1. Activities During 4/11/07 IR Access HBD Working Group Meeting 4/17/07 B.Azmoun, T.Hemmick, J.Kamin, S.Stoll, C.Woody Brookhaven National Lab / SUNY SB

2. 4/17/07B.Azmoun, BNL2 4/11 Access: Flash Lamp Tests 4/11/2007 CF4 VGEM = 100V Vref = 6.5V 2x16nS New Scope (1Mohm) H2O ppm (W/E) = 3.3/6.2 O2 ppm (W/E) = 4.0/2.7 Flow (W/E)=3.75/4slpm 12/24/2006 CF4 VGEM = 100V Vref = 6.5V 2x16nS New Scope (1Mohm) H2O ppm (W/E) = 16.7/8.9 O2 ppm (W/E) = ? Flow=2slpm  QE Degradation between 4/11/07 – 12/24/06 (is it real???) Consistency between Lamp Up/Down  Results are Reproducible (+/- 10?) We know lamp orientation is same on 4/11 - 12/14, at least in E-Lamp Bot. measurement. In cases where the rel. QE is above 1.0 may be explained by the variability in the measurement and/or lower ppm levels on 4/11 Look for Correlations that could explain these alarming results G-M Short

3. 4/17/07B.Azmoun, BNL3 History of Flash Lamp Tests: 12/14/06 – 12/04/06 12/14/2006 Ar VGEM = 100V Vref = 5.5V --> Correction: 6.5V/5.5V--> 1.35 2x16nS --> Correction: 4x16nS/2x16nS--> 0.65 New Scope (1Mohm) H2O ppm (W/E) = 16.7/8.9 O2 ppm (W/E) = ? Flow=2slpm 12/4/2006 Ar VGEM = 100V Vref = 6.5V 4x16nS + 18" RG59 New Scope (1Mohm) H2O ppm (W/E) = 4.5/10.6 O2 ppm (W/E) = 7.9/6.9 Flow=2slpm  Results are consistent btw 12/14 and 12/4  No QE degradation Before CF4 Flow Before HV ON

4. 4/17/07B.Azmoun, BNL4 History: 12/04/07 - 10/18/07 12/4/2006 (BNL) Ar Assumed: VGEM = 100V Vref = 6.5V 4x16nS + 18" RG59 New Scope (1Mohm) --> Few % diff. btw old&new H2O ppm (W/E) = 4.5/10.6 O2 ppm (W/E) = 7.9/6.9 Flow=2slpm 10/18/2006 (SUNY SB) Ar VGEM = 100V Vref = 6.5V 4x16nS + 18" RG59 Old Scope (1Mohm) H2O ppm (E)~20.5 O2 ppm (E)~3.1 Flow~6slpm ???  Comparison of PC response at SUNY SB and BNL Clear correlation btw sectors along phi implies some systematic error like a difference in lamp Orientation in the two measurements

5. 4/17/07B.Azmoun, BNL5 History: 10/18/06 - 10/17/06 10/18/2006 (SUNY SB) Ar VGEM = 100V Vref = 6.5V 4x16nS + 18" RG59 Old Scope (1Mohm) H2O ppm (E) ~20.5 O2 ppm (E) ~3.1 Flow~6lpm ??? 10/17/2006 (SUNY SB) Ar VGEM = 100V Vref = 6.5V 4x16nS + 18" RG59 Old Scope (1Mohm) H2O ppm (E) = 20.5 O2 ppm (E) = 3.1 Flow~6lpm ???  The consistency in results here (where nothing has presumably changed in 2 days) makes a statement about the stability/reproducibility of the lamp intensity  this is the best we can do since we don’t have a lamp monitor.

6. 4/17/07B.Azmoun, BNL6 Correlations: GEM Resistor Values 0 = inf. Hypothesis: Larger resistor values compensate for (extra) corona current, which may damage the CsI.  The top GEM, likely the most important, shows little correspondence btw Resistor values and Flash lamp response (higher resis. values even correspond to a ratio ~1.0)

7. 4/17/07B.Azmoun, BNL7 CsI Thickness Hypothesis: Thinner CsI layers are damaged more readily by harmful mechanism responsible for diminished response of PC’s.  There is no obvious correspondence btw CsI thickness and Flash Lamp Response

8. 4/17/07B.Azmoun, BNL8 Abs. # of Trips Hypothesis: Damage incurred by the PC’s is proportional to the absolute number of trips sustained by the GEM module.  There is no obvious correspondence btw the abs. # of trips and Flash Lamp Response

9. 4/17/07B.Azmoun, BNL9 Enhanced Gain through Photon Feedback? Hypothesis: Photon Feedback is responsible for the enhanced gain observed for many HBD modules, and thus should correlate with PC QE.  There is no obvious correspondence btw the gain of the HBD modules and Flash Lamp Response

10. Gotta keep looking…any ideas?

11. 4/17/07B.Azmoun, BNL11 Gas Trans. w/ HBD in Bypass Mode As suspected, the heightened H2O/O2 levels observed in the return gas from the HBD is coming from the HBD itself.