Wed·Sep 3, 2014Wednesday·September 3, 2014

1. 01*

   Ion counting efficiencies at the IGISOL facility

   A. Al-Adili · K. Jansson🇸🇪 · M. Lantz🇸🇪 · A. Solders🇸🇪 · C. Gustavsson🇸🇪 · A. Mattera🇸🇪 · A. V. Prokofiev🇸🇪 · V. Rakopoulos🇸🇪 · D. Tarrío🇪🇸 · S. Wiberg · M. Österlund🇸🇪 · S. Pomp🇸🇪

   At the IGISOL-JYFLTRAP facility, fission mass yields can be studied at high precision. Fission fragments from a U target are passing through a Ni foil and entering a gas filled chamber. The collected fragments are guided through a mass separator to a Penning trap where their masses are identified. This simulation work focuses on how different fission fragment properties (mass, charge and energy) affect the stopping efficiency in the gas cell. In addition, different experimental parameters are varied (e. g. U and Ni thickness and He gas pressure) to study their impact on the stopping efficiency. The simulations were performed using the Geant4 package and the SRIM code. The main results suggest a small variation in the stopping efficiency as a function of mass, charge and kinetic energy. It is predicted that heavy fragments are stopped about 9% less efficiently than the light fragments. However it was found that the properties of the U, Ni and the He gas influences this behavior. Hence it could be possible to optimize the efficiency.

   nucl-ex3 citations
2. 02*

   In-medium effects for nuclear matter in the Fermi energy domain

   O. Lopez · D. Durand · G. Lehaut · B. Borderie · M.F. Rivet · R. Bougault · E. Galichet · D. Guinet · N. Le Neindre · P. Marini · P. Napolitani · M. Pârlog and 4 other authors

   We study nuclear stopping in central collisions for heavy-ion induced reactions in the Fermi energy domain, between $15$ and $100$ A\,\textrm{MeV}. Using the large dataset of exclusive measurements provided by the $4\pi$ array \emph{INDRA}, we determine the relative degree of stopping as a function of system mass and bombarding energy. We show that the stopping can be directly related to the transport properties in the nuclear medium. By looking specifically at free nucleons (here protons), we present for the first time a comprehensive body of experimental results concerning the mean free path, the nucleon-nucleon cross-section and in-medium effects in nuclear matter. It is shown that the mean free path exhibits a maximum at ${\lambda }_{NN}=9.5\pm 2$ \textrm{fm}, around $E_{inc}=35-40$ A\,\textrm{MeV} incident energy and decreases toward an asymptotic value ${\lambda }_{NN}=4.5\pm 1$ \textrm{fm} at $E_{inc}=100$ A\,\textrm{MeV}. After accounting for Pauli blocking of elastic nucleon-nucleon collisions, it is shown that the effective in-medium \emph{NN} cross section is further reduced compared to the free value in this energy range. Therefore, in-medium effects cannot be neglected in the Fermi energy range. These results bring new fundamental inputs for microscopic descriptions of nuclear reactions in the Fermi energy domain.

   nucl-exnucl-thPRC(2014)·86 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.