Aw. Carbonari et al., AN IRRADIATION RIG FOR NEUTRON TRANSMUTATION DOPING OF SILICON IN THEIEA-R1 RESEARCH REACTOR, Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms, 83(1-2), 1993, pp. 157-162
An irradiation rig with simple design has been constructed and install
ed in the IEA-R1 research reactor for neutron transmutation doping (NT
D) of silicon with phosphorus. Crystal ingots with 3 and 4 in. diamete
r can be irradiated in this device. By adopting a procedure in which t
wo ingots of 20 cm long each are irradiated simultaneously and their p
ositions interchanged at a point when precisely half the total necessa
ry neutron dose has been received, it has been possible to achieve the
desired axial uniformity of the neutron dose. This method avoids the
use of neutron absorbing shields around the crystals which necessarily
compromise the overall irradiation capacity of the reactor. Test irra
diations were performed with 50 float zone silicon crystals, and the r
esults of radial and axial uniformities in the final resistivity value
s as well as the doping accuracy obtained in the test irradiations sho
w an excellent doping quality achieved.