Since July 23, 2008 and in complement to SER testing facilities, ASTEP has been now providing in situ real-time neutron monitoring using a super 3-NM64 neutron monitor installed in a new extension of the ASTEP building (Fig. 1).

The Plateau de Bure Neutron Monitor (PdBNM) is composed of three high pressure (2280 Torr) cylindrical LND He3 detectors surrounded by lead rings and a polyethylene box (Fig. 2). Assembled and previously operated in Marseille during the year 2007-2008, the PdBNM allowed us to experimentally determine the acceleration factor (AF) of the ASTEP location from its barometric response.

Fig. 3 (below) shows the variation of the counting rate as a function of the atmospheric pressure. The difference between the counting rates of the two clouds of experimental points directly gives the value of the acceleration factor of ASTEP with respect to Marseille location, here estimated to 6.7. Taking into account latitude, longitude and altitude corrections for Marseille location with respect to the reference one, i.e. New-York City, the final value of the acceleration factor is AF=6.7x0.94=6.3. This value is very close to 6.21, the average acceleration factor reported in the JEDEC standard JESD89A.

Fig. 1. External view ASTEP building showing the new extension (first floor) designed to host the Plateau de Bure Neutron Monitor (PdBNM). Fig. 2. View of the extremities of the cylindrical neutron detector tubes connected to the charge amplifiers and to the acquisition module (electronic counters).

Fig. 3. Experimental determination of the ASTEP acceleration factor (AF) from the barometric response of the neutron monitor successively installed in Marseille (2007-2008) and on the Plateau de Bure since July 2008. Experimental clouds correspond to one month recording (one point per hour).

Related documents available for download:

PdBNM design & construction

PdBNM installation & operation