1. GLAST LAT Project LAT Instrument Analysis Meeting – May 26, 2006 Hiro Tajima, TKR Efficiency Trending 1 GLAST Large Area Telescope: TKR Efficiency Trending Hiro Tajima (SLAC) TKR htajima@slac.stanford.edu 650-926-3035 Gamma-ray Large Area Space Telescope

2. GLAST LAT Project LAT Instrument Analysis Meeting – May 26, 2006 Hiro Tajima, TKR Efficiency Trending 2 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.

3. GLAST LAT Project LAT Instrument Analysis Meeting – May 26, 2006 Hiro Tajima, TKR Efficiency Trending 3 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)

4. GLAST LAT Project LAT Instrument Analysis Meeting – May 26, 2006 Hiro Tajima, TKR Efficiency Trending 4 FM4 (Bay 13) Layer Efficiencies Layer X13 (plane# 26) shows significant efficiency drop. + LICOS runs + PSR runs Layer ID Efficiency

5. GLAST LAT Project LAT Instrument Analysis Meeting – May 26, 2006 Hiro Tajima, TKR Efficiency Trending 5 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. Strip ID Efficiency

6. GLAST LAT Project LAT Instrument Analysis Meeting – May 26, 2006 Hiro Tajima, TKR Efficiency Trending 6 SSD Wafer Dependence? Occupancy does not depend on SSD wafer in the ladder. Efficiency loss is well correlated with GTFE boundaries. Strip ID Occupancy (arbitrary unit) Strip ID GTFE boundaries Ladders GTFE Wafer 0 Wafer 3 Wafer 2 Wafer 1 – Wafer 0 – Wafer 1 – Wafer 2 – Wafer 3

7. GLAST LAT Project LAT Instrument Analysis Meeting – May 26, 2006 Hiro Tajima, TKR Efficiency Trending 7 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. –Mainly to reduce trigger occupancy. –It may not fix the efficiency loss since we had some efficiency loss even when these strips were quite. Root Cause of Efficiency Loss LICOS runs PSR runs Strip ID Occupancy (arbitrary unit) Strip ID 1142 1141, 1143 Sugizaki

8. GLAST LAT Project LAT Instrument Analysis Meeting – May 26, 2006 Hiro Tajima, TKR Efficiency Trending 8 FMA (Bay 0) Layer Efficiencies Slight efficiency loss in Y0, Y3, Y4. + LICOS runs + PSR runs Layer ID Efficiency

9. GLAST LAT Project LAT Instrument Analysis Meeting – May 26, 2006 Hiro Tajima, TKR Efficiency Trending 9 FMA Y3, Y4 Strip-Level Efficiencies No localized significant efficiency loss observed. –Some intermittent strips in green circles could be a cause. disconnected strips ladder disconnected strips ladder disconnected strips and healthy strips are mixed and averaged out.

10. GLAST LAT Project LAT Instrument Analysis Meeting – May 26, 2006 Hiro Tajima, TKR Efficiency Trending 10 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.

11. GLAST LAT Project LAT Instrument Analysis Meeting – May 26, 2006 Hiro Tajima, TKR Efficiency Trending 11 FMA (Bay 0) Layer X0, X2 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. Old efficiency calculation X1 bad channel region run ID (-77000000) Relative efficiency Efficiency strip ID Efficiency

12. GLAST LAT Project LAT Instrument Analysis Meeting – May 26, 2006 Hiro Tajima, TKR Efficiency Trending 12 FM6 (Bay 12) Layer Y5 Noise flare according to Mutsumi. run ID (-77000000) Relative efficiency Efficiency strip ID Sugizaki

13. GLAST LAT Project LAT Instrument Analysis Meeting – May 26, 2006 Hiro Tajima, TKR Efficiency Trending 13 FM13 (Bay 7) Layer X15 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) Relative efficiency Efficiency strip ID Sugizaki

14. GLAST LAT Project LAT Instrument Analysis Meeting – May 26, 2006 Hiro Tajima, TKR Efficiency Trending 14 FM14 (Bay 2) Layer Y0 No noisy strip found. Need further investigation. run ID (-77000000) Relative efficiency # of hits per strip strip ID Efficiency strip ID