160603 SCT DESYweeklycsander/Talks/160603_SCT_DESYweekly.pdf · Semi-Conductor Tracker Barrel • 4 Layers • 2112 identical modules Endcaps • 2 end-caps, 9 disks each • 1976

C. Sander DESY Weekly Meeting - 03 Jun 2016 1

SCT Activities Nick Bedford, Mateusz Dyndal, Alexander Madsen,

Edoardo Rossi, Christian Sander

DESY ATLAS Weekly Meeting – 03. Jun. 2016

C. Sander DESY Weekly Meeting - 03 Jun 2016

Semi-Conductor Tracker

Barrel • 4 Layers• 2112 identical modules

Endcaps • 2 end-caps, 9 disks each• 1976 modules

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Modules• Two sides, back-to-back, 40 mrad• 285 μm thick, high-resistivity p-strips on n-bulk• [-5,-10] ºC• 17 μm resolution in R-φ plane

3

End-cap modules • 3 rings of different modules• Outer and middle: 4 sensors/module• Inner: 2 sensors/module• 57-94 μm pitch• CIS and Hamamatsu

Barrel modules • 4 sensors/module (2 e/side)• Identical• 768 strips/side• 80 μm pitch• Hamamatsu


Activities - OverviewDESY joined SCT operation (monitoring+calibration) effort in 2011 as institutional responsibility

What are we doing?• Keep 24h calibration loop working (Mateusz, Christian)• Maintenance and development of monitoring code (Mateusz, Christian)• Long-term monitoring of SCT noisy strips (Christian)• Performance studies (Nick B., Edoardo)• DCS on-call expert (Alex, starting this fall)

Further activities (not covered here)• SONAR (Cecile, Abby, Alex)• Heater pads (Alex)• MC Tuning (Akanksha, Mahsana, and Thorsten from Zeuthen)

Regular meetings together with Zeuthen on Thursdays 1:30pm

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Prompt Calibration LoopData taking (cosmics or collisions)

“Online” partial reconstruction; special calibration streams 5-10 Hz; e.g. data from beam gaps to study noisy strips

Prompt calibration loop; offline monitoring• Dead strips• Efficiency• Noise occupancy• Lorentz Angle• Bytestream errors• Noisy strips: <occupancy> > 1.5% → masked

Bulk reconstruction at TIER0

5

t = 0

t = 24-48h

Uploaded to conditions data base (COOL)

Data Quality Monitoring

Recent activities: • Update cron job scheduling to

avoid upload problems • Fixed some bugs (e.g. web

mail form, mail bombs …) • Manual re-running of wrongly

released jobs (hopefully not needed in the future)

• …


Monitoring of Noisy Strips• Total number of noisy

strips per run shows no alarming increase in 2016

• Large fluctuations from run to run, resulting in warnings (so far, not critical)

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Date12/2009 12/2010 01/2012 12/2012 12/2013 12/2014 01/2016 12/2016

Num

ber o

f noi

sy s

trips

210

310

410

0

2

4

6

8

10

12

14

duration (sec)0 10000 20000 30000 40000 50000 60000 70000 80000

num

ber o

f def

ects

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

• Hint of trend:longer runs → more noisy strips

• For this purpose: added LB dependent HitMaps to prompt calibration loop


#NS/module vs. time (in LB)Run 299584 (so far longest run in 2016)

Plot shows distribution of #noisy strips per module (x axis) for barrel (left) and end-cap C (right) in bins of 20 luminosity blocks (y axis)

Red: <number of noisy strips per module> ×50

For end-cap C, large number of modules show strange time dependence

7

0

10

20

30

40

50

60

70

Number of noisy strips vs. Lumi block

100 200 300 400 500 600 700 800 900 1000

20

40

60

80

100

NNS2D_ECEntries 42340Mean x 14.16Mean y 66.94RMS x 58.51RMS y 29.6


0

20

40

60

80

100


100 200 300 400 500 600 700 800 900 1000

20

40

60

80

100

NNS2D_BEntries 70180Mean x 2.198Mean y 65.92RMS x 11.66RMS y 31.27



Single Modules EC-C (Disk 2, 3 & 4)Plots show occupancy for single modules as function of time (in units of 20 LB)Striking time dependent feature, not constrained to single chipsPattern shows “some correlation” of affected strips for each diskPatterns seem to be “in sync” for each diskOften, the module is “ok” for a significant fraction of time but will be marked as noisy for most strips

8

chips

0 1 2 3 4 5


Properties of Suspicious ModulesIn end-cap C all affected modules ( ˜20) …• are from CIS• are located in middle ring

