Development of a Scintillator Cluster Detector and Microcontroller Integrated Detector Circuit

This thesis reports on the development of a prototype cluster scintillator detector
hermetically sealed in an aluminium housing for use in the HYPATIA array. The HYPATIA
array will consist of GaGG and CeBr3(Ce) scintillators, however, this prototype uses four
NaI(Tl) crystals to optimise the design and validate the encapsulation process before the
final device is constructed. The NaI(Tl) crystals, 30x30x80 mm3 were mounted to 2x2
SiPM arrays. The energy and time resolution, energy calibration and linearity of the
detector were measured for each detector element as well as add-back being used for
each detector pairing. The long-term performance of the hermetic seal was tested over a
two-month period and showed no degradation in detector performance outside of
measurement error. The best performing crystal had a FWHM energy resolution of
7.79±0.02% while the FWHM coincidence time resolution between a pair of crystals was
23.1±0.2 ns. A proposal for a redesign of the aluminium housing and associated clamping
system is also presented. The redesign aims to minimise the external dimensions of the
can and in particular its lid in order to enable the detector to better fit with other detectors
of the same design in the HYPATIA array. The suggested redesign allows for a closer
packing of the quad clusters in the array, reducing the dead space within the active solid
angle of the array from 8.5±0.1% to 2.2±0.4%.
Also reported in this thesis is the development of a microcontroller integrated detector
circuit. This circuit used an Arduino Nano BLE33 microcontroller on a solderless
breadboard with a peak hold circuit. The circuit had a maximum nonlinearity of
1.24±0.03% and an average FWHM channel resolution of 44.5±0.2. The motivation behind
this work was to extend the use of the Hypatia cluster into the societal applications regime
by enabling a portable, high efficiency scintillator detector.
The conclusions from the present study regarding the performance of the prototype
cluster detector validate the technological choices for the assembly methods and
materials for canning and informs future choices for the final HYPATIA clusters.