A Triple GEM Detector for the central Region of Muon Station 1

A Triple GEM Detector for the central Region of Muon Station

1M. Alfonsi1, G. Bencivenni1, W. Bonivento2,

A.Cardini2,

C. Deplano2, P. de Simone1, F. Murtas1, D. Pinci3,

M. Poli-Lener1, D. Raspino2 and B. Saitta2

1. Laboratori Nazionali di Frascati - INFN, Frascati , Italy

2. Sezione INFN di Cagliari – Cagliari, Italy

3. Sezione INFN di Roma 1, Roma, Italy

CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 2

This is the proposal for using a Triple-GEM Detector for the inner region (R1) of the first Station (M1) of the LHCb Muon Detector.

Triple-GEM detectors are very interesting devices with the following main characteristics:

High rate capability Very good spatial resolution Extremely low spark probability Intrinsically radiation hard Good time performances Light detector


These characteristics make GEM-based detector an attractive device for M1R1 (~0.6m2), for which the requirements are:

Rate Capability up to 0.5 MHz/cm2

Station Efficiency > 96% in a 20 ns time window (*) Cluster Size < 1.2 for a 10x25 mm2 pad size Radiation Hardness 1.6 C/cm2 in 10 years (**) Chamber active area 20x24 cm2

(*) A station is made of two detectors “in OR”. This improves time resolution and provides some redundancy (**) Estimated with 50 e-/particle at 184 kHz/cm2 with a gain of ~ 6000

In this presentation we will show that Triple-GEM detectors with pad readout are the appropriate choice for M1R1


10x10 cm2 GEM foils are stretched and then glued on frames

The Triple-GEM prototype is assembled inside a gas tight box.

FEE electronics is connected to the pads.


Large (20x24 cm2) GEM foils, divided in 6 sectors, are stretched with the tool shown above and then glued on frames.


Sensitive gapsASDQ FEE Boards

M1R1 Full Size Prototype


In these 3 years of R&D a large amount of measurements were performed on many different Triple-GEM prototypes.

With radioactive sources:

gain (55Fe), charge-transfer optimization (90Sr), sparking (137Am), global aging (60Co)

With 5.9 keV X-ray tubes:

Local aging, gain, charge-transfer optimization

With low intensity hadron beam (CERN PS, Frascati BTF):

Time resolution, efficiencies, cluster size, cross-talk

With high intensity hadron beam (PSI):

Spark probability, large-area aging, time resolution, efficiencies

With cosmic rays:

Time resolution, cluster size, cross-talk, electronics optimization, grounding studies


Gain uniformity ~ 10-15 %

Gain & Gain Uniformity


9.7 ns 5.3 ns

4.5 ns 4.5 ns

Single Chamber Time Spectra


Working region, upper limited by Cluster Size = 1.2, is found to be 70 V wide, a large plateau for a micro-

pattern gaseous detector!

Clu

ster

Siz

e

OR

Effi

ciency

in 2

0 n

s

2.0 fC

3.0 fC

G~4000 G~20000

Working region


At PSI we exposed three detectors to a particle flux up to 300 MHz.

Each detector integrated, without any damage, about 5000 discharges.

In order to have no more than 5000 discharges in 10 years in M1R1 the discharge probability has to be kept below 2.5 10-12 (G < 17000).

This limit is conservative because up to 5000 discharges no damage was observed.

G~4000 G~17000

Working region

Discharge Studies


Local Aging: performed with a high intensity 5.9 keV X-ray tube, irradiated area of about 1 cm2 (~ 5000 GEM holes). Integrated charge 4 C/cm2 25 LHCb years.

Large Area Aging: performed by means of the PSI M1 positive hadron beam, with an intensity up to 300 MHz and an irradiated area of about 15 cm2. Integrated charge 0.5 C/cm2 3 LHCb years.

Global Aging: performed at Casaccia with a 25 kCi 60Co source. Detectors were irradiated at 0.5 16 Gray/h. Integrated charge up to 2 C/cm2 12.5 LHCb years.

