  The indium activation diagnostic was calibrated on an accelerator neutron
source in order to diagnose deuterium-deuterium (DD) neutron yields of
implosion experiments on Shenguang-III facility. The scattered neutron
background of the accelerator room was measured by placing a polypropylene
shield in front of indium sample, in order to correct the calibrated factor of
this activation diagnostic. The proper size of this shield was given by Monte
Carlo simulation software. The affect from some other activated nuclei on the
calibration was verified by judging whether the measured curve obeys
exponential decay and contrasting the half life of the activated sample. The
calibration results showed that the linear range reached up to 100 cps net
count rate in the full energy peak of interest, the scattered neutron
background of accelerator room was about 9% of the total neutrons and the
possible interferences mixed scarcely in the sample. Subtracting the portion
induced by neutron background, the calibrated factor of our sample was
4.52*10^-7 counts/n with uncertainty of 4.3%.
