1. 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning1/16 Ageing Phenomena in the LHCb Outer Tracker 1 November 2007 IEEE2007 Niels Tuning On behalf of the LHCb Outer Tracker Collaboration oIntroduction oAgeing Phenomenon oCause oTreatments

2. 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning2/16 LHCb in a nutshell Aim: look for new physics by measuring CP violation and rare decays pp with  s =14 TeV L = 2.10 32 cm -2 s -1 10 12 b-hadrons per year b s s b b s μ μ

3. 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning3/16 The LHCb Tracking System Tracking Detectors Outer Tracker Straw tube technology Gaseous  Momentum  B-mass Trigger Tracker Inner Tracker Si strip detector Vertex Locator n-on-n Si strip detector 8mm from LHC beam  Impact parameter  B-lifetime

4. 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning4/16 Outer Tracker 340 mm  Total nr of channels: 53.760  Gas: Ar/CO 2 70/30  Anode: 25µm W/Au  Cathode: Kapton XC/Al One large straw tube module:  34 x 490 cm 2  4 x 64 = 256 straw tubes 5m

5. 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning5/16  Position Good Example: Check detector response: Current from 90 Sr β-source Pulse height from monochromatic 55 Fe γ- source Full scan of the entire module  Every cm 2 of the OT is checked Wire locators Final Module Check: radioactive source scan  Current (nA) Example of uniform response 5 meter Bad Example: # Wire +20%

6. 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning6/16 Ageing Phenomenon (I) oGain loss “in the neighborhood” of the irradiation point: Croissant? Bean? Kidney?  Only at moderate intensity  Upstream of gas flow A real surprise – this was not seen in the aging tests performed over the last years with test modules Ratio Plot: I after /I before Irradiate with 2 mCi 90 Sr source 150nA Gas flow

7. Ageing Studies in R&D phase with test module: o12 MeV proton beam oHadronic environment (in situ HERA-B) o9 keV X-ray tube: Intermezzo: Ageing Studies in R&D phase 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning7/16 IEEE 2004 NSS-MIC conference (Oct 2004, Rome) by Sebastian Bachmann  Session N39: Radiation Damage Effects II - Aging of Gaseous Detectors  Title: Ageing Studies for the Straw Tube Detectors for the LHCb Outer Tracking System Accumulated 3 C/cm in 120 days No effects seen

8. Ageing Phenomenon (II) 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning8/16 oGain loss “in the neighborhood” of the irradiation point:  Only at moderate intensity  Upstream of gas flow Gas flow Relative gain

9. 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning9/16 Wire Inspection Deposit on the surface? Carbon Non-irradiated wire Irradiated wire SEM-EDX: Optical:

10. 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning10/16 Find the Culprit(s) Philosophy: Create module without glue Add component by component, until it ages Normal F-module: 20 hrs, 20mCi Test module (straws): 480 hrs, 20mCi Test module

11. 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning11/16 Find the Culprit Put fresh glue at straw entrance  Ageing Test module: 17 hrs, 2 mCi In parallel, new test modules are built with different glue  Confirm malicious effect of glue Glue: Araldite AW103, HY991

12. Ageing: Treatments (I) 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning12/16 Beneficial effects:  Heating (2 weeks at 45 o C)  Flushing  HV training No heating: 20 hrs 2mCi 90 Sr With heating: 325 hrs 2mCi 90 Sr

13. Ageing: Treatments (I) 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning13/16 Beneficial effects:  Heating (2 weeks at 45 o C)  Flushing  HV training  Flushing Time (weeks)  Gain loss (%) No heating: 20 hrs 2mCi 90 Sr With heating: 325 hrs 2mCi 90 Sr ½ year Detector is installed, and flushing since 1 year

14. 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning14/16 Ageing: Treatments (II) Beneficial effects:  Heating  Flushing  HV training (24 hrs, 1900V, G~700k)  Dark current ~ 10µA / wire  Wire inspection promising; no carbon deposits despite large currents 2 nd HV training 1 st HV training 3 rd HV training  Relative Gain  Irradiation Time (hours) Other beneficial effects:  Lower gas flow during operation  Addition of O 2 to counting gas

15. Ageing: Treatments (III) 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning15/16 Other beneficial effects:  Lower gas flow during operation Ar/CO 2 70/30, 22hrs, 20 l/hr Ar/CO 2 /O 2 70/27.5/2.5, 46hrs, 10 l/hr  Addition of O 2 to counting gas

16. 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning16/16 Summary oObserved serious gain loss with modest irradiation  No gain loss at highest intensity  No gain loss downstream the source oOutgassing glue is found to be the cause oVarious treatments have been identified  Flushing  Heating  HV training  Lower gas flow  Addition of O 2

17. What science we’ll know in 2050 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning17/16 oThe December 1999 issue of Scientific American, cited eight questions to which science is likely to have found the answers by the year 2050: Can physics be unified? Can aging be postponed? How was the Universe born? How does the mind work? What secrets do genes hold? Can robots be intelligent? Is there life in outer space? How much do we change the climate?

18. Backup slides 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning18/16

19. Consequence for LHCb? 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning19/16 oDifficult to predict consequence:  Relate source to LHCb SourceLHCb nA/straw/cm

20. Consequence for LHCb? 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning20/16 oDifficult to predict consequence:  Relate source to LHCb  Add all beneficial effects Multiplicative ?  Extrapolate damage to 10 8 s Linearly? Exponentially? 20 hrs 90 Sr 320 hrs 90 Sr (~10 6 s) Gas flow 5l/h (1V/3.6 h) Extrapolate exponentially to 3×10 7 s Extrapolate linearly to 3×10 7 s ×1/2×7×26 Heated Module-2%1%7%26% Flushed Module2%15%8%56%- NB All numbers are for the region of maximum damage (“hot spot”) E.g. 10 cm (in Y) away from that, numbers have to be scaled down by a factor 2  3

21. Consequence for LHCb? 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning21/16 oDifficult to predict consequence:  Relate source to LHCb  Add all beneficial effects Multiplicative ?  Extrapolate damage to 10 8 s Linearly? Exponentially?  Low gas gain  cell efficiency Gain drop of 50% is roughly equivalent to a HV step of ~70 V Assume an initial operational voltage of 1520 V  Gain drop of 50% ~ effective HV reduction of 70V  ~15% lower drift-cell efficiency

22. Consequence for LHCb? 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning22/16 oDifficult to predict consequence:  Relate source to LHCb  Add all beneficial effects Multiplicative ?  Extrapolate damage to 10 8 s Linearly? Exponentially?  Low gas gain  cell efficiency  Cell eff  track efficiency Tracking efficiency OT-cell efficiency Nominal An OT-cell efficiency 15% lower than nominal over the entire detector surface induces a 8% reduction of the tracking efficiency CAVEAT This study is purely illustrational!  tracking is not optimized to handle significant reductions of cell efficiencies  the gain loss and thus the reduction of cell efficiency is far from being uniform!

23. 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning23/16

24. 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning24/16 Reverse gas flow Only ageing close to input Polution not caused at curing time  Classical outgassing after all Gas flow Close to output Close to input (12 Jun 07, #24)

25. 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning25/16 Reverse gas flow, check other output now Only ageing close to input Polution not caused at curing time  Classical outgassing after all Gas flow Close to input (14 Jun 07)

26. Confirm Gain Loss with 55 Fe pulse height 1 Nov 2007IEEE NSS (N48-3) - Ageing in the LHCb Outer Tracker - N. Tuning26/16 Gain loss measured with  Current from 90 Sr  Pulse height from 55 Fe