3D-printing of transparent granulate materials for light guides and scintillation detectors

Additive manufacturing techniques have advanced significantly and get more and more interesting also for the development of active parts of particle detectors. The main advantages are the flexibility in building 3D-forms, as well as fast prototyping cycles. For many detector applications it is crucial to use well-tested materials to avoid aging problems. Printers working with granulates allow the direct printing of original materials, including the usage of several different materials at the same time. This is very attractive, for example, for segmented and 3D-integrated detectors like calorimeters or trigger veto systems based on plastic scintillators coupled to photodetectors. In this work, we focus on the printing of transparent plastic granulates. We compare different thermoplastics as base material, particularly polymethylmethacrylate (PMMA) and polystyrene (PS). The printing process is ARBURG Plastic Freeforming featuring in-line drying, plasticizing with melting points up to 350 degrees C and high-frequency droplet discharging. The main challenges are the transparency of the printed parts and their surface quality. The former is investigated using a UV/Vis spectrometer, the latter using a confocal 3D-microscope. We present a comparison to reference samples and discuss potential future applications of this technology.