itzhak tserruya, bnl, may13, 20031 hbd r&d update: demonstration of hadron blindness a. kozlov,...
TRANSCRIPT
Itzhak Tserruya, BNL, May13, 2003
1
HBD R&D Update: HBD R&D Update: Demonstration of Hadron BlindnessDemonstration of Hadron Blindness
A. Kozlov, I. Ravinovich, L. Shekhtman and I. Tserruya
Weizmann Institute, Rehovot May 13, 2003
Itzhak Tserruya, BNL, May13, 2003
2
Detector R&D Goals Detector R&D Goals (Feb. 14, 2003)(Feb. 14, 2003)
Gain and stability: demonstrate that the detector can operate at a gain of 104. demonstrate stability at 104. operate at 104 in presence of highly ionizing particles.
Aging effects aging of GEM. aging of CsI.
Ion back-flow (feed-back)
Response to mip and electrons * demonstrate hadron blindness.
* optimize detector operation.
Other issues * CsI quantum efficiency and bandwidth. * CF4 scintillation.
“Prototype” in-beam test
Last missing milestone
Itzhak Tserruya, BNL, May13, 2003
3
Detector R&D Goals Detector R&D Goals
Gain and stability: demonstrate that the detector can operate at a gain of 104. demonstrate stability at 104. operate at 104 in presence of highly ionizing particles.
Aging effects aging of GEM. aging of CsI.
Ion back-flow (feed-back)
Response to mip and electrons
* optimize detector operation.
Other issues * CsI quantum efficiency and bandwidth. * CF4 scintillation.
“Prototype” in-beam test
demonstrate hadron blindness.
Itzhak Tserruya, BNL, May13, 2003
4
What happened since Feb. 14, 2003? What happened since Feb. 14, 2003?
First attempt to demonstrate hadron blindness using the cosmic trigger failed: we observed only a very small difference in the detector response between a mip and a high energy cosmic muon trigger.
Decide to first demonstrate the principle using UV lamp, Am241 alpha source and Fe55 x-ray source.
System modified to have UV lamp and sources inside the radiator detector box.
Itzhak Tserruya, BNL, May13, 2003
5
OutlineOutlineMeasurements with UV lamp Photoelectron detection efficiency vs. ED Single and triple GEM gain curve CsI Photoelectron emission CsI photocathode stability
UV-photon absorption vs. water content in CF4
Measurements with Am241
Charge collection in drift gap vs. ED
Am241 -spectra vs. ED
Conclusions and Outlook Proof of Principle R&D completed. But ….
Itzhak Tserruya, BNL, May13, 2003
6
Set-up
Mesh
GEM1
GEM2
GEM3
PCB
Am241 or Fe55
1.5mm
1.5mm
1.5mm
2mm
Detector Box
(9 3x 3 cm2 pads)
Powering scheme
Independent poweringof the mesh
R
R
R
R
R
R = 10M
HV
HV
R
2R
Resistive chainPowering of triple GEM
50 cm long CF4 Radiator
Detector box
D2 UV Lamp
Overall Set-up
Itzhak Tserruya, BNL, May13, 2003
7
CsI Photoelectron Emission
HV(+)ED
pA
HV(-)
ED
pA
( 14.04)
( 24.04)
( 14.04)
Itzhak Tserruya, BNL, May13, 2003
8
Gain Curve: Triple GEM with CsI in CF4:
(I) Current at PCB
pA
ET
ED
ET
EI
G
G
G
T
T
I
DIPE
IPE D
Measurements done at ED = 0
IPCB = IPED (G T . G T . G I) = (IPED) Geff Geff (G T)3
Itzhak Tserruya, BNL, May13, 2003
9
Gain Curve: Triple GEM with CsI in CF4:
(II) Effective Gain
V of 20 V gain increase of factor 3
Itzhak Tserruya, BNL, May13, 2003
10
Gain Curve: Single GEM with CsI in CF4:
(I) Current at PCB
pA
ET =500V/1.5mm
ED = 0
GT
DIPE
IPE D
IPCB = IPED (G T) = (IPED) Geff Geff (G T)
11
Gain Curve: Single GEM with CsI in CF4:
(II) Effective Gain
At 500V*), single GEM effective gain = 20Expect 8 103 for triple GEMConsistent with measurement
*) The single and triple GEM effective gains can be compared only at VGEM =500 since the single GEM gain curve was determined at a fixed ET = 500 V.
Itzhak Tserruya, BNL, May13, 2003
12
Photoelectron Detection Efficiency measure detector response vs ED at fixed gain
pA
ET
ED (+)
ET
EI
G
G
G
T
T
I
DIPE
Very efficient detection of photoelectrons even at negative drift fields !!
Itzhak Tserruya, BNL, May13, 2003
13
CsI Photocathode Stability
5% shadow of Fe55
support
~15’ Exposure to air
5% shadow of Fe55 +
6% shadow of Am241
supports
No shadow
HV(-)
ED
pA
Current on mesh measured under vacuum, almost every day, at VGEM-mesh = 600 V
CsI photocathode is very stable
Itzhak Tserruya, BNL, May13, 2003
14
UV Photon Absorption in H2O(in 40 cm of CF4)
~ 10% UV absorption per ppm of water!!!
Itzhak Tserruya, BNL, May13, 2003
15
Charge Collection in Drift Gap:(I) Am241 -spectra
ET
ED (+)
ET
EI
G
G
G
T
T
I
D
Am241
NP
Itzhak Tserruya, BNL, May13, 2003
16
Charge Collection in Drift Gap : (I) Mean Amplitude
At ED = 0 charge signal drops dramatically as anticipated in our proposal
Itzhak Tserruya, BNL, May13, 2003
17
Charge Collection in Drift Gap : (II) Rate
Rate also drops dramatically at ED =0. This was not expected and is not fully understood
Itzhak Tserruya, BNL, May13, 2003
18
Hadron Blindness
At slightly negative ED, photoelectron detection efficiency is preserved whereas charge collection is largely suppressed.
Itzhak Tserruya, BNL, May13, 2003
19
OutlookOutlook (Feb. 14, 2003) (Feb. 14, 2003)
The original goal of completing the detector R&D before the end of 2003
is well within reach.
Our TDL:
Last milestone: demonstrate HBD properties of the detector
Start detector design
Repeat all measurements under much better controlled conditions (monitor gas density, monitor oxygen and water content of gas).
Measure the QE of CsI
Measure CF4 scintillation
Endurance tests
Study gas mixtures: CF4 – Ne or CF4 – Ar ?
Itzhak Tserruya, BNL, May13, 2003
20
Outlook Outlook
The original goal of completing the detector R&D before the end of 2003
is well within reach.
Our TDL:
Last milestone: demonstrate HBD properties of the detector
Start detector design
Repeat all measurements under much better controlled conditions (monitor gas density, monitor oxygen and water content of gas).
Measure the QE of CsI
Measure CF4 scintillation
Endurance tests
Study gas mixtures: CF4 – Ne or CF4 – Ar ?
But ….
Itzhak Tserruya, BNL, May13, 2003
21