1. GLAST Large Area Telescope:
Gamma-ray Large Area Space Telescope
GLAST Large Area Telescope:
TKR NRL
Hiro Tajima (SLAC)
TKR

2. From Previous Efficiency Trending
Some layers (Bay 3 Y6, Bay 5 X14, Bay 5 Y12, Bay 6 Y3, Bay 7 Y16, Bay 8 X11, Bay 8 X7) showed non-negligible efficiency drop.
No apparent cause (dead, disconnected or hot strips, noise flare).
Add more runs between and
Lower minimum duration limit to 500 seconds.

3. When efficiency drop started?
Efficiency drop started between run# (5/29) and (6/1).
Common cause?
Vibe Z axis performed on 5/31.
Michael Kuss found no issue with TKR tower internal alignment.
No change in TKR related register values
Bay 3 Y6
Bay 5 X14
Bay 6 Y3
Bay 5 Y12
Bay 7 Y16
Bay 8 X11
Bay 8 X7

4. More Efficiency Loss More layers with similar efficiency loss
Total 39 layers were affected.
Some layers fully recovered.
Some layers recovered half way.
Some layers no receovery.

5. TKR Muon Peak Trending
Charge scale: muon peak normalized to expected MIP peak.
Requires 4 hours of muon data.
Mean value of muon peak has been drifting since last TOT calibration performed on 4/19.
Spread of muon peak is also increasing.
Requested new TOT calibration.
mean
RMS