R3B Collaboration Meeting

The ongoing analysis of the recent SOFIA2 experiment will be presented. The identification of the nuclear charge of the fission fragments will be detailed.

SOFIA (Study On FIssion with Aladin) is an innovative experimental program aiming at providing complete isotopic yields (nuclear charge and mass) for both fragments over a broad range of fissioning nuclei. Relativistic secondary beams are produced by the fragmentation of the primary beam of 238U and selected by the FRS and sent for fission in Cave C. The nuclear charge can be derived from the energy loss measurement in an ionization chamber while the mass is determined through the Bρ - ∆E - ToF technique. Both Bρ and ∆E depend on q, not Z. At very high energies, heavy nuclei of elements like U or Pb are mostly fully stripped but they still have significant chance to carry one or two electrons. To overcome this charge state issue, a dedicated ionization chamber - Triple-MUSIC - has been developed. In this talk, first results of the Triple-MUSIC analysis and the identification map of secondary beams centering at 236U, 207Fr, 194Bi and 187Tl will be presented.

Proton-neutron interactions towards the drip-line from the study of F neutron-rich isotopes

Investigation of the Shell Structure of Oxygen Isotopes in Quasi-free Knockout Reactions at the R3B Experiment

Analysis steps and status.

Summary of analysis steps, first results and ongoing tasks.

In the S393 experiment several different settings in the FRS were used producing a wide range of isotopes from Li to Ne. To identify the outgoing fragments from the target reactions "Ralf's tracker" is used. This is a program developed by Ralf Plag which tracks a fragment from the target through Aladin and all the way to the TOF-wall. The track is compared to the measured hit positions in the SSTs, GFIs and TFW. By changing the mass of the tracked fragment, the path through Aladin will change and hence also the hit positions in the GFIs and TFW. The mass of the fragment is found by minimising the residual at these detectors. For this approach to work it is very important that all the detectors are given the same positions in the tracker as during the experiment. It is also important that the charge identification and beta of the fragment is correct. It has turned out to be hard to find a detector setup that works for all different FRS-settings. This in turn has made it necessary to recalibrate the tracker for each setting by slightly moving the detectors to get reasonable mass identifications. I will present how this can be avoided by carefully aligning the SSTs and using a time-dependent incoming TOF-calibration.