LAT Instrument Analysis Meeting – May 26, 2006
GLAST LAT Project
GLAST Large Area Telescope:
Gamma-ray Large
Area Space
Telescope
TKR Efficiency Trending
Hiro Tajima (SLAC)
TKR
htajima@slac.stanford.edu
650-926-3035
Hiro Tajima, TKR Efficiency Trending
1
LAT Instrument Analysis Meeting – May 26, 2006
GLAST LAT Project
Efficiency Trending Result @ IA Workshop
Consistent downward trend observed.
– Inconsistent with stable bad strips.
– Probably due to LAT configuration change.
• Efficiency values depend on track quality and other factors.
• Further improvement on track selections required to make it
more stable.
Efficiency Trend
0
TkrFMA
-0.05
TkrFMB
TkrFM1
Efficiency change (%)
•
TkrFM2
TkrFM3
-0.1
TkrFM4
TkrFM5
TkrFM6
-0.15
TkrFM7
TkrFM9
TkrFM10
-0.2
TkrFM11
TkrFM12
TkrFM13
-0.25
TkrFM14
TkrFM15
-0.3
2TWR
4TWR
6TWR
8TWR
Test Phase
Hiro Tajima, TKR Efficiency Trending
2
16TWR
LAT Instrument Analysis Meeting – May 26, 2006
GLAST LAT Project
Improvement on Efficiency Calculation
•
Use only towers with 6 or more hit layers.
– Much improved. Still more scatter than the statistical error.
• FMA: lower efficiencies in 16-tower and first LICOS muon data.
• FM4: lower efficiencies in PSR muon data.
– Systematically lower efficiency at NRL.
• So is trigger rate. (~500 Hz @SLAC ⇒ ~420 Hz @NRL)
FM# Hand-off 16-tower difference
A 98.59% 98.54%
-0.05%
B 99.84% 99.82%
-0.02%
1 99.74% 99.72%
-0.02%
2 99.74% 99.74%
0.00%
3 99.67% 99.69%
0.01%
4 99.84% 99.81%
-0.03%
5 99.87% 99.92%
0.05%
6 99.81% 99.79%
-0.01%
7 99.87% 99.85%
-0.02%
9 99.90% 99.90%
-0.01%
10 99.85% 99.85%
0.00%
11 99.88% 99.88%
0.00%
12 99.93% 99.91%
-0.02%
13 99.90% 99.90%
-0.01%
14 99.88% 99.86%
-0.01%
15 99.90% 99.89%
-0.01%
LICOS difference
98.53%
-0.06%
99.82%
-0.02%
99.72%
-0.02%
99.73%
-0.01%
99.69%
0.02%
99.80%
-0.04%
99.92%
0.05%
99.80%
-0.01%
99.83%
-0.04%
99.89%
-0.01%
99.85%
0.00%
99.87%
0.00%
99.91%
-0.02%
99.88%
-0.02%
99.86%
-0.01%
99.88%
-0.01%
Hiro Tajima, TKR Efficiency Trending
PSR
difference PER(NRL) difference
98.58%
-0.01% 98.55%
-0.04%
99.83%
-0.01% 99.82%
-0.02%
99.73%
-0.01% 99.71%
-0.03%
99.75%
0.01% 99.74%
0.00%
99.70%
0.03% 99.69%
0.02%
99.76%
-0.08% 99.78%
-0.06%
99.92%
0.05% 99.90%
0.03%
99.81%
0.00% 99.78%
-0.03%
99.86%
-0.01% 99.83%
-0.04%
99.90%
0.00% 99.84%
-0.06%
99.86%
0.01% 99.83%
-0.02%
99.87%
-0.01% 99.81%
-0.06%
99.91%
-0.02% 99.85%
-0.08%
99.90%
0.00% 99.87%
-0.04%
99.87%
-0.01% 99.85%
-0.02%
99.89%
0.00% 99.83%
-0.06%
3
LAT Instrument Analysis Meeting – May 26, 2006
GLAST LAT Project
FM4 (Bay 13) Layer Efficiencies
Efficiency
• Layer X13 (plane# 26) shows significant efficiency drop.
+ LICOS runs
+ PSR runs
Layer ID
Hiro Tajima, TKR Efficiency Trending
4
LAT Instrument Analysis Meeting – May 26, 2006
GLAST LAT Project
FM4 X13 Strip-Level Efficiencies
This is not exact strip efficiency due to accuracy of track extrapolation.
– It gives crude association of efficiency with strip#.
– Efficiency of strips 1024-1152 degraded significantly.
