Freiburg 1999 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 36: Postersitzung / Instrumentation und Anwendungen I

HK 36.24: Poster

Wednesday, March 24, 1999, 10:15–12:00, Foyer

The EUROBALL neutron wall – design, performance and first experiments. — •H. Grawe¹, M. Górska^1,2, Ö. Skeppstedt³, H.A. Roth³, R. Wadsworth⁴, D. Jenkins⁴, M. Moszyński⁵, D. Wolski⁵, M. Kapusta⁵, C. Fahlander⁶, M. Hellström⁶, A. Johnson⁷, J. Cederkäll⁷, B. Cederwall⁷, W. Klamra⁷, J. Nyberg⁸, M. Weiszflog⁸, A. Gadea⁹, and J. Eberth¹⁰ — ¹GSI Darmstadt, Planckstr. 1, D–64291 Darmstadt, Germany — ²IEP, University of Warsaw — ³CUT, Göteborg — ⁴University of York — ⁵SINS, Otwock–Świerk — ⁶Dept. of Physics, Lund University — ⁷RIT, Stockholm — ⁸TSL, Uppsala University — ⁹INFN, Legnaro — ¹⁰IKP, Universität zu Köln

The mechanical design of the EUROBALL Neutron Wall and neutron detectors, and their performance measured with a ^246,248Cm fission source [1]and in a series of in-beam experiments are described. The array consists of 15 pseudohexaconical detector units subdivided into three hermetically separated segments of 149 mm height, and a smaller central pentagonal unit which is subdivided into 5 segments. It covers the forward 1π of EUROBALL. The detectors are filled with Bicron BC501A liquid scintillator, and light is collected in Philips XP4512PA (hexagon segments) and XP4312B (pentagon segments) photomultiplier tubes. The tests of n-γ discrimination performed by the zero-crossing and time-of-flight methods show a full separation of γ- and neutron events down to 50 keV recoil electron energy. The time resolution was measured as 1.56 ns. The total efficiency for the full array is 0.30 for a symmetric fusion-evaporation reaction.

[1] Ö. Skeppstedt et al., Nucl. Instr. and Meth. in Phys. Res. A, in print