Ferber, N.

Fiks, E.

Kaufeld, I.

Kuzminchuk-Feuerstein, N.

Voss, B.

GSI Repository

First beam test of a Cherenkov detector prototype for a TOF measurements atthe Super-FRSN. Kuzminchuk-Feuerstein∗1, N. Ferber1,2, E. Fiks3, I. Kaufeld1, and B. Voss1, and the Super-FRScollaboration11GSI, Darmstadt, Germany; 2RheinMain University of Applied Science, Ru¨sselsheim, Germany; 3National ResearchTomsk Polytechnic University, Tomsk, RussiaIn order to separate and identify fragmentation prod-ucts with the Super-FRS at FAIR a high resolving powerdetection system is required for position and Time-of-Flight (TOF) measurements. For the future TOF measure-ments a Cherenkov detector employing Iodine Naphthalene(C10H7I) with an optical refractive index n=1.705@589 nmis proposed. The liquid is kept in a cuvette with an alu-minium frame (170x50 mm). The entrance and exit win-dow of the cuvette is made out of the borosilicate glass BK7coated with Aluminium (0.15 µm) to act as a mirror for theCherenkov photons. SF-10 glass plates (10x50x2 mm) areglued to the right and left side of the cuvette with an opti-cal glue. Those glass plates make it possible that reflectedphotons escape from the cuvette on the sides where they aretransported via UV-transmissive PMMA light guides (LG)onto two photomultiplier tubes (PMTs) of Hamamatsu typeH2431-50. The layout of the Cherenkov detector is shownin Fig. 1. The proof-of-principal operation of the proto-PMT1 PMT 2LG1 LG 2Ion Iodine NaphthaleneFigure 1: 3D figure of the Cherenkov detector with themain components.type Cherenkov TOF detector has been tested with a Ni59ion beam at CaveC at GSI. In particular the timing reso-lution and detection efficiency were measured. In the ex-periment two plastic scintillator detectors were installed infront and behind the Cherenkov detector and were used asreference detectors for the efficiency measurement. Eachof them were equipped with two PMTs on the left andright ends. The observation of the coincidences betweensignals from two scintillators is used as confirmation thatthe ion beam passed through the Cherenkov detector. Fortraversing particles fulfilling the condition of the emissionof Cherenkov light and photons are created in the liquid co-incidences between PMT1&PMT2 are recorded. The scin-tillator signals coming from 4 photo-multipliers are firsttreated with the constant-fraction discriminators and after-wards used to create coincidences in the logic unit (AND).When coincidences between the front and back scintilla-tor signals take place the final AND unit delivers a signalfor external triggering of the oscilloscope. Raw waveforms∗ n.kuzminchuk@gsi.de0,1 0,2 0,3 0,4 0,5 0,60,250,300,350,400,450,50 Timing resolution  [ns]Intencity [106 ions/spill]E=1.5 GeV/u300 600 900 1200 150010203040506070103 ions/spill0.1*106 ions/spill Efficiency [%]Energy [MeV/u]Figure 2: Left: Influence of the intensity on the timing reso-lution at maximal energy of 1.5 GeV/u. Right: Relativedetection efficiency depending on the beam energy.from PMT1& PMT2 and from one PMT of each scintil-lator are stored with a digital oscilloscope LeCroy. Timestamps of the waveformes were determined with a softwareCFD method. The timing resolution of the detector is con-sidered as a jitter between time signals detected by PMT1and PMT2. For more details about the measurements anddata analysis see [2]. The measurements were done withinseveral regimes of low/high energies as well as low/high in-tensities. After passing through all the materials installed infront of the detector the lowest energy of 288 MeV/u usedin this test was just enough for the creation of Cherenkovphotons. According to the calculation at this energy about11687 Cherenkov photons were created in a range of wave-lengths of 390-650 nm. Poor detection efficiency and tim-ing resolution were measured in this case. Increasing thebeam energy to 1.5 GeV/u as well as increasing the particleintensity from 103 to 0.6·106 ions/spill improve the timingby a factor of 2. Fig. 2 shows the change in the relativeefficiency and timing resolution for 1.5 GeV/u at differentintensities. After the measurement the liquid transmissionspectrum was rechecked with UV spectrometer in order tocheck for aging effects. No degradation of the light outputwas observed. To improve the timing resolution further im-provements of the cuvette construction and electronics arenecessary.References[1] N. Kuzminchuk-Feuerstein et. al.,, GSI Scientific Report2013 (2014) 103GSI SCIENTIFIC REPORT 2014 MU-NUSTAR-FRS-05DOI:10.15120/GR-2015-1-MU-NUSTAR-FRS-05 141[2] N. Ferber, Master thesis, RheimMain University of AppliedScience, Ru¨sselsheim, 2014MU-NUSTAR-FRS-05 GSI SCIENTIFIC REPORT 2014142 DOI:10.15120/GR-2015-1-MU-NUSTAR-FRS-05

First beam test of a Cherenkov detector prototype for a TOF measurements at the Super-FRS

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First beam test of a Cherenkov detector prototype for a TOF measurements at the Super-FRS

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