Performance of a prototype TORCH time-of-flight detector

TL;DR

This paper reports on the development and testing of a TORCH prototype, a novel time-of-flight detector using Cherenkov photons in quartz for charged particle identification, demonstrating performance close to design goals.

Contribution

The paper presents the construction, testing, and performance evaluation of a 1.25 m TORCH prototype module with MCP-PMTs, advancing the development of time-of-flight particle identification technology.

Findings

Photon yield measurements match expectations.

Single-photon time resolution approaches design goals.

Prototype performance is close to full-scale detector requirements.

Abstract

TORCH is a novel time-of-flight detector, designed to provide charged particle identification of pions, kaons and protons in the momentum range 2-20 GeV/c over a 9.5 m flight path. A detector module, comprising a 10mm thick quartz plate, provides a source of Cherenkov photons which propagate via total internal reflection to one end of the plate. Here, the photons are focused onto an array of custom-designed Micro-Channel Plate Photo-Multiplier Tubes (MCP-PMTs) which measure their positions and arrival times. The target time resolution per photon is 70 ps which, for 30 detected photons per charged particle, results in a 10-15 ps time-of-flight resolution. A 1.25 m length TORCH prototype module employing two MCP-PMTs has been developed, and tested at the CERN PS using a charged hadron beam of 8 GeV/c momentum. The construction of the module, the properties of the MCP-PMTs and the readout electronics are described. Measurements of the collected photon yields and single-photon time resolutions have been performed as a function of particle entry points on the plate and compared to expectations. These studies show that the performance of the TORCH prototype approaches the design goals for the full-scale detector.