Speaker
Description
Neutron imaging provides complementary information to X-ray imaging due to the different interactions of these radiation types with matter. This technique is valuable in various fields, including nuclear engineering and non-destructive industrial diagnostics.
Building on advancements in 3D sensor technology, a novel device based on a 3D micro-structured design has been developed for thermal neutron detection and imaging. This device, studied within the INFN HYDE2 project, is fabricated using a streamlined process with planar n-on-p pixels on the front side. On the back side, Deep Reactive Ion Etching (DRIE) creates deep (~25 µm) and narrow cavities, which are then to be filled with neutron-converting materials such as $^6$LiF or $^{10}$B.
The sensor consists of a 256×256 pixel array, with each pixel measuring 55×55 µm², and is integrated with a Timepix readout chip for data acquisition.
A key objective of this work is to optimize the geometry of the cavities (i.e., their width and distance) to maximize the neutron detection efficiency. This requires careful consideration of neutron capture, the detection of the resulting charged particles, and the collection of the generated charge necessary to produce an electrical signal—a challenging problem to solve.
To address this, the study is divided into multiple tasks. First, the energy deposition map of charged particles generated by neutron capture is determined using GEANT4 simulations. Then, TCAD Sentaurus is used to calculate the electrical properties of the silicon device. While TCAD can also be used to determine charge collection efficiency (CCE), evaluating multiple geometries with this approach is computationally intensive.
To overcome this limitation, the energy deposition map and static TCAD simulation results are incorporated into an Allpix2 simulation. Within Allpix2, the Weighting Potential, Electric Field, and Doping Profile—obtained from TCAD—are imported. Next, the DepositionPointCharge module is employed to inject charge into the device according to the energy distribution derived from GEANT4. To account for the specific geometry of the HYDE2 device, a modified version of the TransientPropagation module is implemented, for the transportation of the charge.
Finally, the total CCE is computed for different geometries, and a comparison with transient TCAD simulations in selected geometries is performed to validate the accuracy of the Allpix2 results.
| Will the talk be given in person or remotely? | In person |
|---|
