1.1. Can the LAT produce errors during data Can the LAT produce errors during data acquisition?acquisition?– Choice of Error TypeChoice of Error Type– How often does it happen?How often does it happen?
– Under what condition does it happenUnder what condition does it happen?
2.2. What is the impact of these Errors on-orbit?What is the impact of these Errors on-orbit?
Lost in TranslationLost in TranslationIntroduction
How does it happen???How does it happen???
Tracker
Calorimeter
Tower Electronic Module
Tower Subsystems Tower Subsystems OverviewOverview
Glt Electronics Module
TEM collects them, checks 3-in-a-row and (if TKR triggers) sends it to GEM
GEM opens window on first trigger type and waits for others to arrive (Coincidence Window)
After few ticks CW closes and TAM is sent back to the readout controller to start readout
Readout starts from the
BOTTOM!!!
A particle hits the tower
Trigger Primitives fired by subsystems
TEM CC FIFO ErrorTEM CC FIFO Error– 1 cable stores up to 128 hits
– 8 cables per Tower
– 128 x 8 = 1024 hits per tower
Other Buffer Limits:
– Readout controller: max of 64 hits allowed
– Plane: max of 128 hits allowed (64x2)
– How: Cosmic showers e.g.
– Let’s call an event with FIFO error
“BAD” Cables
Si Planes
Tracker SketchFIFO Definition
How Often?How Often? Statistics Summary
• 6 Towers Runs:• # Runs: 62 (B type)• # Register Config: 3• # Events: 15,346,394• # Bad Events: 1760
• 8 Towers Runs:• # Runs: 81 (B type)• # Register Config: 3 • # Events: 22,391,000• # Bad Events: 2900
• 2 Towers Runs:• # Runs: 48 (all!!)• # Register Config: 19• # Events: 9,564,116• # Bad Events: 915
• 4 Towers Runs:• # Runs: 31 (B type)• # Register Config: 2• # Events: 1,084,655• # Bad Events: 93
• Error Rates for B type Runs:
• 2 Towers: 7.4 · 10-5
» B2: 8.3 · 10-5
» B10: 7.1 · 10-5
» B13: 7.5 · 10-5
• 4 Towers: 8.66 · 10-5
» B10: 8.40 · 10-5
» B13: 8.79 · 10-5
• 6 Towers: 1.13 · 10-4
» B2: 1,15 · 10-4
» B10: 1.09 · 10-4
» B13: 1.20 · 10-4
• Among 2 Towers runs (not B type)
– 135002057-2103– Single RC Right/Left
» ER 2 · 10-4
– 135002166-2168– Single RC R/L + Overlay 10 KHz
» 2,1/2,7 · 10-4
– 135002107– Only Cal Trigger
» 5.9· 10-3
How Often?How Often?Bad Events Rates
What’s that?2 orders of magnitude?
Can we explain this?
B2: Flight Settings
B10: Cal 4 range
B13: Zero Suppression OFF
Cables
Planes
• RC on one side only:• Max hits per plane is 64
• RC try to read its entire plane!– An event that had 70 hits on a
plane now saturates the plane!
– It’s easier to have more hits on the same Cable!!
Single RC ER Anomaly
• The factor 2-3 of difference is not so strange!!
»This can be a first order explanation!!
30 40
70
1. CAL LE has more probability to be triggered by high energy events.
2. Energetic events have more probably high hits occupancy
3. Is it enough to explain the big difference?
• No other runs to compare rates!!
Cal Only Trigger Anomaly
ER = 5.9· 10-3
The run has few events:3000 instead of 300,000!
NOT STRANGE!!
Do you believe me?Do you believe me?
BUT...BUT...We can REPRODUCE that!!!
Cut on CAL LE triggered Events!!
What comes out is ER ~ 3.6 · 10-3!!!
# Events: 3048
# Bad Events:18
You clearly recognize Eduardo when he’s been working late in the night
When do Bad Events happen to good When do Bad Events happen to good people?people?
• Which primitive triggers are there?
» GemConditionsWord
• When do they arrive?» Are there temporal
patterns?
• Is a Bad Event influenced by the previous one?
» GemDeltaEventTime
• How are hits distributed?
• Are there odd configurations?
• You understand “odd” later
» Stay tuned…
Trigger Hits Occupancy
Trigger Topology• GemConditionsWord:– Tells which primitive
triggers arrived in the CW– Possible combinations:
• TKR (2)• CAL LE (4)• CAL HE (8)• TKR + CAL LE (6)• TKR + CAL HE (10)• CAL LE + CAL HE (12)• TKR + both CAL (14)
B10 runs 2 towers B10 runs 2 towers
Trigger Types
GoodBad
•No 8s, 10s, 12s:
•This was expected!!
•Bad Events are “big”!
–High Multiplicity
We expect that the TKR often arrives first!
