Aumann, T.

Scheit, H.

Schrock, P.

Simon, H.

GSI Repository

Development of a Thin Large-Area Fiber Detector for Radioactive-BeamExperiments∗P. Schrock†1, T. Aumann1, H. Scheit1, H. Simon2, and the R3B Collaboration1TU Darmstadt, Darmstadt, Germany; 2GSI, Darmstadt, GermanyThe R3B setup at FAIR will allow kinematically com-plete measurements in order to study various astrophysicaland nuclear structure questions. For the identification ofbeamlike particles their mass number A is determined fromthe deflection of the beam in a magnetic field B which fol-lows the relation Bρ ∝ A/Z . To calculate the radius ρ ofthe trajectories in the magnetic field the position of the par-ticles need to be measured at various positions. To achievean adequate mass resolution a new fiber detector for track-ing of heavy fragments has been designed and tested duringseveral experiments.The detector is built of 1024 scintillating optical fibers,each with a width of 250 μm plus 30 μm optical cladding.All individual fibers are read out separately. The needed1024 electronic channels are realized by using four 16×16multianode position sensitive photomultiplier tubes [1] andNXYTER (neutron-X-Y-time-energy read-out) chips [2].The NXYTER is a self-triggered ASIC with 128 indepen-dent channels which buffer charge and time informationfor each hit in each fiber. It is included in the triggeredR3B-LAND setup by using Gemex front-end boards [3].Two variants of Gemex were in use: original boards witha switched power supply and modified versions with linearregulators.The noise level and baseline position of the NXYTER sig-nals are highly temperature dependent. So, special atten-tion to the cooling is required, especially if the detector isused in vacuum.In the s415 experiment (Pb at 500 AMeV) one unmodi-fied Gemex and a modified one were used in parallel. Ex-ample energy spectra of the signals produced by the beamare shown in Fig. 1. It can be seen that the modified variantprovides under the given experimental conditions a muchbetter energy resolution. Both versions can be used fortracking since the signals can be distinguished from the in-trinsic noise of the detector. (Note: The ADC producesinverse spectra, i. e. the noise is supposed to be betweenchannel 2000 and 2500, but in these cases it was cut viaNXYTER slow control.)During the s412 experiment (Sn at 300 to 600 AMeV)the detector was used with unmodified Gemex boards.Fig. 2 shows the position correlation between the new fiberdetector and an old one being located around 2.7 m and12 m after the center of the magnetic field, respectively. Aclear correlation is visible. The gaps stem from a not work-ing connector at one PMT.∗Work supported by HIC for FAIR, NAVI, GSI - TU Darmstadt Coop-eration, HGS-HIRe and the BMBF project 06DA7047I.† P.Schrock@gsi.deFor the future work the missing channels have to be re-covered in order to get a complete spatial coverage. AllGemex boards will be modified to linear regulated powersupply.energy / channel0 500 1000 1500 2000 2500counts012345energy / channel0 500 1000 1500 2000 2500counts02468101214Figure 1: Shown are two examples of energy spectra. Theupper and lower panel show one NXYTER channel froman unmodified and a modified Gemex board, respectively.Both spectra were recorded at the same time and stem fromthe same beam.x1 / cm-6 -4 -2 0 2 4 6x2 / cm-10-50510152005101520253035Figure 2: Position correlation of the new fiber detector (x1)and an other tracking detector (x2).References[1] http://sales.hamamatsu.com/assets/pdf/parts H/H9500.pdf[2] A.S. Brogna et al., NIMA 568 (2006) 301[3] B. Voss et al., GSI Scientific report 2011, p. 247GSI SCIENTIFIC REPORT 2012 PHN-ENNA-EXP-69203

Development of a Thin Large-Area Fiber Detector for Radioactive-Beam Experiments

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Development of a Thin Large-Area Fiber Detector for Radioactive-Beam Experiments

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