Abuhoza, A.

Frankenfeld, U.

Hehner, J.

Schmidt, C. J.

Schmidt, H. R.

GSI Repository

Construction and commissioning of a setup to study ageing phenomena in highrate gaseous detectorsA. Abuhoza1,2, U. Frankenfeld1, J. Hehner1, C.J. Schmidt1, and H.R. Schmidt31GSI, Darmstadt, Germany; 2Goethe-Universita¨t, Frankfurt, Germany; 3Eberhard-Karls-Universita¨t, Tu¨bingen,GermanyA setup, dedicated to the investigation of ageing prop-erties of gaseous detectors due to materials used for theirconstruction has been constructed and commissioned atthe GSI detector laboratory. An outstanding feature of thesetup is that tedious and repetive measurements can be con-ducted fully automated.Figure 1: Photograph of the setup mounted in a metallicenclosure and the associated data acquisition system (top).Sketch of the components of the ageing setup (bottom).The setup consists of three identical Multi Wire Propor-tional Chambers (MWPCs) mounted onto a moving plat-form, an X-ray generator to produce ionizing radiation andan 55Fe source for gain diagnostics. A second moving plat-form holds an aluminium collimator plate which has threedifferent apertures. Two of the chambers are flushed withgas which has passed through outgassing boxes containingthe materials under investigation. One of the chambers isoperated with clean gas for reference purposes. All gaslines are equipped with individual Mass Flow Controllers.Accumulated charge     [mC/cm]0 5 10 15 20 25 30 35 40 45Normalized gain  [a.u.]0.50.60.70.80.91RTV-3145Gerband 705Figure 2: Normalised gain of chamber tested with Gerband705 (blue) and chamber tested with RTV-3145 (black) as afunction of accumulated charge per unit length of the anodewires.The measurements are carried out with a premixed gas mix-ture of ArCO2 (80/20). The data acquisition and controlsystem based on LabView is configured to allow fully au-tomated measurements during long term tests. Figure 1shows a photograph of the setup and a sketch of the com-ponents.Before fabrication of the MWPCs, simulations of theirelectric field and gain had been done using a combina-tion of a gas simulation program (Magboltz) and a electricfield simulation program (Garfield). The accuracy of thegas temperature measurement has been greatly improvedwhich allows a very accurate correction of the gain mea-surement. Over a period of eight months, cleaning proce-dures have been developed and all sources of contamina-tion of the equipment have been eliminated. Thereafter,the setup has been operated with very stable behaviour, ev-idenced by the fact that around 0.5% peak-to-peak residualvariation of the normalised gain has been achieved. Thusthe setup shows the required high stability to be used forprecise ageing studies.First ageing tests have been carried out with two materi-als over two weeks: Aluminium tape named Gerband 705and a adhesive/sealant named RTV-3145. At the end ofthese two weeks, the ageing rate (R) caused by Gerband705 was about 0.3%/mC/cm while it was 3%/mC/cm forRTV-3145. The blue and black curves of Fig. 2 illustratethe normalised gain of the MWPC contaminated with Ger-band 705 and RTV-3145, respectively, as a function of theaccumulated charge per wire length.MU-NQM-CBM-54 GSI SCIENTIFIC REPORT 201492 DOI:10.15120/GR-2015-1-MU-NQM-CBM-54

Construction and commissioning of a setup to study ageing phenomena in high rate gaseous detectors

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Construction and commissioning of a setup to study ageing phenomena in high rate gaseous detectors

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