Neutron Beam Monitor in Square Section Aluminum

Features

• Follow-up of the fluctuation of scattered primary neutron beams
• Input-output thin entrance windows in A5 aluminum (2 mm)
• Detection area: 10 x 4 cm
• detection thickness: 4 cm
• Detection efficiency: 10^-5 (10^-2 for thermal neutrons)
• Also available: high sensitivity square section detectors

Description

The MNH10/4.2F neutron beam monitor has been designed to be placed in the high flux primary neutron beam of a research reactor channel, in order to correct the experimental data of a neutron scattering experiment in accordance with the intensity fluctuations of the incident beam due to the reactor power changes.
These detectors countain small quantities of Helium-3 and operate in proportional mode.

Due to the very high neutron flux at this point, the detection efficiency must be sufficiently low - between 10-5 and 10-2- so to not saturate the measurement system. The order of magnitude of a good efficiency for thermal neutrons, as a function of the beam intensity, must be specified when ordering: a count rate of 1 000 counts per second is recommended.

The two opposite windows (beam input and output) are made of A5 aluminum and absorb only a negligible part of the neutron beam which can be then used to cover the scattering experiment needs.
Moreover, the electric internal structure of the detector has been designed to ensure an excellent count rate stability over long time periods.
The standard detector area (10 x 4.2 cm) is adapted to the dimensions of most neutron beams; upon request, the length may be increased up to 20 cm.

For other different applications in which square section or aluminum covering can be of interest, the same mechanical structure may be filled with high pressure Helium-3, thus providing high neutron sensitivity (31NH10/4F and 39NH10/4F presented overleaf).