Online-raw-data-nov-2012

Energies/Charges and Times

Cuts: E>0, 0<t<32 usec

TOF

FCAL

BCAL

FDC

CDC

TOF

TAG

Event Sizes and Compression

The data format for N=1 block mode readout is very verbose and redundant. Much of this is needed to allow the DAQ system to verify all crates/slots are responding properly. But once data integrity is confirmed the redundant data can be removed (perhaps at the ROC and EB levels). Note that for initial detector checkout and perhaps for early engineering runs we will write data in this format.

I propose the following strategy for removing redundant information:

• ADC: replace block header, event header, trigger time and block trailer with single "slot header" word.
• TDC: same as for ADC, additionally remove chip header and chip trailer words.
• Store trigger time in one place only.
• Remove slots with no hits.
• Remove crates with no hits.

Initial studies show a factor of 4 reduction in data size following this strategy.