High Performance Glass Scintillators for Nuclear Physics Experiments

C49-34d-271279High performance scintillator materials are needed for particle identification and measurements of energy and momentum of electromagnetic particles in modern nuclear physics experiments. Achieving high-quality science at nuclear physics facilities requires the measurement of particle energy with excellent calorimeter energy resolution in the momentum range 0.1 – (10-20) GeV/c. Crystals such as lead tungstate (PbWO4) have been used in precision calorimeters but their production is slow and expensive. This Phase I/II/IIA project addresses the need for alternative high performance scintillator materials by developing the basis to replace such crystals with scintillating glass that is simpler and faster to produce in large quantities while meeting the desired specifications. Phase I, established the formulation and fabrication techniques for producing small batches of SciGlass blocks. During Phase II, considerable progress was made on improvement of glass properties and the manufacturing process for blocks of ~15 radiation lengths (X0). Beam tests with a small detector prototype indicate, along with Geant4 simulations, that SciGlass has an energy resolution comparable to PbWO4 for block sizes of a comparable number of radiation lengths. The glass samples have excellent radiation resistance (no damage up to 1000 Gy electromagnetic and 1015 n/cm2 hadron irradiation, the highest doses tested to date), response time of 20-50 ns, and near-UV transmittance (78% at 440 nm). Phase II progress was impacted by Covid19 delays, particularly with respect to beam time. Phase IIA will allow for completing the balance of the Phase II objectives. Sufficient SciGlass bars will be produced to meet the objective of testing a larger, e.g., 5x5 detector prototype. This objective is supported by characterization results, simulations, and community feedback, and additional information that has become available on the EIC detectors. In addition, the block size will be optimized relative to the Moliere radius and the objective of demonstrating the ability to produce bars of various shapes will be completed, which, with newer information on the EIC detectors, is now much more relevant than when the original Phase II award started. The Phase IIA program is aligned to make SciGlass blocks available to meet the needs of key nuclear physics experiments, e.g., the large-volume calorimeters for the Electron-Ion Collider or JLab, that require high performance scintillator material in large quantities on specific schedules. Other SciGlass benefits include reduced time and complexity of manufacturing, resulting in an estimated 80% cost reduction, and increased flexibility in shape and size for the final detector. The ability to manufacture novel high-performance glass scintillators will prove useful not only for electromagnetic calorimeters but also for homeland security applications where such scintillators would significantly reduce the false alarm rate in passive nuclear detection systems and allow for large range of deployment. Fast response time and radiation hard glass ceramics will find use in the scintillator market for security applications as active material for radiation portal monitors, in particular, at ports where cargo screening with large throughput is required.