The event header consists of ten words of two bytes:
word hexmask description 0 0x80nn total #words in event 1 0xmmnn nn clean ge counts; mm is the MTM bit pattern at MAIN 2 0xmmnn dirty ge and bgo only counts, respectively 3 0xffff trigger time, ttH (16 bits) 4 0x7fff trigger time, ttM (15 bits) 5 0xffff trigger time, ttL (16 bits) 6 0x0nnn tac1(usec tac; next usec tic vs. master trigger) 7 0x0nnn tac2 (usually rf tac: next rf vs. pre-trigger) 8 0xnnnn sum of ge_low energies (within ge time window) 9 0xnnnn sum of BGO energies (within BGO time window)
The first word marks the start of a header by having the highest bit set.
In the event stream, the order of the events are: first the clean germaniums, then follows the dirty germaniums (if they are read out) and finally any events where only the BGO detectors fired (if they are read out). The bits in the ModeFlags tells what is written to the data stream.
The summed energy values at the end of the header are generated from the low res ge signal and bgo signals compressed by a factor of four. To generate the summed energy signal, it is enough to add the "sum of ge_low values" and "sum of ge_low values" since the clean germaniums are already added to this sum.
The summed (and time gated) germanium and BGO energies are contracted by a factor of 4. Thus, if your lo res calibration was 4kev/ch (typical) and bgo energy calibration was 2.5 kev/ch (typical) then the calibration of your summed ge and BGO energy signals in the header will have the calibration
If you find errors in this GAMMASPHERE documentation; please send E-mail to Torben.