Kavli Affiliate: Tadayuki Takahashi
| First 5 Authors: Shunsaku Nagasawa, Shunsaku Nagasawa, , ,
| Summary:
We have developed a wide-gap CdTe double-sided strip detector (CdTe-DSD) for
the fourth and fifth flights of the Focusing Optics X-ray Solar Imager sounding
rocket experiment (FOXSI-4/FOXSI-5). This detector features a 30 um strip width
and a variable gap width from 30 um to 70 um, enabling position resolution
finer than the strip pitch by inducing charge sharing across adjacent strip
electrodes and utilizing this shared energy information for position
reconstruction. However, this wide-gap configuration introduces complex
detector responses, such as charge loss in the gap regions and electric field
distortion near the electrodes, requiring a more advanced modeling approach for
interpreting observation results in FOXSI-4/FOXSI-5 and for further
optimization of future detector design. To address these complexities, we have
constructed a first-principles simulation framework to model the detector
response. The simulation integrates Geant4-based Monte Carlo simulations of
energy deposition, finite element calculations of electric and weighting fields
using COMSOL Multiphysics, charge transport modeling incorporating trapping and
diffusion, and calculation of the induced charge on the electrodes based on the
Shockley-Ramo theorem. By introducing a surface conductive layer, which causes
electric field distortion, the model successfully reproduces the experimentally
observed charge loss on the cathode side. In addition, the model reproduces the
distinct charge sharing behavior on the cathode and anode sides. These results
validate the effectiveness of the model in characterizing the wide-gap
CdTe-DSD.
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