Various embodiments of the present invention are directed to a distributed lock and distributed locking protocol to allow multiple communicating entities to share access to a computing resource. The rear rack includes right and left chassis bars and a support platform positioned above the chassis bars. The scintillator crystal may comprise a crystal selected from the group comprising NaI, LaBr3:Ce, La\u2014Cl3:Ce, La-halides, and La-mixed halides.