Publications by Johan Fopma

TORCH — a Cherenkov-based time-of-flight detector

Acta Physica Polonica B Jagiellonian University 7 (2014) 711-718

MWU van Dijk, NH Brook, EN Cowie, D Cussans, C D'Ambrosio, R Forty, C Frei, T Gys, D Piedigrossi, L Castillo García, J Fopma, R Gao, N Harnew, T Keri

TORCH is an innovative high-precision time-of-flight system to provide particle identification in the difficult intermediate momentum region up to 10 GeV/c. It is also suitable for large-area applications. The detector provides a time-of-flight measurement from the imaging of Cherenkov photons emitted in a 1 cm thick quartz radiator. The photons propagate by total internal reflection to the edge of the quartz plate, where they are focused onto an array of photon detectors at the periphery. A time-of-flight resolution of about 10-15 ps per incident charged particle needs to be achieved for a three sigma kaon-pion separation up to 10 GeV/c momentum for the TORCH located 9.5 m from the interaction point. Given ∼ 30 detected photons per incident charged particle, this requires measuring the time-ofarrival of individual photons to about 70 ps. This paper will describe the design of a TORCH prototype involving a number of ground-breaking and challenging techniques.

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