Update on time calibration with optical beacons

Collaboration MeetingRoma, 7-10 May 2012

Agustín Sánchez LosaIFIC (CSIC – Universitat de València)

Outline

• Reminder of the time calibration with OBs• Intraline calibration: T0s– Nothing new since CERN’12

• Interline calibration: Time offsets– Laser position and its impact in offsets

• Some order in the DB tables of T0s• To-Do List

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Time calibration recipe:– Flash various OMs at the same time by an OB– Plot the distribution of hit arrival times for each ARS– Fit such distribution with a Gauss@Exponential function– Determine Tpeak , the time of the function peak– Plot Tpeak vs distance– Deviations from the straight line fit will be used as corrections to the T0s

F 2

F 3

F 4

F 5

F 6

F 7

F 8

F 9

F 10

F 1

Reminder of the time calibration

waterOBOM c

OMOBdttt ),(

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LED

LED

Laser

Reminder of the time calibration

• T0 in the same line• LED OB• Early-photon region

Intraline calibration

• time offsets between lines• Laser OB• Photo-electron level region

Interline calibration

IntralineT0s in the same line by means of the

LED OBs

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Nothing newsince CERN'12

7-10 May 2012 Agustín Sánchez Losa – Roma Collaboration Meeting

InterlineTime offsets between lines by means

of the Laser OB

6

Interline: Laser position impact on offsets

• Was detected the use of an incorrect position of the laser (Ciro’s curiosity fault)

• Laser offsets recomputed for all the periods (from Aug'09 to Dec'11)

• The impact in the laser offsets has been measured and estimated

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L3

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L5

L7

L10 L11 L12

L8

F 4

F 10

F 1

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F 5

F 10

Early photonRegion

PhotoelectronLevel RegionF 10

F 3 - F 4F 8 - F 9

F 1

L1 L2 L9

L1 L2

L3 L4 L6L5

L7 L8 L10L9

L11 L12

LINES

OLD NEW MEASS.DIFF

1 -2,7 -3,3 -0,7

2 -2,8 -3,3 -0,7

3 0,2 -0,1 -0,4

4 -1,8 -2,1 -0,5

5 -3,4 -3,6 -0,3

6 -0,4 -0,6 -0,3

7 -0,5 -0,4 0,0

8 7,5 7,6 0,0

9 -0,2 0,1 0,2

10 -0,7 -0,4 0,2

11 4,0 4,6 0,5

12 0,7 1,3 0,5

ESTIM.DIFF

-0,6

-0,8

-0,4

-0,5

-0,3

-0,5

0,0

-0,1

0,3

0,0

0,5

0,5

Interline: Laser position impact on offsets

Interline: T0s tables in the DB

• Some order have been done in the T0s DB tables:– All official T0s LABEL field have a clear ordered #id– OFFICIAL value has a clear use:• OFFICIAL = 2 → Best T0s available without any interline offset added• OFFICIAL = 3 → Best T0s available with interline offset added (see

USER_COMMENT field explains which ones)– Now APP_START field is coherent for all the periods

– Sample SQL call:

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select version_id, label, app_start, user_comment, udate, official from antares.ars_t0 where official = 2 or official = 3

order by official, app_start desc

Interline: T0s tables in the DB• Sample SQL call:

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To-Do List

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• Intraline calibration by OB:– Compute intermediate T0s– Recompute old T0s with updated TVCs and study the

impact of using ones or another– Research & Improvement on intraline calibration:

Calibrate the first floors of each line, study the impact of a calibration with independent sections, Study unstable PMTs since HV tuning in Summer'10, etc.

• Interline calibration by OB:– Research & Improvement on interline calibration.

Thank youfor your attention