1. .- 1 - 17/06/2015 Christian J. Schmidt GSI Production of ALICE TRDs Progress and Quality Development Alice TRD Chamber Production Meeting Darmstadt Feb. 27th 2006

2. L4 and L5 chambers often show severe gain inhomogeneities up to +- 40% Problem can be cured by shimming side ledges with 100 or 200 micron shims, depending upon the outcome of pre-glue scan(s). Homogeneity Distortions Could be Resolved

3. Final Glueing Alters Things Slightly

4. Statistics on Homogeneity over Current Production

5. Statistics on Maximum Deviations (Histogram) Maximaly deviating points per chamber collected. Outlyers may be attributed to various problems

6. Leakage Currents Apply HV immediately after chamber installation, initial leakage currents would identify surface leakage. Ever since the employment of the cleaning procedure, no more leakage across glue surfaces encountered. Leakage due to dust and dirt remains but seldom in winter Leakage due to bad HV-cables with missing currents has resurfaced due to bad cables that had been used in the past.

7. Gas Leak Determination Normal behaviour: Time constant of Oxygen level ~ 12 h By now quite a few cases ( ~ 8 ) with  ~ 50 to 100 h Strong indication for virtual leaks No external leaks measurable Oxygen level scales inversely with gas flow Taken typical initial Oxygen content of 80 ppm at 20 l/h, implying a leak of 8 mbar l/h, the time constant would indicate a hidden volume of several hundred ml. too little for the radiator too much for the pad plane At GSI chambers in doubt are rapidly moved to a separate leak test stand where they can be flushed for many days.

8. Statistics on Leakage over Current Production

9. Statistics on Gain Measurements Histogram on measured gain at 1600 V Anode voltage Gain determination is difficult at GSI as strong EMI disturbances are intermittendly present.

10. Mistakes on Radiator Unveiled Just intended as an example for funny data and straight forward explanations: Diagnosis: one out of seven radiator pads missing in one compartment

11. Dubna Chambers under Repair Out of 18 chambers, 4 have a broken radiator towards the inside of the chamber All 18 chambers need to be refurbished: Radiator needs to be carefully reworked and closed again. Yuri and Nicolai are at GSI until March 11 th to work on chambers They are experimenting on best techniques for refurbishment Bernd Voss (GSI) has successfully repaired one of the broken chambers

12. Proposed Reassembly Procedure Pressure applied through slab: 5 g/cm 2 ~ 5 mbar Radiator Pad- panel Gas Volume Spacer support bars Gas Inlet

13. Conclusion on Current Situation at GSI Production is running smoothly Production rate at 1.5 chambers per week, limited by infrastructure Various problems have been settled and quality is improving Dubna chambers are under repair, no reason to be pessimistic here.