Aprodu, V.

Balaceanu, A.

Bartos, D.

Caragheorgheopol, G.

Constantin, F.

Deppner, I.

Duta, V.

Herrmann, N.

Loizeau, P.

Petris, M.

Petrovici, M.

Prodan, L.

Radu, A.

Radulescu, L.

Simion, V.

Simon, C.

GSI Repository

High counting rate test of the basic structure for the inner zone of the CBMRPC-TOF ∗A. Baˇlaˇceanu1, V. Aprodu1, D. Bartos¸1, G. Caragheorgheopol1, F. Constantin1, I. Deppner2,V. Dut¸aˇ1, N. Herrmann2, P. Loizeau2, M. Petris¸1, M. Petrovici1, L. Prodan1, A. Radu1, L. Raˇdulescu1,V. Simion1, and C. Simon21NIPNE, Bucharest, Romania; 2Physikalisches Institut der Universita¨t Heidelberg, GermanyA basic structure for the inner zone of the CBM-TOFwall using multi-strip multi-gap low resistivity glass RPCswas designed, built and successfully tested in terms of timeresolution and efficiency [1]. The performance as a func-tion of counting rate was tested exposing the counter inhigh intensity proton beam of 2.5 GeV/c at COSY-Ju¨lichon a rather limited surface corresponding to the size of thebeam spot [2]. In the present contribution we report forthe first time results obtained exposing the whole detectorsurface at counting rates up to 104 particles/(cm2·s).Figure 1: Left side - experimental geometry. Right side -the architecture based on four RPC cellsThe in-beam test was performed at the SIS18 accelera-tor of GSI-Darmstadt. The RPC prototype was exposed tocharged particles produced by colliding 1.7 A·GeV Ni ionswith a 1 mm thick Pb - target at the highest intensity perspill delivered by SIS18. Fig. 1 shows the geometry of theexperiment (left side) and the staggered structure of the 4RPC cells (right side). The spill length was varied between5 s and 2.5 s. The analysis is based on ROOT [3] and Go4[4]. The detector was operated in a standard gas mixture of85% C2F4H2+10% SF6+5% iso C4H10 and at an electricfield strength of 157 kV/cm. Signals of 16 strips of eachcell were processed by NINO fast amplifiers [5], their dif-ferential outputs being converted by FPGA TDCs [6]. TheFigure 2: Left side - cluster size as a function of countingrate. Right side - number of clusters per event for a count-ing rate of 8x103 part/(cm2·s) .number of simultaneously recorded signals (calles clustersize) is shown in Fig.2 left side as function of the counting∗Work supported by EU-FP7/HP3 Grant No 283286,NASR/CAPACITATI-Modul III contract nr. 179EU and NASR/NUCLEUProject PN09370103rate. A decrease of about 7% is observed. On the right sideof Fig.2 the number of clusters per event is represented forone of the RPC cells.The time resolution was obtained using the time differ-ence between two RPC cells overlapped along the strips,i.e. RPC2-RPC1 or between two RPCs overlapped acrossthe strips, i.e. RPC1-RPC3. For the first case, where theoverlap is at the edge of the strip, some influence of edgeeffects is not excluded. After walk correction, a time reso-lution of ≈70 ps was obtained, including electronic resolu-tion and considering an equal contribution of the two RPCcells. For the overlap across the strips a time resolution of≈60 ps was obtained. The corresponding time differencespectrum for a flux of 104 part/(cm2·s) is presented in Fig.3left side. The non-Gaussian tails are at the level of 1-2%.The time resolution as a function of counting rate is shownin Fig.3 right side. A slight deterioration of the time resolu-tion of about 5% is observed up to 3·103 particles/(cm2·s)counting rate followed by a levelling off, within the errorbars, up to 104 particles/(cm2·s), the highest counting rateaccessed in the experiment.Figure 3: Left side -time difference between two over-lapped strips of RPC1 and RPC3 cells. Right side - timeresolution as a function of particle rate.These results together with the previous reported ones[1],[2] show that such RPC architecture, based on low re-sistivity glass electrodes conserves their excellence perfor-mance in counting rates up to 104 particles/(cm2·s) on thewhole area of the detector. Such tests will continue at evenhigher rates and longer exposure periods in order to con-firm that these type of RPCs can be used even for the mostforward regions of the CBM-TOF wall with negligible age-ing effects.References[1] M. Petris et al.,CBM Progress Report 2012, p. 68[2] M. Petrovici et al., JINST 7 (2012) P11003[3] R. Brun and F. Rademakers Linux Journal 1998 July Issue 51[4] J. Adamczewski et al, IEEE TNS 51(2004)565[5] F. Anghinolfi et al., Nucl.Instr.and Meth. A533(2004)183[6] J. Fru¨hauf et al., CBM Progress Report 2012, p. 71NQM-CBM-26 GSI SCIENTIFIC REPORT 201342 doi:10.15120/GR-2014-1-NQM-CBM-26

High counting rate test of the basic structure for the inner zone of  the CBM RPC-TOF

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High counting rate test of the basic structure for the inner zone of the CBM RPC-TOF

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