Itzhak Tserruya, BNL, May13, 2003

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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

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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

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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

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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

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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

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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

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CsI Photoelectron Emission

HV(+)ED

pA

HV(-)

ED

pA

( 14.04)

( 24.04)

( 14.04)

Itzhak Tserruya, BNL, May13, 2003

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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

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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

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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)

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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

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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

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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

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UV Photon Absorption in H2O(in 40 cm of CF4)

~ 10% UV absorption per ppm of water!!!

Itzhak Tserruya, BNL, May13, 2003

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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

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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

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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

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Hadron Blindness

At slightly negative ED, photoelectron detection efficiency is preserved whereas charge collection is largely suppressed.

Itzhak Tserruya, BNL, May13, 2003

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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

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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

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