DABC data acquisition input for slow control variables

The Data Acquisition Backbone Core (DABC) is a software framework to run DAQ with distributed event building on high performance Linux clusters [1]. There are several use cases, especially in test beam times where the setup during data taking is intentionally changed very often, and the interpretation of the acquired detector data depends on the experimental set-up. Usually, the set-up is managed by a slow control system like EPICS [2], which has powerful tools to archive the set-up values. For online analysis, however, a direct access to such values in the DAQ data stream can be very useful, e.g. for a conditional analysis depending on certain settings. Moreover, it is possible to perform a fast scan of detector properties with the control system and record simultaneously the measured data in the same file. Because of this an EPICS data input for DABC was developed.