The steel drill string attached to a drilling bit during typical rotary drilling operations used to drill oil and gas wells is used for a second purpose as the casing that is cemented in place during typical oil and gas well completions. An annihilation event is detected by a scintillator crystal and photomultiplier tube, which produces an energy signal that is continuously under-sampled by an analog-to-digital converter. Each ring defines on first or second parts of the structure an outer support lip to hold independent protection interfaces on each side of the coin. Upon reinsertion of the removable module, a user attempting to use the removable module is first authenticated. The display unit has an engagement member, which is removaly engaged with the braking mechanism.