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Alhussein Abuhoza, S. Biswas, U. Frankenfeld, J. Hehner, C. Schmidt

GSI, Darmstadt, Germanyand

H.R. Schmidt University of Tübingen, Germany

Construction and commissioning of a setup to study ageing phenomena in

high rate gas detectors

TIPP14 Amsterdam (2-6.6.2014)

Introduction What is the detector ageing? Why ageing studies?

Ageing setupSetup-ISetup-II

Summary

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Plan

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Introduction What is the detector ageing? Why ageing studies?

Ageing setupSetup-ISetup-II

Summary

Symptoms

Losses in gas gain

Decrease of resolution

or efficiencyExcessive currents Etc...

Detector ageing

It is the deterioration of the detector performance.

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Introduction What is the detector ageing? Why ageing studies?

Ageing setupSetup-ISetup-II

Summary

~1.5 C/cm2 Estimated accumulated charge in the fourth layer of

Muon Chamber (MuCh) in CBM Ex. in

10 years.

~300 C/cm2 Estimated

accumulated charge in the first

layer of Muon Chamber (MuCh)

in CBM Ex. in 10 years.

~11 C/cm2 Estimated

accumulated charge at TRD1 in CBM Ex. in 10

years.

Experiment like Compressed Baryonic Matter (CBM)

at future FAIR facility at Darmstadt, Germany needs

detectors with long term (~10 years) stable operation

at high rates.

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Introduction What is the detector ageing? Why ageing studies?

Ageing setupSetup-ISetup-II

Summary

Ageing setup

1. Studying ageing phenomena of gaseous detectors.2. Investigating the ageing properties of the materials used

for the construction of gaseous detectors.3. Monitoring the performances of gaseous detectors, in

particular those used in CBM.

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Setup-I

• Two MWPCs in serial were used in setup-I.

• A mixing station fids one gas line.• One sensor for temperature and one

for pressure.• The MWPC configured of two cathodes

(Al-Kapton foils) and on anode (multi-wire plane).

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Setup-I (Test approach)

t

t

Q Q

MaMa

Mr Mr

Fully Automatic

Ageing Chamber

Reference Chamber

High rate

X-ray55Fe

monitor

X-ray

Ageing Ch.Refernce Ch.

Nor

mal

ized

gai

n

∑Q

No ageing

Ageing

Gain in MWPC

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Ageing study :1. Gain is the major parameter to monitor detector performance.

2. Gain normalization: Gain ratio of two detectors (ageing and reference).

Extrapolating gas density effect by fitting approach (needs precise measurement of gas temperature and pressure).

3. Variation of normalized gain should be < 1%

p/T

G

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1. Cathode of Al-Kapton foil has been replaced with a multi-wire plane

2. Premixed gas bottle will be used instead of a mixing station (temperature effect on the MFCs).

3. Moving platforms have to be presented (to avoid the continuous exposure of 55Fe-source and to test two materials or more in parallel).

4. Metal housing of chamber instead of fiberglass .5. Individual gas lines (to avoid any pressure drop in-between the chambers).

Findings from setup-I

[1] A Abuhoza, S Biswas, U Frankenfeld, J Hehner, CJ Schmidt, and HR Schmidt. Physics Procedia, 37:442–447, 2012.[2] A Abuhoza, HR Schmidt, S Biswas, U Frankenfeld, J Hehner, and CJ Schmidt. NIM Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012.

Introduction What is the detector ageing? Why ageing studies?

Ageing setupSetup-ISetup-II

Summary

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Setup-II (components)

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Setup-II• Three parallel lines (two for ageing test, one reference).• Premixed gas (no mixing station).• Two motion platforms (collimator and chambers).• Metal housing of the chambers.• Multi wire anode + multi wire cathode.