–TKR is big: high probability to
trigger first
Trigger TopologyTrigger Primitives Arrival Times
Chained B10 runs 2 towers Chained B10 runs 2 towers
TKR arrives soon!!!This is no surprise!
~80%
The number of events goes down very rapidly!!
Ticks
1 tick = 50 ns
Trigger TopologyTrigger Primitives Timing
• CAL LE should open when TKR is not the first:
» CAL LE is faster than CAL HE!
» # Times CAL LE opens CW is consistent!!
This is odd!!
Explanation???Just a case? Remember Log Scale
Ticks
Ticks
3 events
Trigger Topology
Temporal Correlations
The time between a Bad Event and the previous one is long!!
Good Bad
The minimum Delta Time is longer than for Good events
Just low statistics probably
1000 ticks 2000 ticks
Hits OccupancyEvent Display
Cliffhanger
Salt and Pepper
No Cal
Hits only in upper layers
“Recognizable track”
Cal lit up where “track” arrives
Hits everywhere
Drittoni(big straight)
50% 25%
20%
Hits Occupancy
1. Qualitatively: you can distinguish the single layers, one by one, from the other.
2. Hits are only on the borders and are uniformely distributed.
Evt 135002052-268476
CablesRea
dout
Con
trol
lers
Characteristic signature: everything’s FULL
PuffettaePuffettae
Puffettae• There is a Puffetta in 6 Towers
Runs too!!• None found in 4 and 8 towers runs
• It looks exactly the same as the 2 towers one.
135004119-115100
Puffettae Dumps
• Looking at Dumps you find this:
• 0040 (hex) = 64 (dec)
• For every single RC above 1 on every CC.
2
8
1
LDF Dump file
Puffettae Data
EventID CalEneSum (MeV)
Gem
Word
Tkr Cal Le Cal He Delta
Time
Gem
Discarded2 Towers
6 Towers
There is no obvious hint of electronics gone wild!!
Are these energies consistent with showers that big? • Delta Times are long
• GemDiscarded seems reasonable (TOT very long)
115099 117 2 2 31 31 10221 3607
115100 351303 14 3 0 2 47043 3607
115101 26 2 0 31 31 56818 3615
268475 0 2 0 31 31 46600 1367
268476 87766 14 2 0 9 65535 1367
268477 0 2 0 31 31 65535 1367
From Russia with… CAL!
Too good to be true!!!!CAL says:“Everything normal pal!! Just big shower!!”
Layers
Ene
rgy
(GeV
)
Asimmetry
LAT
6 towers
1. At sea level we see 10% of Ep (Tune)
2. From graph 106 e- at sealevel (Tune)
High multiplicity shower of 10 MeV e-
350 GeV measured
All strips hit 10⇒ 4 particles in 6 towers
350GeV/10000 = 35 MeV per particle
10 MeV particles don’t go through the TKR!!
p
For Ep=105 GeV (for consistency with the observed rate)
NO PUFFETTAE!!
What happens on-What happens on-orbit?orbit?
• There will be high-energy photons!!– Will these be high multiplicity events in the TKR?
• Let’s see what MC has to say about this!!• Used photons coming from 45°-60° from the vertical axis
• Energy of 300 GeV
• Searching for behaviours like those observed in FIFO errors
• Backsplash?Total # MC photons 105
# Triggered Events 13006
#1 Towers Saturated: 38
300 GeV
ConclusionsConclusions1. The TKR works (poor me…) too well!!
• FIFO errors are no mistery anymore!!• We know how to characterize AND understand
them!
– Rates are low: • 1 (lonely) bad guy every 100 thousands!!!!
– No influence on other events!!!
2. Bad Events are consistent with showers3. High energy photons MC needs to be
further studied– What about reducing lower layers buffer
bandwidth to improve recon??
TACK Favorite saying:
“I told you NOT my Camaro!! Now I’m angry…”
Anders Borgland
High energy Muon shower
Eduardo do Couto e Silva
Favorite saying: THIS IS TOO COOL!!!!
HIM
…trying to sneak home early… 1 AM…
ME
EM Showers
To be in the core area 3.14x4202=5.5x105 m2
Freq = 2 x 10-2/s (~4-8 e/ m2)To be in a 10 times denser area Freq ~ 2 x 10-3/s (~40-80 e/ m2) To be in a 100 times denser area Freq ~ 2 x 10-4/s (~400-800 e/ m2)
To be in the core area 3.14x4202=5.5x105 m2
Freq = 2 x 10-4/s (~40-80 e/ m2)To be in a 10 times denser area Freq ~ 2 x 10-5/s (~400-800 e/ m2) To be in a 100 times denser area Freq ~ 2 x 10-6/s (~4000-8000 e/ m2)
107 Gev
108 Gev• Need ~ 104 particles
• Total Energy ~ 350 GeV
• <Ep> ~ 35 MeV
• Let’s say initial total energy was 105-106 GeV
• We get at sealevel ~ 106 particles
• Assume for such initial energy, Freq ~ 2 x 10-4/s
• The 6 tower data acquisition lasted ~ 1 day
~ 16 Puffettae (or like)
Saturated tower:> 64 hits on each of the 4 bottom planes(both on x and y)
Is this consistent with Is this consistent with Showers?Showers?