(i_eta = 1)• are facing air gap (link-0)• from disk 7 show some

pattern in φ (only odd modules show feature, those closer to support structure)

• from other disks show no pattern in φ

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Increased Noise for HPK Modules

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A noise anomaly has been detected in end-caps: All modules affected are …• Hamamatsu• link-0 (chip 0-5) modules• link-1at module boundaries (6 & 11) shown even/odd differences

study by Taka Kondo and Mutsuto Hagihara


Facing the Airgap

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Ion Wind?Hypothesis: radiation ionises air between disks, creating ion-wind → increased noisePlan: use ion gun to monitor noise levels on test module (in future @DESY)First step: estimate ion flux on modules, see if gun can provide itFor given module, Nick integrated number of expected charged particles over volume of air gap next to module, and calculate expected number of produced ions from average path length

This assumes, that all ions do reach the modules! Is this true?How about dissipation? Idea: solve diffusion equation (1D, no Bx and By); no drift

c: concentration of ionsq: source term (produced ions from charged particles passing air gap)𝛼: radiative recombination coefficient

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@

@tc(~x , t) = D�c(~x , t) + q(~x)� ↵c(~x , t)2

�ions =A⌘�2⇡

· fLHC ·dN±

d⌘· dNionsL

· hLi ⇡ 10 ... 80 nA


Solution with MATHEMATICA

Nick’s preliminary results show that dissipation is important!Consequence: flux reaching module surface is much reduced w.r.t. naive estimateCurrent challenge: calculate the flux on modulesSimple estimate

does not work!(limited numerical accuracy)

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without dissipation with dissipation

time

[s]

time

[s]

x [cm]x [cm]

c [cm-3] c [cm-3]

�(x , y , z = L) =1

2

Z L

0

q(~x)dz �Z L

0

↵c(~x)2dz

!


Summary• Several SCT activities ongoing, e.g. maintenance of prompt calibration loop• New time-dependent HitMaps allow for detailed further studies• Some modules, in particular in end-cap C, show suspicious time dependent noise

patterns → under investigation• Increased noise for HPK modules in end-caps facing air gaps under investigation

• Ongoing: estimation of expected ion flux• More studies are ongoing (heater pads, SONAR, MC tuning), or will start soon

(beam induced “noise”)

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Backup

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SCT Indexing SchemeiBEC_iLayer_iPhi_iEta_iSide -2/0/+2 0..8 0…55 -6…+6 0/1

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Single Modules EC-C (Disk 7)

17

? ?


Another Run (00300415)This run shows same structures for same modules as before (for disk 3), modules of disk 2,4,7 seem not to be affected

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0

10

20

30

40

50

60

70

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90

100


100 200 300 400 500 600 700 800 900 1000

5

10

15

20

25

30

NNS2D_ECEntries 7425Mean x 17.1Mean y 20.92RMS x 79.18RMS y 7.376



Diffusion EquationDetermine ion flux on modules facing air gaps

c: concentration of ionsq: source term (production of ions from charged particles passing the air gap)𝛼: radiative recombination coefficient

D: diffusion coefficient; in strong Bz field

with

T: temperature [K]M1 and M2: molar masses [g/mol]p: pressure [atm]𝜎12: collision diameter [Å]

𝛺: collision integral (≈1)

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@

@tc(~x , t) = D�c(~x , t) + q(~x)� ↵c(~x , t)2

D =

0

@0 0 00 0 00 0 Dzz

1

A

Dzz =1.858 · 10�3T 3/2

p1/M1 + 1/M2

p�212⌦

https://en.wikipedia.org/wiki/Mass_diffusivity

https://en.wikipedia.org/wiki/Mass_diffusivity


DissipationRadiative recombination (e- + N2+ → N2) can reduce the number of ions reaching surface of modulesFor nitrogen:

If recombination is not a sizeable effect, all the ions which are produced are reaching the surface → Nick’s previous calculation will hold (maybe reduced by factor 1/2)

If recombination is sizeable, the ion flux on modules is (in the static case) given by

To understand if the system will reach a static behaviour we have to solve the diffusion equation, no?If not static … things will become more complicated!!!

20

↵ = 2.2 · 10�7✓Te300 K

◆�0.39cm3

s�1

Journal of Geophysical Research, Vol. 109, 2004

�(x , y , z = L) =1

2

Z L

0

q(~x)dz �Z L

0

↵c(~x)2dz

!

Documents

160603 SCT DESYweeklycsander/Talks/160603_SCT_DESYweekly.pdf · Semi-Conductor Tracker Barrel • 4 Layers • 2112 identical modules Endcaps • 2 end-caps, 9 disks each • 1976