(components)

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Setup-II

Dimension of setup box : 110×130×83 cm

Dimension of MWPC: 20×20 cmActive area: 10×10 cm LabView program operates all

the functions automatically

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Setup-II (Gas system)

Outgassing box

Ageing material

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Setup-II(Test procedure)

motor

motor

CH-0CH-2CH-1

x-ray

CH-1

CH-0

CH-2

tN

orm

aliz

ed g

ain

∑Q

ageing

No ageing

1. 55Fe2. X-ray (filter)

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Commissioning and ageing tests of setup-II

Ageing and recovery behavior in the first test.

Investigation of setup cleanness.

Improving of gain normalization.

Ageing tests.

Ageing and recovery behavior in the first test.

In this setup all the components are new:+ Detector Lab (D.L.) global gas-line + Mass flow Controller (MFC)+ rigid steel tubes inside the lab + outgassing box (in line-1 and line-2) + flexible steel tube (inlet) + detector + flexible steel tube (outlet)

55Fe1mm

55Fe+x-ray1mm+3cm

Effect of the high rate of x-

ray ??

Where is the contamination source in the new setup??

ΔG=7%

ΔG=4%

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Investigation of contamination source

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Investigation of contamination source

(ΔG/G0)CH-0 = 5%(ΔG/G0)CH-1 = 11%

Using two lines

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Investigation of contamination source

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Investigation of contamination source

• Two ageing tests using gas scheme-2 revealed that there is still a source of ageing.

ΔG/G0 = 2.5%

Using one line

ΔG/G0 = 20%

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Investigation of contamination source

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Investigation of contamination source

Gas system: ball gas flow regulator + flexible steel tube + flexible steel tubes (inlet) + detector + flexible steel tubes (outlet) + outgassing box (some tests)

ΔG/G0 = 5%

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Investigation of contamination source

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Investigation of contamination source

Gas system: ball gas flow regulator + copper tube (inlet) + detector + copper tube (outlet)

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Flexible tubes were cleaned by the supplier with a cleaning and degreasing agent is called

commericialy “A062-K21 hebro®lan TN” contains:

• Phosphoric acid• Alkyl alcohol ethoxylate• Methylethyl ester• Amins• Alhkyldmiethyl• N-oxides

Investigation of contamination source

Cleaning procedures of flexible tubes:1. Distilled water, iso-propanol and dry air are pumped through

the rigid and flexible tubes (without taking them out from the setup).

2. Ultrasonic bath + iso-propanol pumping.

Gain variation = 0.3%

ΔG/G0 = 5%

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Improving of gain normalization .

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• RTV-3145

• Al-tape (Gerband 705)

Area=135 cm2

R= 300 %/C/cm

Area=135 cm2

R= 3180 %/C/cm

• Ageing test of RTV-3145 and Al-tape (Gerband 705)

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Summary

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Precise measurement of ageing are necessary to implement studies in reasonable time and in real conditions.

Very clean and stable apparatus dedicated to ageing studies is operational in GSI DetLab.

Ageing acceleration by x-ray needs to be investigated. Obtained gain stability is < 0.5% peak-to-peak. Cleaning and degreasing agent “A062-K21 hebro®lan TN” reveals

ageing effect on the MWPC. Ageing test for two materials have been carried out (accelerated by x-

ray generator): RTV-3145 : R=3180 %/C/cm Gerband 705: R=300%/C/cm

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•Back up

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R= 960 %/C/cm2 , Q=0.117 C/cm2

R= 92 %/C/cm2 , Q=0.037 C/cm2

10 years = 10*2*30*24= 14400 hQ=e·n·r·G·t

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• Polyacrylat

Ageing tests:

1 min 1 min 1 min + 40 min x-ray

Ch-2Ch-1Ch-0

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Residual instability has been observed due to

change in the gas density and detector geometry

resulting from the change of ambient parameters (T,

P etc.)

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Modification in the design

Inner windows

Outer windows

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To avoid the residual fluctuation of the gain resulting from the change of geometry of the

chamber, extra outer windows have been added with two holes in inner windows

• Diethornís formula

Unstable proportionality of the gain with T/p ratio

T/P (K/bar)

Stable proportionality of the gain with T/p ratio

T/P (K/bar)

With outer windows

Very stable operation after

correction

Unstable after correction

Without outer

windows

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