A Detector Testing Chamber for the Nab Experiment*

The Nab experiment is being performed to study the neutron decay correlations in the search for BSM physics and verification of CKM unitarity.  It will use pixelated silicon detectors to detect the decay electron energy and proton time of flight for complete kinematic reconstruction of each event.  It is important to characterize timing and energy response of the 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 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, and the recovery of particle energies in multipixel events.

Sealed sources will be used for energy calibration.  We report on the design of a detector testing chamber with a calibration source and timing detector assembly.  We will move a collimated source over detector pixel edges to study the response of the pixel and its neighbors.  I will present the requirements, current design and implementation of the detector testing chamber and this source positioner.