SHREC - Search for Element 120

Following the ionization and acceleration of heavy ions such as 48Ca and 50Ti, these impinging on thin foils comprising isotopically enriched, radioactive actinide material such as 244Pu or 249Cf, fusion-evaporation may lead to the very (very) rare production of superheavy nuclei. Examples are 48Ca+244Pu → 288Fl+4n or 50Ti+249Cf → 296-120+3n. The recoiling superheavy nuclei are sent through electromagnetic separators which highly suppress primary beam and unwanted reaction products, while the superheavy nuclei are guided into custom-made radiation detectors. These detectors register their arrival and subsequent radioactive alpha decays or spontaneous fission. Position and time correlations of such "implantation-decay-chains" form the basis of identification and study of (new) superheavy elements (SHE). 

In the context of the search for element 120 at LBNL, we provided the detector for SuperHeavy RECoils (SHREC), illustrated on the right hand side. SHREC comprises six layers of double-sided silicon strip detectors: an implantation plane, an identical veto plane behind, and four upstream sections. They form a rectangular box with a granularity of 3x58x58~10000 silicon pixels for the implantation detector. Here, each of these pixels serves as a potential position for detecting a given decay chain of an implanted superheavy nucleus.

SHREC was developed and built in Lund starting ~2019 and delivered to Berkeley in 2022. Since then, it has successfully served in various preparatory SHE experiments needed to ensure an appropriate search for the new element with proton number Z=120. Press releases at Lund and LBNL concerning the milestone experiment 50Ti+244Pu provide a more general introduction of the promising path towards new elements.

See links "Main Publications" and "Student Theses" for more detailed scientific information.