# Saturated Towers
1 2 3 4 5 6 7 8
6 Towers Data 78 6 3 1 1 2 / /
8 Towers Data 145 11 3 3 2 1 0 4
91
169
=
V.H.E. Cosmic Rays and Air Shower Profile
Take a proton with Ep=107GeV=1016eV
Flux is 6.8/E1.75 per cm2, second, steradianand bin-width of E where E= 107GeV.We then get, Flux(Ep=107GeV)=3.8x10-12 /cm2/s/sr for a bin-width of 107GeV
Step 1) Read off the flux of 107GeV proton rate
Step 2) Estimate the lateral distr. of particles
Distance from the core is about 14X = 420m
Normalized density of 10-2 /X2 = 10-2 /(30m)2
X=Rad. length of atmosphere=36g/cm2=30m
Observationproton
Electron Component in Hadronic ShowerN
e/E0 [
1/G
eV]
Step 3) Estimate the number of electrons in a 107GeV air shower at sea level.
These are shower measured profiles for 105GeV proton. Since there is no measurement for 107GeV, we assume one sample profile from these.
This gives highest number of electrons at sea level: use as an upper limit.
For a 107GeV proton we get Number of e = 0.2x107 = 2x106
Electrons and Gammas within an EM Shower
Step 4) Calculate electron density per m2
From Step 3) Total number of electrons = 2x106 electronsFrom Step 2) Assume they are distributed uniformly in r=14X=420m of the core. Electron density is then 1.8x10-6 (1/m2) times 2x106 = 3.6/m2
Uncertainty: a) Fluctuation: Trade-off with frequency. Can give a factor of 10-100? b) Low critical energy for LAT? Ec=10MeV > 1.5MeV: a factor of 2? (see Figure)
Step 5) Calculate frequency:
From Step 1) 3.8x10-12 /cm2/s/srFrom Step 2) core radius=14X=420m
To be in the core area 3.14x4202=5.5x105 m2
Freq = 2 x 10-2/s (~4-8 e/ m2)To be in a 10 times denser area Freq ~ 2 x 10-3/s (~40-80 e/ m2) To be in a 100 times denser area Freq ~ 2 x 10-4/s (~400-800 e/ m2)
Horizontal Air Shower? (1/2)Ref: S. Mikamo et al., ICR-Report-100-82-3 (1982) [Spires]; Lett. Nuovo Cimento 34 (1982) 273
Ordinary air shower initiated by protons and nuclei lose ~all energy for zenith ang. >50 deg.
A different population “hirizontal” shower has been detected. If LAT is hit horizontally the electron multiplicity can be much lower.
Step 6) Take horizontal air showers with Ne>104
Intensity = 2 x 10-13 /cm2/s/ster (see the right fig.)Likely zenith angle = 65, 75, 85 deg. (see the fig. in the next slide.)Overburden=1kg/cos(65,75,85deg)=2.4, 3.9, 11.5 kg = 67, 108, 319 X (the shower hist. may be shorter.)Typical lateral size: assume to be half the detector size of the Akeno exp. > radius=20m
Horizontal Air Shower? (2/2)Ref: S. Mikamo et al., ICR-Report-100-82-3 (1982) [Spires]; Lett. Nuovo Cimento 34 (1982) 273
Step 7) Calculate frequency and electron density
Core area = 1250m2
Electron density = >104/1250 = >8/m2
Freq = 2.5x10-6/s/sr
To be in the core area (1250m2)
Freq ~ 2.5 x 10-6/s (>8 e/ m2)To be in a 10 times denser area Freq ~ Prob. of 10 fold fluct. x 2.5 x 10-7/s (>80 e/ m2)
Conclusion1) Frequency of LAT being within the core radius (~420m for 107GeV) is high (~1/min) but average electron density is only ~4-8/m2.2) Electron density probably fluctuate as much as 100 times, but the product of frequency and multiplicity remains constant for a given shower energy. Freq ~ 2 x 10-2/s (~4-8 e/m2) Freq (x 10) ~ prob. of 10 fold fluct. x 2 x 10-3/s (~40-80 e/m2) Freq (x 100) ~ prob. of 100 fold fluct. x 2 x 10-4/s (~400-800 e/m2)3) Guestimate for 108GeV protons: Frequency 1/100, multi. is 10 times. Freq ~ 2 x 10-3/s 2 x 10-4/s (~40-80 e/m2) Freq ~ prob. of 10 fold fluct. x 2 x 10-5/s (~400-800 e/m2) Freq ~ prob. of 100 fold fluct. x 2 x 10-6/s (~4000-8000 e/m2)4) Horizontal showers are likely to produce high multiplicity events than normal showers.