrometer has been commissioned at CERN with the aim of detecting

Measurement of R and search for new heavy quarks in e+e- annihilation at 50 and 52 GeV centre-of-mass energies

\pi^+ \pi^-

Performance and radiation damage of a BaF2 calorimeter

atoms produced by a 24 GeV/

Detection of π+π− atoms with the DIRAC spectrometer at CERN

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Neutron Emission from Fracture of Piezoelectric Materials in Deuterium Atmosphere

high intensity proton beam in thin foil targets. A challenging apparatus is required to cope with the high interaction rates involved, the triggering of pion pairs with very low relative momentum, and the measurement of the latter with resolution around 0.6 MeV/

Proposed Method to Produce a Highly Polarized e+ Beam for Future Linear Colliders

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Differential cross sections of proton compton scattering in the resonance region

. The general characteristics of the apparatus are explained and each part is described in some detail. The main features of the trigger system, data-acquisition, monitoring and setup performances are also given.

Construction of polarized slow-positron beams using a compact cyclotron

Abstract The total cross section for the process of the e+e- annihilation into hadrons has been measured at the centre-of-mass energies of 50 GeV and 52 GeV and a search has been made for new heavy quarks. The ratios R = σ(e+e- → hadrons)/σpoint(e+e- → μ+μ-) obtained are 4.4±0.5 at 50 GeV and 4.7±0.3 at 52 GeV, respectively. An additional systematic uncertainty is 10%. From the event shape analysis we found no evidence for a new quark with charge 2 3 e .

Bismuth silicate as a scintillating material for electromagnetic shower detectors

The performance of a barium fluoride (BaF2) scintillator as an electromagnetic shower calorimeter is investigated for electrons in the energy range 0.25–5 GeV. The energy resolution (fwhm) is expressed by 0.098E14 [GeV] and compared with a Monte Carlo simulation. For radiation damage a dose of 1 × 105 Gy (1 Gy (1 Gy = 100 rad) shortens the optical attenuation length to 14%. The deterioration is compared with that of BGO.