glast lat project lat instrument analysis meeting – may 26, 2006 hiro tajima, tkr efficiency...

GLAST LAT Project LAT Instrument Analysis Meeting – May 26, 2006

Hiro Tajima, TKR Efficiency Trending 1

GLAST Large Area Telescope: GLAST Large Area Telescope:

TKR Efficiency Trending

Hiro Tajima (SLAC)

TKR

[email protected]

Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope



Efficiency Trending Result @ IA WorkshopEfficiency 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

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

2TWR 4TWR 6TWR 8TWR 16TWR

Test Phase

Efficiency change (%)

TkrFMA

TkrFMB

TkrFM1

TkrFM2

TkrFM3

TkrFM4

TkrFM5

TkrFM6

TkrFM7

TkrFM9

TkrFM10

TkrFM11

TkrFM12

TkrFM13

TkrFM14

TkrFM15



Improvement on Efficiency CalculationImprovement 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 LICOS difference PSR difference PER(NRL) differenceA 98.59% 98.54% -0.05% 98.53% -0.06% 98.58% -0.01% 98.55% -0.04%B 99.84% 99.82% -0.02% 99.82% -0.02% 99.83% -0.01% 99.82% -0.02%1 99.74% 99.72% -0.02% 99.72% -0.02% 99.73% -0.01% 99.71% -0.03%2 99.74% 99.74% 0.00% 99.73% -0.01% 99.75% 0.01% 99.74% 0.00%3 99.67% 99.69% 0.01% 99.69% 0.02% 99.70% 0.03% 99.69% 0.02%4 99.84% 99.81% -0.03% 99.80% -0.04% 99.76% -0.08% 99.78% -0.06%5 99.87% 99.92% 0.05% 99.92% 0.05% 99.92% 0.05% 99.90% 0.03%6 99.81% 99.79% -0.01% 99.80% -0.01% 99.81% 0.00% 99.78% -0.03%7 99.87% 99.85% -0.02% 99.83% -0.04% 99.86% -0.01% 99.83% -0.04%9 99.90% 99.90% -0.01% 99.89% -0.01% 99.90% 0.00% 99.84% -0.06%

10 99.85% 99.85% 0.00% 99.85% 0.00% 99.86% 0.01% 99.83% -0.02%11 99.88% 99.88% 0.00% 99.87% 0.00% 99.87% -0.01% 99.81% -0.06%12 99.93% 99.91% -0.02% 99.91% -0.02% 99.91% -0.02% 99.85% -0.08%13 99.90% 99.90% -0.01% 99.88% -0.02% 99.90% 0.00% 99.87% -0.04%14 99.88% 99.86% -0.01% 99.86% -0.01% 99.87% -0.01% 99.85% -0.02%15 99.90% 99.89% -0.01% 99.88% -0.01% 99.89% 0.00% 99.83% -0.06%



FM4 (Bay 13) Layer EfficienciesFM4 (Bay 13) Layer Efficiencies

• Layer X13 (plane# 26) shows significant efficiency drop.

+ LICOS runs+ PSR runs

Layer ID

Eff

icie

ncy



FM4 X13 Strip-Level EfficienciesFM4 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

Eff

icie

ncy



SSD Wafer Dependence?SSD Wafer Dependence?

• Occupancy does not depend on SSD wafer in the ladder.

• Efficiency loss is well correlated with GTFE boundaries.

Strip ID

Occ

up

ancy

(ar

bit

rary

un

it)

Strip ID

GTFE boundaries

Ladders

GTFE

Wafer 0

Wafer 3

Wafer 2

Wafer 1

– Wafer 0– Wafer 1– Wafer 2– Wafer 3



• 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 LossRoot Cause of Efficiency Loss

LICOS runs PSR runs

Strip ID

Occ

up

ancy

(ar

bit

rary

un

it)

Strip ID

1142

1141, 1143

Sugizaki



FMA (Bay 0) Layer EfficienciesFMA (Bay 0) Layer Efficiencies

• Slight efficiency loss in Y0, Y3, Y4.

+ LICOS runs+ PSR runs

Layer ID

Eff

icie

ncy



FMA Y3, Y4 Strip-Level EfficienciesFMA 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.



Automated Layer Efficiency TrendingAutomated 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.



FMA (Bay 0) Layer X0, X2FMA (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)

Rel

ati

ve

eff

icie

ncy

Eff

icie

ncy

strip ID

strip ID

Eff

icie

ncy



FM6 (Bay 12) Layer Y5FM6 (Bay 12) Layer Y5

• Noise flare according to Mutsumi.

run ID (-77000000)

Rel

ati

ve

eff

icie

ncy

Eff

icie

ncy

strip ID

Sugizaki



FM13 (Bay 7) Layer X15FM13 (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)

Rel

ati

ve

eff

icie

ncy

Eff

icie

ncy

strip ID

Sugizaki



FM14 (Bay 2) Layer Y0FM14 (Bay 2) Layer Y0

• No noisy strip found.• Need further investigation.

run ID (-77000000)

Rel

ati

ve

eff

icie

ncy

# o

f h

its

per

str

ip

strip ID

Eff

icie

ncy

strip ID

glast lat project lat instrument analysis meeting – may 26, 2006 hiro tajima, tkr efficiency...

Documents

efficiency of strips

lower efficiency

efficiency values

strip id efficiency

efficiency trending

exact strip efficiency

layer id efficiency

efficiency calculation