Speaker
Description
The discovery of the Super Heavy Elements (SHE) with atomic number Z=113-118 as well as new neutron excess isotopes of the elements with Z=104-112 was one of the outstanding scientific results of the last decades. These high priority experiments were carried out on the cyclotron U400 of the FLNR (JINR, Dubna, Russia). The synthesis of the new super heavy elements stimulated works on the development of methods of their identification by means of the technique called Isotope Production On-Line (ISOL). Thereto, in the FLNR there was designed and put into commissioning the mass separator MASHA - Mass Analyzer of Super Heavy Atoms. The uniqueness of this mass spectrometer consists in ability to measure "on line" the masses of the synthesized isotopes of the super heavy elements simultaneously with detection of their alpha decays and spontaneous fission.
Another progress in the investigation of superheavy elements is the registration of other particles than alphas and fission fragments in the decay chain of superheavy elements such as beta particles and X-rays, which increase the reliability of their identification. The position-sensitive quantum counting hybrid pixel detectors of the TIMEPIX type satisfy the requirements while providing high spatial resolution and single-quantum detection. Two main characteristics of TIMEPIX are the most important for experimental studies of synthesis of super heavy elements. The first one is the position sensitivity and tracking detection of single particles; the second one is the capability of detection of alpha particles and fission fragments in wide energy range. So far the signature of identification of superheavy elements was mainly based on the lifetime and the alpha energy of nuclei in the decay chain. The mass separator MASHA adds the mass measuring with high accuracy and TIMEPIX adds the position sensitivity and tracking detection. Although the superheavy elements decay predominately by alpha emission the beta emission is not excluded and has never measured before. These capabilities of TIMEPIX increase the reliability of identification of superheavy elements which is quite important in such rare processes.
A few experiments with heavy ion beams were carried out to test the isotope identification method with the help of tracks in pixel detectors. The mercury and radon isotopes were produced in complete fusion and multinucleon transfer reactions. A new software, based on the neural network approach and principal component analysis, for the particle recognition and data analysis of experimental results was developed and used.
The next experiments at the modernized mass separator MASHA with “Cryogenic Gas Stopping Cell” and gas-filled magnetic separator placed at the accelerator DC280 (“Factory of Superheavy Elements”, JINR, Dubna) are discussed. The “Cryogenic Gas Stopping Cell” uses IGISOL technique (Ion-Guide Isotope-Separator On-Line) and can extract the produced isotopes with life time up to 10 ms. The main goal of MASHA setup will be the mass measurement and study of decay properties of super heavy elements (Z = 112 - 118) in complete fusion reactions induced by heavy ion beams.
