CANEL, shown in the figure below, is a modular device that is placed around the target of the T400 neutron generator to produce these realistic neutron fields. Only two examples of the device, which is mentioned as an example in the ISO 12789 standard, exist worldwide.
The principle of CANEL is that it generates a fission neutron spectrum within a depleted uranium shell. The fission neutrons are then moderated using elements representing shielding used in the nuclear industry: an iron shield with a polyethylene plate, all placed in a polyethylene duct 70 cm in diameter and 1 m in length. This polyethylene duct confines the scattered neutrons within the containment and directs the neutron field forwards. The equipment calibration point is along the axis of the deuteron beam, 50 cm from the output from CANEL.
CANEL device on the T400
Although only one configuration of CANEL is currently used, its modularity means that the thickness of the iron and polyethylene shields can be varied to generate realistic fields with different energy distributions.
Fluxes and dose equivalent rates determined 50 cm from CANEL/T400 and the relative contribution of the different neutron energy domains to these values(1). These values are given for nominal operation of the T400 accelerator corresponding to a diode count of 3,000 per second.
(1)In terms of fluence, more than half of the neutrons have an energy of less than 0.5 eV, but it is the fast neutrons (energy above 100 keV) that make the main contribution (nearly 80%) to the dose equivalent.