Minimizing Dead Time of the Belle II Data Acquisition System With Pipelined Trigger Flow Control

The Belle II detector at the SuperKEKB collider is a general purpose spectrometer to study B meson, charm hadron and τ lepton decays with an unprecedented high luminosity of 8 × 10
³⁵
cm
^-2
s
^-1
. At Belle II, detector signals are digitized inside or near the detector and collected via high-speed optical serial links. The maximum design trigger rate is 30 kHz, for which we have to record data from 7 subdetectors with a minimum dead-time fraction. Due to complex constraints in the front-end electronics of the Belle II subdetectors, a straightforward dead-time control method does not meet our requirement. We report a pipelined trigger flow control scheme which will keep the dead-time fraction due to the trigger distribution and readout system to about 1%.