FERA data readout

Here are some notes on how data from external detectors are inserted into the regular GAMMASPHERE data stream. The notes are from a setup of the CHICO array; but are generic in nature.

Trigger electronics

The figure below shows the logic of the trigger signals involved:



Sequence of events:

Readout

If the master trigger test above was successful, the data from the FERAs are read out as indicated on the next figure:

For more details of the readout procedure consult John Weizeorick's fera_brd.ps document.

CAMAC - CNAF

The branch highway is used to issue CNAF commands for the setup and control of the FERA modules in the CAMAC crate. How that is done is documented here

Pre-trigger setup

The pretrigger conditions should be:
         10    1     1
        255  255   255
              64    64 
with "GS+EXT" main and late on and all others off on the "MTM Status and Control" screen. On the "pretrigger logic" screen "ext OR mask" should be on and everything else off.

The two relevant EPICS screens should look as:





In addition to the overlapped particle/GS pretrigger signals, which is the main external pretrigger signal, there is also a scaled down particle singles signal or-ed to the final external pretrigger signal feed to the MTM.


Scalers

Still to be written... I don't know how they work!
Notes and FAQs:

If you find errors in this GAMMASPHERE documentation; please send E-mail to Torben@anl.gov.