FAST MULTILAYER FISSION CHAMBER WITH PU-239

For the investigation of neutron induced fission of heavy nuclei in th e resonance energy range the fast multilayer ionization fission chambe r with a Pu-239 content of 1.6 g was constructed. The chamber is compa ct and a minimum of material has been used for its construction. The c hamber is divided into 19 sections containing no more than 100 mg of P u-239 in a section whose intrinsic capacity is less than 100 pF. By us ing fast preamplifiers and constant fraction discriminators together w ith the combined method of amplitude and pulse length discrimination t he background due to alpha-particles is suppressed and a less perturbe d pulse height distribution is obtained. The absolute fission fragment s detection efficiency of the chamber is (60 +/- 8)%. Its time resolut ion does not exceed 2.6 ns.