You are looking at a silicon detector at the end of the inflector region of the Muon g-2 experiment. This region is the area in which a specialized magnet bends muons after they exit the Muon Delivery Ring (the former Antiproton Debuncher) and enter the Muon g-2 storage ring, which curves to the left in the picture.
Todd Nebel of the Fermilab Test Beam Facility helps unload the prototype hadronic calorimeter built by the PHENIX collaboration at Brookhaven National Laboratory’s Relativistic Heavy Ion Collider as part of the sPHENIX upgrade proposal. The calorimeter, shipped from Brookhaven on Jan. 21 and to be used in the T-1044 test experiment, is a five-ton steel-scintillator calorimeter that is read out using silicon photomultipliers. The sPHENIX experiment is designed to measure jet energy loss in heavy-ion collisions to characterize the quark gluon plasma near the transition temperature.