Production and commissioning of a large prototype Digital Hadron Calorimeter for future colliding beam experiments

A new detector technology is being developed for future colliding beam experiments that is based on the use of fine-grained calorimetry, to optimize the use of Particle Flow Algorithms (PFAs) in measuring hadronic jets. Instead of traditional tower geometry and energy summation from many sampling layers, the new approach measures energy deposition in 1 cm² cells on each sampling layer using discriminators. Jets are reconstructed using hit patterns from each layer, combined with information from inner tracking and the electromagnetic calorimeter. We have built a 480,000 channel prototype detector that is based on Resistive Plate Chambers (RPCs) to demonstrate this concept. The development is part of the CALICE Collaboration. The readout system uses a 64-channel custom integrated circuit called DCAL to record hits from each cell and apply a global timestamp. The chips mount directly on sophisticated front-end boards that are not only an integral part of the charge collection of the detector chambers, but also incorporate digital signal transmission, clock and control, and power and ground. The readout of data is serial, multiplexed into high-speed serial streams and sent to a “back-end” VME system for time-sorting and higher-level triggering. The system can be operated with an external trigger or be self-triggered, and can produce trigger signals from the front-end chips. The construction, installation, and commissioning of this prototype system is now complete. We have begun a measurement program using a test beam at Fermilab. An overview of the system is described. Experiences in building this large prototype system are reported. Results from the test beam are presented.