Contribution Oral presentation
Development and Construction of the Belle II TOP Detector
A Time-of-Propagation (TOP) detector is a ring-imaging Cherenkov detector that images a Cherenkov ring using propagation times and detected x- and y-positions of Cherenkov photons. It has been developed for particle identification in the barrel region of the Belle II spectrometer, which will probe new physics beyond the Standard Model with a luminosity of 8x10³⁵/cm²/s. The TOP detector is intended to achieve good π/K separation in the momentum range up to around 3 GeV/c under the high-luminosity environment. The detector construction has been started and the remaining development is being finalized toward the installation into the spectrometer in early 2015. A single detector module mainly consists of a synthetic silica plate, as the Cherenkov radiator, and an array of micro-channel plate (MCP) photomultiplier tubes (PMTs) with readout electronics. Optical components for the first detector module are being delivered one after another. The delivered components are in process of optical inspections and assembly preparation. Mass production of the MCP-PMTs is on going smoothly. The performance details are being inspected under the operational magnetic field of 1.5 T. Although the lifetime of an MCP-PMT has been an issue concerning the high-luminosity environment, atomic layer deposition on MCPs has improved the lifetime significantly. Development of the readout electronics is being finalized. Their high-speed waveform sampling ASICs and circuit board stacks are in preproduction. Preproduction for the mechanical structure of a detector module is about to start. It is crucial to establish the optical and electrical contacts between the optics, MCP-PMTs and readout electronics. A beam test on a detector module prototype has been carried out using a 2 GeV/c e⁺ beam at the LEPS beam line of SPring-8 in June 2013. The prototype consists of the optics and MCP-PMTs that have nearly final and final specifications, respectively. The test results have demonstrated the detector principle reasonably.