Fused Silica Raman Spectroscopy for the ATLAS Zero Degree Calorimeter

The Nuclear Physics Laboratory (NPL) at the University of Illinois collaborates on the development of an improved Zero Degree Calorimeter (ZDC) to replace the current ZDC in the ATLAS experiment at the Large Hadron Collider (LHC). A prototype detector is presently designed for test beam studies at the CERN SPS in November 2018. The prototype is a tungsten-quartz sampling calorimeter that consists of two modules and contains a reaction-plane detector (RPD). Each module is made of 11 alternating layers of tungsten and 12 layers of fused silica fibers. The charged shower particles produced by an incident neutron emit Cherenkov light in the fused silica fibers. The Cherenkov light will be detected by photomultiplier tubes (PMTs). The high radiation that the fused silica rods experience due to their presence in the beamline causes different types of changes to the structure of the silica. The purity of the fused silica strongly impacts the defects that form within the rod. Raman spectroscopy is used as a method to study the specific defects present in the irradiated fused silica rods. The results of Raman spectroscopy measurements will be presented.