Veto Dead Time Measurements for GPD runs

The veto dead time is measured by comparing the rates of a trigger signal without a veto to the rates of a trigger signal with a delayed - i.e. out of time - veto signal. As the veto composition (Vtot) for all muon triggers is the same, we measure the dead time exemplary for the middle trigger (MT).


The spill-by-spill veto dead times for each 2009 run can be found in the last row of several txt files on afs:


WXX is the data taking period: W38, W39, W40

Details can be found in N. du Fresne's release note from September 2012, p.19.

The veto dead time is extracted from the MYSQL database. In the beamdb2009 table, from DAQScaler, tbname SCMSC1__, input25 is the middle trigger signal with a delayed veto whereas input27 is the middle trigger without veto. The veto dead time can be calculated as DT = 1 - input25/input27.

It is recommended to use the txt files: If some information was not recorded in the DB, an average of the period is taken for the txt files. Only spills which passed the quality checks are saved to the txt files.


In 2012, the veto dead time is measured in the same way as in 2009, with the exception that the table is called beamdb2011 and instead of input25 it is input15: DT = 1 - input15/input27. The txt files will be provided shortly after the run finishes.

Additionally, the real veto dead time without effects from beam debunching etc. is measured by a sampling method (cf. Master thesis Oliver Freyermuth, Bonn 2012). It can be retrieved from trigger_daCoMo_data in the beamdb2011 table: VDT = duty2 / clock

-- JohannesBernhard - 2012-11-21

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Topic revision: r4 - 2012-11-22 - unknown
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