Andre, C.

Boutachkov, P.

Bräuning, H.

Dorn, C.

Forck, P.

Glück, E.

Graf, Horst

Hoffmann, T.

Lavrik, V.

Lieberwirth, A.

Reiter, A.

Shutko, Y.

Walasek-Höhne, B.

GSI Repository

In-beam tests of PMTs and voltage dividers for particle detectors at FAIR∗P. Boutachkov1, A. Reiter1, C. Andre1, H. Bra¨uning1, C. Dorn1, P. Forck1,2, E-M. Glu¨ck1, H. Graf1, T.Hoffmann1, V. S. Lavrik2, A. Lieberwirth3, Y. Shutko3, and B. Walasek-Ho¨hne11GSI, Darmstadt, Germany; 2Goethe University, Frankfurt, Germany; 3IKP, Darmstadt, GermanyScintillation counters are used for beam intensity, beamloss and spill structure measurements at GSI, they will beutilized at FAIR too, see [1] and the references therein.The presented study was started due to the phase out ofthe Photonis XP2972 photomultiplier, which is presentlyused in the beam diagnostic counters at GSI. Possible re-placement photomultipliers (PMTs) and active voltage di-viders (AVDs) were selected based on their characteristicsand laboratory tests [1]. From the tested PMTs, Hama-matsu R6427 had the largest gain variation, while the ETEnterprises and the GSI in-house developed AVDs demon-strated stable operation at counting rates above 10 MHz.The response of the selected PMT and AVDs to the mod-ulated spill structure of slowly extracted SIS beam was in-vestigated.Measurements and ResultsThe tested PMT and AVD was coupled to a 1 mm thickBC400 scintillator, in a configuration illustrated in Fig. 1of Ref. [2]. Three scintillators were placed behind eachother. The heavy ion beam penetrates the 3 mm plastic,depositing similar energy in the three detectors. The gener-ated signals were recorded with a broad band oscilloscope,which was triggered at a programmable delay relative tothe beginning of the spill extraction. A representative mea-surement is shown in Fig. 1, demonstrating the better per-formance at high counting rates of the GSI-AVD. Operat-ing at these rates is advantageous for applications where anintegrating detector, as an ionization chamber, is calibratedrelatively to a scintillator counter.The amplitude spectra shown in Fig. 2 illustrates twotypical cases which can lead to inaccurate measurements:a radiation damaged scintillator and irregular spill struc-ture. An amplitude measurement or a comparison of thecounting rates above two different thresholds will providea criteria of the measurement reliability, as shown in theinset of Fig. 2.In conclusion, based on the tests described in this con-tribution and in Ref. [1], the optimum PMT-AVD combi-nation for the future counters at FAIR and GSI is a Hama-matsu R6427 PMT powered by the GSI-AVD. In spite ofthe better PMT-AVD performance, a reliable measurementwith the scintillation counters at instantaneous rates above13 MHz would require amplitude information.∗ It is pleasure to acknowledge the members of the GSI operating teamfor their support during the experiments.Figure 1: Pulses from 238U ions at 300 MeV/u and averagein spill intensity of 1 MHz. At Time∼1 ms, the signal am-plitude grows and falls down as the instantaneous beam in-tensity increases above 13 MHz. Signals from R6427 PMTpowered by: GSI-AVD (in red), E220BFN2-01 (in green)and H7415MOD-AVD (in blue). The GSI-AVD withstandhigher counting rates compared to the other AVDs.Figure 2: Signal amplitudes for normally operating PMT-AVD in blue, overloaded detector during parts of the spillin red and radiation damaged scintillator in green. The ratioof counts with amplitudes larger than 50 mV and 20 mV isshown in the inset.References[1] P. Boutachkov, et al., “Bench Tests of PMTs and Voltage Di-viders for Counting Applications at FAIR”, GSI ScientificRep. (2014)[2] P. Forck, T. Hoffmann, DIPAC01, Grenoble, p. 129 (2001)FG-GENERAL-46 GSI SCIENTIFIC REPORT 2014464 DOI:10.15120/GR-2015-1-FG-GENERAL-46

In-beam tests of PMTs and voltage dividers for particle detectors at FAIR

http://repository.gsi.de/record/184178/files/FG-GENERAL-46.pdf

In-beam tests of PMTs and voltage dividers for particle detectors at FAIR

Abstract

Similar works

Full text

Available Versions

GSI Repository