Transcript ppt
Gamma-ray Large Area
Space Telescope
Update on
PDU Voltage
Noise Dependence
Claudia Cecchi
Stefano Germani
Monica Pepe
INFN Perugia
Instrument Analysis Meeting
May 5, 2006
GLAST LAT Project
IA Meeting, May 5, 2006
Outline
• Update on Noise Study with External Triggers (Tkr)
– Strip Occupancy
– List of Noisy Strips
• Comparison with 28V Flight Software
– New Selection Definition: one Track Events (no ExtTrigger)
• Comparison between selection with Ext Trigger vs oneTrack
• Cal Study with External Triggers
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Data Files
We used data from the following runs:
27V-supply
• 077002818 36-sec cosmic with 5 KHz fixed f external trigger
• 077002819 36-sec cosmic with 6.5 KHz fixed f external trigger
• 077002820 36-sec cosmic with 1 KHz random f external trigger
• 077002821 36-sec cosmic with 3KHz random f external trigger
• 077002822 36-sec cosmic with 5KHz random f external trigger
• 077002823 36-sec cosmic with 10KHz random f external trigger
29V-supply
• 077002837 36-sec cosmic with 5 KHz random f external trigger
• 077002838 36-sec cosmic with 10 KHz random f external trigger
We used SVAC, Merit and Digi files!
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Data Files (2)
Following Eduardo’s suggestion we analyzed also four 28V
supply Flight Software Runs:
• 077002163
• 077002165
See Also Andrea’s Presentation on April 21, 2006
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Tracker Study Event Selection
We want to select only noise events (Empty) therefore we ask for:
•
•
•
•
External Trigger Only
– GemConditionsWord == 128
No reconstructed Tracks
– TkrNumTracks == 0
No Energy in the Cal
– CalEnergyRaw == 0
No ACD Hits
– AcdTileCount == 0 && AcdRibbonCount == 0
Then we compute the StripOccupancy:
StripHits/EventSelected
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Noisy Events /EventSelected
27V Supply
12 13 14 15
8
9
10 11
4
5
6
7
0
1
2
3
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Strip Occupancy
Tower 5
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Tower 13
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Noisy Strips Tower 13
27V–29V Comparison
All Runs have the same
Occupancy Level!
All 27 V Runs
Normal Strips Level ~ 10-5
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Noisy Strip Tower 5
All 27V
27V-29V Comparison
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Tracker Study Event Selection
with No External Trigger
We want to select only noisy events therefore we ask for:
•
•
•
Only One Track
– TkrNumTracks == 1
Track Contained in One Tower
– StartTower == EndTower
Exclude towers neighbour to the crossed one
– Selected Towers
– Excluded Towers
– Crossed Tower
•
•
Green filled: Selected
Red filled : Excluded
12 13 14 15
8
9
10 11
4
5
6
7
0 1 2 3
No Xtal Hit in Selected Towers
– CalNumHit[tower] <= 0
No Extra ACD Hits
– ΣAcdTkrIntSecTileHit[iTkrIntSec]>0 ==AcdTileCount+AcdRibbonCount
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Methods Comparison (Tw 13)
27V
The number of Selected Events
Is different
29V
Noisy strips show the same
Occupancy Level!
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Methods Comparison (Tw 5)
27V
29V
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Flight Software Runs
Tower 5
Tower 13
Results Similar to the other Runs!
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Noisy Stripls List
(From External Trigger Runs)
Tower
Plane
Strip
Occupancy
1
10
270
1.2e-4 +- 4e-5
5
34
276
1e-2 +- 3e-4
5
35
1194
2e-4 +- 5e-5
6
21
919
1.4e-4 +- 4e-5
8
25
1056
1e-4 +- 3e-5
11
20
905
5e-4 +- 7e-5
12
20
1154
4e-4 +- 7e-5
13
19
124
1.2e-3 +- 1e-4
13
26
1141
2.5e-2 +- 5e-5
13
26
1143
2.9e-2 +- 5e-5
13
32
1148
2.4e-4 +- 5e-5
13
32
1150
2.1e-4 +- 5e-5
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Cal Study Event Selection
We want to select only noisy events therefore we ask for:
•
•
•
•
External Trigger Only
– GemConditionsWord == 128
No Tracker Digis
– TkrNumDigis == 0
No ACD Digis
– AcdNumDigis == 0
No Reconstructed Mips
– CalMipNum == 0
Then we compute the fraction of noisy events which have Hit
Xtals:
Tower Occupancy: CalNumHit[tower] >0
Xtal Occupancy: CalXtalEne[tower][layer][col][end] >0
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27 and 29V Tower Cal
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27 and 29 V Tower 8 Cal
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Conclusions
• Tracker
– New selection implemented to check noise effect
– No difference between Trk Sel and Trigger Sel
• Same behaviour for strips or clusters
– List of noisy strips available
• CAL noise analysis
– Just started, only one tower shows noise due to 2 crystals
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