1. 1 A.Tsirigotus Hellenic Open University N eutrino E xtended S ubmarine T elescope with O ceanographic R esearch The NESTOR O.M.

2. 2 Hamamatsu PMT R2018-03 (15”) Benthos spheres μ-metal cage power supply Single p.e. conditions The Detector

3. 3 dc/dc converter PMT base Silica Al disk Hamamatsu PMT inside theBENTHOS sphere Pressure gauges The NESTOR Optical Module

4. 4 Extensive Lab tests On single p.e. conditions Detector Preparation Optical Modules L.E.D. Reference Relative timing Pulse Height (mV) LED Calibration Run Time Difference in PMTs Response Time (ns)

5. 5 Detector Preparation Attenuation Correction Reference waveform Coaxial cable Electronic delay lines and amplifier Fourier Transform-Comparison Frequency (MHz) Phase (rad) Amplitude

6. 6 Data from a depth of 4000 m Single PMT Rates Trigger: ≥4fold Coincidence

7. 7 Waveform Reconstruction Sample Offset (ADC counts)Sample Offset (ADC counts) Before the F.F.T. and the attenuation corrections After the F.F.T. and the attenuation corrections Rise Time 16 ns 9 ns Double pulse separation Time (ns) Voltage (mV)

8. 8 single p.e. LED Run single p.e. pulse height distribution two p.e. s pulse height distribution dark current pulse height distribution sum of the above Data from a depth of 4000 m PMT Pulse Height Distribution Calibration

9. 9 Calibration Data Analysis Calibration Database Quality Histograms LED Calibration Data Gain Monitors Data from a depth of 4000 m Calibration Run Time Difference (ns) Number of Events Time Difference (ns) : 0.6 ± 0.1 ns σ : 3.3 ± 0.1 ns : 0.2 ± 0.1 ns σ : 3.3 ± 0.1 ns

10. 10 Data from a depth of 4000 m Calibration Run