Karlsruhe 2011 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 74: DAQ und Trigger I

T 74.3: Vortrag

Montag, 28. März 2011, 17:15–17:30, 30.23: 2-11

Monitoring L1Calo Fine timing stability of the ATLAS detector at the Large Hadron Collider (LHC). — •Rohin Narayan¹ and John Taylor Childers² — ¹Physikalisches Institut, Universtät Heidelberg, Germany — ²Kirchoff Institute für Physics, Universität Heidelberg, Germany

The ATLAS Trigger system is designed to reduce the LHC proton-proton event rates of 40 MHz to a managable 200 Hz which can be saved to disk. This is achieved using three trigger levels, the Level-1 (L1), Level-2 and Event Filter. The L1 Trigger is a hardware based trigger with a decision latency of upto 2.5 µs. It consists of three systems, the L1 Muon, L1 Calorimeter (L1Calo) and Central Trigger Processor.

The Preprocessor Module(PPM) of the L1Calo conditions and digitizes about 7200 pre-summed analog signals from the calorimeters at the LHC bunch crossing frequency. It also performs bunch-crossing identification (BCID) and energy measurement for each input signal. The BCID and energy measurement depend on precise timing adjustments which are done to achieve correct sampling of the input signal peak. For an energy measurement of better than 2 % in the trigger, the peak should be sampled within ± 5 ns. The calibration of timing delays in PPMs is expected to fullfill this requirement in all the input channels.

The present work is monitoring the signal peak sampling offset, averaged to each luminosity block for the real data. This is done by measuring the signal peak location to the nanosecond level and monitoring this value as a function of time to verify signal stabilty.