1 Alhussein Abuhoza, S. Biswas, U. Frankenfeld, J. Hehner, C. Schmidt GSI, Darmstadt, Germany and H.R. Schmidt University of Tübingen, Germany Construction and commissioning of a setup to study ageing phenomena in high rate gas detectors TIPP14 Amsterdam ( )

 Introduction  What is the detector ageing?  Why ageing studies?  Ageing setup  Setup-I  Setup-II  Summary 2 Plan

3  Introduction  What is the detector ageing?  Why ageing studies?  Ageing setup  Setup-I  Setup-II  Summary

Symptoms Losses in gas gain Decrease of resolution or efficiency Excessive currents Etc... Detector ageing It is the deterioration of the detector performance. 4

5  Introduction  What is the detector ageing?  Why ageing studies?  Ageing setup  Setup-I  Setup-II  Summary

~1.5 C/cm 2 Estimated accumulated charge in the fourth layer of Muon Chamber (MuCh) in CBM Ex. in 10 years. ~300 C/cm 2 Estimated accumulated charge in the first layer of Muon Chamber (MuCh) in CBM Ex. in 10 years. ~300 C/cm 2 Estimated accumulated charge in the first layer of Muon Chamber (MuCh) in CBM Ex. in 10 years. ~11 C/cm 2 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. 6

7  Introduction  What is the detector ageing?  Why ageing studies?  Ageing setup  Setup-I  Setup-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. 8

9 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).

10 Setup-I (Test approach) t t Q Q MaMa MaMa MrMr MrMr Fully Automatic Ageing Chamber Reference Chamber High rate X-ray 55 Fe monitor X-ray Ageing Ch. Refernce Ch. Normalized gain ∑Q No ageing Ageing

Gain in MWPC 11 Ageing study : 1.Gain is the major parameter to monitor detector performance. 1.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). 2.Variation of normalized gain should be < 1% p/T G

12 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 55 Fe-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, [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 setup  Setup-I  Setup-II  Summary 13

Setup-II (components) 14

15 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)

16 Setup-II

17 Setup-II (Gas system) Outgassing box Ageing material

18 Setup-II (Test procedure) motor CH-0 CH-2 CH-1 x-ray CH-1 CH-0 CH-2 t Normalized gain ∑Q ageing No ageing Fe 2.X-ray (filter)

19 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) 55 Fe 1mm 55 Fe+x-ray 1mm+3cm Effect of the high rate of x-ray ?? Where is the contamination source in the new setup?? ΔG=7% ΔG=4% 20

Investigation of contamination source 21

Investigation of contamination source (ΔG/G 0 ) CH-0 = 5% (ΔG/G 0 ) CH-1 = 11% Using two lines 22

Investigation of contamination source 23

Investigation of contamination source Two ageing tests using gas scheme-2 revealed that there is still a source of ageing. ΔG/G 0 = 2.5% Using one line ΔG/G 0 = 20% 24

Investigation of contamination source 25

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/G 0 = 5% 26

Investigation of contamination source 27

Investigation of contamination source Gas system: ball gas flow regulator + copper tube (inlet) + detector + copper tube (outlet) 28 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 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). 1.Ultrasonic bath + iso-propanol pumping. Gain variation = 0.3% ΔG/G 0 = 5% 29

 Improving of gain normalization. 30

RTV-3145 Al-tape (Gerband 705) Area=135 cm 2 R= 300 %/C/cm Area=135 cm 2 R= 3180 %/C/cm Ageing test of RTV-3145 and Al-tape (Gerband 705) 31

Summary 32  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 34

35 R= 960 %/C/cm 2, Q=0.117 C/cm 2 R= 92 %/C/cm 2, Q=0.037 C/cm 2

10 years = 10*2*30*24= h Q=e·n·r·G·t 36

37 Polyacrylat

Ageing tests: 1 min 1 min + 40 min x-ray Ch-2 Ch-1 Ch-0 38

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.) 40

Modification in the design Inner windows Outer windows 41 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 42