– This region had lower efficiencies in previous runs.
Efficiency
•
Strip ID
Hiro Tajima, TKR Efficiency Trending
5
LAT Instrument Analysis Meeting – May 26, 2006
GLAST LAT Project
SSD Wafer Dependence?
Wafer 3
• Occupancy does not depend on
SSD wafer in the ladder.
• Efficiency loss is well correlated
with GTFE boundaries.
Wafer 1 GTFE
Ladders
Occupancy (arbitrary unit)
Wafer 2
GTFE boundaries
– Wafer 0
– Wafer 1
– Wafer 2
– Wafer 3
Strip ID
Hiro Tajima, TKR Efficiency Trending
Strip ID
6
Wafer 0
LAT Instrument Analysis Meeting – May 26, 2006
GLAST LAT Project
Root Cause of Efficiency Loss
•
New hot strip around 1141, 1143 (close to edge of the SSD)!
– 1142 was masked in previous runs.
– Hot strips is due to large leak current from junction break down.
• Mechanism for efficiency loss in two GTFEs is not understood.
• New hot strip schema files released to mask these hot strips.
Occupancy (arbitrary unit)
– Mainly to reduce trigger occupancy.
– It may not fix the efficiency loss since we had some efficiency
loss even when these strips were quite.
Sugizaki
LICOS runs
PSR runs
1141, 1143
1142
Strip ID
Hiro Tajima, TKR Efficiency Trending
Strip ID
7
LAT Instrument Analysis Meeting – May 26, 2006
GLAST LAT Project
FMA (Bay 0) Layer Efficiencies
Efficiency
• Slight efficiency loss in Y0, Y3, Y4.
+ LICOS runs
+ PSR runs
Layer ID
Hiro Tajima, TKR Efficiency Trending
8
GLAST LAT Project
LAT Instrument Analysis Meeting – May 26, 2006
FMA Y3, Y4 Strip-Level Efficiencies
• No localized significant efficiency loss observed.
– Some intermittent strips in green circles could be a cause.
ladder disconnected strips
and healthy strips are mixed
and averaged out.
ladder disconnected strips
disconnected strips
Hiro Tajima, TKR Efficiency Trending
9
GLAST LAT Project
LAT Instrument Analysis Meeting – May 26, 2006
Automated Layer Efficiency Trending
• Tower efficiency is not very sensitive to local efficiency loss.
– Useful for overall efficiency trending.
• Layer efficiency is more sensitive for local efficiency loss.
– Too many layers to be trended by human eyes.
– Automated outlier detection script developed.
• Take out systematic effects that affect all layers in each
tower.
• Take truncated (remove highest and lowest 10% of
efficiencies) and weighted average of all runs for each
layer.
• Tag instances of efficiencies if it is 5 away from the
above average.
• Produce efficiency strip profile plots of outliers in
comparison with the reference and save them as GIF for
human inspection.
Hiro Tajima, TKR Efficiency Trending
10
LAT Instrument Analysis Meeting – May 26, 2006
GLAST LAT Project
Old efficiency calculation
strip ID
Efficiency
Relative efficiency
• X0 and X2 do not have bad
channels in these regions.
– Shadow of bad strips
in X1 (1270-1500).
– Inefficient regions are
slightly shifted.
– Old efficiency calculation
is more susceptible.
Efficiency
FMA (Bay 0) Layer X0, X2
X1 bad channel region
run ID (-77000000)
Hiro Tajima, TKR Efficiency Trending
strip ID
11
LAT Instrument Analysis Meeting – May 26, 2006
GLAST LAT Project
FM6 (Bay 12) Layer Y5
Sugizaki
Efficiency
Relative efficiency
• Noise flare according to Mutsumi.
run ID (-77000000)
Hiro Tajima, TKR Efficiency Trending
strip ID
12
LAT Instrument Analysis Meeting – May 26, 2006
GLAST LAT Project
FM13 (Bay 7) Layer X15
Sugizaki
Efficiency
Relative efficiency
• Another noise flare
– Only 1st ladder is affected.
– GTRC buffer limit is not
cause of inefficiency.
– Probably due to dead time
of preamplifier.
run ID (-77000000)
Hiro Tajima, TKR Efficiency Trending
strip ID
13
LAT Instrument Analysis Meeting – May 26, 2006
GLAST LAT Project
• No noisy strip found.
• Need further investigation.
# of hits per strip
FM14 (Bay 2) Layer Y0
Efficiency
Relative efficiency
strip ID
run ID (-77000000)
Hiro Tajima, TKR Efficiency Trending
strip ID
14