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Presentation

The goals of the Nuclear Reactions (NR) group, belonging to Centro de Física Nuclear da Universidade de Lisboa (CFN-UL), are the experimental study of nuclear reactions relevant to nuclear astrophysics and the development of nuclear reactions based analytical methods.

At the national level, the experimental work has relied upon Laboratory of Accelerators and Radiation Technologies (LATR), based on the 2.5MV Van de Graaff accelerator. For the Tandem 3MV accelerator, activities related to the experimental study of astrophysical relevant nuclear reactions are planned, that will take advantage of the possibility of using heavy ions and of the high sensitivity of the accelerator mass spectroscopy (AMS) system, with a lateral resolution of 30 mmAMS line.

Internationally, the group has joined LUNA [Laboratory for Underground Nuclear Astrophysics, at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy] collaboration and also established collaboration with Prof. Claus Rolfs group of Bochum University.

The work related to analytical techniques has been centered in the development of a standard free PIGE (Proton-Induced Gamma-Ray Emission) method. For energies below 2.5 MeV the work will be concluded soon, to be extended for higher energies in connection to the Tandem 3MV accelerator. This technique, complementary of other analytical capabilities of the IBL, will open new perspectives of applied work for environment, materials, health sciences and geology.

1. Main Activities

In relation to astrophysics relevant reactions, the Nuclear Reactions group was involved, within LUNA collaboration, in the measurement down to the Sun Gamow peak of the 14N(p,g)15O reaction of the CNO cycle and in a systematic study of electron screening effects. In CTN, the experimental study of 6,7Li(p,a)3,4He and 7Li(p,p)7Li reactions was performed.

Future plans for the new Tandem 3MV accelerator will take advantage of the possibility of using heavy ions and of the high sensitivity of the AMS line.

In order to implement a standard free PIGE (Proton-Induced Gamma-Ray Emission) method, the ERYA (Emitted Radiation Yield Analysis) code was developed to integrate the relevant nuclear reactions cross sections along the depth of the samples. For that purpose (p,p'g) reactions in Li, B, F, Na, Mg and Al have been measured for energies up to 2.4 MeV. Validation of the method was done by comparison of calculated and experimental yields for samples of known composition. The method will be extended to higher energies in connection to the new Tandem 3MV accelerator and to other elements as Be, C and O.

Running projects:

  • Gamma-inducing nuclear reactions in Be, C, O and Mg;
  • Study by AMS of nuclear reactions relevant for nuclear astrophysics;
  • Electron screening effects in medium mass isotopes.

2. Technical Services

Technical services provided:

  • Quantification of Li, B, F, Na, Mg and Al contents in solid samples by PIGE (Proton-Induced Gamma-Ray Emission) with sensitivities from 2-600 ppm. Depth profiling by resonant nuclear reactions is also available.

Please contact the person in charge by email.

3. Equipment and Infrastructures

Nuclear reaction line at the Van de Graaff Accelerator (see map) including:

  • one 45% Ge (HP) detector and associated electronics;
  • two movable (between 90° and 165°) particle detectors and associated electronics;
  • one X-Y sample holder.

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