Abstract
Our evaluation of a high-resolution digital imaging
detector capable of providing millisecond time resolution and high
sensitivity for neutrons is presented. This detector is a modified version
of the high-resolution -ray imager developed previously at
Radiation Monitoring Devices, Inc. (RMD, Inc.), and consists of an
Electron Multiplying Charge Coupled Device (EMCCD) attached
to a neutron-sensitive scintillator via a fiberoptic taper. By virtue of
its internal gain, the EMCCD permits high speed readout without
introducing additional noise, thereby enabling high frame rate operation
with an enhanced signal-to-noise ratio (SNR). Detector sensitivity
is enhanced through the use of a back-thinned EMCCD,
which provides high quantum efficiency over a typical emission
range for many neutron-sensitive scintillators. Preliminary evaluations
conducted at the Liquids Reflectometer beam port of the
Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory
(ORNL) demonstrate that this new detector has the sensitivity
to detect individual neutrons and the acquisition speed to perform
energy-selective imaging with a temporal resolution of milliseconds.
While substantial improvements in timing and imaging
performance are planned, this prototype detector has already generated
the first ever images of the SNS Liquids Reflectometer beam
profile and was also used to demonstrate a technique for obtaining
Bragg edge transmission imaging using energy-selective neutrons.
The preliminary data, along with the detector design, evaluation,
and planned developments are discussed in this paper.
