1. VLV T09 A. Belias 1 A Light Intensity Measuring System for sedimentation measurements on KM3NeT Optical Modules Representing the KM3NeT consortium A.Belias NOA-NESTOR

2. VLV T09 A. Belias 2 Optical Modules options Optical Modules options considered by KM3NeT (a) Down looking at an angle (b) Some Down looking some Up looking  Need sedimentation / bio-fouling measurements on the lower and upper hemisphere of glass spheres

3. VLV T09 A. Belias 3 Light Intensity Measuring System Objective: To measure sedimentation on the KM3NeT glass housings. Concept: Shine light onto glass sphere and measure the response of light sensors inside the glass sphere. LED: 472nm, 15 o, coupled to plexiglass casing with gel & light sensor (reference) Light sensor:1.8mm diameter Glass sphere LED Beacon (Up) LED Beacon (Down)

4. VLV T09 A. Belias 4 LIGHT SENSORS DISTRIBUTION Light source

5. VLV T09 A. Belias 5 A5200 A4500 3 YEARS WORTH OF DATA FROM LIMS DEPLOYED AT SITES Nestor 5.2 AND Nestor 4.5 Scale: 425m/mm in A4 paper, always check A4: Location at 4500m depth A5: Location at 5200m depth P: Pylos M: Methoni M P

6. VLV T09 A. Belias 6 Data projections Data were collected every 3 hours Then 10 data points averaged (  30 hours) and divided by the reference light sensor. Then normalized to first five days average.

7. VLV T09 A. Belias 7 Zenith Zenith +10 o Zenith +20 o May.2007Oct.2007Apr.2008Dec.2008 NESTOR4.5 Depth:3200m

8. VLV T09 A. Belias 8 May.2007Oct.2007Apr.2008Dec.2008 Zenith +30 o Zenith +40 o Zenith +55 o NESTOR4.5 Depth:3200m

9. VLV T09 A. Belias 9 May.2007Oct.2007Apr.2008Dec.2008 Zenith Nadir NESTOR4.5 Depth:3200m

10. VLV T09 A. Belias 10 Data projections Data averaged (every 30 hours), divided by the reference photodiode. Normalized to the first five days average. Average over azimuth positions.

11. VLV T09 A. Belias 11 NESTOR4.5, Oct. 2007 – Apr. 2008, Depth:3200m

12. VLV T09 A. Belias 12 Data analysis method Data averaged (every 30 hours) divided by the reference photodiode. Normalized with the first five days average.  Linear Fit of data ( in 90 hours steps) and calculation of the slope of the fit in %/week.  Average of the slopes over the azimuth positions.

13. VLV T09 A. Belias 13 NESTOR4.5, May 07 – Oct. 07, Depth: 3200m Two channels at same Zenith Blue line Green line

14. VLV T09 A. Belias 14 Angle from Zenith ( o ) NESTOR5.2, May 2007 – Oct. 2007, Depth: 3870m Average Mean of Slopes (%/week) Light Intensity variations are Zenith independent, within errors.

15. VLV T09 A. Belias 15 Average Mean of Slopes (%/week) NESTOR4.5, May 2007 – Oct. 2007, Depth: 3240m Angle from Zenith ( o ) Light Intensity variations are Zenith independent, within errors.

16. VLV T09 A. Belias 16 NESTOR4.5, May 2007 – Oct. 2007, Depth: 4130m Angle from Zenith ( o ) Light Intensity variations are Zenith independent, within errors. Average Mean of Slopes (%/week)

17. VLV T09 A. Belias 17 LIMS data and Sediment Trap data NESTOR4.5, Oct. 2007 – Apr. 2008, Depth:3200m

18. VLV T09 A. Belias 18 LIMS data and Currentmeter data NESTOR4.5, Oct. 2007 – Apr. 2008, Depth:3200m

19. VLV T09 A. Belias 19 Conclusions The rate of change, within the errors, does not depend on the angle from zenith of the glass sphere. No apparent correlation has been observed between the LIMS data and the sediment trap data from the relevant time period. Analysis of all LIMS data is still in progress We have prepared an autonomous PMT rate measurement system to study sedimentation and bio- fouling on the glass sphere using the K40 activity. DAQ session T. Athanasopoulos

20. VLV T09 A. Belias 20 Backup slides

21. VLV T09 A. Belias 21 Light sensor details