Program - Brookhaven National Laboratory

CALIFA, a Calorimeter for the R3B/FAIR experiment
D. Cortina-Gil, for the R3B collaboration
Universidad de Santiago de Compostela
The R3B experiment (Reactions with Relativistic Radioactive Beams) at FAIR (Facility for Antiproton and
Ion Research) is a versatile setup dedicated to the study of reactions induced by high-energy radioactive
beams. It will provide kinematically complete measurements with high efficiency, acceptance and resolution,
making possible a broad physics program with rare-isotopes that addreses very relevant questions
such as the structure of the atomic nucleus at the extreme of nuclear stability or reactions of astrophysics
interest. CALIFA (CALorimeter for In-Fligth emitted pArticles), is a complex detector based on scintillation
crystals, that will surround the target of the R3B experiment. CALIFA will act as total absorption
gamma-calorimeter and spectrometer, as well as identifier of charged particles from target residues. This
versatility is its most challenging requirement, demanding a huge dynamic range, to cover from low energy
gamma-rays up to 300 MeV protons. This fact, along with the high-energy of the beams determine the
conceptual design of the detector that will be presented in this paper together with the technical solutions
proposed for its construction.
HF 7 5:30 PM
Atomic Number Determination of Fission Products by Digital Techniques
J. Matarranz, I. Tsekhanovich
Universite de Bordeaux-1/CENBG, 33175 Gradignan Cedex, France
A.G. Smith, J.A. Dare, L. Murray, A.J. Pollitt
Department of Physics and Astronomy, The University of Manchester, M13 9PL Manchester, UK
T. Soldner, U. Koster
Institut Laue-Langevin, 6 rue J. Horowitz, 38042 Grenoble, France
D.C. Biswas
Bhabha Atomic Research Centre, Trombay, 400085 Mumbai, India
Determination of atomic numbers of non-accelerated fission products by non-radiative methods is a longstanding
experimental problem. Correct fragment identification (i.e., by mass and atomic number) is
relevant to the production probability (yield) of nuclei in low-energy fission reactions and is of interest to
different domains of research incuding nuclear data for industry and spectroscopic studies of exotic nuclei.
The difficulty in atomic number assignment is determined by the difference in the energy lost in a detector
by fragments with adjacent nuclear charges. This difference is small and comparable to the detector
energy resolution, whereas the range of nuclei to identify is relatively wide. An additional complication
comes also from the fact that these subtle changes in the loss of energy between nuclei do not remain the
same over the range of kinetic energies with which nuclei are produced in fission. Therefore assignment
of atomic numbers to fission products is possible only if thorough care is given to the collection of the
ionisation produced in the detector and to the consequent electronic treatment of signals. This approach
is implemented in the design of the two-arm spectrometer of fission products (STEFF) recently built at
the Manchester University. In addition to the identification of masses, by the double energy / double
velocity measurement, the spectrometer is capable of delivering information on nuclear charges of fission
products, on the event-by-event basis. This is achieved from the analysis of the fragments’ pulse shapes and
ranges in gaseous detectors, both obtained using digital electronics in conjunction with specially developped
algorithms. The technique has been optimised with beams of fission products with known kinetic energy
and isobaric composition, as well as tested in the 235 U(nth, f) experiment at the ILL in France. The details
of the method will be presented and explained, results on the identification of atomic numbers in the light
group of fission products will be demonstrated and the perspectives discussed.
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