The IceCube Neutrino Observatory consists of a lattice of 5160 photomultiplier tubes (PMTs)which monitor one cubic kilometer of deep Antarctic ice at the geographic South Pole.IceCube was primarily designed to detect neutrinos of energies greater than O(100 GeV).Due to subfreezing ice temperatures, the photomultipliers' dark noise rates are particularlylow which enables IceCube to search for neutrinos from galactic supernovae by detectingbursts of MeV neutrinos emitted during the core collapse and for several seconds following.For that purpose, a dedicated online supernova DAQ system records the total number of hitsin the detector, without any further information from the PMTs, and generates supernovacandidate triggers in case of a significant detector rate enhancement. A new feature to thestandard DAQ, called HitSpooling, was implemented in IceCube during this thesis. TheHitSpooling system is implemented in the standard DAQ system and buffers the completeraw data stream of the photomultipliers for several hours or days. By reading out time periodsof HitSpool data around supernova candidate triggers, generated by the online supernovaDAQ system, we overcome the limitations of the latter and have access to the entire informationof the detector in case of a supernova. Furthermore, HitSpool data is a powerfulsource for studying and understanding the noise behavior of the detector as well as backgroundprocesses coming from atmospheric muons. The idea of HitSpooling was developed in thescope of this thesis and is the basis of the work at hand. The developed interface between thestandard DAQ and the supernova DAQ system is presented. The correlated dark noise componentin optical modules of IceCube is quantified for the first time and possible explanationsare discussed. The possibility of identifying triggering and subthreshold atmospheric muonsin HitSpool data and subtracting them from a possible supernova signal is analyzed. Furthermore,the conversion from HitSpool data to supernova DAQ type data was developedwhich allows for a comparison of both data types with respect to lightcurves and significancesof selected supernova candidate triggers.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished