  To address the challenges of providing high performance calorimetry in future
hadron collider experiments under conditions of high luminosity and high
radiation (FCChh environments), we are conducting R&D on advanced calorimetry
techniques suitable for such operation, based on scintillation and
wavelength-shifting technologies and photosensor (SiPM and SiPM-like)
technology. In particular, we are focusing our attention on ultra-compact
radiation hard EM calorimeters, based on modular structures (RADiCAL modules)
consisting of alternating layers of very dense absorber and scintillating
plates, read out via radiation hard wavelength shifting (WLS) solid fiber or
capillary elements to photosensors positioned either proximately or remotely,
depending upon their radiation tolerance. The RADiCAL modules provide the
capability to measure simultaneously and with high precision the position,
energy and timing of EM showers. This paper provides an overview of the
instrumentation and photosensor R&D associated with the RADiCAL program.
