The Hawaii Muon Beamline.

Abstract

High Energy Physics (HEP) instrumentation development programs often require extensive tests of experimental equipment such as silicon pixel detectors, single photon sensitive detectors for Cherenkov radiation, particle time of ight systems, etc. These tests are usually conducted at accelerator research facilities where available beam-time is not only limited, but also expensive. The Hawaii Muon Beamline (HMB) will use cosmic-ray generated muons to enable performance evaluations of such devices under test. HMB is a beam telescope constructed out of four posi- tion sensitive tracking detectors and a calorimeter system for measurement redundancy. Position tracking detectors are built using an array of geiger-mode avalanche photodiodes, also known as Multi-pixel Photon Counter (MPPCs), coupled to square Polyvinyl Toluene (PVT) scintillator blocks. The MPPCs are positioned orthogonally along the block edges. Charged particles traveling through a scintillation block emit detectable amounts of light. The analog output pulses from the MPPCs trigger the TARGETX waveform digitizing ASIC which samples at 1 Giga Sample per second (GSPS). From the pulse amplitudes, being proportional to the amount of light, the charged particle penetration position can be estimated in a 2D plane. To construct the HMB, each pair of tracking detectors need to be placed vertically, one on top of the other, providing the entrance and exit position of the beam. In between both pairs, space is made available for a device under test. In addition, a separate calorimeter system composed of four rectangular blocks of Sodium Iodide (NaI) crystals coupled to photomultiplier tubes (PMT) is placed below and o -axis of the lower pair tracking system. This calorimeter system is used to measure the deposited energy of the particle exiting the system and to veto shower events. HMB enables to handle sub-nanosecond timing of signals, and its digital processing core is implemented on an FPGA, which instructs a PC to read out from each detector subsystem via Gigabit Ethernet. The collected data allow post-processing algorithms to determine the precise trajectory of the passing particle, hence enables the use of this information to categorize the device under test. This document focuses on the construction of HMB. It describes in detail its electronic readout system and presents some initial results.