1 HBD HV Commissioning Itzhak Tserruya, HBD meeting, February 27, 2006

2 Last week highlights nCompletion of the module by module conditioning. n2 nd round of Bertan tests on 54 GEMs. nResistor changes on the entire detector completed. In the majority of cases the changes produced the anticipated change of bringing dI close to zero. The few cases where the change did not work are fullly understood. n A group of seven modules from the upper part of the detector (EN3, EN4, EN5, ES3, WN3, WN5, WS5) were brought together to 3600V: u West: 1 massive trip in 7h u East: 5 massive trips in 7h (some of them could have been triggered by ES5 that draws negative current).

3 2 nd round of Bertan test nPerformed on 54 GEMs (53 successful, 1 inconclusive). nComparison of 1 st and 2 nd round: Total T M B u no change u improvement 2 2 u deterioration* u new problem * Deteriaration generally means that a non-ohmic behavior became more non-ohmic getting closer to a dead short.

4 Single & group conditioning n The 7 modules (EN3, EN4, EN5, ES3, WN3, WN5, WS5) were selected because they were stable over the last days and with dI close to zero. nSummary of single module conditioning: trips during ramping up trips at 3600 V EN3 0 0/4.8h EN4 Failed (13 trips/2h at 3400/3550) This module was drawing dI = -0.9% EN5 0 1/4.8 ES3 0 0/6.5h Group 2 3/7h* WN3 1 0/4h WN5 0 0/4h WS5 2 0/8h Group 0 1/7h * 2 could have been triggered by ES3 that was by mistake added to the group for about 3h. Conclusions: nEN4 should be conditioned again separately. nWe should require each module to be stable at 3600V before adding it to the group.

5 Comments and recommendations n Resisitors should be changed if: F Bertan test and HV_Gui give a consistent picture AND F the module showed stability over at least one week bracketing the Bertan test. nThe vast majority of trips is harmless. Only a very small fraction produces some damage that is evidenced by a sudden jump in dI right after a trip. nWe should find a quick way to alert us when a sudden change in current occurs.

6 Comments & Recommendations nMany of the damaging trips have occurred on Feb. 6-8 when magnet operations took place. Coincidence or real effect? nFor the time being, whenever magnet operations take place I recommend to ramp down to zero the entire detector. After completion of magnet operation, we should restore HV very cautiously. Modules may require reconditioning after changes in magnetic field configuration. I recommend to restore HV module by module the first time.

7 What’s next?  Select a group of good modules from the lower part of the detector and follow the same procedure as for the group of 7 from the upper part of the detector, i.e.:  One by one ramp the up to 3600 V, stay 1 h at 3600V and then back to 3200V  Ramp the entire group to 3600 V and stay there at least 6h.  Take the two groups together to 3600 V  Work/watch the other modules.  Since RHIC is delayed by two weeks we should do one operation at a time to allow unambiguous diagnostics.

8 Resistor change ES4 Resistor change 2% EN4 Resistor change -1.3% -4% A classical example of an unstable module where resistors should have not been changed A classical example of a good decision to change resistor