Development of the "GP2" Detector: Modification of the PImMS CMOS Sensor for Energy-Resolved Neutron Radiography

This paper reports on the development and commissioning of the GP2 detector. GP2 was developed to address the requirement for a high-resolution event-mode imaging detector, for application in energy-resolved neutron radiography. The name GP2 derives from the use of gadolinium as a neutron conversion material, combined with a second-generation mass spectrometry sensor known as PImMS2. Theoretical and measured characteristics of GP2 are compared, with emphasis on the usability and functionality of the detector. The development of the detector has been steered by a design philosophy which was established to ensure that the detector has unique and novel impact. The motivation and consequences of the design philosophy are discussed. The key parameters reported are the neutron detection efficiency (7.5% at 2.5 Å), gamma sensitivity (1.5 × 10 -3 ), and a spatial resolution (modulation transfer function at 10%) of 6.4 lp/mm for a 4-μm-thick natural gadolinium neutron converter film.