Ameil, F.

Bednarczyk, P.

Cortes, M. L.

Gerl, J.

Koch, K.

Kojouharov, I.

Kotula, J.

Pietralla, N.

Pietri, S.

Schaffner, H.

Sulek, Z.

Voss, B.

GSI Repository

Development and test of a segmented Time-of-Flight plastic detector∗M. L. Corte´s†1,2, H. Schaffner2, I. Kojouharov2, B. Voss2, F. Ameil2, K. Koch2, S. Pietri2, J. Gerl2,N. Pietralla1, P. Bednarczyk3, J. Kotuła3, Z. Sułek3, and the PreSPEC and AGATA collaborations1TU Darmstadt, Darmstadt, Germany; 2GSI, Darmstadt, Germany; 3IFJ PAN, Krako´w, PolandIntroductionImproved SIS primary beam intensities converts directlyinto higher yields of exotic nuclei. Improvements to theFRS [1] tracking detectors are necessary to allow for higherrates. This concerns in particular the rate at the intermedi-ate focal plane S2 where tracking detectors allowing forrates higher than 106s−1 are needed.In September 2010 a first Finger detector made of 15strips of plastic scintillator, 14 mm wide each, was suc-cessfully commissioned and used [2]. As an upgrade fromthat detector, a new Finger detector was developed consist-ing of 51 strips, 4.4 mm wide, of BC420 plastic scintillator.This detector is used as a test case for further developmentsfor HISPEC/DESPEC at FAIR.SetupEach pair of strips was glued to a bended UV-transparentPMMA light guide using a 2 component silicon glue. Thelight guides were then optically coupled to HamamatsuR9880U-01 photo-multiplier tubes (PMTs) using siliconpads. To power up the PMTs, 13 power supplies were used,each one powering up 4 tubes. Independent potentiometerswere added to the setup to allow independent adjustmentof the voltages. Figure 1 shows the new Finger detectormounted.Figure 1: The new Finger detectorThe PMTs are read-out using the LANDFEE discrimi-nator. This electronics determines the leading and trailingedges of the incoming PMT pulses as time signals. These∗Work partially supported by HIC4FAIR† m.l.cortes@gsi.detwo times are then recorded using two CAEN V1290 Mul-tihit TDCs. Using the two times given by the electronics itis possible to obtain, apart from the time of occurrence, thetime-over-threshold (ToT) of the signal, which provides ameasure of the signal amplitude. TRIPLEX cards [3] areused for the remote control of the thresholds and to obtainan OR signal and an analogue sum of the signals for mon-itoring. One of the TRIPLEX cards is connected with anetwork module which makes the system remote control-lable via Ethernet by a lab-view program.In-beam testThe New Finger detector was tested from Februaryto April 2014 as part of the PreSPEC-AGATA setup atGSI [4]. Time and ToT spectra were obtained for Fe andNi beams with different intensities. The efficiency of thenew Finger detector was in average 2% lower than the oneof the standard scintillator at S2, mainly because of gapsbetween the strips. Figure 2 shows a typical ToT spectrumrecorded in one of the PMTs. Using these spectra it is pos-ToT (arb. units)6 8 10 12 14Counts110210310Finger_FingerToF_ToT026Entries  38885Mean     7.32RMS     0.866Underflow       0Overflow        0Integral  3.888e+04Skewness   3.689ToT026  17:58:27  2014-04-12  Analysis/Histograms/Finger/FingerToF/ToT/Finger_FingerToF_ToT026Figure 2: Time-over-threshold spectrumsible to decide which strip had the higher charge collectionand therefore which was the strip that was hit. Position andtiming information from that strip were used for each eventand a preliminary analysis was performed. Figure 3 showsthe correlation between the strip selected as being hit andthe position determined in TPCs. In spite of the clear cor-relation, background is also present, coming from two dif-ferent sources: The high rate present as S2, which reducesthe performance of the TPCs and the possibility of havingGSI SCIENTIFIC REPORT 2013 NUSTAR-GS-03doi:10.15120/GR-2014-1-NUSTAR-GS-03 117TPC position (mm)-100 -80 -60 -40 -20 0 20 40 60 80 100Finger strip01020304050Finger_XXcorrelationTPC_first_vs_secondEntries  49747Mean x   11.39Mean y   26.51RMS x   46.54RMS y   9.847Integral   4.801e+04Skewness x  -0.1367Skewness y  -0.1014       0       0       0      41   48011     178       0    1517       0first_vs_second  20:53:14  2014-04-11  Analysis/Histograms/Finger/XXcorrelationTPC/Finger_XXcorrelationTPC_first_vs_secondFigure 3: Strip number vs. position projected from TPCstwo particles hitting the Finger detector during the sametrigger, which gives the possibility of a wrong strip selec-tion. To study this effect, the number of PMTs fired perevent was calculated. When all fired PMTs are consecutivethey are considered as coming from a single particle inter-action. When they are not consecutive, a second particlecould have produced the signals. The number of this setsof consecutive PMTs is called cluster multiplicity. Figure 4shows the number of clusters recorded versus the numberof PMTs fired. We can see that for the case of one particleNumber of clusters0 1 2 3 4 5 6 7Number of PMTs fired0246810121416Finger_FingerToF_cluster_multiplicity_vs_MultiplicityEntries  251586Mean x   1.919Mean y   3.781RMS x  0.6496RMS y   1.771Integral   2.516e+05Skewness x  0.9962Skewness y  0.9361       0       0       0       0  251586       0       0       0       0110210310410cluster_multiplicity_vs_Multiplicity  21:03:17  2014-04-11  Analysis/Histograms/Finger/FingerToF/Finger_FingerToF_cluster_multiplicity_vs_MultiplicityFigure 4: Cluster multiplicity vs. PMT multiplicitythe most likely is to have two PMTs fired, correspondingto one strip. The rest of the events can be properly recon-structed with more detailed analysis.Using the timing information given by the strip selected,the Time-of-Flight (ToF) between the new Finger detectorand the scintillator placed in the last focal point of FRS(S4) was calculated. Figure 5 shows the ToF versus theatomic number of the particles obtained from the MUSICionization chambers.ToF (arb. units)154 156 158 160 162 164 166 168Z21.021.522.022.523.023.524.024.5Finger_FingerTofVsZ_first_vs_secondEntries  94158Mean x   163.2Mean y   22.77RMS x   2.167RMS y  0.4292Integral   2.952e+04Skewness x   -1.48Skewness y  -0.7013    7415    6037   16832   13725   29516   18655     444     735     799first_vs_second  17:57:47  2014-04-12  Analysis/Histograms/Finger/FingerTofVsZ/Finger_FingerTofVsZ_first_vs_secondFigure 5: Time of flight vs. atomic numberThis plot presents a preliminary identification plot andcan be further improved by a more detailed analysis whichincludes strip selection, considering multiple particles andproper calibrations.OutlookA new Finger detector with higher count rate capabilitieswas developed and tested. ToT technique to select the stripwas proved to be feasible. The preliminary analysis of thedata obtained during the PreSPEC-AGATA campaign 2014show a reasonable efficiency and the possibility to charac-terize multiple particles hitting the detector. The outcomeof this study will be used to optimize further developmentsfor a Time-of-Flight detector at the Super FRS.References[1] H. Geissel et al. Nucl. Instr. Meth. B70 (1992) 286[2] F. Ameil et al. “Time of flight with a segmented plastic fin-ger detector at high particle rate”, GSI Scientific Report 2011(2012) 171[3] K. Koch et al., “TRIPLEX, an Upgrade for the TACQUILASystem”, GSI Scientific Report 2010 (2011) 235[4] H.J.Wollersheim, “Relativistic Coulomb Excitation: FromRISING to PreSPEC”, Acta Phys. Pol. B42 (2011), 705NUSTAR-GS-03 GSI SCIENTIFIC REPORT 2013118 doi:10.15120/GR-2014-1-NUSTAR-GS-03

Development and test of a segmented Time-of-Flight plastic detector

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Development and test of a segmented Time-of-Flight plastic detector

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