Triggering of Pb+Pb collisions at 5.02TeV with the ATLAS detector

With an recording rate of around 1kHz, it was not possible to record all events during the heavy ion run in 2015 given the inelastic Pb+Pb collision rate of more than 20 kHz with the ALTAS experiment at the HLT. To reduce the event rate but to still maintain a high efficiency of selecting events of interest, dedicated algorithms were put in place to collect the most interesting trigger signatures like jet, e/gamma, muon, central and azimuthally asymmetric events as well as a sizable minimum bias sample. Contrary to the slowly changing underlying event conditions in nominal pp collisions, the underlying event in Pb+Pb collisions varies from event to event. Therefore specialized approaches have been for triggering in Pb+Pb collisions to assure even performance in the environment of peripheral and central events. The selection strategies of the various trigger signatures including minimum bias and their performance will be presented.