1. Status report on studying and preventing ageing in the LHCb OT S.Bachmann (on behalf of the LHCb OT group) Physikalisches Institut Heidelberg Many thanks to A.Pellegrino and U.Uwer for providing material! LHCC Referee Meeting, Sep 24, 2007

2. Outer Tracker Aging Investigations on Ageing: Status oUnderstanding ageing: Epoxy (Araldite AY103) has been identified as cause for ageing. oPreventing ageing: Main line: Long term flushing + heating of modules. More studies on: Adding new component to gas, i.e. oxygen (beneficial) and CF 4 (non-beneficial). HV training (inspection of wire after training, long term). Detailed study of chemical properties of AY103/HY991.

3. Glue Tests in Mini OT Modules: Constructed mini OT modules to test effect of different glues o 32 channels, 1m long o materials and procedure in so far as possible from mass production Could consider constructing a real OT module with different glue (e.g. Tra-Bond 2115 epoxy, from TRA-CON) to test our ability to produce modules not affected by the ageing problem o availability of components (F or S module?)

4. Araldite at straw entrance: No araldite used: Test module (straws): 480 hrs, 20mCu Finding the culprit for ageing using an openable test chamber:

5. Glue Tests in Openable Chamber Normal F-module: 20 hrs, 20mCu Openable chamber: 17 hrs, 2 mCu Gas flow

6. Glue Tests in Openable Chamber (cont’d) Openable chamber: 17 hrs, 2 mCu Gas flow oIrradiation damage related to gas flow Pollution transported ono ageing if glue is removed  out-gassing of AY103/HY991

7. Effect of long term flushing: Taken from PhD thesis T. Haas Exponential to black dots c = 18.3 m 3 c = 22.6 m 3 c = 15.7 m 3 Note: All detectors have been installed and continuously flushed since November ’06 (C-side) and June ’07 (A-side)

8. A warm-up of the modules (10 days at 40 o C while being flushed) leads in many cases to additional improvement. 12% 10% 14% 10% 43h 112h Before heating After heating 20h 90h source Effect of heating:

9. Summary of the heating of nine modules (taken from PhD thesis T.Haas)

10. Preparation of possibility to warm-up the modules Bar to protect the modules Electrical Heating blankets: -4 blankets per side -8 blanktes per C frame Avoid heating of the vertical C arm

11. 5950 475 985 475 5000 Heating area First Prototype 2 point regulation

12. Temperature sensors Uniformity test in vertical position: 2 blankets on mini C frame w/ 4 modules

13. Measured between module & blanket Measured between modules Temperature results in vertical position Module length Heat sink at bottom

14. Larger heating zones also work T nominal ~40 o C  2 o C

15. Installation at the pit

17. Lessons learned from prototypes: 5160 520 2060 electrical and mechanical design ok homogeneous warm-up of a complete frame possible account for possible heat sinks located at the upper and lower C frame arm  Modification of the heating zones: Still to be checked that no heat is spread to the vertical arm of the C-frame (1 st warm-up test is situ planned after LHCb Magnet test)

18. Monitoring ageing in situ: Module Scanning Tool for ageing-test in situ is ready for installation (using 90 Sr radioactive source(s))  Monitor evolution of module performance under continuous flushing  Give Feed-Back about heating  Monitor long-term effects during regular beam operations (tool “parked” out of acceptance, usable during access)

19. C-Frame Warm-Up Status Status oA full set of blankets (improved design) has been ordered 1 st blanket ready, being checked at Heidelberg, test at LHCb after Magnet Test oExpect delivery of remaining blankets by end of October oControl system (including safety interlocks) being worked on Monitoring oPrepare ageing-test system to be operated in situ to (sample) check results of warm-up Scanning tool being built o During 1 st warm-up, careful monitoring of the mechanical clearances that could be affected (e.g. module supports) special attention to the temperature monitoring in the vicinity of the RICH2

20. C-Frame Warm-Up Outlook Realistic (pessimistic?) scenario: o fully operation from the beginning of November o serial operations (one C-Frame at the time) Side C Side A

21. Backup slides

22. Update on Ageing Studies: Although attention focused on preparations for warming-up and monitoring tools in situ, a number of ageing studies was carried on during the summer: o Further warm-up tests on the bench with F and S modules (see summary talk(s) from September 2007 LHCb Week) o Resume studies with added O 2 to gas mixture (see summary talk(s) from September 2007 LHCb Week) o Further investigations of treatment with high-currents (direct and reverse polarity) wire inspection after treatment o Studies with openable test vessel to establish origin of the problem o Detailed studies of the AY103/HY991 properties (degree of polymerization, out-gassing, etc.) in cooperation with the CERN chemistry department (P. Chiggiato, R. Setnescu, I. Sorin, B. Teissandier, D. Letant-Delrieux, …) studies in progress, joint report in preparation

23. Cure – Negative HV Training: Trained straws Before Training ~60 hours at -1480 V repairs the damage previously inflicted by irradiation

24. Cure – Positive HV Training: Gas flow 340 hrs After HV 340+350 hrs 2 nd HV training1 st HV training3 rd HV training ~20 hours at +1900 V repairs the damage previously inflicted by irradiation HV training repeatable

25. Wire Inspection after HV Training: 11 Sep 2007 Recommendation of the Ageing Workshop panel: 1: not irradiated, trained 25/17 1: not irradiated, trained 4: irradiated, trained 12: new wire off the shelf inspect wire after HV training to check that high currents have no “burning” effects on the anode surface quality Took various samples of wire from openable chamber from the trained and non-trained region and from the irradiated and non-irradiate region, and compare with wire from new spool No effect on wire surface from optical inspection (  20   50 magnification)

26. Glue Tests in Mini OT Modules: Constructed mini OT modules to test effect of different glues o 32 channels, 1m long o materials and procedure in so far as possiblefrom mass production Could consider constructing a real OT module with different glue (e.g. Tra-Bond 2115 epoxy, from TRA-CON) to test our ability to produce modules not affected by the ageing problem o availability of components (F or S module?)