A Detector Testing Chamber for the Nab Experiment *

The Nab experiment is studying the decay electrons and protons from neutron beta decay in the search for BSM physics.  It will use pixelated silicon detectors to detect these decay particles. It is important to characterize timing and energy response of these Nab detectors and the impact of charge sharing among detector pixels to understand the systematic errors.  This includes the timing response to the decay protons and electrons, which must be measured under controlled conditions.  We will use a proton beam at the University of Manitoba to test the detector response to protons as a function of energy, position, and angle of impact.  We will also study multipixel events, charge sharing, individual channel trigger thresholds and their impact on total measured energy.  In addition, how well we can recover particle energies in multipixel events.

In addition to proton studies at Manitoba, sealed sources will be used to give us a known output that we can compare to our measured signals.  We report on the design of a detector testing chamber with a calibration source and timing detector assembly.  The source positioner requirements will be discussed in detail.  We will move a collimated source over detector pixel edges to study the response of the pixel and its neighbors.  I will present the current design and implementation of this source positioner as well as the Geant4 studies currently in progress.