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

2. 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_run _TimeResolution-ATWD0

3. 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

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

5. Roundtrip time

6. Time delta measurement

7. 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

8. Laser-correlated signal

9. Laser-correlated signal
crossover
centroid
le threshold
le intercept

10. Time resolution results

11. Conclusions
Time calibration precision is ns for centroid and crossover, and 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)

12. 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 ns for the majority of tested DOMs
Laser time resolution setup can be used for DOM verification tests?