Time resolution measurement with Madison test-DAQ Dmitry Chirkin, Spencer Klein, LBNL IceCube meeting in Uppsala, 2004

IceCube/2004/09/15/UWDAQ1_run0002141_TimeResolution-ATWD0 Dataset laser run: 1.5 kHz 75 ps wide attenuated by beam splitters: optical occupancy set at 0.1 46*2+1+1 DOMS: 1 SYNC board connected to laser (here: DOM 37) 175 ns early 1 REF PMT (room T) (here: DOM 62) (info by Kael Hanson) files from: IceCube/2004/09/15/UWDAQ1_run0002141_TimeResolution-ATWD0

DOM time calibration concept Calibration event time: Tc_dor=Tc_dom+delta Tc_dor = {dor_tx+dor_rx-d(wf_dor)}/2 Tc_dom = {dom_tx+dom_rx-d(wf_dom)}/2 Roundtrip time: Td+Tu = dor_rx-d(wf_dor)-dor_tx- {dom_tx-[dom_rx-d(wf_dom)]} Time delta: delta(Tc_dom)=Tc_dor-Tc_dom

DOM/DOR received waveforms COMM Waveform fit algorithms: centroid crossover leading edge intercept leading edge threshold laser SYNC board

Roundtrip time

Time delta measurement

ATWD feature extraction Bin size to time conversion is done for each OM using info from the monitoring files: frequency = 20 MHz * (slope*850+intercept) ~ 300 MHz, e.g., bin size ~3.3 ns. (info by John Kelly) time direction

Laser-correlated signal

Laser-correlated signal crossover centroid le threshold le intercept

Time resolution results

Conclusions Time calibration precision is 0.5-1.5 ns for centroid and crossover, and 1-2.5 ns for leading edge intercept and threshold. However, centroid and le threshold give higher values for ~30% of DOMs (could be improved by modifying the algorithm?) Although round trip time depends on the algorithm used to fit the COMM waveforms, time correction does not (with differences between methods 1-3 ns)

Conclusions clock stability is < 0.5 ns between calibrations time resolution obtained with the laser method does not depend on the algorithm used to fit the COMM Waveforms and is 1-3.5 ns for the majority of tested DOMs Laser time resolution setup can be used for DOM verification tests?