Experimental set-up

Christelle Stodel 

 

    The super heavy elements are produced by complete fusion between incident and target ions. The beam irradiates a target located in front of the Wien filter. After de-excitation at the target stage, the evaporation residues (ER) are separated from the incident beam using the LISE3 Wien Filter. After implantation in a double-stripped Si-detector, the ER's are identified by their alpha-decay chains. 

  •  BEAM

    The beam is produced by the high intensity ECR Ion Sources of GANIL, it is then accelerated to low energies (4 - 5.5 MeV/u) in the CSS1 cyclotron and driven through the LISE spectrometer.

  •  TARGETS

Rotating Target    For targets with a low melting point (Pb, Bi, ...), two wheels, with a diameter of 670 mm, bearing 36 targets are mounted on a same axis to rotate in coincidence at 2000 rpm. Targets (300 mg/cm2) are mounted on the first wheel and carbon foils on the second one. the targets are "sandwiched" between two carbon foils of 40 and 10 mg/cm2.

 

 

 

 

 

  •  WIEN FILTER LISE3

Wien Filter    The incident beam is deflected out after the first half of the velocity filter. During the first tests, the distance between the beam axis and the upper electrode of the first section of the Wien filter was 5 cm and an opening of  10 cm long has been built at its exit, allowing a better suppression of scattered incident particles. This suppression will be improved by increasing the distance between the beam axis and the upper electrode to 7 cm. A dipole magnet at the exit of the filter improves also the suppression of unwanted products.

 

 

 

  •  DETECTORS

    A Si detectors continuously monitors the status of each target. The tagging of implanted particles as well as their velocities are obtained with two micro channel plate detectors. thier kinetic energy and localization are given by a X-Y silicon implantation detector. The energy of alphas and fission fragments escaping from the implantation detector is measured with a "tunnel" of 8 silicon detectors. A silicon veto detector is installed behind the implantation detector. In order to measure long half-life products without background, the implantation detector is moved out and replaced by a second one when a possible interesting event is registered.

  •  ACQUISITION

    Specific electronics with a double trigger data acquisition system have been developed. The dead time between two successive events is 10 μs.