[Paper Review] Additive manufacturing of fine-granularity optically-isolated plastic scintillator elements

S. Berns, E. Boillat+15 more|arXiv (Cornell University)|Feb 22, 2022

Additive Manufacturing and 3D Printing Technologies4 citations

TL;DR

This paper demonstrates the first 3D-printed matrix of fine-grained, optically isolated plastic scintillator cubes using fused deposition modeling (FDM), achieving a uniform light yield of ~45 photoelectrons per cosmic muon and optical crosstalk below 2%. The method integrates scintillating and white reflective filaments in a single printing process, marking a critical step toward fully additive manufacturing of particle detectors with 3D granularity.

ABSTRACT

Plastic scintillator detectors are used in high energy physics as well as for diagnostic imaging in medicine, beam monitoring on hadron therapy, muon tomography, dosimetry and many security applications. To combine particle tracking and calorimetry it is necessary to build detectors with three-dimensional granularity, i.e. small voxels of scintillator optically isolated from each other. Recently, the 3DET collaboration demonstrated the possibility to 3D print polystyrene-based scintillators with a light output performance close to that obtained with standard production methods. In this article, after providing a further characterization of the developed scintillators, we show the first matrix of plastic scintillator cubes optically separated by a white reflector material entirely 3D printed with fused deposition modeling. This is a major milestone towards the 3D printing of the first real particle detector. A discussion of the results as well as the next steps in the R&D is also provided.

Motivation & Objective

• Develop a scalable, cost-effective method for producing fine-grained, optically isolated plastic scintillator elements for particle detectors.
• Overcome challenges in traditional manufacturing of small, precisely shaped scintillator voxels through additive manufacturing (AM).
• Enable three-dimensional granularity in scintillator detectors for combined particle tracking and calorimetry.
• Optimize FDM 3D printing for polystyrene-based scintillators with stable optical and mechanical properties.
• Demonstrate the feasibility of printing both scintillating and reflective materials in a single integrated process.

Proposed method

• Utilized fused deposition modeling (FDM) 3D printing with custom-developed scintillating filament composed of polystyrene doped with 2% p-terphenyl and 0.05% POPOP, plus 5% byphenyl as a plasticizer.
• Produced a white reflective filament optimized for FDM to ensure high reflectivity and mechanical stability between scintillator voxels.
• Printed a 3D matrix of 1 cm³ scintillator cubes separated by the white reflective material, forming a fully integrated, optically isolated structure.
• Measured light yield using vertical cosmic muons and calibrated signals via 90Sr β-source exposure to determine MPPC gain and pedestal correction.
• Quantified optical crosstalk by comparing light signals in a main cube to those in adjacent cubes, using the ratio M_xtalk / M_trk.
• Employed MPPCs read out via CAEN DT5702 front-end boards, with signal processing including pedestal subtraction and gain correction for photoelectron (p.e.) extraction.

Experimental results

Research questions

• RQ1 Can FDM 3D printing produce optically isolated plastic scintillator voxels with performance comparable to conventional methods?
• RQ2 What is the light yield uniformity and optical crosstalk level in a 3D-printed matrix of scintillator cubes?
• RQ3 Can a single FDM process simultaneously print both scintillating and reflective materials with sufficient optical and mechanical stability?
• RQ4 How does the attenuation length and transparency of 3D-printed polystyrene scintillator compare to standard extruded or molded scintillators?
• RQ5 Can the 3D-printed scintillator matrix support combined particle tracking and calorimetry with sub-ns timing resolution?

Key findings

• The 3D-printed scintillator matrix achieved a uniform average light yield of approximately 45 photoelectrons per cosmic muon across all cubes.
• Optical crosstalk between adjacent scintillator cubes was measured at less than 2%, confirming effective optical isolation.
• The scintillator filament maintained stable optical properties after printing, with no significant degradation in light output or transparency.
• The 3D-printed reflector material effectively isolated adjacent scintillator voxels, preventing significant light leakage.
• The method demonstrated reproducibility in printing both scintillating and reflective components in a single integrated process.
• The results represent a major milestone toward the realization of a fully 3D-printed particle detector with 3D granularity.