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Tandem accelerator based fast neutron source

The high intensity quasi mono-energetic neutron source at JRC-Geel is driven by a vertical 3.5 MV Tandem accelerator producing either continuous or pulsed ion beams. This facility is complementary to the GELINA neutron time-of-flight facility. Quasi mono-energetic beams of neutrons are produced in the energy range up to 24 MeV. Especially in the MeV neutron energy domain where the resonance structure of the cross-sections is averaged out, the high-resolution measurements at GELINA can be complemented by measurements at MONNET, where the experimental conditions are more favourable for weak cross sections and low sample quantities.

The MONNET facility is a 3.5 MV electrostatic accelerator for the production of continuous and pulsed proton-, deuteron- and helium ion beams. Ion beams can be produced with a current of up to 100 mA on target in DC mode and up to 10 mA in pulsed mode. The pulse repetition rates are 2.5, 1.25 or 0.625 MHz and the ion pulse-lengths are < 2 ns FWHM depending on the ion energy. The voltage stability is better than +/- 0.01 %.The energy of the mono-energetic neutrons used for the measurements is defined by a combination of three factors:

  •  type and energy of the accelerated particle (protons, deuterons or helium ions);
  •  neutron production target (lithium, deuterium or tritium targets);
  •  emission angle under which the neutrons for the experiments are selected.

Neutron fluence fields can be produced with peak energies in the regions 0.3 - 10 MeV and 16 - 24 MeV at 0 degree measurement angle.

One beam line with dedicated experimental set-ups for activation, fission and scattering experiments are attached to the accelerator. In contrast to GELINA, here, only one set-up can be used at a time. The facility is operated continuously during weeks, on a 24-hours/day basis, 7 days per week basis.

Tandem accelerator tank

©JRC European Commission, Tandem accelerator tank