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The DEMON cell

Dernière mise à jour : mercredi 7 juin 2006, par Nicolas Busser

DEMON consists of 100 individual large size NE213 liquid scintillator cells. Each cell is 20 cm long, has a diameter of 16 cm and contains 4.5 litres of a liquid rich in Hydrogen.

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DEMON cell parts


A neutron coming into the scintillator interacts mainly with the protons which results in the ionization of the atoms of the scintillator.

The subsequent deexcitation induces a light emission which has two components : a fast one and a slow one.

The outcoming light is transformed into an electrical signal by a specially designed XP4512B photomultiplier tube. The shape analysis of this pulse allows the discrimination between incident neutrons and &gamma which have different slow components.

The signal is analysed by an electronic chain which has been developed in the VXI standard.

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Scheme of a DEMON cell equiped with its SYREP scintillator

SYREP : Proton Rejection System

DEMON operates in the atmosphere. Therefore slow charged particles don’t reach the scintillators.

To avoid the contamination of the neutron spectra by very energetic protons which may reach the neutron detectors, DEMON disposes of 24 NE102 scintillators (3 mm thin) coupled to photomultipliers which can be mounted in front of the DEMON cells. These plastic scintillators are nearly 100% efficient to the protons and less than 0.5% to the neutrons. In this way the protons can be rejected in the analysis of the data by an anti-coincidence between the two signals delivered by the two photomultipliers.

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Forward view of DEMON cells equiped with SYREP scintillators
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Backward view of DEMON cells equiped with SYREP scintillators


  • The French-Belgian neutron multidetector facility : the DEMON project. - G.Bizard, Y.el Masri, F.Hanappe, B.Heusch, Nuclear Physics News 1, n°5(1991)15.
  • Comparative study of new 130 mm diameter fast photomultipliers for neutron detectors. - M.Moszynski, G.J.Costa, G.Guillaume, B.Heusch, A.Huck and S.Mouatassim, Nuclear Instruments and Methods A307(1991)97.
  • Study of n-γ discrimination by digital charge comparison method for a large volume liquid scintillator. - M.Moszynski, G.Bizard, G.J.Costa, D.Durand, Y.el Masri, G.Guillaume, F.Hanappe, B.Heusch, A.Huck, J.Péter, Ch.Ring and B.Tamain, Nuclear Instruments and Methods A317(1992)262.
  • Identification of different reaction channels of high energy neutrons in liquid scintillators by the pulse shape discrimination method. - M.Moszynski, G.J.Costa, G.Guillaume, B.Heusch, A.Huck, S.Mouatassim, Y.el Masri, P.Leleux, P.Lipnik, I.Tilquin, F.Hanappe, G.Bizard, D.Durand, J.Péter and B.Tamain, Nuclear Instruments and Methods A343(1994)563.
  • Study of n- discrimination with NE213 and BC501A liquid scintillators of different size. - M.Moszynski, G.J.Costa, G.Guillaume, B.Heusch, A.Huck, S.Mouatassim, Nuclear Instruments and Methods A350(1994)226.
  • The light yield response of NE213 organic scintillators to charged particles resulting from neutron interactions. - S.Mouatassim, G.J.Costa, G.Guillaume, B.Heusch, A.Huck, M.Moszynski, Nuclear Instruments and Methods A359(1995)530.
  • Detection efficiency of the neutron modular detector DEMON and related characteristics. - I.Tilquin, Y.el Masri, M.Parlog, Ph.Collon, M.Hadri, Th.Keutgen, J.Lehmann, P.Leleux, P.Lipnik, A.Ninane, F.Hanappe, G.Bizard, D.Durand, P.Mosrin, J.Péter, R.Régimbart, B.Tamain, Nuclear Instruments and Methods A365(1995)446.
  • Contribution à la réalisation du DEtecteur MOdulaire de Neutrons [DEMON] : étude des performances par mesures et simulations. - S.Mouatassim, PhD Thesis, Université Louis Pasteur de Strasbourg, France, July 4, 1994 - CRN94-40, N°1838.