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Van de Graaff accelerator

The high intensity quasi mono-energetic neutron source at IRMM is driven by a vertical 7 MV Van de Graaff accelerator producing either continuous or pulsed ion beams. The installation has two pulsing systems. One is a fast beam pulsing generating a minimum ion beam pulse width of 2 ns and pulse repetition rates of 2.5, 1.25 or 0.625 MHz, and the other a slow pulsing system giving a minimum pulsing width of 10 μs at an adjustable frequency up to 5 kHz.

The neutron fields that have well defined energies are produced by the nuclear reactions Li(p,n), T(p,n), D(d,n) or T(d,n) giving neutrons within the energy regions 0.3 – 10.0 MeV and 14.5 - 24 MeV.

The IRMM Van de Graaff facility houses six experimental set-ups in two large laboratory halls. The accelerator is operated 24 hours a day and seven days a week and it provides a stable neutron field for more than a week without interruption. Neutron fluxes and neutron energy spectra are monitored and characterised with high precision by long counters, proportional counters, BF 3 counters, Bonner spheres, time-of-flight systems, fission chambers and activation foils. Absolute neutron fluencies are measured using a calibrated recoil proton telescope. Several shadow cones are available for measurements of possible neutron scattering.



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