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Optical Beacon Status

Optical Beacon Status. ANTARES Calibration Workshop 4/12/2007, CERN, Geneva. Laser ARS_T0 computation in the DR. ARS_T0 correction method. Studies about flashing procedure. OM gain reduction check with LOB. Conclusions & Plans. Paco Salesa IFIC (CSIC – Universitat de València).

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Optical Beacon Status

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  1. Optical Beacon Status ANTARES Calibration Workshop 4/12/2007, CERN, Geneva • Laser ARS_T0 computation in the DR. • ARS_T0 correction method. • Studies about flashing procedure. • OM gain reduction check with LOB. • Conclusions & Plans. Paco Salesa IFIC (CSIC – Universitat de València)

  2. Laser ARS_T0 estimation in the DR • There will be 2 new Laser Beacons for Line 7 and 8 located at the anchor. These Beacons will complement the LOB calibration. • The new Laser model emit at l = 532 nm and its intensity is variable (for more details see the internal note: ANTARES-Cali/2007-004). • The T0 for the ARS reading the internal photodiode was measured for both Laser Beacons using as reference a LOB. • The offsets computed are: 48.0 ± 0.6 ns for Line 7, and 43.0 ± 0.6 ns for Line 8. LINE 7 LINE 8 LOB –Laser OB (ns) LOB –Laser OB (ns)

  3. ARS_T0 correction method • Compute time differences ARS-LOB for the several storeys above the LOB (Line divided in 4 regions). • Fit the values to a straight line as suggested by the studies about early photon (the storey where the LOB is placed is not taken into account). • For each storey correct one ARS_T0 value by using the fit. • The other 5 ARS_T0s remaining corrections in each storey are obtained from the intra-storey relative correlations. OM 0 OM 1 OM 2

  4. Check of the LOB-ARS fit Only 4 storeys used in the fit OM-OM OM-OM (correction) 2 4 6 8 10 2 4 6 8 10 As a check of the fit we can take directly the fitted values as the good ones (this will not be the final ARS_T0 correction!) +

  5. Check of the LOB-ARS fit • The correction is not so good for the last storeys. • Taking only the correction from the fit improves the values of the OM-OM intra-storey correlation.

  6. Studies about flashing procedure 1 RUN = 1 LOB flashing 1 RUN = 2 LOBs flashing OM-OM intra-storey correlation using one LOB per run is in agreement with the values obtained when flashing two LOB per run (LOB S.2 + S.15 & LOB S.9 + S. 21)

  7. Studies about flashing procedure • Test with 4 LOBs flashing simultaneously performed in Lines 3 & 4. • The LOB rate and AVC & TVC distributions are the same for the case where 1 LOB is flashing and for the case where 4 LOBs are flashing. • A secondary peak appears in some TVCs distribution of the OMs, not yet understood. OMs L4 S11 ? ? ?

  8. OM gain preliminary checks OM 0 • The LOB-OM time difference evolution in time give hints about OM gain changes. • The effects seems to go in the expected way. If the gain decreases the time dif. increases (walk effect). • Difficult to quantify and the comparison with K40. K40

  9. Conclusions & Plans • The ARS_T0s for the Laser Beacons computed. The results are similar for Line 7 and 8. • The new Laser OBs will complement the ARS_T0 computation with LED OBs. • ARS_T0 correction method presented. Some checks shown. • Using intra-storey correlation + line fit, the values of the ARS_T0s will be updated in the DB. • Multi-LOB flash for 2 LOB per run seems ok, not for 4 LOB per run. More studies needed. • Preliminary studies about OM gain changes using LOBs done. Work in progress.

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