Aging Studies


G/G ~ 0

G/G ~ -10%for 0.15 C/cm2

Norm

aliz

ed

Cu

rrents

(%

)

1.4 LHCb years

Casaccia / Big Detector A / 16 Gray/hCasaccia / Big Detector B / 16 Gray/hCasaccia / Big Detector C / 0.5 Gray/hCasaccia / Small Detector D / 16 Gray/hX-Ray / Small Detector / Local Aging

2 clearly different trends !

Integration time: 3 35 days


Casaccia / Big Detector A / 16 Gray/hCasaccia / Big Detector B / 16 Gray/hCasaccia / Big Detector C / 0.5 Gray/hCasaccia / Small Detector D / 16 Gray/hX-Ray / Small Detector / Local Aging

Norm

aliz

ed C

urr

ents

(%

)

12.5 LHCb years2 clearly different trends !

PSI

Good timing performances were also measured at the PS after the PSI test No significant aging effects

CO2 problem

H2O injection


There is a clear inconsistency between data taken under very high global irradiation rate (16 Gray/h) and those taken at a lower irradiation rate (0.5 Gray/h), with X-Rays and at PSI.

This systematic effect could be due to the fact that for the highly irradiated detectors the gas flow was not increased proportionally with the irradiation rate, due to a limitation in the detector gas-output impedance.

Aging Test Gas Flow (cc/min)

Current (A) Current/gas flow

Lab. Tests 100 0.01 0.05 ~ 0

X-rays 100 0.2 0.4 0.002 0.004

PSI 200 30 0.15

Casaccia big 350 800 1000 2.3 2.9

Casaccia small 200 100 150 0.5 0.75

Casaccia monitor 350 60 0.17

Sauli (Hamburg) 80 3 12 0.04 0.15

M1R1 (peak) 100 9 (@ 184 kHz/cm2)

0.09


Aging Summary X-Rays, PSI and Low-irradiated chamber at

Casaccia show similar trend, the detector current reduction is negligible.

Tests on heavily-irradiated chambers at Casaccia are not compatible with previous results. This might indicate that an accelerated aging test requires an increased gas flow.

According to X-Ray, PSI and low-irradiation tests Triple-GEM Detectors can stand 10 years in M1R1 at LHCb without detector performances being affected.


After 17/9 LHCb Tech. Board


Clarify aging mechanism:

Physical/Chemical analysis of irradiated detectors in progress

Understanding different chamber behavior:Investigation on the Gas-flow effect

Absolute Gain Measurement: in progress

Gain Uniformity: in progress

Gain/Efficiency Recovery by voltage increase:A gain recovery by a factor 2 has already been performed during the Casaccia test

Casaccia aging test at lower rate

Work in progress


The 2000-2003 Triple-GEM Detector R&D has shown that these detectors fulfill the requirements for M1R1:

Good time resolution & efficiency in 20 ns Cluster size below 1.2 in a large HV range Very low discharge probability Very robust against sparks Good radiation hardness

Triple-GEM technology appears to be adequate to be used for the central

region of the first Muon Station

Conclusions


According to the Buddhism precepts:

“Following the ancient tradition, people take refuge in the triple-Gem”

(see, for example, “Going for the refuge, taking the precepts”, by Bhikkhu Bodhi)


Altre Trasparenze


- Maxwell 3D GEM electric field model- Garfield tools: Heed (ionization

mechanism) + Magboltz (drift velocity and diffusion) Imonte 4.5 (Townsend and attachment

- Electronics simulated with SPICE

(t) = 1/nv

n: clust/mmv: e- velocity

Ed Optimal value

Ar/CO2/CF4

(45/15/40)

Simulation


Single chamber Efficiency Curve

Low THR ~ 2 fC

Effi

cie

ncy in

20 n

s

A Triple GEM Detector for the central Region of Muon Station 1

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