1 Sasha Milov DC meeting... March 7, 2007 HBD status Sasha Milov March 7, 2007

2 Sasha Milov DC meeting... March 7, 2007 Detector status All gems in all modules were tested individually with external power supply. 54 out of 72 GEMs were found problematic. most GEMs have 1 or 2 problems. this is ~60% more then 2monts ago there are more problems on West then on the East. two modules on the West have more severe problems and are likely not recoverable. most problems are curable on expense of loosing ~3.5% of single module area per problem. Rest of the detector was brought to 3600V (~1/3 of operational gain) and several to 3720V (full gain). We saw cosmic signals from more than one module We found the reason and fixture to the most severe problem hitting us for long time: the massive trips on the detector

3 Sasha Milov DC meeting... March 7, 2007 Detector gain snapshot:

4 Sasha Milov DC meeting... March 7, 2007 Massive trip solution We found a problem in the voltage divider not adequately responding to the LeCroy trips. That would cause a detector to spark Spark produces enough light to cause modules at HV to trip We fixed 3 modules yesterday and ran a conclusive test. not at full V didn’t trip tripped induced trip When we induced trip in fixed modules there was no follow up, except ES0  ES1, but ES1 is one with high current. When we did in unfixed modules there was 100% follow up, or none except EN5. When we induced trip in both fixed and unfixed modules in a different way, such that a spark occurs, we saw 100% follow up. Right now Mike Lenz is fixing all modules on both HBDs es en

5 Sasha Milov DC meeting... March 7, 2007 Peripheral events (60-100%) –An alternate of p+p collisions Many basic features can be checked Single particle efficiency can be used (no embedding is needed) –Run4 data: ~250Mevts out of 700Mevts(MB) ~ phi’s in PHENIX acceptance –If we have fake pair rejection of ~100, We can see the peak at ~25Mevts out of 70Mevts. –We may want to have 2-3 times of it as an initial check? Peripheral event filtering

6 Sasha Milov DC meeting... March 7, 2007 ~20%Loss ~23%Loss 2.0slpm  3.5slpm 30-40%  20% in photon loss 27pe  31pe in primary electron statistics CF4 IN HBD W HBD E Input Gas is flat as always 3slpm

7 Sasha Milov DC meeting... March 7, 2007 Next steps. Fix modules and continue conditioning to full operational voltage Do one more gem-by-gem test to adjust currents in modules where they are different from nominal by more then 0.3%. We expect that after fixing the trip problem detector will be not only more stable but will significantly slow deterioration. Start look at cosmic and noise at full HV (was very good so far). Continue work on monitoring. If we do not bump in more problems, the detector has a good chance (full East and most of West) to be in working condition when the beam comes.

8 Sasha Milov DC meeting... March 7, 2007 BACKUPS

9 Divider again…

10 Sasha Milov DC meeting... March 7, 2007 Floating Mesh MT only happen between the two modules sitting at high enough voltage?  our killer question from Friday studies (!) MT are confined to one arm, and have no other patterns Prototype was more stable, then real detector More short problems in top GEMs Two modules with mesh-gem shorts

11 Sasha Milov DC meeting... March 7, 2007Solutions