THE MODIFIED MINI-FOBOS SETUP

The 4π spectrometer FOBOS was proved to be a high-efficiency tool for investigation of the characteristics of multi-body decays of hot heavy nuclei produced in nuclear reactions induced by heavy ions. The time-offlight measurements of charged fragments employing the radio-frequency (RF) signal of the cyclotron U400-M to deduce the START signal require no special START detectors and, hence, the big fraction of the total solid angle is available for particle detection. The lack of the RF signal in experiments aimed at search for the exotic decay modes in spontaneous fission enforces to use an additional START detector. The complicated target station equipped by a START detector shadows a large portion of detector modules making thus no sense to use the whole powerful detection system in such experiments. Therefore, it has been decided to build a simplified facility consisting of several standard FOBOS modules only. The miniFOBOS setup, a prototype of the FOBOS spectrometer, has been chosen for that purpose. It was exploited mainly to solve various method tasks related to the construction of the FOBOS spectrometer. The general idea of the modified miniFOBOS setup (MMF) consists in using a small reaction chamber which can be then unique for each experiment and the basic universal system maintaining the detectors. The special mounting cones are used to joint detectors with the reaction chamber (Fig. 1, 2). Such cones can be used, in particular, to build the high efficiency system joining six modules in the form of 3Dcross.