Abstract
This paper describes the design of a high-speed, single-photon sensitive, Hybrid Photon Detector (HPD). The detector consists of a vacuum tube, containing a Micro Channel Plate (MCP) and 4 CMOS pixel readout chips, sealed with a transparent optical input window with a photocathode. The design described here utilizes currently available technologies, specifically the Timepix readout chips and the Photonis Planacon MCP-PMT vacuum tubes. The aim of the project is to demonstrate the feasibility of a 4-side buttable square MCP-HPD with high packing fraction sensitive area. Presented here is the mechanical and thermal design of the prototype detector.