# Presentation: 694353

## 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

## 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**

- B.Azmoun, BNL

- 4/17/07

## 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

- B.Azmoun, BNL

- 4/17/07

## 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

- B.Azmoun, BNL

- 4/17/07

## 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.

- B.Azmoun, BNL

- 4/17/07

## Correlations: GEM Resistor Values

- _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)

- B.Azmoun, BNL

- 4/17/07

## 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

- B.Azmoun, BNL

- 4/17/07

## 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

- B.Azmoun, BNL

- 4/17/07

## 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

- B.Azmoun, BNL

- 4/17/07

## Gotta keep looking...any ideas?

## 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.

- B.Azmoun, BNL

- 4/17/07